Beam station treatment planning and radiation delivery method

Abstract

Described herein are methods of beam station delivery for radiotherapy in which a patient platform is moved to a series of discrete patient platform positions or beam stations determined during a treatment plan and stopped at each of these positions as a radiation source rotates about the patient, radiation is delivered to a target area that intersects the radiation beam path, and then moved to the next position after a prescribed dose of radiation (e.g., according to the calculated fluence map) for that position has been delivered to the patient.

Description

[0001] This application is a divisional application of the Chinese patent application "Beam Station Treatment Planning and Radiation Delivery Method" with application number 201980025224.9 (filing date February 13, 2019).

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Patent Application No. 62 / 629,881, filed on February 13, 2018, the entire contents of which are incorporated herein by reference. Background Art

[0004] Radiation therapy is a planning process that requires an extensive treatment planning phase in order to determine an effective way to deliver a prescribed radiation dose to a target region of the patient (e.g., a tumor region) while avoiding radiation-sensitive organs and / or structures (e.g., organs at risk or OARs). The treatment planning system integrates patient information (e.g., the size, shape, and location of the target region and OARs) and radiotherapy system machine parameters (e.g., the therapeutic radiation source beam generation capabilities and range of motion relative to the patient, the configuration of the beam shaping components, the patient platform's degrees of freedom and motion, etc.) to generate a fluence map, which includes a set of beamlets that deliver the prescribed dose to the target region. The fluence map is then segmented into a series of machine instructions that are executed by the radiotherapy system, with the assumption that once a set of instructions has been fully executed, the prescribed dose target has been achieved.

[0005] In an effort to speed up radiation delivery and shorten treatment session times, radiation therapy systems may have a continuously moving patient platform as well as a continuously moving radiation source. For example, in helical tomotherapy, therapeutic radiation is delivered to the patient from a radiation source that rotates around the patient as the patient continuously moves through the plane of the treatment beam. In this way, the patient target area can be moved through the treatment beam without pausing.

[0006] However, due to the continuous motion of the patient platform, it may be difficult to apply any radiation dose that is missed due to radiation therapy system failure (e.g., collimator failure, random magnetron arcing, etc.) or unexpected patient and / or target area movement because the patient platform will move the target area through the treatment beam plane, and it may be difficult to accurately determine the exact location of the target area relative to the therapeutic radiation source. This may result in insufficient dose delivered to certain target areas. In addition, target areas where increased dose levels are prescribed may not receive the full prescribed dose within the duration that the target area is within the treatment beam plane. Therefore, improved radiation delivery methods (and corresponding treatment planning methods) are desired. Summary of the invention

[0007] Methods for beam station delivery of radiation therapy are described herein, wherein a patient platform is moved to a series of discrete patient platform positions and / or orientations determined during treatment planning, and stops at each of these positions and / or orientations as a radiation source rotates around the patient to deliver radiation to a target area that intersects a radiation beam plane or path, and then moves to the next position and / or orientation after a prescribed dose of radiation for that position and / or orientation (e.g., according to a calculated fluence map) has been delivered to the patient. These discrete platform orientations and / or positions or steps (e.g., along the IEC-Y axis) at which therapeutic radiation is delivered while the platform is stopped (i.e., not moving, static) may be referred to as beam stations, and may be defined by a treatment planning system prior to a treatment session. Beam stations may be specified by coordinates in IEC-X, -Y, and -Z, and / or may be specified by an orientation of the patient platform (e.g., roll, yaw, and pitch of the patient platform). In some variations, the therapeutic radiation source may be mounted on a rotatable gantry that can continuously move or rotate the therapeutic radiation source during a treatment session even when the patient platform is stopped at the beam station. The therapeutic radiation source may be rotated or moved around the patient platform one or more times, such as two or more times, while the platform is stopped at the beam station. The gantry may rotate 360° in a single direction (e.g., clockwise or counterclockwise) to deliver radiation from a firing position located within a 360° plane around the patient platform, or may sweep around the patient platform in an arc of less than 360° in both directions (e.g., alternating between clockwise and counterclockwise directions to deliver radiation from a firing position located along an arc). The treatment planning system can generate a required dose distribution curve (profile) corresponding to a prescribed dose of radiation to each target area, define a series of beam stations based on the geometry and location of the target area, generate one or more fluence maps for each beam station using a dose optimization method, and can optionally segment the one or more fluence maps for each beam station into machine instructions (e.g., dynamic multi-leaf collimator or MLC configuration, therapeutic radiation source or linear accelerator pulse parameters, etc.) for execution by the radiation therapy system during a treatment session.

[0008] Because the radiation therapy system fires at predetermined or specified firing positions and / or patient platform positions and orientations, beam station radiation delivery can allow for "digital dose delivery." A fast-spinning gantry (e.g., rotating at a speed of about 15 RPM or more, about 50 RPM or more, about 60 RPM or more, about 70 RPM or more) can position the therapeutic radiation source at each firing position multiple times while the patient platform is stationary at the beam station. In this way, the radiation fluence or dose can be delivered in discrete dose quanta over multiple gantry revolutions. In addition, because the patient platform is stationary during radiation delivery, the dose can vary greatly between beam stations (i.e., the dose is highly modulated). For example, when the patient platform is at a first beam station, the therapeutic radiation source may deliver radiation in a single gantry revolution (e.g., short dwell time and / or delivering radiation during one of the multiple revolutions, and little or no radiation during the other revolutions), and when moved to a second beam station, the therapeutic radiation source may deliver a large amount of radiation over multiple revolutions (e.g., longer dwell time and / or delivering radiation during most or all of the multiple revolutions). A radiation therapy system with a fast rotating gantry (e.g., rotating at a speed of about 15 RPM or more, about 50 RPM or more, about 60 RPM or more, about 70 RPM or more) may be able to deliver radiation in multiple gantry revolutions in a relatively short period of time (e.g., without significantly increasing the treatment time). In most helical delivery systems with constant and / or consistent platform motion, this dose modulation range is not available because the platform dwell time at any position along the longitudinal axis of the platform (i.e., the IEC-Y axis) remains relatively constant. Sudden increases or decreases in platform speed may be unsettling to the patient, causing unnecessary discomfort, which may cause the patient to shift position. Since the platform is stationary during dose delivery, beam station delivery can also mitigate any dose delivery variations due to patient platform motion or velocity variations. This can help relax the specifications (i.e., increase tolerances) of the platform motion system and eliminate platform motion as a factor affecting dose delivery. The beam station radiation delivery method can also use a radiation therapy system including a fast rotating gantry (e.g., rotating at a speed of about 15 RPM or more, about 60 RPM or more, about 70 RPM or more) and / or a gantry with a large rotational inertia in combination with an external breathing sensor to help facilitate gated radiation delivery.

[0009] One variation of a radiation therapy system may include a circular gantry capable of rotating about a longitudinal axis, a therapeutic radiation source mounted on the gantry, a patient platform capable of moving to a plurality of beam stations at predetermined positions along the longitudinal axis, and a controller in communication with the gantry, the radiation source, and the patient platform. The controller may be configured to move the patient platform to a first beam station, stop the patient platform at the first beam station, activate the therapeutic radiation source to emit a radiation fluence when the patient platform is at the first beam station, and deactivate the therapeutic radiation source when the patient platform is moved from the first beam station to a second beam station. The controller may be configured to stop the patient platform at the second beam station, activate the therapeutic radiation source to emit a radiation fluence when the patient platform is at the second beam station, and deactivate the therapeutic radiation source when the patient platform is moved from the second beam station to a third beam station. The gantry may be configured to rotate at a speed of about 60 RPM. Some variations may also include an imaging system in communication with the controller and configured to acquire imaging data. For example, the imaging system may be a PET imaging system including one or more PET detectors configured to detect line of response (LOR) data, and / or a CT imaging system including one or more kV radiation detectors configured to acquire CT data. The imaging system may be mounted on the gantry. The controller may be configured to calculate the radiation fluence emitted at the first beam station by using the imaging data acquired by the imaging system. In some variations, the controller may be configured to continuously monitor the radiation fluence emitted at the first beam station, and compare the emitted radiation fluence with the planned radiation fluence for the first beam station to calculate the remaining fluence. The controller may be configured to split the remaining fluence into instructions for the therapeutic radiation source and a dynamic multi-leaf collimator (MLC) disposed in the beam path of the therapeutic radiation source, and activate the therapeutic radiation source to emit the remaining fluence when the patient platform stops at the first beam station. Optionally, the controller can be configured to determine whether the remaining fluence is below a predetermined remaining fluence threshold, and if the remaining fluence is below the remaining fluence threshold, the controller can be configured to deactivate the therapeutic radiation source and move the patient platform to the second beam station. In some variations, the predetermined remaining fluence threshold is zero. The controller can be configured to calculate the emitted radiation fluence at the second beam station using imaging data acquired before the therapeutic radiation source was moved to the second beam station. The emitted radiation fluence at the second beam station can be calculated using imaging data acquired when the patient platform is located at the first beam station.Alternatively or additionally, the controller may be further configured to: split the radiation fluence emitted at the second beam station into instructions for the therapeutic radiation source and a dynamic multi-leaf collimator (MLC) before the therapeutic radiation source emits radiation at the second beam station. The radiation fluence emitted at the second beam station may be compared with the calculated radiation fluence for emission at the second beam station, and if the difference between the emitted radiation fluence and the calculated radiation fluence is below a predetermined threshold, the controller is configured to move the patient platform from the second beam station to the third beam station.

[0010] In some variations, the system controller can be configured to sequentially move the patient platform to each of the plurality of beam stations more than once. For example, the controller can be configured to sequentially move the patient platform to each of the plurality of beam stations in a first direction along the longitudinal axis, and sequentially move the patient platform to each of the plurality of beam stations in a second direction opposite to the first direction. The radiation fluence emitted at each of the plurality of beam stations when the patient platform is moved along the first direction can be different from the radiation fluence emitted at each of the plurality of beam stations when the patient platform is moved along the second direction. In some variations, the radiotherapy system can also include a dynamic multi-leaf collimator (MLC) disposed in the beam path of the therapeutic radiation source, wherein the configuration of the MLC for the second beam station can be determined based on the calculated radiation fluence for emission at the second beam station. Alternatively or additionally, the controller can be configured to detect one or more failures of one or more of the gantry, the therapeutic radiation source, and / or the dynamic MLC during radiation fluence emission, calculate an amount of radiation fluence not delivered due to one or more detected failures, split the amount of radiation fluence not delivered into instructions for the therapeutic radiation source and the dynamic MLC for irradiation, and activate the therapeutic radiation source to emit the remaining fluence when the patient platform stops at the first beam station. The gantry can be configured to rotate around the patient platform at least twice when the patient platform is at each of the plurality of beam stations. In some variations, each gantry rotation is about 360° around the patient platform.

[0011] The controller can be configured to stop the patient platform at each of the plurality of beam stations for a predetermined dwell time. For example, the predetermined dwell time can be from about 5 seconds to about 5 minutes. Alternatively or additionally, each of the plurality of beam stations is separated by a step distance from about 1 mm to about 2 cm (e.g., about 2.1 mm). The step distance between each of the plurality of beam stations can be the same or different.

[0012] A method for calculating a fluence map for radiation delivery by a beam station may include: determining a plurality of beam stations based on one or more patient target regions, calculating a set of candidate radiation sub-beams for each beam station, and generating a fluence map for each beam station by calculating a set of sub-beam weights corresponding to the set of candidate radiation sub-beams for each beam station, so that the radiation dose delivered to the one or more target regions by all candidate radiation sub-beams meets predetermined dose constraints and treatment parameters. The plurality of beam stations may be evenly spaced from each other, and the spacing of the beam stations or the step distance between the beam stations may be about 2 mm. In some variations, the step distance between each of the beam stations may be variable, and the step distance between each of the beam stations and the number of beam stations in the set of beam stations may be user-selectable. The set of candidate radiation sub-beams may include a matrix of multi-leaf collimators (MLC) configured for each radiation firing position around the patient platform, the matrix defining a set of radiation sub-beams intersecting the one or more patient target regions. Calculating a set of sub-beam weights may include: calculating a dose calculation matrix, the dose calculation matrix including the contribution of each candidate sub-beam to the one or more target regions. Calculating a set of sub-beam weights may include: generating a penalty function representing a treatment plan quality metric, and using an iterative optimization method to calculate the set of sub-beam weights that minimizes the penalty function. The method may also include quantizing the fluence map for each beam station to generate a quantized fluence map, wherein each sub-beam weight is an integer value of a dose quota that can be delivered by the movable therapeutic radiation source. In some variations, the predetermined dose constraint may include a user-defined dose constraint, and / or a user-defined dose target, and / or a maximum dose level, and / or a dose coverage metric. The treatment parameters may include a treatment time duration and / or a beam station dwell time. The fluence map for each beam station may include an l×f matrix, where l is the number of leaves in a multi-leaf collimator located in a beam path of the therapeutic radiation source, and f is the number of therapeutic radiation source firing positions around the patient platform. The multi-leaf collimator may be a binary multi-leaf collimator having 64 leaves (e.g., l=64). In some variations, there may be 50 firing positions (e.g., f=50) and / or there may be 100 firing positions (e.g., f=100). In some variations, the method may further include generating a plurality of fluence maps for each beam station. The plurality of beam stations include a plurality of discrete patient platform positions along a longitudinal axis of the patient platform (e.g., along IEC-Y).

[0013] One variation of a method for beam station radiation delivery may include moving a patient platform to a first beam station in a set of beam stations, delivering radiation to a patient target area according to a first fluence map by moving a therapeutic radiation source around the patient platform while the platform is stationary at the first beam station, and comparing the delivered radiation to the first fluence map and calculating a fluence difference. If the fluence difference does not exceed a predetermined threshold, the method may include moving the patient platform to a second beam station in the set of beam stations. If the fluence difference reaches or exceeds a predetermined threshold, the method may include delivering the fluence difference by continuing to move the therapeutic radiation source around the patient platform before moving the patient platform to the second beam station. The therapeutic radiation source may be mounted on a gantry capable of continuous rotation around the patient platform, and wherein the method may further include rotating the gantry around the patient platform a plurality of revolutions while the patient platform is at the first beam station. In some variations, the number of revolutions of each beam station in the set of beam stations can be from about 5 to about 300 and can vary for each beam station in the set of beam stations or can be constant for each beam station in the set of beam stations. The patient platform can be non-stationary at the beam station where the fluence value of the fluence map of the beam station is zero. In some variations, delivering radiation to the patient target area according to the first fluence map includes: segmenting the first fluence map into a multi-leaf collimator configuration for each firing position around the patient platform; and adjusting a multi-leaf collimator disposed in a beam path of the therapeutic radiation source to the multi-leaf collimator configuration at each firing position. A method for beam station radiation delivery can also include: storing a multi-leaf collimator configuration and a firing position for which no radiation was delivered in a memory of a controller; and moving the therapeutic radiation source to the firing position to re-deliver radiation. In some variations, a mouth of an adjustable opening can be disposed in the beam path of the therapeutic radiation source, and delivering radiation can include adjusting a width of the mouth opening according to the fluence map. The width of the mouth opening may vary for each beam station in the set of beam stations, or may be constant for each beam station in the set of beam stations. In some variations, the patient target area may move when the patient platform is located at the first beam station, and delivering radiation to the patient target area may include directing radiation to the patient target area if it is within a predetermined treatment position and not directing radiation to the patient target area if it is outside of the predetermined treatment position.

[0014] Another variation of a method for beam station radiation delivery may include moving a patient platform to a first beam station in a set of beam stations, delivering radiation to a patient target area according to predetermined treatment parameters by moving a therapeutic radiation source around the patient platform while the platform is stationary at the first beam station, and determining whether the delivered radiation complies with the predetermined treatment parameters. If the delivered radiation complies with the predetermined treatment parameters, the method may include moving the patient platform to a second beam station in the set of beam stations. If the delivered radiation does not comply with the predetermined treatment parameters, the method may include continuing to move the therapeutic radiation source around the patient platform before moving the patient platform to the second beam station. In some variations, the predetermined treatment parameters may include one or more dose measurements, or one or more radiation delivery instructions. Examples of one or more radiation delivery instructions may include at least one of the following: beam station dwell time, mouth opening width, number of therapeutic radiation sources around the patient platform, therapeutic radiation pulse parameters, and / or MLC leaf configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic representation of a variation of a radiation therapy system is depicted.

[0016] Figure 2A A flow chart representation of a variation of a method for treatment planning for beam station delivery is depicted.

[0017] Figure 2B A flow chart representation of a variation of a treatment planning method for calculating beam station dwell times and treatment session durations is depicted.

[0018] Figure 2C Depicted is a flow chart representation of a variation of a method for converting a treatment plan for helical radiation delivery to a treatment plan for beam station delivery.

[0019] Figure 3 A flowchart representation of a variation of a method for beam station delivery is depicted.

[0020] Figure 4 A flow chart representation of a variation of a method for gated beam station radiation delivery is depicted. DETAILED DESCRIPTION

[0021] system

[0022] A radiation therapy system that can be used in beam station radiation delivery can include: a rotatable gantry that rotates around a patient treatment area, a treatment source mounted on the rotatable gantry, and a patient platform that can be moved within or through the patient treatment area. The rotatable gantry can be configured to rotate 0°-360° around the patient platform (e.g., a continuously rotatable gantry), and / or rotate only along an arc segment that sweeps a subset of angles around the patient platform (e.g., 0°-180°, 0°-270°, etc.), and / or move to a fixed number of angles around the patient platform. For example, the rotatable gantry can be configured to continuously move through each firing position while emitting therapeutic radiation, or can be configured to step to each firing position that emits therapeutic radiation only when the radiation source stops at the firing position. In some variations, the gantry can be configured to move to discrete, predetermined circumferential firing positions or firing angles as it rotates. Some systems have about 50 firing positions or angles (e.g., from about 0° to about 360°, where each firing position is separated by regular angular intervals). Some systems may have about 100 firing positions. Alternatively or additionally, some systems may be configured to have a discrete set of firing positions at any angle around the patient platform (e.g., at 0°, 45°, 90°, 135°, 180°, etc.). The gantry may be an annular or circular gantry, an arc gantry, a C-arm gantry, or a robotic arm gantry. An example of a therapeutic radiation source is a linear accelerator (LINAC). Other examples of therapeutic radiation sources may include, but are not limited to, high-energy photons, particles produced by radiation or radioactive isotopes (e.g., iridium or cobalt-60), high-energy electrons, proton beams, neutron beams, and heavy ion beams. One or more beam shaping elements may be disposed in the beam path of the therapeutic radiation source to define a treatment plane. For example, the beam shaping element may include a mouth and a dynamic multi-page collimator (MLC). The dynamic MLC may be a binary MLC or a 2-D MLC. A binary MLC may be an MLC in which each leaf may be moved to and retained in an open configuration or in a closed configuration, while a 2-D MLC may be an MLC in which each leaf may be moved to and retained in any set of positions between a fully open configuration and a fully closed configuration. The mouth may be located between the therapeutic radiation source and the MLC, or may be located below the MLC. Alternatively, the mouth may be a split mouth in which a first portion of the mouth is located between the therapeutic radiation source and the MLC (i.e., an upper mouth), and a second portion of the mouth is located below the MLC (i.e., a lower mouth) and coupled to the first portion of the mouth so that the two portions move together. The width of the mouth opening or hole through which the radiation beam passes may be adjustable, and the width of the mouth opening may be adjusted one or more times during a treatment session. Optionally, the mouth may be movable within the beam of the therapeutic radiation source so that a treatment plane defined by the mouth may be displaced in a direction parallel to the movement of the patient platform.Some variations of radiotherapy systems may include a radiation detector mounted on a gantry opposite a radiotherapy source. For example, some variations may include an MV radiation detector opposite a linear accelerator.

[0023] A patient platform of a radiotherapy system may be configured to move along its longitudinal axis (i.e., along the IEC-Y) within a patient treatment region so that a patient target region sequentially moves through a treatment radiation beam plane. The patient platform may be configured to move continuously at a constant or variable speed during radiation delivery. Alternatively or additionally, the patient platform may be configured to move to discrete locations or beam stations and may be stationary at a beam station during radiation delivery. The rate and extent of patient platform movement may be calculated prior to a treatment session and / or at the start of a treatment session. For example, the number of beam stations and the locations of the beam stations (e.g., relative to the system isocenter) may be determined by a treatment planning system, and / or the rate at which the patient platform moves between beam stations may be selected by a clinician (e.g., based on the desired treatment time and / or patient comfort). In some variations, the distance between beam stations (e.g., step size, the distance between two beam stations (including two adjacent beam stations)) may be constant throughout a treatment session, or may be variable between different beam stations. For example, the step size can be about 0.5 mm, about 1 mm, about 1.1 mm, about 1.5 mm, about 2 mm, about 2.1 mm, about 2.5 mm, about 3 mm, about 3.5 mm, about 4 mm or more, 10 mm or more, 1 cm or more, 2 cm or more, and can optionally correspond in some variations to the thickness of a CT image slice used during treatment planning. Alternatively or additionally, the step size can be selected based on the resolution and / or thickness of the treatment planning images, and / or the resolution and / or thickness of any imaging system (e.g., a PET imaging system, a CT or X-ray imaging system, etc.) used to acquire imaging data during the treatment session, and / or the field of view size of the treatment radiation beam (e.g., less than or equal to the full-width half maximum of the radiation beam size). The beam station step size can be adjusted so that the step size is smaller where the planned / calculated fluence map has a larger fluence gradient for the patient target area (e.g., at the edge of the patient target area) and larger where the fluence gradient for the patient target area is smaller (e.g., in the middle portion of the patient target area). The number of beam stations in a set of beam stations and the distance between the first and last beam stations can be determined by the treatment planning system based on the size and location of one or more patient target areas and / or the current or desired width of the oral opening. Alternatively or additionally, the beam station step size between each beam station can be the same, but if the fluence to be delivered at a particular beam station is zero, the patient platform can bypass / skip that beam station (e.g., not stop at that beam station, not activate the therapeutic radiation source when the patient platform is at that beam station) and move the platform to the next beam station where the fluence to be delivered has a non-zero value. This can result in the delivery of radiation at beam stations that are at different distances (i.e., multiples of the step size value) from each beam station.For a continuously moving patient platform, the speed may be maintained constant throughout the radiation delivery process, or may vary according to the fluence gradient of the planned / calculated fluence map to the patient target area. For example, the speed of the patient platform may be lower where the fluence gradient of the planned / calculated fluence map to the patient target area is larger (e.g., at the edge of the patient target area, and / or in an area with a relatively large prescribed dose), and the speed may be higher where the fluence gradient to the patient target area is smaller (e.g., in the middle of the patient target area, and / or in an area with a relatively small prescribed dose). The patient platform may include one or more position sensors, motion sensors, accelerometers, and / or encoder-decoders that communicate with a controller of the radiation therapy system so that the controller can monitor and / or confirm that the patient platform is located at and / or oriented toward a designated beam station prior to the delivery of the radiation therapy. For example, the X-, Y-, Z-, pitch, yaw, and roll values ​​of the patient platform may be compared to the beam stations specified by the treatment plan, and if a difference or deviation is detected, the controller may be configured to generate an audio and / or visual notification to the clinician.

[0024] The radiotherapy system may also include a system controller that communicates with all components of the radiotherapy system and may, for example, generate commands to the therapeutic radiation source, and / or the gantry, and / or the beam shaping element, and / or the patient platform. The system controller may also include a processor and a memory. The controller memory may store treatment plan data, segmentation data, and / or instructions, and any data acquired by any sensor or detector of the radiotherapy system (e.g., a PET detector, a kV detector, an MR sensor, a MV detector, a position sensor, a motion sensor, an accelerometer, and / or an encoder-decoder). The controller processor may be configured to segment the treatment plan fluence map (or any fluence map that may be generated after the start of a treatment session) into machine instructions (e.g., MLC leaf configuration for each firing position at a specific beam station, linear accelerator pulse instructions), therapeutic radiation source emission characteristics / features (e.g., pulse energy, pulse amplitude, pulse width, pulse frequency, duty cycle, etc.), and / or calculate the delivered dose or fluence based on machine parameters (e.g., linear accelerator pulse frequency, duty cycle, energy, dose chamber, MLC leaf opening, etc.). The radiation therapy system may also include one or more displays and one or more speakers.The controller processor may be configured to generate visual and / or audio alerts / notifications that may be sent to the displays and / or speakers.

[0025] Optionally, some radiotherapy systems may include one or more PET detectors, which may be mounted on the same rotatable gantry as the therapeutic radiation source, or on a separate / second gantry from the therapeutic radiation source, which may or may not rotate around the patient treatment area. In some variations, the PET detector and the therapeutic radiation source may be coplanar (i.e., the imaging plane is coplanar with the treatment beam plane) or non-coplanar (i.e., the imaging plane is not coplanar with the treatment beam plane). A line of response (LOR) defined by a pair of 511keV photons emitted by a positron annihilation event may be detected by the PET detector and sent to a system controller. In some variations, a PET tracer may be injected into the patient prior to the treatment session, and the LOR from the PET tracer may be detected by the PET detector. The PET tracer may accumulate in areas of the patient with increased metabolic rate, such as tumor areas. As an alternative or in addition to the PET detector, some radiotherapy systems may include a CT imaging system, an X-ray imaging system, an ultrasound imaging system, and / or an MRI imaging system.

[0026] A variation of the radiation therapy system Figure 1 Shown in. Figure 1 A variation of a radiotherapy system that can be used in beam station radiation delivery is depicted. The radiotherapy system (100) can include a gantry (102) that can rotate around a patient treatment area (104), one or more PET detectors (106) mounted on the gantry, a therapeutic radiation source (108) mounted on the gantry, a beam shaping module (110) disposed in a beam path of the therapeutic radiation source, and a patient platform (112) that can move within the patient treatment area (104). The beam shaping module (110) can include a movable mouth and a dynamic multi-leaf collimator (MLC). The beam shaping module can be arranged to provide a variable collimation width (e.g., the width of the treatment beam plane) of 1 cm, 2 cm, or 3 cm in the longitudinal direction (e.g., IEC-Y) at the system isocenter (e.g., the center of the patient treatment area). In some variations, the treatment beam planes for adjacent beam stations can overlap (i.e., the treatment beam plane width is similar to or wider than the distance between the beam stations). The mouth can be located between the therapeutic radiation source and the MLC, or can be located below the MLC. Alternatively, the beam shaping module may include a split mouth, wherein a first portion of the mouth is located between the therapeutic radiation source and the MLC, and a second portion of the mouth is located below the MLC and coupled to the first portion of the mouth such that the two portions move together.

[0027] The gantry (102) can be configured to rotate at a rate from about 15 RPM to about 70 RPM (e.g., about 50 RPM or more, about 60 RPM or more), the binary dynamic MLC can be configured to change leaf configurations in about 15 ms or less (e.g., about 10 ms or less, about 8 ms or less), and the patient platform (112) can be configured to move at a rate of about 0.5 mm / s or less. In some variations, the gantry can be a circular gantry. For example, the high-speed binary multi-leaf collimator can include a leaf actuation mechanism having a spring system that operates in conjunction with and is coupled to a pneumatic system to provide sufficient power to move the MLC leaves between open and closed configurations within the above-mentioned time constraints. As the gantry (102) rotates, the gantry (102) can move the linear accelerator (108) to discrete, predefined circular firing positions. Some systems have about 50 firing positions or angles (e.g., from about 0° to about 360°, with each firing position spaced at regular angular intervals). Some systems may have about 100 firing positions. Alternatively or additionally, some systems may be configured to have a discrete set of firing positions at arbitrary angles around the patient platform (e.g., at 0°, 45°, 90°, 135°, 180°, etc.).

[0028] In some variations, a radiation therapy system may optionally include a first array of PET detectors (106a) and a second array of PET detectors (106b) disposed opposite the first array, a linear accelerator (108) or a linear accelerator, and a beam shaping module (110) including a mouth and a dynamic binary MLC. The system may further include a controller in communication with the gantry, the PET detectors, the linear accelerator, and the MLC, wherein the controller has one or more memories that can store treatment plans, radiation firing matrices, fluence maps, system instructions / commands, and a processor configured to perform the calculations and methods described herein. A patient located on a patient platform (112) within a patient treatment region (104) may have been injected with a positron-emitting PET tracer, and the PET tracer may accumulate in a specific region of the patient (e.g., a tumor region). An annihilation positron with a nearby electron may result in the emission of two photons traveling in opposite directions to define a LOR or positron annihilation emission path. The PET detector may detect one or more LORs. In some variations, the PET detector can be a time-of-flight PET detector, which can help identify the location of positron annihilation events. As the patient moves through the patient treatment region (e.g., in a predefined patient platform beam station, or in continuous movement of the patient platform through the patient treatment region and / or treatment plane), the treatment planning fluence map can be updated using LOR data and / or PET imaging data and / or MV detector data (e.g., from an MV detector located opposite the linear accelerator (108) on the gantry). Optionally, the radiation therapy system (100) can include a CT imaging system (e.g., a kV radiation source and a kV detector mounted opposite the kV radiation source), which is mounted on the same gantry as the treatment radiation source, or on a separate gantry, and can be coplanar with the radiation source (i.e., the imaging plane is coplanar with the treatment beam plane) or non-coplanar with the treatment radiation source (i.e., the imaging plane is non-coplanar with the treatment beam plane). Optionally, the radiation therapy system can include an optical imaging system (e.g., one or more optical sensors or cameras) mounted on the same gantry as the therapeutic radiation source, which can be configured to acquire patient images as the gantry rotates around the patient platform. Additional details and examples of PET-based radiation therapy systems are described in U.S. Patent Application No. 15 / 814,222, filed on November 15, 2017 (which is incorporated herein by reference in its entirety). Imaging data from optional PET detectors, and / or kV detectors, and / or optical sensors can be configured to track patient position and / or motion (e.g., patient body shifting, breathing, fidgeting, etc.), so that radiation delivery can be adjusted to account for such motion.For example, radiation delivery may be synchronized (eg, gated) with respiratory motion such that radiation is delivered to the patient when the patient target region is within the treatment position and not delivered to the patient when the patient target region is outside the treatment position.

[0029] Although the examples and variations disclosed herein are described in the context of a radiotherapy system having a therapeutic radiation source (e.g., a linear accelerator) mounted on a circular gantry configured to continuously rotate and / or step through firing positions around a patient platform (e.g., 360° rotation), it should be understood that the treatment plans and radiation delivery methods described herein can be used with radiotherapy systems that do not have a continuously rotating circular gantry. For example, the treatment plans and radiation delivery methods described herein can be used with a radiotherapy system that includes a therapeutic radiation source mounted on a robotic arm or an arc or C-shaped gantry. The path of travel of the patient platform can be along a longitudinal axis (e.g., IEC-Y), and the arm or C-shaped gantry can be away from the path of travel of the patient platform (e.g., not positioned along the longitudinal axis). For example, the radiotherapy system can include a patient platform configured to move and stop at predetermined discrete positions (e.g., beam stations) along the longitudinal axis, a therapeutic radiation source, and a movable arm or gantry on which the therapeutic radiation source can be mounted, wherein the arm or gantry (e.g., C-shaped gantry) is configured to move the radiation source around the patient platform. The arm or gantry may be located on either side of the longitudinal axis so that platform movement is unimpeded, but the arm or gantry may move the therapeutic radiation source to various positions above the platform (some of which may be parallel to the longitudinal axis) so that radiation may be applied to a patient on the platform from multiple firing positions. Optionally, such a radiation therapy system may include an imaging system (e.g., PET, CT, X-ray, MRI, ultrasound, etc.), which may be mounted on the same or different arm or gantry as the therapeutic radiation source and may also be positioned at a location that is not in the path of travel of the patient platform. Although Figure 1 The radiation therapy system in is an open-cell system, but the methods described herein can also be used with closed-cell systems.

[0030] Beam Station Treatment Planning Method

[0031] The treatment planning system may be configured to generate a fluence map suitable for delivery at a beam station. A treatment planning method may include: identifying one or more patient target regions from a set of images (e.g., CT images) and a user-defined contour; prescribing a desired dose distribution to the one or more target regions; and calculating a fluence map including a set of radiation sub-beams that, when delivered, will deliver radiation according to the desired dose distribution. Some treatment planning methods may include calculating and optimizing dose on a beam station basis, wherein the treatment plan may include one or more fluence maps (and / or, optionally, dose maps) for each beam station. For example, in some variations, the beam station step size may be matched to the slice thickness of the planning CT image, and the treatment planning method may include calculating a 2D fluence map for each beam station, wherein the fluence map represents the fluence to be delivered at a particular beam station to achieve the overall dose distribution prescribed by the clinician. Each 2D fluence map slice may be an l×f matrix, where l is the number of leaves in a dynamic MLC (e.g., a binary MLC) and f is the number of firing locations. Each entry of the l×f matrix may represent the configuration and / or position of an MLC leaf l when the therapeutic radiation source is at firing position f. For example, a fluence map generated by a treatment planning system for a radiotherapy system having a 64-leaf binary MLC and 51 firing positions around a continuously rotatable gantry may be a (64×51) matrix representing each leaf of the 64 leaves at each of the 51 firing positions. Some treatment plans for beam station delivery may generate one or more fluence maps for each beam station, depending on the prescribed dose at that beam station and the amount of radiation that can be delivered by the radiotherapy system within a single revolution around the patient platform. In some variations, the fluence map calculation for a beam station may assume that all firing positions at a given beam station can be used to deliver radiation sub-beams. For example, a treatment planning method may calculate a fluence map based on 50 firing positions, even though delivery may be achieved by delivering a fluence for one firing position at two adjacent sub-firing positions. In this example, the treatment planning method can further calculate a sub-fluence map for each sub-firing position, thereby generating 100 sub-fluence maps for the 100 sub-firing positions. Some variations of the treatment planning method can include defining a set of beam stations (e.g., positions and / or orientations at which the patient platform may stop during the delivery of therapeutic radiation, the number of beam stations, and / or the step distance between beam stations), the dwell time at each beam station, the fluence and / or dose map for each beam station, the mouth configuration (e.g., mouth width) for each beam station, and / or therapeutic radiation source (e.g., linear accelerator) pulse parameters, and / or the number of times each patient target area crosses or passes through a treatment plane (e.g., a therapeutic radiation beam plane).

[0032] As described herein, the number and location of beam stations and the beam station step distance can be determined during treatment planning. In some variations, the clinician can specify the desired beam station step distance (e.g., it can match the slice thickness of the CT planning image, and / or can be an absolute step distance or spacing value such as about 2.1 mm). For example, for a beam station step distance or spacing of about 2.1 mm, the treatment planning system can perform 3D dose optimization on the patient target area identified in the planning CT image, which has a planning CT grid recalculated for all patient target areas with a fixed spacing of 2.1 mm. The number and location of beam stations can be determined by the size and / or location of one or more patient target areas and the beam station step distance. For example, a larger number of beam stations can be assigned to a larger patient target area or a patient target area that is far away from each other than a smaller target area or a target area that is close to each other. Alternatively or additionally, the distance between beam stations can be determined by the mouth opening setting. For example, for a mouth opening width of about 1 cm, about 2 cm, or about 3 cm or more, a larger beam station step distance can be selected. In some variations, the beam station step size may be uniform between a group of beam stations, while in other variations, the beam station step size may be non-uniform between a group of beam stations. In some variations, the treatment beam planes for adjacent beam stations may overlap (i.e., the treatment beam plane width is similar to or wider than the distance between the beam stations). Alternatively or additionally, the beam station step size may be selected based on the resolution and / or thickness of the treatment planning images, and / or the resolution and / or thickness of any imaging system (e.g., a PET imaging system, a CT or X-ray imaging system, etc.) used to acquire imaging data during the treatment session, and / or the field of view size of the treatment radiation beam (e.g., less than or equal to the full width at half height of the size of the radiation beam). In some variations, the number of beam stations and / or step size may be determined clinic-wide, and / or may be a hardware constraint or mode of the radiation therapy system set during manufacturing and / or at system installation. In some variations, the distance between beam stations may vary depending on the fluence gradient of the patient target area. For example, a beam station covering an area with a high fluence gradient (e.g., an edge or border of a patient target area) may have a smaller beam station step size than a beam station covering an area with a low (or no) fluence gradient (e.g., a central portion of a patient target area).

[0033] As previously described, the beam station can be any platform position and / or orientation determined during treatment planning, wherein the platform stops or is stationary during the emission of therapeutic radiation. When the patient platform is in motion (e.g., moving from one beam station to another), the therapeutic radiation source does not emit radiation to the patient. In some variations, the beam station positions specified by the treatment planning system can all be located on a plane defined by the IEC-X and IEC-Y axes. That is, the trajectory of the patient platform during the treatment session can be on a single plane (e.g., a horizontal plane with little or no vertical movement). For example, a set of beam stations selected by the treatment planning system can be positioned along a line along the IEC-Y axis (e.g., a linear trajectory), and / or can be located on a nonlinear (e.g., along one or more curves and / or multiple line segments that may or may not be collinear) trajectory on a plane. The treatment planning system can specify beam stations that are not all located on a single plane defined by IEC-X and IEC-Y. That is, the trajectory of the patient platform during the treatment session may not be limited to a single plane, but may be located in two or more planes in 3D space. For example, the beam stations can be specified by coordinates in IEC-X, -Y, and -Z, and / or can be specified by the orientation of the patient platform (e.g., the roll, yaw, and pitch of the patient platform). Different beam stations can have the same X-, Y-, and / or Z-coordinates, but can have different patient platform orientations (e.g., different roll, yaw, and / or pitch values). Alternatively or additionally, different beam stations can have the same patient platform orientation (e.g., the same roll, yaw, and / or pitch values), but have different X-, Y-, and / or Z-coordinates. Beam stations with patient platform tilts (e.g., with non-zero roll, yaw, and / or pitch values) can allow non-coplanar delivery of radiation to irradiate a target area that may be adjacent to (e.g., located behind) an OAR. Although the examples and variations of the methods described herein are limited to beam stations that form linear trajectories along the IEC-Y during a treatment session, it should be understood that similar methods can also be used for beam stations that form any non-linear and / or non-coplanar trajectories in two or more dimensions, and these beam stations may differ from each other based on patient platform orientation values.

[0034] In addition to determining the number and / or positions of beam stations by the size and / or position of one or more patient target areas, the number and / or positions of beam stations may be determined by whether any patient positioning devices will be used during the delivery of therapeutic radiation. For example, if a head positioning device (e.g., a head tilt device or a pillow) is to be used during a treatment session to orient the patient's head in a particular manner (e.g., at a particular tilt, etc.), the treatment planning method may calculate the position of one or more beam stations to account for the orientation of the head positioning device. Alternatively or additionally, if it is determined that a prescribed dose distribution may be more accurately delivered if the position of at least a portion of the patient is adjusted or fixed by a patient positioning device to have a particular orientation and / or position, the treatment planning method may calculate the position of one or more beam stations based on the assumption that, at the time of treatment, a patient positioning device will be provided and configured to provide that particular orientation and / or position.

[0035] In some variations, a treatment planning method may include determining the number of times a patient target area passes through a treatment radiation beam plane or treatment plane. For example, a patient platform of a radiotherapy system may move a patient through a treatment plane a first time in a first direction (e.g., forward along the IEC-Y axis), and then move the patient a second time in a second direction opposite to the first direction (e.g., backward along the IEC-Y axis). Each patient platform "pass" may include moving the patient platform in a direction such that all patient target areas have crossed the treatment plane once. The treatment planning method may include determining the number of passes, and determining a set of patient platform beam stations and corresponding fluence maps for each pass so as to deliver a prescribed dose to each patient target area. In some variations, a first pass may include a first set of beam stations (e.g., patient platform positions and / or orientations), and a second pass may include a second set of beam stations, wherein one or more beam stations in the second set may be the same or different than beam stations in the first set. For example, a first set of beam stations for a first pass may include patient platform positions at IEC-Y coordinates of 1 mm, 3 mm, 5 mm, 7 mm, 9 mm, ..., 99 mm, while a second set of beam stations for a second pass may include patient platform positions at IEC-Y coordinates of 2 mm, 4 mm, 6 mm, 8 mm, ..., 100 mm (traversing in the same direction as the first pass or in the opposite direction). Staggering or alternating beam stations between different passes may facilitate finer-grained delivery of therapeutic radiation and / or oversampling of imaging data by an imaging system (e.g., PET detector, X-ray detector, etc.) mounted on the same gantry as the therapeutic radiation source. Alternatively, the IEC-Y coordinates for the first pass and the second pass may be the same. Optionally, the IEC-Y coordinates for the beam stations in the first and second groups may be the same, while the platform orientation (e.g., pitch, yaw, roll values) may vary between the beam stations in the first and second groups. Some variations of the treatment planning method can include calculating the number of passes, a set of beam stations for each patient platform pass, a fluence map for each beam station for each pass, and / or a dwell time for each beam station (and / or the number of treatment radiation source gantry rotations or translations per beam station). Additional details on multi-pass delivery (e.g., shuttle mode delivery) are provided in U.S. patent application serial number 16 / 138,631 filed on September 21, 2018, the entire contents of which are incorporated herein by reference.

[0036] The duration that the patient platform spends at the beam station may be referred to as the "dwell time". For a radiotherapy system that includes a therapeutic radiation source mounted on a circular gantry that rotates continuously (e.g., 360°), the dwell time may also be expressed in terms of the number of gantry rotations or revolutions while the patient platform is at the beam station (e.g., the number of revolutions multiplied by the period of the revolution). While the patient platform is at the beam station, the therapeutic radiation source may emit radiation for the entire dwell time or a portion of the dwell time. For example, if the dwell time at the beam station is 10 seconds, the therapeutic radiation source may emit radiation to the patient for any duration from about 0.5 seconds to about 10 seconds (and may not emit radiation for the rest of the time). Alternatively, if the dwell time is represented by the number of gantry rotations R, the therapeutic radiation source may emit radiation to the patient during r (where r≤R) rotations, and may not emit radiation during the other (Rr) rotations. For example, if the dwell time is 10 rotations, the therapeutic radiation source may deliver radiation during only 1 rotation (i.e., no radiation delivery for 9 rotations), deliver radiation during 2 rotations (i.e., no radiation delivery for 8 rotations), and so on until radiation is delivered during 10 rotations. Although the dwell time at each beam station may be the same in a set of beam stations, the amount of radiation delivered at each beam station may vary greatly, allowing for high dose modulation across beam stations, depending on the amount of time and / or number of gantry rotations during which the therapeutic radiation source emits radiation. The dwell time at each beam station (i.e., expressed in time units (e.g., seconds or minutes, or number of gantry revolutions)) may be determined during treatment planning by one or more factors (alone or in combination), including, but not limited to: gantry rotation speed, and / or number of gantry revolutions to deliver a fluence map, and / or fluence gradient, and / or mouth opening width setting. Optionally, in addition to these factors, the dwell time at each beam station may be determined by any clinical factors or treatment parameters selected by the clinician, such as total treatment time, correspondence to planned image slice thickness or position (e.g., CT or PET image slice thickness), etc. The dwell time (or number of gantry revolutions) may vary per beam station, or may be constant between all beam stations. For example, the number of revolutions per beam station can be from about 2 to about 300 revolutions (for example, from about 2 to about 5 revolutions, from about 4 to about 7 revolutions, from about 6 to about 10 revolutions, from about 10 to about 15 revolutions, from about 18 to about 24 revolutions, from about 30 to about 45 revolutions, from about 40 to about 50 revolutions, from about 50 to about 100 revolutions, from about 100 to about 120 revolutions, from about 5 to about 150 revolutions, from about 2 to about 200 revolutions, from about 100 to about 200 revolutions, from about 150 to about 250 revolutions, from about 200 to about 300 revolutions, etc.).The dwell time at a beam station can be from about 5 seconds to about 8 minutes (e.g., from about 5 to about 7 seconds, from about 5.5 to about 6.5 seconds, from about 7 to about 10 seconds, from about 6 to about 15 seconds, from about 5 to about 20 seconds, about 20 seconds or longer, from about 20 to about 30 seconds, from about 5 to about 60 seconds, from about 20 to about 120 seconds, from about 60 to about 300 seconds, from about 5 to about 400 seconds, about 350 seconds or longer, from about 5 to about 300 seconds, etc.). Some radiation therapy systems can have a fast rotating gantry configured to rotate the linear accelerator around the patient platform at a speed of about 60 RPM, where the dwell time at each beam station can be less than about 20 seconds and / or sufficient time for at least two gantry revolutions (and up to about 480 seconds), and from about 20 to about 25 revolutions (and up to about 300 revolutions). In some variations, for example, intensity modulated radiation therapy (IMRT) and delivery, the number of revolutions per beam station may not be constant and may be determined by the treatment planning system prior to a treatment session. In some variations, the dwell time of certain beam stations may be much longer than the dwell time of other beam stations. For example, the dwell time of the first and last beam stations may be longer (e.g., more revolutions) than the dwell time of the intermediate beam stations. Due to the complex contours of the edge / border area, the dwell time at the edge / border of the target area may be greater than the dwell time in the central area of ​​the target area. Complex or irregular contours may require multiple MLC configurations and delivery over multiple revolutions to deliver radiation with a specified accuracy. In some variations, for example, radiation delivery based on PET imaging data (e.g., bio-guided radiation therapy or BGRT), the number of revolutions per beam station (or dwell time) may not be calculated during treatment planning, but instead may be calculated by the radiation therapy system controller during a treatment session (e.g., just before the beam station performs radiation delivery). Alternatively or additionally, all beam stations may have the same dwell time (or number of revolutions).

[0037] In some variations, the dwell time may be calculated during treatment planning and updated during treatment sessions. One variation of a method for calculating the dwell time may include determining an amount of fluence (e.g., in MUs) to be delivered at a beam station in order to meet a prescribed dose; determining a fluence emission rate (e.g., in MUs per unit time, in MUs per gantry rotation) of a therapeutic radiation source, and then dividing the amount of fluence to be delivered by the fluence emission rate of the therapeutic radiation source to yield an amount of time or number of revolutions that the patient platform is to remain at the beam station to provide the prescribed dose. The fluence emission rate may depend on, for example, the dose rate, the pulse frequency, the pulse width, etc. Another variation of a method for calculating the dwell time may include segmenting a fluence map for a beam station into a set of radiotherapy system machine instructions (including MLC configurations); and determining a number of gantry revolutions and / or MLC configurations in order to deliver the fluence map. Complex target region geometries (e.g., at the edges of the target region) may require more binary MLC configurations to approximate the geometry than target regions with less complex geometries (e.g., at the center portion of the target region). In some variations, the treatment planning method may set the dwell time for all beam stations to the maximum dwell time for the group of beam stations. An estimated treatment session time may be calculated by multiplying the maximum dwell time by the number of beam stations and optionally the number of passes. Alternatively, the dwell time may be beam station specific, and the estimated treatment session time may be calculated by summing the dwell times for all beam stations and optionally multiplying the sum by the number of platform passes. In some variations, the number of gantry rotations per beam station (e.g., 360° revolution of a circular gantry, 180° sweep of a gantry) may be at least two or more, such as about 50, about 100, about 200, about 300 gantry rotations, etc. Alternatively or additionally, the dwell time per beam station may be about 20 seconds, about 50 seconds, about 100 seconds, about 120 seconds, about 150 seconds, etc. Depending on whether any system components fail during a treatment session and the location and / or geometry of the target area at the time of treatment, the actual dwell time during a treatment session may vary from the estimate generated during treatment planning.

[0038] exist Figure 2AA variation of a treatment planning method for beam station delivery by a radiotherapy system with binary MLC is depicted in . The method (200) may include: identifying (202) patient target regions and organs at risk (OARs) based on a planning image (e.g., a CT image) and a clinician-provided contour, and identifying a system isocenter (i.e., a treatment isocenter) relative to the planning image; and determining (204) a desired dose optimization constraint for each target region and OAR based on clinician-provided dose prescription information. Examples of dose optimization constraints may include a maximum dose threshold to certain structures (e.g., target regions or OARs), an average dose over a target region or OAR (e.g., a maximum average dose of 25 Gy to a kidney or a minimum average dose of 50 Gy to a target region), a specified amount of tissue volume at a specific dose value, and an equivalent uniform dose (EUD) value (e.g., an EUD to compensate for dose heterogeneity, a minimum EUD of 50 Gr at 0.35α). Examples of dose prescription information may include an amount of radiation dose per target region or OAR volume (e.g., >95% coverage of target volume at 50 Gy, no more than 15cc of lunch tissue at 20 Gy, at least 50% of target volume at 50 Gy, etc.). Other examples of dose metrics may include, but are not limited to, critical organ scoring index (COSI), conformality (CN), conformality index (CI), target coverage index (TCI), ratio of prescription isodose to target volume (PITV), homogeneity index (HI), modified dose homogeneity index (MHI), and / or quality factor (QF), etc. Some variations may include constraints such as biological metrics, such as general equivalent uniform dose (gEUD), normal tissue complication probability (NTCP), and / or tumor control probability (TCP). The method (200) may include determining (206) a beam station position relative to a treatment isocenter based on an alignment and spacing provided by a clinician or a system and mapping the beam station position to a corresponding patient platform position. As described above, the number and location of a set of beam stations and the platform X-, Y-, Z-coordinates and orientation for each beam station can be determined based on the number, location, size, and shape of the patient target areas. For example, the first beam station in a set of beam stations can be located at or around the lowermost boundary of the lowermost patient target area, and the last beam station in the set of beam stations can be located at or around the uppermost boundary of the uppermost patient target area. The treatment isocenter can be aligned with the beam station or can be displaced from the beam station, and the distances between the beam stations can be selected or calculated as previously described.

[0039] After determining the beam station positions, the method (200) may include calculating (208) a set of candidate radiation sub-beams for each beam station. A radiation sub-beam may be a portion of a full radiation beam from a therapeutic radiation source, wherein the sub-beam is defined by a multi-leaf collimator leaf opening at a particular firing position relative to the patient region. That is, a sub-beam may be specified by (l, f, b), representing the radiation applied to the patient region when the therapeutic radiation source is at firing position f, the patient platform is at beam station b, and is in an open / closed state of binary MLC leaf l. In some variations, the sub-beam may be further defined by the width of the mouth opening, which may vary per beam station, or may be the same for all beam stations (e.g., as described in the examples provided herein). A candidate sub-beam for beam station b is a sub-beam that intersects the patient target region when the platform is at beam station b.

[0040] The method (200) may then include calculating (210) a dose calculation matrix for each beam station representing the dose contribution of each candidate beamlet to all patient target regions and OARs, assuming a beamlet intensity or beamlet weight of 1. In some variations, the dose calculation matrix may be calculated based on the dose contribution of each candidate beamlet to a set of sample points or voxels selected for each target region and OAR. Calculating the dose matrix on a set of sampled voxels of the target region or OAR rather than on all voxels can help reduce computational resources (e.g., processor speed and memory usage) used for this and other treatment planning calculations and optimization iterations, which can in turn reduce the computational time required to complete such calculations.

[0041] After calculating the dose calculation matrix for each beam station, the method (200) may include: calculating (212) a fluence map for each beam station by calculating a set of candidate sub-beam intensities or weights using a dose optimization technique. The sub-beam weight or intensity is a measure of the dose from the therapeutic radiation source in arbitrary discrete units, and can be represented, for example, by the number of linear accelerator pulses, pulse amplitude, pulse width, leaf open time, etc. The sub-beam weight of non-candidate sub-beams (i.e., sub-beams that do not intersect the target area) is zero. The dose optimization technique calculates a set of sub-beam weights that, when delivered, match or closely approximate the prescribed dose to the target area while satisfying specific dose constraints and / or treatment parameters. The dose constraints and treatment parameters can be specified by the clinician and can include, for example, treatment plan quality metrics, maximum and minimum dose levels, dose distribution characteristics, treatment time, dose modulation across beam stations, etc. (including but not limited to the above-mentioned dose optimization and dose prescription parameters and constraints). In some variations, the dose optimization method may include aggregating one or more of the constraints and parameters into one or more penalty functions, and the optimization method may aim to reduce the value of the penalty function while achieving a specified dose goal. For example, the dose optimization method may calculate a set of candidate beamlet weights that minimize the value of one or more penalty functions while maximizing one or more treatment plan quality metrics. The fluence map assigns a particular beamlet (l 0 , f 0 , b 0 ) and the specified time when the therapeutic radiation source is at the ignition position f 0 And the patient platform is at beam station b 0 The beamlet weights are paired with the amount of radiation (i.e., fluence) to be delivered at the time. For a given beam station, the beamlets can be identified by the MLC leaf index (e.g., leaves 1 to 64) and the firing position (1 to 50) (i.e., (l in the l×f matrix) 0 , f 0 )) where l is the number of MLC leaves and f is the number of firing positions.

[0042] The method (200) may then optionally include quantizing (214) the fluence map for each beam station so that each sub-beam weight is an integer multiple of a dose quota that can be delivered by a therapeutic radiation source (e.g., a linear accelerator). The dose quota can be calculated, for example, based on a set of linear accelerator pulses and the pulse width of each linear accelerator pulse in the set. For example, if for each firing position, the linear accelerator can fire two linear accelerator pulses, and each of those pulses can be one of two pulse widths, then for each firing position, there are four different discrete quotas. The method (200) may include calculating (216) a cumulative patient dose over all fluence maps and all beam stations. In some variations, the cumulative dose distribution can be displayed to a clinician for approval. Optionally, the method (200) may include segmenting the fluence map for each beam station into machine instructions for execution by a radiotherapy system. The machine instructions can be provided to the radiotherapy system and / or can be used to estimate / calculate dwell time, as described below. In some variations, a fluence map for each beam station is provided to the radiation therapy system, and a controller for the radiation therapy system segments the fluence map into machine instructions, such as during a treatment session.

[0043] Optionally, the method (200) may include calculating the dwell time for each beam station so that the clinician can estimate the length of the treatment session. 0 ) can be calculated based on the rotational speed of the gantry (e.g., revolution time or RevT), the highest beam weight in a set of beam weights for that beam station (Max-Weight(b)), and the maximum dose that can be delivered in a single pass or revolution at a single firing position (Max-Dose-fp), for example:

[0044] DW(b 0 )=RevT*Max-Weight(b 0 ) / Max-Dose-fp

[0045] Among them, Max-Weight(b 0 ) and Max-Dose-fp both have dose units. The sum of the dwell times for all beam stations provides an approximation of the overall treatment time:

[0046]

[0047] Where B is the total number of beam stations.

[0048] Alternatively or additionally, beam station dwell times may be calculated based on the segmented fluence map for each beam station. Although radiotherapy system instructions to segment the fluence map may not necessarily be executed by the radiotherapy system (which in some variations may segment the fluence map in real time) during a treatment session, such "simulated segmentation" machine instructions may help provide a more accurate or realistic estimate of the beam station dwell times and, by extension, the duration of a treatment session. Figure 2BThe flowchart in represents a variation of a method for calculating beam station dwell time and treatment session duration. The method (220) for calculating beam station dwell time and / or treatment session duration may include: segmenting (222) a fluence map for each beam station in a set of beam stations into radiotherapy system machine instructions; for each linear accelerator firing position of the beam station, calculating (224) the number of MLC configurations required to deliver radiation based on the fluence map for the beam station and determining the maximum number of MLC configurations at the firing position; and multiplying (226) the maximum number of MLC configurations by the gantry rotation period (e.g., the time per gantry revolution) to obtain the length of time that the patient platform stays at the beam station. In some variations, the method (220) may include: for each beam station, calculating the number of gantry revolutions required to deliver a monitoring unit (MU) specified by the fluence map for the beam station, and the dwell time for the beam station may be calculated by determining the larger of the number of gantry revolutions for MU delivery and the number of MLC configurations, and then multiplying the larger by the gantry period. Optionally, the method (220) may include calculating (228) a treatment session duration by adding all dwell times for all beam stations in a set of beam stations. If there are multiple patient platform passes, the method may include multiplying the sum of the dwell times by the number of passes. Optionally, to calculate the treatment session duration, the method (220) may include: comparing (230) all dwell times for all beam stations in a set of beam stations; selecting (232) the longest dwell time among all beam station dwell times; and calculating (234) the session duration by multiplying the longest dwell time by the number of beam stations in the set. If there are multiple patient platform passes, the method may further include multiplying the product of the longest dwell time multiplied by the number of beam stations by the number of passes. Additional gantry rotations at beam stations may be included to deliver greater fluence and / or deliver fluence to patient target areas with complex geometry (e.g., at edges whose edge contours are best approximated by the sum of multiple binary MLC configurations). Although setting the dwell time for all beam stations to the maximum dwell time may unnecessarily extend the overall treatment time because the fluence at some beam stations does not require the entire dwell time to be delivered, any "extra" dwell time at a beam station can be used to deliver fluence that may have been missed and / or residual due to machine malfunction, and / or can be used to accommodate fluence changes due to any longitudinal patient target shift, an increase in fluence level dictated by the patient's condition on the day of treatment, and / or to compensate for fluence that may not be delivered at other beam stations.

[0049] As previously described, the width of the mouth opening can also be varied or adjusted on a beam station basis. Increasing the mouth opening width can help speed up dose delivery by increasing the size of each beamlet, for example by increasing the minimum dose per beamlet (which can be proportional to the size of each beamlet). This is particularly effective in cases where the fluence gradient of the target area is relatively low (i.e., relatively constant fluence) so that a larger portion of the target area is irradiated per radiation pulse. The mouth opening width can be modulated during treatment planning (e.g., during dose optimization) or can be selected by the clinician. Alternatively or additionally, the mouth opening width can be a fixed value for all beam stations. In some variations, the treatment beam planes for adjacent beam stations can overlap (i.e., the treatment beam plane width is similar to or wider than the distance between beam stations). For example, the distance between beam stations can be about 2.1 mm, and the width of the treatment plane can be from about 10 mm to about 20 mm. In some variations, the treatment plan can specify a wider mouth opening width in an earlier portion of a treatment session than in a later portion of a treatment session. For example, for the first patient platform passage, the mouth opening width may be set to a first width W 1 , then for the second patient platform to pass, it can be set to a second width W 2 , where W 2 Smaller than (i.e., narrower than) W 1 This can help deliver the fluence to larger areas (e.g., central portions of the patient target area) earlier in the session and help deliver the fluence to smaller areas (e.g., edge portions of the patient target area) later in the session. This can help speed up the delivery of radiation to large patient target areas. Some treatment planning methods may include calculating the dose distribution for each mouth opening width in English to determine an optimal fluence map for each beam station at each expected mouth opening width (and optionally for each pass).

[0050] Treatment plans that have been developed for helical delivery (i.e., where the patient platform is in motion during treatment irradiation) can be converted to treatment plans for beam-station delivery (i.e., where the patient platform is stopped at a specified beam station during treatment irradiation). The "helical" descriptor indicates the trajectory of the therapeutic radiation source relative to the continuously moving patient platform (e.g., along the IEC-Y axis). When the patient platform is at a specific position along the IEC-Y, the spiral treatment plan can specify the fluence emitted at each therapeutic radiation source firing position on the gantry (e.g., firing angles on a circular gantry). Figure 2CA variation of a method for converting a spiral delivery treatment plan to a beam station delivery treatment plan is depicted in . The method (240) may include: discretizing (242) the cumulative fluence of the spiral treatment plan into a fluence map for each position (which may be referred to as a sampling point) along the IEC-Y; mapping (244) each sampling point to a beam station in a set of beam stations based on its IEC-Y position; assigning (246) the fluence map of each sampling point to its corresponding mapped beam station; and combining (248) for each beam station the fluence maps assigned thereto to derive a beam station fluence map. In some variations, the beam station fluence maps for all beam stations may be quantized and / or segmented into radiotherapy system machine instructions that may be sent to the radiotherapy system for execution during a radiotherapy session. Alternatively, the beam station fluence maps for all beam stations may be combined and sent to the radiotherapy system during a treatment session for quantization and / or segmentation into machine instructions. As described elsewhere, in some variations, the fluence maps for the beam stations may be updated and / or adjusted (e.g., normalized) using imaging data acquired during the treatment session. Optionally, the method (240) may further include combining (248) the fluence maps for all beam stations to calculate a dose to be delivered to each patient target area, comparing the calculated dose to the prescribed dose for each patient target area (252), and if necessary, the fluence map for each beam station may be adjusted by a conversion or correction factor. For example, if the cumulative fluence maps for all beam stations do not converge to the prescribed dose distribution for the patient, the fluence map for one or more beam stations may be adjusted (e.g., scaled, reduced, and / or increased) by an adjustment or correction factor calculated based on the difference between the calculated dose and the prescribed dose. The spacing of the sampling points along the IEC-Y (i.e., the longitudinal axis of the patient platform and the axis along which the platform moves) may be preselected, and the beam station parameters may be selected based on characteristics of the spiral trajectory. For example, the distance between beam stations can match or correspond to the spacing between sampling points along the IEC-Y, and / or the time between sampling points (or groups of sampling points) can correspond to the beam station dwell time, and / or the orientation and / or position of the beam station can correspond to the patient orientation and / or position. Conceptually, the cumulative fluence map of the discretized (242) spiral treatment plan portion is a spiral segment or "slice" along the IEC-Y. In some variations, a "slice" of fluence can represent the fluence delivered across a "width" corresponding to the spacing between the sampling points in a complete revolution of the therapeutic radiation source. Each fluence "slice" can be binned or mapped to a beam station based on its IEC-Y position. After the spiral treatment plan is converted to a beam station treatment plan, it can be quantized, segmented, and delivered as described elsewhere herein.

[0051] Beam Station Radiation Delivery Method

[0052] Fluence maps for each beam station generated by the treatment planning system, as well as other radiation delivery and dose calculations, may be stored in the radiotherapy system controller. Beam station radiation delivery may include moving the patient platform to each beam station specified during treatment planning and delivering radiation to the patient target area according to the fluence map for that beam station. Fluence may be delivered by a gantry-mounted therapeutic radiation source (e.g., a linear accelerator) in a single revolution of the gantry, or may be delivered in multiple gantry revolutions. The number of gantry revolutions per beam station may be determined during treatment planning, or may be determined during a treatment session based on a segmentation of the fluence map. Alternatively or additionally, the number of arm or gantry arc sweeps may be determined during treatment planning, or may be determined when the fluence map is segmented. The radiotherapy system may calculate a sequence of sub-beams to be delivered at each beam station so that the fluence delivered at that beam station matches or approximates the fluence map calculated by the treatment planning system for that beam station. In IMRT, the fluence to be delivered at each beam station may be determined during treatment planning and may remain constant during a treatment session. The radiotherapy system can calculate the number of revolutions at each beam station to achieve the planned fluence. The radiotherapy system can optionally use multiple passes along the IEC-Y (and / or along all beam stations so that each patient region crosses the transnational treatment beam plane multiple times) to deliver the required fluence, thereby reducing the impact of motion on the dose delivered to the target. Each "pass" includes: moving the patient platform in one direction (e.g., along the IEC-Y axis) through all beam stations determined during the treatment plan, and consecutive passes include: moving the patient platform in the opposite direction (e.g., reverse) through all beam stations. In BGRT (where the radiotherapy system includes one or more PET detectors), the number of gantry revolutions at each beam station can be fixed, and the radiotherapy system can also use multiple passes along the IEC-Y to manage the total delivered fluence at each beam station. Due to differences in patients and / or radiotherapy systems on the day of treatment, additional passes (i.e., in addition to the passes initially specified by the treatment plan) may also be used during the treatment session. For example, a treatment session may include additional passes to deliver fluences (e.g., residual fluences) that were missed due to patient movement and / or radiotherapy system failures.

[0053] In some variations, a pre-scan image may be acquired at the beginning of a treatment session. The parameters of the treatment plan may be updated or adjusted based on the pre-scan data. For example, the treatment plan fluence map may be normalized per pre-scan image data, and / or the dwell time may be adjusted, and / or the mouth width may be adjusted. The number of gantry revolutions per beam station may be determined using a PET pre-scan (or any imaging data, such as MRI, CT, ultrasound, and / or X-ray imaging data) acquired before treatment (e.g., on the day of treatment). In the case of BGRT, where a PET pre-scan image is acquired at the beginning of a treatment session and based on PET data (e.g., SUV, positioning, etc.), the radiotherapy system may normalize the treatment plan and / or adjust the fluence map for delivery. In some variations, the dwell time (e.g., the number of gantry rotations) and / or mouth opening width may be optionally adjusted based on fluence map changes, which may facilitate delivery of a prescribed dose to a patient target area. For example, a PET pre-scan image may show an increase (or decrease) in SUV for a patient target area compared to a treatment plan PET image. This may indicate that more (or less) fluence should be emitted at a particular beam station in order to deliver the prescribed dose to the target area. The controller of the radiotherapy system may widen (or narrow) the mouth opening width to increase (or decrease) the fluence emission. Changes in the fluence map may also reflect changes in the size of the target area, so during the fluence map segmentation during the treatment session, if the target area geometry becomes more (or less) complex, the number of gantry revolutions may be increased (or decreased). In some variations, the number of revolutions per beam station may be varied to reduce treatment time. For example, if LOR data acquired during treatment indicates that there is no PET uptake at a beam station that was previously assigned a non-zero fluence emission value, the dwell time may be reduced and / or the beam station may be skipped entirely. More generally, moving the patient platform through all beam stations in multiple passes so that the patient target area crosses the treatment beam plane multiple times may provide one or more opportunities to deliver any radiation dose missed during previous passes.

[0054] In some variations, the beam station dwell time can be calculated at the beginning of the treatment session based on the PET pre-scan. Alternatively or additionally, the dwell time can be calculated in real time at each beam station based on detected LOR or imaging data and / or system functionality (e.g., if there is any MLC, linear accelerator, gantry failure, more time may be spent at the beam station to ensure the expected fluence is delivered). The step distance between beam stations can be modified based on the pre-scan PET to adjust for any fluence map gradient changes. In some variations, the beam station step distance can be calculated in real time at the beginning of the treatment session based on the pre-scan PET and / or using LOR and / or imaging data. In a target area with a steep fluence gradient, the distance between beam stations can be less than the distance in a target area with a smaller fluence gradient. In some variations, the dwell time of a particular beam station in one patient platform pass can be different from the dwell time of the same beam station in a different pass. For example, in a first pass, the dwell time at a beam station may be a first duration to deliver a large amount of fluence, while in a second (later) pass, the dwell time at the beam station may be a second duration shorter than the first duration to provide a lower amount of fluence (e.g., perhaps a surplus resulting from real-time segmentation errors / estimations).

[0055] In some variations, the fluence map for all beam stations may be segmented into machine instructions at the start of a treatment session, while in other variations, the fluence map may be segmented as the platform moves to the beam stations. In BGRT, because the fluence map may be updated based on imaging data (e.g., PET imaging data) acquired in real time, the segmentation of the updated fluence map for a particular beam station may occur as the platform moves to that beam station. Alternatively or additionally, the segmentation of the updated fluence map may occur between firing positions as the gantry rotates. In some variations, the fluence map for a beam station may be divided into sub-fluence maps for delivery over multiple gantry revolutions and / or sub-firing positions, which may then be segmented into machine instructions for delivery. Before the patient platform advances to the next beam station (or moves from the current beam station), the radiation therapy system controller may calculate the radiation delivered at the current beam station and compare it to the fluence map for the beam station to determine whether the required amount of radiation for that beam station has been delivered. Any fluence differences may be re-delivered as “catch-up” sub-beams in additional gantry revolutions at that beam station. For example, the radiotherapy system may track the occurrence of system component failures that result in missed radiation ignitions (e.g., magnetron arcs that do not turn on (or off) on time, “sticky” MLCs, etc.). In some variations, radiation may be delivered via additional gantry revolutions to help compensate for dose instabilities so that the cumulative delivered dose matches (or better approximates) the planned dose distribution. After the radiotherapy system controller confirms that the radiation has been delivered within acceptable tolerances (e.g., as specified / approved by a clinician), the patient platform may then advance to the next beam station. Alternatively or additionally, the radiotherapy system controller may evaluate one or more radiation delivery metrics or treatment parameters before deciding whether to move the patient platform from the current beam station to the next beam station. For example, the radiotherapy system controller may move the patient platform to the next beam station based on one or more dose metrics (e.g., any of the dose metrics described above, alone or in combination with multiple dose metrics). In some variations, the patient platform may be moved from one beam station to the next based on a set of instructions (e.g., generated by the treatment plan and / or clinician) that may include dwell time, and / or mouth opening width, and / or number of revolutions at a particular beam station, and / or radiation pulse parameters (e.g., number, width, duty cycle, energy, MU, etc.) and / or MLC leaf configuration for each therapeutic radiation source firing location. Patient changes and / or any radiation therapy system component errors or failures may change the dwell time at a beam station based on the dwell time estimated at treatment planning. Real-time segmentation allows radiation delivery that reflects the machine operating status and patient condition at the time of treatment.

[0056] For example, the time a patient platform stays at a beam station during a treatment session can be determined based on the fluence emitted by the therapeutic radiation source and / or the performance of the radiation therapy system components. A method for a radiation delivery system to determine whether to move a patient platform from one beam station to the next (i.e., whether to stop radiation delivery at a beam station and advance the patient platform to another beam station) may include: measuring the emitted fluence; comparing the emitted fluence to a fluence map for the beam station specified during treatment planning (and / or normalized at the beginning of the treatment session); and calculating the difference between the emitted fluence and the treatment plan fluence map. If the calculated fluence difference is zero and / or below a predetermined threshold, radiation delivery is stopped and the patient platform is advanced to another beam station. Any fluence difference or fluence remainder may be stored in a memory of a radiation therapy system controller. Alternatively or additionally, a method for determining whether to move a patient platform away from a beam station may include measuring an amount of time that the patient platform has been at a beam station; determining whether the time direction exceeds a predetermined threshold (e.g., an upper or maximum threshold); and generating an audio, visual, and / or tactile notification / alert to a clinician (e.g., an operator of a radiotherapy system) if the threshold is reached or exceeded. The threshold may be a maximum dwell time, a maximum number of gantry revolutions, and / or an amount of maximum fluence (e.g., number of MUs) emitted by a linear accelerator. In some variations, when the radiotherapy system has determined that the threshold has been reached or exceeded, the method may include generating a visual representation of any fluence difference between the emitted fluence at the beam station and the planned fluence for the beam station. For example, the radiotherapy system may display a graphical representation of the fluence difference to a display monitor or screen, and / or may display a numerical value (e.g., metric) and / or statistical data (e.g., emitted MUs versus planned MUs, emitted MUs per gantry rotation, number of gantry rotations, number of linear accelerator pulses, etc.) representing the emitted and / or planned fluence or dose. The clinician and / or radiation therapy system operator can view the visual representation and / or fluence metrics or statistics to determine whether to proceed with the radiation therapy session. In some variations, the radiation therapy system can be configured to automatically stop radiation delivery and generate a notification to the clinician and / or operator if the emitted fluence exceeds an upper threshold (e.g., a safety margin) and / or if the emitted fluence or dose profile has not converged to a fluence map for a particular beam station after the patient platform has been positioned at the beam station for a predetermined time threshold or number of gantry rotations.

[0057] Figure 3A variation of a method for beam station radiation delivery is depicted. The method (300) may include: loading (302) a fluence map and dose data from a treatment planning system into a memory of a radiation therapy system controller; and determining (304) whether to deliver an entire fraction or dose specified by a fluence map (e.g., a cumulative planning fluence map, and / or a fluence map for all beam stations). If the clinician determines that an entire fraction is to be delivered in a treatment session, the method (300) may include: determining (306) a total number of treatment passes for the treatment session, and starting a first pass (308) by moving (310) the patient platform for a first beam station and optionally setting a desired mouth width. Each pass may be a complete scan of the treatment area in the IEC-Y direction of one patient platform. The method (300) may include: prior to starting the first pass (308), calculating (307) a fluence map to be delivered at each pass. The fluence map to be delivered at each pass may be stored in the radiation therapy system controller. The method (300) may then include segmenting (312) a planned fluence map (e.g., a per-pass fluence map) for a first beam station into a sequence of sub-beams to be delivered at the beam station. The segmented fluence map may include a particular MLC leaf configuration, the number and width of linear accelerator pulses at each firing position, etc. In some variations, the fluence map segmentation may occur once at the start of delivery at the beam station and / or may occur continuously as the radiation source rotates through the firing positions. For example, some methods may include segmenting the fluence map each time the linear accelerator reaches a new firing position (e.g., from about 25 to about 100 times per second or more, about 50 times per second, about 100 times per second), wherein segmenting the fluence map includes calculating the fluence still to be delivered at the beam station by subtracting the emitted fluence from the planned / prescribed fluence, determining the amount of fluence that can be delivered at the new firing position, and segmenting the amount of deliverable fluence into the MLC leaf instructions and / or linear accelerator pulse parameters. The patient platform remains stationary at the beam station (314) while the therapeutic radiation source rotates around the platform and delivers radiation according to the segmented fluence map. The method (300) may also include recording (316) the sub-beams actually delivered, for example by storing each instance of all system components operating without failure. Optionally, the system may record the time of any system component failure (e.g., MLC leaf motion delay, MLC compressor constraint, linear accelerator misfire, magnetron arc, external sensor (including external gating sensor, such as breathing sensor, etc.) failure), the firing position and / or MLC leaf configuration at the time of the component failure, etc. The method (300) may then include: determining (318) whether all planned sub-beams or fluence maps have been delivered at the current beam station, and if so, determining (320) whether the planned sub-beams or fluence maps have been delivered for all beam stations.Alternatively or additionally, the method (300) may include determining whether radiation delivery has been performed according to a prescribed dose metric (e.g., any of the metrics described above) and / or desired treatment parameters (e.g., beam station dwell time, mouth opening width, number of gantry revolutions, treatment pulse parameters, MLC leaf configuration) that have been predetermined by the treatment planning system and / or clinician and / or radiation therapy system (e.g., predetermined at an earlier point in the treatment session). Notably, if no radiation is to be delivered at a beam station, the patient platform may be advanced past that beam station to the next beam station to which a non-zero radiation dose is to be delivered. If the planned sub-beams for all beam stations have not yet been delivered, the method (300) may include moving the platform to the next beam station and repeating (312)-(318). If all deliveries to all beam stations have been completed, the method (300) may include determining (326) whether all passes have been completed. If not, the method (300) may then begin the next pass (328), possibly in the opposite direction, repeating (312-320) until all passes have been completed. If the controller determines that not all planned sub-beams or fluence maps have been delivered at the current beam station, i.e., when some sub-beams have been missed due to, for example, magnetron arcing and / or any machine failure described herein, the method (300) may include re-delivering (322) the missed sub-beams at the current beam station until all such missed or "catch-up" sub-beams have been delivered (324). Sub-beams may be missed due to failure of any of the system components described above. In some variations, this may extend the dwell time at the beam station beyond that calculated in the treatment plan. Alternatively, this may not extend the dwell time, but may change the fluence emitted during the revolution and / or firing position after the radiotherapy system failure. Once all sub-beams have been delivered, the radiotherapy system may continue to advance the platform to the next beam station or the next pass, whichever is applicable.

[0058] If the fluence for one pass has been delivered according to the calculated fluence map, the method (300) may include calculating the fluence to be delivered at the next pass. In some variations, the fluence to be delivered at each pass may have been calculated at the beginning of the treatment session (e.g., before the first pass at 307) and stored in the controller member. Alternatively or additionally, the fluence map for the next pass may be calculated by determining the difference between the cumulative delivered fluence and the cumulative planned fluence and dividing or distinguishing the remaining undelivered fluence over the remaining passes. In some variations, the fluence delivered at each pass may be the same or may be different for certain beam stations and / or firing positions, depending on the quantization of the fluence map for each beam station. For example, a treatment session may have four passes, and therefore, a particular firing position for a particular beam station may be encountered at least four times in the treatment session. If the fluence to be delivered from the firing position for the beam station requires three linear accelerator pulses, one pass may be fired for three passes, and no pulse may be fired on the fourth pass.

[0059] In some variations, the treatment session may be a supplemental or "make-up" treatment session to deliver a dose missed in a previously interrupted treatment session. In this case, it may be determined (304) that the entire portion need not be delivered, but rather delivery may be continued from the point where the previous session stopped. The method (300) may then include determining (330) the last interrupted beam station and pass based on the record from the previous treatment session. The radiation therapy system may move the platform (332) to the last interrupted beam station and segment (334) the fluence map for that beam station (particularly if any system parameters have changed since the last treatment session), and continue delivering radiation in accordance with (312)-(328). Segmenting (334) may include generating a set of MLC leaf configurations or patterns, pulse numbers, and pulse widths for each firing location based on the fluence map for the beam station. In some variations, the fluence map may be updated and / or normalized using any new and / or updated imaging or pre-scan data. As described above, the radiotherapy system continuously tracks and records the time of any system component failure (e.g., MLC leaf motion delay, MLC compressor constraint, linear accelerator misfire, magnetron arc, external sensor (including external gating sensors, such as respiratory sensors, etc.)), the firing position and / or MLC leaf configuration at the time of component failure, etc., which can be used later in the same or different treatment session to restore dose delivery (i.e., localized portions). Because such data is recorded, treatment can be resumed from the same beam station when an interruption occurs (although not necessarily at the same firing angle). This may be more accurate than resuming delivery in a spiral delivery where the patient platform is constantly moving during radiation delivery, because the synchronization of the platform motion (which may include platform position and velocity) and the gantry rotation at the time of the interruption may be difficult to accurately replicate later.

[0060] The treatment process may be interrupted due to failure of one or more components of the radiotherapy system, one or more patient-specific factors, and / or based on clinician and / or operator instructions. Examples of component failures that may trigger a session interruption include, but are not limited to, "sticky" MLC leaves that slow and / or cannot move due to insufficient power and / or other failures, arcing of the magnetron, gantry rotation errors, loss of synchronization between patient platform and / or treatment radiation source position and / or gantry rotation and / or MLC operation, etc. Examples of patient factors that may trigger a session interruption may include, but are not limited to, discomfort, inability to remain still, physical or mental decline, poor and / or non-specific PET tracer uptake, etc. Clinicians and / or operators may pause or end a treatment session for a variety of reasons, for example, if they determine that the treatment plan is not suitable for delivery during the treatment session, and / or if the delivered fluence appears to deviate from the fluence specified in the treatment plan, and / or any patient safety issues, and / or any mechanical related issues, etc. In some variations, the radiotherapy system may include a system shut-off mechanism that automatically stops the emission of radiation from the therapeutic radiation source and / or closes the MLC leaves and / or closes the mouth when activated by the patient and / or operator. For example, the shut-off mechanism may include a button, lever, switch, or any other mechanical trigger accessible to a patient positioned on the platform. Alternatively or additionally, the shut-off mechanism may include a button, lever, switch, or any other mechanical trigger accessible to a clinician and / or operator. When the shut-off mechanism is activated, a signal may be sent to the therapeutic radiation source to stop the emission of radiation, and the system configuration data at the time the shut-off mechanism was activated is stored in the system controller memory. Examples of system configuration data that may be stored when a treatment session has been interrupted may include beam station data (e.g., current beam station data, which beam stations have been accessed, which beam stations have not been accessed, etc.), gantry rotation configuration or revolution, beam station dwell time when the session is interrupted, firing position (or firing angle) index, MLC configuration, patient platform pass index, etc. The cumulative fluence delivered during the treatment session until the interruption and / or the fluence delivered at the current beam station until the interruption may be stored in the system controller memory. The system configuration data may be used to resume treatment at a later time.

[0061] In some variations, a treatment session may be resumed without a new patient setup and registration (i.e., the patient remains on the platform after the interruption and radiation delivery resumes in the same session or day), while in other variations, a treatment session may be resumed after a new patient setup and registration (i.e., the patient is removed from the platform after the interruption and radiation delivery resumes at a later time or on another day). In variations where radiation delivery is based on PET shots (e.g., LOR) and / or imaging data acquired at the time of treatment (e.g., in BGRT), resuming a treatment session at a different time may include: obtaining a PET prescan; normalizing the treatment plan using the PET prescan data; moving the patient platform to the beam station where the previous treatment session was interrupted; positioning the therapeutic radiation source at the firing position where the previous treatment session was interrupted; and delivering radiation according to the treatment plan that has been normalized to the updated PET prescan. Additional details regarding normalization of treatment plans based on imaging data acquired in real time may be found in U.S. Patent Application No. 16 / 138,631, filed on September 21, 2018, the entire contents of which are incorporated herein by reference. Alternatively or additionally, the interrupted treatment session may be resumed at a later time by moving the patient platform to the beam station where the previous treatment session was interrupted, positioning the therapeutic radiation source at the firing position where the previous session was interrupted, and delivering radiation according to the treatment plan (i.e., without normalizing the treatment plan based on imaging data acquired in real time). (1…x) In an IMRT treatment plan for a sequence of , these control points specify, for example, the fractionation fluence map for each beam station, the firing position, and / or the pass in the treatment session, the resumption of an interrupted treatment session (where the interruption occurs at the control point cp interrupt The interruption may include: establishing and registering the patient according to the establishment and registration in the interrupted treatment session; moving the patient platform to the control point cp where the interruption occurs interruptand delivering therapeutic radiation according to the next control point cp(interrupt+1), and so on, until radiation is delivered to the patient according to all treatment plan control points (e.g., from cp(interrupt+1), ..., cp(x-2), cp(x-1), cpx). Delivering radiation to the patient target area only when the patient platform stops at a beam station can help the radiotherapy system resume radiation delivery more accurately after an interruption, and even resume radiation delivery in the same session shortly after the interruption occurs. In a spiral delivery system in which the patient platform moves continuously as radiation is delivered (e.g., where radiation is delivered from a continuously movable therapeutic radiation source), it is challenging to accurately record the position of the patient platform and the position of the therapeutic radiation source (e.g., ignition position or angle) at the time of the interruption because the platform may have moved after the interruption, and / or the position and / or time synchronization between the patient platform and the therapeutic radiation source (and optionally, the MLC associated with the therapeutic radiation source) may be difficult to determine or maintain. For example, a treatment session may be interrupted due to a failure of an MLC leaf. During beam station delivery, the radiotherapy system may be configured to determine the fluence that should have been delivered using the defective MLC leaf and split the fluence that was not delivered (due to the defective leaf) to be delivered at alternative firing positions and / or using other MLC leaves. Since the patient platform has not yet moved from the beam station where the interruption occurred, the missed fluence may be delivered during the same session and treatment may be resumed. Alternatively, if the magnetron arcs, the radiotherapy system may hold the patient platform at the beam station to wait until the magnetron stabilizes and attempt to re-deliver. However, in a helical delivery system where the patient platform is in constant motion, the fluence that was not delivered due to an MLC leaf error may be difficult to deliver in the same session because the platform will change its position when the leaf error is detected and the fluence is re-splited. If the magnetron arcs during radiation delivery, the helical radiotherapy system may have difficulty delivering the missed fluence because the platform has changed its position when the magnetron stabilizes.

[0062] As previously described, the mouth opening width can be changed at each beam station. Changing the mouth opening width can help control the IEC-Y dose or fluence gradient. For example, when a higher IEC-Y dose or fluence gradient is required, a smaller mouth width (e.g., about 1 cm or less) can be used, and when a lower IEC-Y dose or fluence gradient is required, a larger mouth width (e.g., greater than about 2 cm) can be used to deliver the dose. In some variations, increasing the mouth opening width can cause the irradiation field at one beam station to overlap with the irradiation field at one or more adjacent beam stations. In cases where a relatively low dose gradient or fluence gradient is prescribed (e.g., for tumors larger than about 4 cm in the IEC-Y dimension), or in cases where the prescribed dose to the patient area is zero, non-overlapping irradiation fields may be desired between beam stations because this can help improve delivery efficiency and reduce treatment time. During beam station delivery (for IMRT or BGRT), the fluence in the axial plane (XZ) can be adjusted by setting the width of the mouth opening that produces an irradiation field that overlaps with adjacent beam stations and by performing multiple revolutions per beam station, where each revolution has a different MLC leaf configuration for each firing position. For beam stations that require higher dose or fluence modulation levels, radiation can be delivered over more revolutions than for beam stations that require lower dose or fluence modulation levels. In some variations, there may not be any dose or fluence modulation across beam stations, for example, an unmodulated treatment mode where the modulation factor is 1. In this case, the MLC leaf configuration for one or more firing positions does not change through multiple revolutions, and may not generate a variable intensity pattern for each firing position in the axial plane, but may instead be used to shape the aperture of the beam around the tumor size at each firing position. For example, for each firing position, the beam aperture can be defined by the width of the leaf opening along the X direction and the width of the mouth opening in the IEC-Y direction, which coincides with the patient target area boundaries (e.g., PTV boundaries) in the beam line of sight at each firing position. That is, the radiotherapy system can perform 3D conformal delivery while the platform remains stationary at the beam station. Unmodulated delivery can help reduce treatment time and also help reduce the complexity and computational intensity of treatment planning because optimization is only done on beam station dwell time and mouth width (not MLC leaf configuration). In some variations, beam station radiation delivery can include: maintaining a therapeutic radiation source at a specific (e.g., first) firing position as the patient platform is moved to each designated beam station during treatment planning. While the platform remains stationary at the beam station, radiation sub-beams defined by the MLC leaf configuration and beam station for that (e.g., first) firing position can be delivered. As specified by the fluence map, the MLC leaf configuration may change for each beam station.After the patient platform is positioned at each beam station (e.g., from beam stations 1, 2, 3, ..., N) and the designated radiation sub-beam has been delivered from a particular (e.g., first) firing position, the gantry can move the therapeutic radiation source to the next (e.g., second) firing position and the patient platform can be moved through each beam station, wherein the MLC leaf configuration is adjusted for that firing position at each beam station. In some variations, for the next (e.g., second) firing position, the patient platform can be moved to each beam station in a reverse order (e.g., from beam stations N, N-1, N-2, ..., 1), wherein the direction of the patient platform movement alternates as the therapeutic radiation source changes its firing position. Alternatively or additionally, the therapeutic radiation source can be maintained at a single firing position while the patient platform is moved across all beam stations twice, i.e., in two passes, wherein the first pass is from beam stations 1, 2, ...N-1, N and the second pass is from beam stations N, N-1, ...2, 1. The number and direction of passes at each firing location may vary depending on whether the desired or prescribed dose has been delivered according to the dose target.

[0063] Beam station radiation delivery can also be used to facilitate gated radiation delivery, wherein emission of a therapeutic radiation beam is timed based on movement of the target region and / or patient. In some variations, imaging data and / or images (e.g., PET imaging data) acquired in real time may be used to identify the changing position of the target region and / or patient while the patient platform is positioned (i.e., stationary) at a given beam station. The radiation therapy system can "wait" for the target region to move into a predetermined (e.g., during treatment planning) range of treatment positions before applying radiation. This type of delivery is not possible with spiral delivery because the patient platform is constantly moving while the target region is also moving, and the relative motion between the platform and target region may be difficult to trigger for radiation delivery. Figure 4A variation of a method of gated beam station radiation delivery is depicted in . The method (400) may include: moving (402) a patient platform to the beam station and stopping at the beam station while the therapeutic radiation source continuously rotates about the platform; and determining (404) whether a target area is located in a predetermined treatment position or is in a phase indicating treatment based on the target position and / or motion data calculated based on imaging data acquired in real time. If it is determined that the target area is not in the predetermined treatment position and / or the movement of the target area is in a phase not indicating treatment, radiation is not delivered and the platform remains at the beam station (402). If it is determined that the target area is not in the predetermined treatment position and / or the movement of the target area is in a phase indicating treatment, the method (400) may include delivering (406) a planned sub-beam or fluence for the current firing position and recording in the system controller memory that the sub-beam or fluence has been delivered. This may be repeated (408) until all sub-beams or fluences for that beam station have been delivered (see also Figure 3 ), after which the patient platform may be moved (410) to the next beam station. The method (400) may be repeated until all sub-beams or fluences for all beam stations have been delivered.

[0064] Although various inventive variations have been described and shown herein, a person of ordinary skill in the art will readily conceive of a variety of other means and / or structures for performing functions and / or obtaining results and / or one or more advantages described, and each of such variations and / or modifications is considered to be within the scope of the inventive variations described herein. More generally, it will be readily understood by those skilled in the art that all parameters, dimensions, materials, and configurations described herein are exemplary, and that actual parameters, dimensions, materials, and / or configurations will depend on one or more specific applications to which the teachings of the present invention are used. Those skilled in the art will recognize or be able to determine many equivalents of the specific inventive variations described herein using only routine experiments. Therefore, it should be understood that the above variations are given only by way of example, and within the scope of the appended claims and their equivalents, the inventive variations may be practiced in a manner different from that specifically described and claimed. The inventive variations of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, if such features, systems, articles, materials, kits, and / or methods are not mutually contradictory, two or more such features, systems, articles, materials, kits, and / or methods are included within the scope of the invention disclosed herein.

Claims

1. A method for calculating a fluence map of radiation delivery by a beam station, the method comprising: determining a plurality of patient platform beam stations based on the one or more patient target regions; calculating a set of candidate radiation sub-beams for each beam station; as well as A fluence map is generated for each beam station by calculating a set of sub-beam weights corresponding to the set of candidate radiation sub-beams for each beam station so that the radiation dose delivered to the one or more target areas by all candidate radiation sub-beams satisfies predetermined dose constraints and treatment parameters.

2. The method according to claim 1, wherein: The plurality of beam stations are evenly spaced apart.

3. The method according to claim 1, wherein: The step distance between adjacent beam stations is smaller than a width of a treatment beam plane including the set of candidate radiation sub-beams.

4. The method according to claim 1, wherein: The step distance between each of the beam stations is variable.

5. The method according to any one of claims 1 to 4, wherein: The step size between each of the beam stations and the number of beam stations in the set of beam stations are user selected.

6. The method according to any one of claims 1 to 4, wherein: The set of candidate radiation sub-beams includes a matrix of multi-leaf collimator (MLC) configurations for each radiation firing location around the patient platform, the matrix defining a set of radiation sub-beams that intersect the one or more patient target regions.

7. The method according to claim 6, wherein: Calculating a set of beamlet weights includes calculating a dose calculation matrix including a contribution of each candidate beamlet to the one or more target regions.

8. The method according to claim 6, wherein: Calculating a set of beamlet weights includes generating a penalty function representing a measure of treatment plan quality, and using an iterative optimization method to calculate the set of beamlet weights that minimize the penalty function.

9. The method of claim 6, further comprising quantizing the fluence map for each beam station to generate a quantized fluence map, wherein each sub-beam weight is an integer value of a dose quota deliverable by the movable therapeutic radiation source.

10. The method according to any one of claims 1-4 and 7-9, wherein: The predetermined dose constraints include user-defined dose constraints, and / or user-defined dose targets, and / or maximum dose levels, and / or dose coverage metrics.

Images