High speed sliding window delivery through a high speed multi-leaf collimator

Abstract

The system for delivering a radiation dose includes a gantry that moves around a target to be irradiated, a radiation source mounted on the gantry and directed inwardly toward the target, and a collimator mounted on the gantry and forward of the radiation source that shapes a radiation beam directed at the target, the collimator modulating sub-beam intensities of the radiation beam across a plurality of sub-beams that subdivide the fluence field into a two-dimensional (2D) grid, such that a plurality of independent two-dimensional (2D) sub-beam intensity patterns are delivered from a plurality of gantry angles while the gantry moves continuously. [Selected Figures] Figures 5A and 5B

Description

[Technical field]

[0001] (Related Applications) This application claims the benefit under 35 U.S.C. §119(e) of U.S. patent application Ser. No. 16 / 055,507, filed Aug. 6, 2018, the entire contents of which are incorporated herein by reference.

[0002] (Technical field) The present disclosure relates to high speed sliding window delivery via high speed multi-leaf collimators (MLCs) in radiation therapy systems. [Background technology]

[0003] In radiation therapy, a dose of radiation delivered via a radiation therapy beam from a source outside the patient's body is delivered to a target site within the body to destroy tumor cells. Care must be taken to maximize the amount of radiation delivered to the intended treatment site while minimizing the amount of radiation delivered to non-treatment sites. In radiation therapy, the aperture of the radiation therapy beam is shaped to fit as closely as possible to the intended target site. The aperture of the radiation therapy beam is typically defined by the MLC.

[0004] The present disclosure will become more fully understood from the detailed description given below and from the accompanying drawings of various embodiments of the present disclosure. [Brief description of the drawings]

[0005] [Figure 1A] FIG. 1 illustrates a helical radiation delivery system according to embodiments described herein. [Figure 1B] FIG. 1 illustrates a robotic radiation therapy system that can be used in accordance with embodiments described herein. [Figure 1C] FIG. 1 illustrates a C-arm gantry-based radiation therapy system according to embodiments described herein. [Figure 2A]FIG. 2 illustrates a multi-leaf MLC for providing a radiation therapy dose to a target site according to embodiments described herein. [Figure 2B] 1 illustrates a bottom view of a multi-leaf MLC according to embodiments described herein. [Figure 2C] 1 shows a perspective view of a multi-leaf high speed MLC according to embodiments described herein. [Figure 2D] 2 illustrates a top view of the leaves of a multi-leaf high speed MLC according to embodiments described herein. [Figure 2E] FIG. 2 illustrates an exemplary leaf arrangement for a multi-leaf high speed MLC according to embodiments described herein. [Figure 3A] FIG. 13 illustrates an exemplary leaf opening time profile according to embodiments described herein. [Figure 3B] FIG. 13 illustrates an exemplary leaf opening time profile according to embodiments described herein. [Figure 3C] FIG. 13 illustrates an exemplary leaf opening time profile according to embodiments described herein. [Figure 3D] FIG. 13 illustrates an exemplary optimized leaf opening time profile according to embodiments described herein. [Figure 3E] FIG. 13 illustrates an exemplary optimized leaf opening time profile according to embodiments described herein. [Figure 3F] FIG. 13 illustrates an exemplary optimized leaf opening time profile according to embodiments described herein. [Figure 3G] FIG. 13 illustrates an exemplary leaf opening time profile incorporating maximum velocity according to embodiments described herein. [Figure 4A] 1A-1C illustrate various exemplary leaf configurations that fit target sites according to embodiments described herein. [Figure 4B] 1A-1C illustrate various exemplary leaf configurations that fit target sites according to embodiments described herein. [Figure 4C]1A-1C illustrate various exemplary leaf configurations that fit target sites according to embodiments described herein. [Figure 5A] 4 is a flow chart illustrating a method for fast sliding window with high speed MLC according to embodiments described herein. [Figure 5B] 1 is a flow chart illustrating a method for binary MLC transmission with per-leaf field widths according to an embodiment. [Figure 6] 1A-1D illustrate examples of different systems that can be used to generate radiation treatment delivery in accordance with embodiments described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Described herein are embodiments of methods and apparatus for high speed sliding window delivery via a high speed MLC in a radiation therapy system where opposing banks of MLC leaves can be used to create one or more patterns that shape a radiation therapy beam to fit a target area.

[0007] For target areas of non-uniform shape, IMRT can be utilized to deliver more complex radiation therapy doses. Intensity Modulated Radiation Therapy (IMRT) essentially includes a variety of radiation therapy techniques that vary the intensity of the radiation therapy beam directed at the target area. In IMRT, rather than the MLC shaping the radiation therapy beam to fit a specific contour, the MLC is instead used to generate an array of beam shapes that, via overlapping radiation fields of (possibly) different intensities, produce the desired intensity modulation and the desired 3D dose distribution.

[0008] In some embodiments, the binary MLC includes multiple leaf pairs arranged in two opposing banks. Each bank of leaves is used to form a treatment slice by positioning the leaves in a closed or open position relative to the beam. In some embodiments, the sup-inf field width (e.g., the width formed by the openings of the leaf pairs of the MLC) is constant across all leaves of the MLC. Disadvantageously, this means that such systems cannot adapt the field of the radiation therapy beam to the target profile along the length of the target. Due to this limitation, the field size of the binary MLC is generally limited to less than 5 cm. Larger field sizes are generally not desirable for treating a large portion of the target site due to the radiation exposure to non-target sites.

[0009] One solution to the above problem is to use dynamic jaws to better adapt the field to the target site on the top and bottom ends. However, such an approach does not adapt the field to the edges of the target along its length, since the field size is defined by the jaws and is constant across the MLC. Another solution is to use a non-binary shape-fitting MLC. Such MLCs can be slow, which can negatively impact treatment time. Another solution is provided herein.

[0010] Advantageously, the embodiments described herein allow the MLC to adapt the treatment beam field to the target site while minimizing radiation exposure to non-treatment sites. Additionally, the embodiments described herein allow for larger field sizes (e.g., larger than 5 cm), which can increase treatment speed. Additionally, the embodiments described herein allow the MLC to modulate the fluence field not only in the IEC-Xb direction, but also in the IEC-Yb direction, as described herein. Additionally, the embodiments described herein allow for more opportunities for longitudinal modulation. This allows the pitch of the treatment plan to be looser (e.g., closer to 1), with the sup-inf modulation being handled by the longitudinal modulation of the MLC leaves. Alternatively, a tighter pitch can be maintained using the additional opportunity to modulate the treatment beam over the same sup-inf site.

[0011] The systems and methods described herein achieve the above advantages through the use of high speed MLC. One example of such a high speed MLC is the electromagnetic MLC (eMLC) described herein. However, it should be noted that alternative variations of high speed MLC can be used to perform the operations described herein. In this disclosure, high speed MLC can be any MLC capable of extremely fast leaf movement (e.g., approximately capable of traversing a 5 cm field in less than 100 milliseconds). It should be noted that although "eMLC" is used throughout this disclosure, the systems and methods described herein are compatible with any other form of high speed MLC as well.

[0012] Additionally, in this specification, the terms "fluence", "intensity" and "dose" are used as follows: fluence is the number of photons or x-rays that cross a unit area perpendicular to the radiation beam. Fluence rate is the fluence per unit time. Intensity is the energy that crosses a unit area per unit time. Fluence and intensity are independent of what happens to the patient, and more specifically, are not doses. Dose is the amount of energy absorbed by tissue due to the radiation that impacts it. Radiation dose is measured in units of grays (Gy), where each Gy corresponds to a certain amount of energy absorbed by a unit mass of tissue (e.g., 1 Joule / kg). Dose is not the same as fluence, but dose increases and decreases as fluence increases and decreases.

[0013] The terms "target" and "target area" can refer to one or more fiducials near (within some defined proximity to) a treatment area (e.g., a tumor). In another embodiment, a target can be a bone structure. In yet another embodiment, a target can refer to the soft tissue of a patient. A target can be any defined structure or area that can be identified and tracked, as described herein.

[0014] FIG. 1A illustrates a helical radiation delivery system 800 according to an embodiment of the present disclosure. The helical radiation delivery system 800 can include a linear accelerator (LINAC) 850 mounted on a ring gantry 820. The LINAC 850 can be used to generate a radiation beam (i.e., a treatment beam) by directing an electron beam to an X-ray emitting target. The treatment beam can deliver radiation to a target site (i.e., a tumor). The treatment system further includes a multi-leaf collimator (MLC) 860 coupled to a distal end of the LINAC 850. As described herein, the MLC 860 can be an eMLC. The MLC includes a housing that contains multiple leaves that are movable to adjust an aperture of the MLC to enable shaping of the treatment beam. The ring gantry 820 has a toroidal shape, where the patient 830 extends through the bore of the ring / toroid, and the LINAC 850 is mounted around the periphery of the ring and rotates about an axis through the center to irradiate the target area, with the beam being delivered from one or more angles around the patient. During treatment, the patient 830 can be moved simultaneously through the bore of the gantry on the treatment couch 840.

[0015] The helical radiation delivery system 800 includes an imaging system with a LINAC 850 as an imaging source and an X-ray detector 870. The LINAC 850 can be used to generate a megavoltage X-ray image (MVCT) of a region of interest (ROI) of the patient 830 by directing a series of X-ray beams incident on an X-ray detector 870 on the opposite side of the LINAC 850 to the ROI to image the patient 830 for setup and to generate pre-treatment images. In one embodiment, the helical radiation delivery system 800 can also include a secondary imaging system consisting of a kV imaging source 810 mounted orthogonally (e.g., 90 degrees away) to the LINAC 850 on the ring gantry 820 and aligned to project an imaging X-ray beam at the target site and illuminate the image plane of the detector after passing through the patient 130.

[0016] FIG. 1B illustrates a radiation therapy system 1200 that can be used in accordance with an alternative embodiment described herein. As illustrated, FIG. 1B illustrates a configuration of the radiation therapy system 1200. In the illustrated embodiment, the radiation therapy system 1200 includes a linear accelerator (LINAC) 1201 that serves as a radiation therapy source and an MLC 1205 (e.g., eMLC) coupled to a distal end of the LINAC 1201 to shape the treatment beam. In one embodiment, the LINAC 1201 is mounted at the end of a robotic arm 1202 that has multiple (e.g., 5 or more) degrees of freedom to position the LINAC 1201 to irradiate a pathological anatomy (e.g., a target) with beams delivered from multiple angles and in multiple planes in a working volume around the patient. Treatments can include beam paths with a single isocenter, multiple isocenters, or a non-isocentric approach.

[0017] The LINAC 1201 can be positioned at multiple different nodes (predefined positions where the LINAC 1201 can be stopped to deliver radiation) during treatment by moving the robotic arm 1202. At the nodes, the LINAC 1201 can deliver one or more radiation therapy beams to the target, where the radiation beam shape is determined by the leaf positions in the MLC 1205. The nodes can be positioned in an approximately spherical distribution around the patient. The particular number of nodes and the number of therapy beams applied at each node can vary depending on the location and type of pathological anatomy being treated.

[0018] In another embodiment, the robotic arm 1202 and the LINAC 1201 at its end can be moved continuously between nodes while radiation is being delivered. The shape and two-dimensional intensity map of the radiation beam is determined by rapid movement of the leaves in the MLC 1205 during the continuous movement of the LINAC 1201.

[0019] The radiation therapy system 1200 includes an imaging system 1210 having a processing device 1230 connected to X-ray sources 1203A and 1203B (i.e., imaging sources) and stationary X-ray detectors 1204A and 1204B. Alternatively, the X-ray sources 1203A, 1203B and / or the X-ray detectors 1204A, 1204B can be mobile, in which case they can be repositioned to maintain alignment with the target, or to image the target from various orientations, or to acquire many X-ray images and reconstruct a three-dimensional (3D) cone beam CT. In one embodiment, the X-ray source is an array of X-ray sources rather than a point source, as will be appreciated by those skilled in the art. In one embodiment, the LINAC 1201 serves as an imaging source, where the power level of the LINAC is reduced to an acceptable level for imaging.

[0020] The imaging system 1210 can perform computed tomography (CT), such as cone-beam CT or helical megavolt computed tomography (MVCT), and the images generated by the imaging system 1210 can be two-dimensional (2D) or three-dimensional (3D). Two x-ray sources 1203A and 1203B can be mounted in fixed positions on the ceiling of the operating room and can be aligned to project x-ray imaging beams from two different angular positions (e.g., 90 degrees apart) to intersect at a machine isocenter (referred to herein as a treatment center, which provides a reference point for positioning the patient on the treatment couch 1206 during treatment) and to illuminate the imaging planes of the respective detectors 1204A and 1204B after passing through the patient. In one embodiment, the imaging system 1210 provides stereoscopic imaging of the target and the surrounding volume of interest (VOI). In other embodiments, the imaging system 1210 can include more or less than two x-ray sources and more or less than two detectors, any of which can be movable rather than fixed. In yet another embodiment, the positions of the X-ray source and the detector can be swapped. The detectors 1204A and 1204B can be made of a scintillation material (e.g., amorphous silicon) that converts X-rays into visible light, and an array of CMOS (complementary metal oxide silicon) or CCD (charge-coupled device) imaging cells that convert the light into a digital image that can be compared to the reference image during an image registration process that converts the coordinate system of the digital image to that of the reference image, as is well known to those skilled in the art. The reference image can be, for example, a digitally reconstructed X-ray image (DRR), which is a virtual X-ray image generated from a 3D CT image based on simulating the X-ray image formation process by casting a light beam through the CT image.

[0021] In one embodiment, the IGRT delivery system 1200 also includes a secondary imaging system 1239. The imaging system 1239 is a cone beam computed tomography (CBCT) imaging system, such as a medPhotonImagingRing system. Alternatively, other types of volumetric imaging systems can be used. The secondary imaging system 1239 includes a rotatable gantry 1240 (e.g., a ring) mounted on an arm and rail system (not shown) that moves the rotatable gantry 1240 along one or more axes (e.g., along an axis extending from the head to the foot of the treatment couch 1206). An imaging source 1245 and a detector 1250 are mounted on the rotatable gantry 1240. The rotatable gantry 1240 can rotate 360 ​​degrees about an axis extending from the head to the foot of the treatment couch. Thus, the imaging source 1245 and the detector 1250 can be positioned at many different angles. In one embodiment, the imaging source 1245 is an x-ray source and the detector 1250 is an x-ray detector. In one embodiment, the secondary imaging system 1239 includes two independently rotatable rings. The imaging source 1245 can be attached to the first ring and the detector 1250 can be attached to the second ring. In one embodiment, the rotatable gantry 1240 is placed at the foot of the treatment couch during radiation treatment delivery to avoid collision with the robotic arm 1202.

[0022] 1B, the image-guided radiation therapy system 1200 can further be associated with a treatment delivery workstation 150. The treatment delivery workstation can be located remotely from the radiation therapy system 1200, in a room different from the treatment room in which the radiation therapy system 1200 and the patient are located. The treatment delivery workstation 150 can include a processing device (which can be the processing device 1230 or another processing device) and memory that modifies treatment delivery to the patient 1225 based on detection of target motion based on one or more image registrations as described herein.

[0023] FIG. 1C shows a C-arm radiation delivery system 1400. In one embodiment, in the C-arm system 1400, the beam energy of the LINAC can be adjusted during treatment, making the LINAC usable for both X-ray imaging and radiation therapy. In another embodiment, the system 1400 can include an on-board kV imaging system for generating X-ray images and a separate LINAC for generating higher energy therapeutic radiation beams. The system 1400 includes a gantry 1410, a LINAC 1420, an MLC 1470 (e.g., eMLC) coupled to a distal end of the LINAC 1420 to shape the beam, and a portal image detector 1450. The gantry 1410 is rotated to an angle corresponding to a selected projection and can be used to acquire an X-ray image of a VOI of a patient 1430 on a treatment couch 1440. In embodiments including a portal imaging system, the LINAC 1420 can generate an x-ray beam that passes through a target in the patient 1430 and impinges on the portal imaging detector 1450 to create an x-ray image of the target. After the x-ray image of the target is generated, the beam energy of the LINAC 1420 can be increased so that the LINAC 1420 can generate a radiation beam to treat the target area of ​​the patient 1430. In another embodiment, a kV imaging system can generate an x-ray beam that passes through a target in the patient 1430 and generates an x-ray image of the target. In some embodiments, the portal imaging system can acquire portal images while treatment is being performed. The portal imaging detector 1450 can measure the exit radiation fluence after the beam passes through the patient 1430. This allows internal or external fiducials or portions of anatomy (e.g., tumors or bones) to be localized in the portal image.

[0024] Alternatively, the kV imaging source or portal imager and operation methods described herein can be used in other types of gantry-based systems. In some gantry-based systems, the gantry rotates the kV imaging source and LINAC about an axis that passes through the isocenter. Gantry-based systems include a generally toroidal shaped ring gantry, where the patient's body extends through the bore of the ring / toroid, and the kV imaging source and LINAC are mounted around the ring and rotate about an axis that passes through the isocenter. Gantry-based systems can also include a C-arm gantry, where the kV imaging source and LINAC are cantilever-mounted and rotate about an axis that passes through the isocenter. In another embodiment, the kV imaging source and LINAC can be used in a robotic arm-based system, including a robotic arm to which the kV imaging source and LINAC are attached as described above. Aspects of the present disclosure can also be used in other such systems, such as gantry-based LINAC systems, static imaging systems associated with radiation therapy and radiosurgery, proton therapy systems using integrated image guidance, interventional radiology and intraoperative x-ray imaging systems.

[0025] 2A illustrates a multi-leaf collimator (MLC) 31 for providing a radiation therapy dose to a target site according to embodiments described herein. The MLC 31 includes two banks of opposing leaves 33, each leaf 37 which can be positioned successively across the radiation field. The two banks of leaves 33 are positioned to collimate the beam 30 to a desired shape. In one embodiment, each leaf 37 can be moved beyond the midpoint of the collimator to provide flexibility in achieving the desired collimation. This configuration illustrates fully open (41), partially open (43), and closed (45) leaf states.

[0026] In a radiation therapy example, each gantry angle has one beam associated with that particular gantry angle, and the beam 30 is then collimated into multiple shapes by the MLC. The treatment beam 30 passes through a shaped aperture 47 formed by the leaves 37. The resulting collimated beam continues to the target 14 in the patient 38. FIG. 2A also shows how the treatment beam can be visualized or conceptualized as many different beamlets 49. The leaves 37 of the MLC 31 move to various positions to achieve a desired shape or aperture for a specified time period to achieve a fluence map 51 for that particular beam. Modulation of the conceptualized beamlets is done by monotonically moving the leaves sequentially to the desired positions to achieve the desired shape or aperture such that the time the conceptualized beamlet is exposed controls the intensity of that beamlet. In one embodiment, "monotonic" herein refers to an ordered sequence of apertures where the order is determined by a continuum from one aperture to the next, or where individual leaves increment in one direction during a given series of apertures. In other words, the sequence of apertures will be determined by the mechanical limitations of the MLC rather than by what can achieve more optimal treatment delivery. In one embodiment, the sequence will proceed from aperture 1, then 2, then 3, and so on, rather than going from 1 to 3, then 5, then back to 2. The MLC can deliver a series of shapes rather than using a single conformal shape. The net amount of radiation received at any given gantry position is based on the extent to which the various shapes allow radiation to pass or be blocked. As can be seen in FIG. 2A, the shapes of the MLC 31 shown do not directly correspond to the beamlet intensities of the fluence map 51. As will be appreciated, the depicted fluence map shows the accumulation of intensities of multiple shapes taken by the MLC for that particular gantry angle.

[0027] A common limitation of conventional shaped MLCs is that the leaves that define the shape move relatively slowly. Using multiple shapes, or shapes that require large leaf movements, can lengthen patient treatment. Similarly, leaf speed can limit the ability of conventional shaped MLCs to deliver time-dependent treatments, such as those that utilize synchronous movement of delivery components (e.g., gantry, couch, x-ray energy, etc.). For one of these reasons, conventional 2D intensity map delivery techniques are limited to beams delivered from static positions. Alternatively, conventional systems that allow continuous movement of the radiation source generally only allow a single aperture shape, or morphing from one aperture shape to another as the radiation source moves, and are not capable of delivering a 2D intensity map from each radiation source position.

[0028] FIG. 2B shows a bottom view of a multi-leaf MLC 61 according to an embodiment described herein. The binary MLC 61 has multiple leaves 63 arranged in two banks 65, 67. Each bank of leaves is used to shape a treatment slice by positioning the leaves in a closed or open position relative to the beam. As shown in FIG. 2B, the leaves can work together such that both are open (A), both are closed (B), or only one leaf is open / closed (C). In a conventional binary MLC, the leaves 63 open to the same uniform width throughout a single position section (A). In a conventional shaped MLC, the leaves 63 can open to a variety of different widths throughout a single position section (A). A common limitation of conventional binary MLCs is that the leaves 63 may not open to a variety of different widths some portion of the time during each position section. Thus, it may be difficult to shape a radiation beam to a target site while simultaneously minimizing radiation exposure to non-target sites. Advantageously, the methods and systems described herein enable the advantages of shaped MLC (e.g., leaves 63 can open to a variety of different widths at any portion of the time between each position section) while maintaining the speed of binary MLC.

[0029] FIG. 2C shows a perspective view of a multi-leaf high speed MLC 62 according to an embodiment described herein. In one embodiment, the radiation modulation device 34 includes an electromagnetically actuated MLC (eMLC) 62 including a plurality of leaves 66 operable to move from position to position to provide intensity modulation. The leaves 66 can be moved to any position between a minimum open position and a maximum open position with sufficient speed that the ordering or positioning of the leaves is not significantly affected by the previous or future positions of any individual leaf. Stated differently, the leaf speed is sufficient so that the mechanism of the MLC does not unduly affect the determination of the leaf position at any given time of the delivery of a radiation therapy treatment or portion. Each leaf 66 is independently controlled by an actuator (not shown, described more fully below), such as a motor or magnetic drive, to controllably move the leaves 66 to fully open, fully closed, or any position between open and closed, as described in more detail below. The actuators can be suitably controlled by a computer 74 and / or a controller.

[0030] In one embodiment, the MLC 62 is coupled to a distal end of a LINAC of a radiation therapy delivery system. The processing device of the computer 74 can control the multiple leaf pairs 66 of the MLC 62 such that for each of the multiple radiation beam delivery position sections corresponding to a range of radiation beam positions over a discrete time interval, each leaf pair of the multiple opposing leaf pairs 66 is open to a fixed aperture for a portion of the time in the discrete time interval and closed for the remaining portion of the time in the discrete time interval while the radiation beam of the radiation therapy system is active. In one embodiment, the fixed apertures and the time portions form overlapping radiation fields of different intensities that combine to result in an intensity modulated fluence field that is delivered to the treatment target. In one embodiment, the fixed aperture fits the contour of the treatment object and is back-projected onto the MLC along the radiation beam and is within the maximum range of movement of the multiple leaf pairs within the MLC. This concept is further described with respect to FIGS. 4A-C and 5B.

[0031] In one embodiment, the processing device of computer 74 can control MLC 62 to modulate sub-beam intensities of a radiation beam across multiple sub-beams that subdivide the fluence field into a 2D grid, where multiple independent 2D sub-beam intensity patterns are delivered from multiple gantry angles while the gantry is moving continuously. This concept is further described with respect to Figures 3A-F and 5A.

[0032] In one embodiment, the LINAC including the MLC 62 is mounted to a rotating gantry and the radiation beams delivered from a range of radiation beam positions rotate around the treatment target. The treatment target can move axially through a bore of the rotating gantry and the radiation beams delivered from a range of radiation beam positions can follow a helical path around the treatment target. In another embodiment, the LINAC and MLC 62 are mounted to a robotic arm and the radiation beams delivered from a range of radiation beam positions are not coplanar.

[0033] 2D shows a top view of the leaves of a multi-leaf high speed MLC 240 according to an embodiment described herein. The central portion 302 of the MLC 240 includes an inner leaf guide 302, an aperture 1050, and 14 leaf pairs (1010-1039) at various locations between the leaf guide inner supports 301. Although 14 leaf pairs are shown, more or fewer leaf pairs may be provided depending on the design requirements of a particular system. In one embodiment, there are 64 leaf pairs. In another embodiment, there are 96 leaf pairs. In yet another embodiment, there are 32 leaf pairs. As will be appreciated, radiation is collimated through this section 302 of the collimator.

[0034] In FIG. 2D, each leaf is positioned at a particular location to define a particular aperture or shape 1050 through which radiation can pass, also referred to herein as a state. Leaf pairs 1010 and 1011-1038 and 1039 are controlled using the control schemes and drivers described herein to allow simultaneous modulation of volume and intensity. In an alternative embodiment, one or more controllable jaws are used to provide primary collimation of the beam defined by inner edge 310i and frames 97A, 97B (i.e., the jaws block the open space between support frame B and leaf pair 1010 / 1011 and between support frame A and leaf pair 1038 / 1039). Additionally or alternatively, one or more pairs of jaws can be adjusted to reduce the size of the primary collimated beam to less than the frame size.

[0035] FIG. 2E illustrates an exemplary leaf arrangement for a multi-leaf high speed MLC according to embodiments described herein. A collimated field 1040 having a centerline 1030 is provided by a pair of jaws or other collimator device. In an exemplary embodiment, two leaves form a complementary leaf pair for shaping and modulating the collimated field 1040. For example, leaves 1010 and 1011 are one leaf pair. Leaves 1018, 1019 are another leaf pair, and leaves 1024, 1025 are yet another leaf pair. Each leaf of each pair can be positioned anywhere within the field 1040. The inner edges of each leaf in a leaf pair can face each other to create an opening, and the collection of openings formed by each leaf pair forms an aperture 1050. The aperture 1050 corresponds to the aperture of FIG. 2D described above and is set according to the treatment plan. In one embodiment, the aperture 1050 is determined prior to administering radiation treatment to the patient in the treatment planning process and occurs at a specific point during delivery of the treatment plan. The aperture 1050 can vary according to several factors, such as, for example, the three-dimensional shape of the treatment site, the intensity modulation, the fluence, and the beamlets within the treatment volume, as described herein. The high-speed MLC embodiments described herein provide volume and intensity modulation alone or in combination simultaneously by providing snap-state control.

[0036] 3A-C show exemplary leaf opening time profiles according to embodiments described herein. Unlike using conventional MLC, using eMLC (or other suitable high speed MLC) allows precise control of the amount of fluence transmitted at each point along the leaf pair travel direction (such as the IEC-Yb direction) while at the same time the constantly moving radiation source (e.g., LINAC) traverses an arc short enough to be considered as one position. To plan such high speed MLC, a leaf opening time profile can be determined. In one embodiment, the leaf opening time profile indicates the opening time of the leaf pair at discrete time intervals.

[0037] To generate an eMLC plan, the leaf opening time profile of each leaf pair in each position section can be divided into individual beamlets. An optimizer can determine the ideal leaf opening time for each beamlet, as described below. From the leaf opening time profile, a front leaf and a back leaf motion profile can be generated for each leaf pair, where the leaves can only move in one direction in each position section. In one embodiment, the leaves alternate between back-to-front and front-to-back movement in successive position sections, so that when a leaf pair finishes moving in one position section, it is in a position to start moving in the next position section.

[0038] 3A shows an example leaf opening time profile. As shown, the opening times of the leaf pairs, represented by the bars on the IEC-Yb axis, can vary from leaf pair to leaf pair. Note that in the leaf motion profile algorithm above, the total time required to deliver the opening times of all leaf pairs is:

number

number

[0039] 3D-F show exemplary optimized leaf open time profiles according to embodiments described herein. In one embodiment, a modulation factor constraint can be applied to the leaf open time profile to prevent the leaf open time from becoming too large (thus slowing down the treatment time). To generate the modulation factor, the average beamlet open time is calculated for all non-zero beamlets across all leaves and position sections. A discrete time interval is then determined as the average open time multiplied by the desired modulation factor. For each position section and leaf, the beamlet open time is adjusted such that the total leaf open time does not exceed the discrete time interval corresponding to the position section.

[0040] There are several ways to make this adjustment: In one embodiment, as shown in Figures 3D-F, individual beamlet open times that are greater than the discrete time interval can be reduced to be equal to the projection time, and then the minimum beamlet open time can be increased until the total leaf open time is less than or equal to the discrete time interval.

[0041] FIG. 3G shows an exemplary leaf opening time profile incorporating maximum velocity, according to an embodiment described herein. Note that the leaves of a fast MLC move quickly, but not instantaneously. To generate a practically viable plan, the leaf motion profile can take into account the finite leaf velocity of the MLC. In one embodiment, this can be done by incorporating the maximum leaf velocity (and possibly leaf acceleration) into the generated leaf profile. In one embodiment, the algorithm can try to keep the area of ​​each row constant. In the exemplary profile 306, the instantaneous leaf motion has been changed to a finite velocity leaf motion. Note that the integral opening time of the beamlets is not affected, since the leaf motion of each segment may start a little earlier. In one embodiment, if the start of the movement in the next projection overlaps with the end of the movement in the current projection, the leaf may change direction before reaching the end of its movement, resulting in slightly less fluence being delivered to the target site. The operation of FIGS. 3A-G is further described with respect to FIG. 5A.

[0042] 4A-C show various exemplary leaf arrangements to fit a target site 401 according to embodiments described herein. Each leaf pair is positioned in a particular way such that the leaf pair opening defines a particular aperture or shape to fit the target site 401. During treatment, radiation passes through the aperture defined by the combined leaf pairs and impinges on the target site below. A fast MLC (e.g., eMLC) such as those described herein opens and closes each leaf pair to an open or closed state during a discrete time interval. Each leaf pair can be open for a different time portion (e.g., an open time portion) during the discrete time interval, and each leaf pair can be open to a different width during the corresponding open time portion. Furthermore, the treatment beam can be active during the entire discrete time interval.

[0043] Advantageously, by activating the treatment beam for an entire discrete time interval and allowing each leaf pair to open to a specified width (which may differ from the width of the other leaf pairs) for only a portion of the discrete time interval, precise doses of radiation can be delivered to a variety of complex target site shapes. The operation of Figures 4A-C is further described with respect to Figure 5B.

[0044] 5A is a flow chart illustrating a method 500 of fast sliding window with fast MLC according to embodiments described herein. In general, the method 500 may be performed by processing logic that may include hardware (e.g., a processing device, circuitry, dedicated logic, programmable logic, microcode, hardware of a device, etc.), software (e.g., instructions running or executed on a processing device), or a combination thereof. In some embodiments, the method 500 may be performed by processing logic of the radiation therapy system 800 of FIG. 1A.

[0045] 5A, the method 500 may begin at block 502, where processing logic shapes a radiation beam directed to a target through a collimator mounted on a gantry of a radiation therapy system. In one embodiment, the collimator is a multi-leaf collimator (MLC) that includes multiple leaf pairs. The MLC may be a high-speed MLC (e.g., eMLC) as described herein.

[0046] The processing logic of block 504 can modulate, by a processing device, sub-beam intensities of the radiation beam across a plurality of sub-beams that subdivide the fluence field into a 2D grid. In one embodiment, the sub-beam intensities are modulated by independently modulating the travel speeds of the front and rear leaves of each leaf pair as each leaf pair moves in a single pass from one end of a corresponding line of travel to the other end of the corresponding line of travel. Additional details corresponding to modulating the sub-beam intensities are provided with respect to Figures 3A-G.

[0047] In various embodiments, the 2D grids described herein are rectangular grids. In other embodiments, the 2D grids are of any shape. In one embodiment, a first axis of the 2D sub-beam grid is determined by the index of the leaf pairs along one axis of the MLC, and a second axis of the 2D grid is along the line of movement of the leaf pairs.

[0048] The processing logic of block 506 can deliver multiple independent 2D sub-beam intensity patterns from multiple gantry angles. In one embodiment, the multiple independent 2D sub-beam intensity patterns can be delivered from multiple gantry angles while the gantry moves continuously. In one embodiment, each of the multiple leaf pairs changes direction when delivering a fluence pattern for each subsequent gantry angle.

[0049] In one embodiment, the processing logic can constrain the movement of multiple leaf pairs used to deliver a 2D fluence pattern from a particular gantry angle to occur in less than a preselected time period (as described with respect to FIGS. 3D-F). In one embodiment, the processing logic can center the movement of leaf pairs for a particular gantry angle within a preselected time period (as described with respect to FIGS. 3A-F) less than the preselected time period. In one embodiment, a first leaf of a leaf pair that follows a second leaf of the leaf pair when delivering an intensity pattern from a particular gantry angle does not reach the end of its movement until it reverses direction to deliver the intensity pattern for the subsequent gantry angle (e.g., a leaf pair that does not have to wait for the other leaf pair to finish moving before reversing direction).

[0050] In one embodiment, the continuous motion of the gantry can be a helical motion. For example, the processing logic can continuously rotate the gantry, where a 2D sub-beam intensity pattern for a particular gantry angle is approximated by delivering an intensity pattern on a small arc. As used herein, a "small arc" can refer to a partial arc of a full gantry rotation that is small enough that it can be treated as a single gantry angle for purposes of planning the intended dose distribution. In one embodiment, a "small arc" can refer to approximately 7 degrees around a full gantry rotation. In other embodiments, other arc sizes can be used to deliver a one-dimensional beamlet intensity pattern.

[0051] In one embodiment, the processing logic moves the target axially through the center of the gantry via an axial support (e.g., treatment couch), and the gantry and axial support move simultaneously during irradiation of the target to perform the helical delivery. In one embodiment, the helical pitch during irradiation of the target is 0.5 or greater. In other embodiments, other helical pitches greater or smaller than 0.5 can be used.

[0052] 5B is a flow chart illustrating a method 501 for binary MLC sending with field width per leaf, according to an embodiment. In general, the method 501 can be performed by processing logic that can include hardware (e.g., a processing device, circuitry, dedicated logic, programmable logic, microcode, hardware of a device, etc.), software (e.g., instructions running or executed on a processing device), or a combination thereof. In some embodiments, the method 501 can be performed by processing logic of the radiation therapy system 800 of FIG. 1A.

[0053] 5B, method 501 may begin at block 503 with processing logic determining a plurality of radiation beam delivery location sections to include MLC leaf control instructions while the radiation beam is active. In one embodiment, as described herein, each of the plurality of radiation beam delivery location sections corresponds to a range of radiation beam positions (e.g., along an arc of a gantry of a radiation therapy system) over a discrete time interval. For example, the radiation beam delivery location sections (e.g., projections) may correspond to radiation beams delivered from at least one of different positions or different directions.

[0054] In other words, a location section can be considered to be a location node where the LINAC can deliver a radiation therapy beam in a particular direction. A location section can include a range of locations (e.g., a zone). For example, an arc in a helical therapy delivery system can be divided into multiple separate location sections (e.g., where each location section includes several angles around the arc). In one embodiment, a location section can include approximately 7 degrees around the arc (e.g., 7 degrees of gantry rotation). In other non-helical embodiments, a location section can be defined with respect to three-dimensional space. In one embodiment, the different directions remain constant, but the different locations follow a linear trajectory that sweeps the radiation beam over the length of the treatment target. In one embodiment, the different directions are not coplanar.

[0055] At block 505, the processing logic generates a plurality of apertures for each of the plurality of radiation beam delivery location sections, each of the plurality of apertures corresponding to one of the plurality of leaf pairs of the MLC. Advantageously, each of the plurality of apertures for each of the plurality of location sections can correspond to a different width. For example, in one embodiment, two or more of the plurality of apertures correspond to different widths within the same location section. In one embodiment, the plurality of apertures conform to a contour of the treatment object, back projected along the radiation beam onto the MLC, and within a maximum range of movement of the plurality of leaf pairs in the MLC.

[0056] At block 507, the processing logic generates a plurality of leaf open time portions for each of the plurality of radiation beam delivery location sections, each of the plurality of leaf open time portions corresponding to one of the plurality of leaf pairs of the MLC. In one embodiment, the leaf open time portions are discrete amounts of time less than the discrete time interval. In another embodiment, the leaf open time portions can be discrete amounts of time equal to the discrete time interval. Advantageously, the leaf open time portions allow each of the plurality of leaf pairs to be open for a different amount of time during the discrete time interval. For example, in this embodiment, two or more of the plurality of leaf open time portions during the discrete time interval can be different.

[0057] In block 509, the processing logic causes the processing device to control the multiple leaf pairs of the MLC such that each leaf pair of the multiple leaf pairs is open to a corresponding aperture of the multiple apertures for a corresponding leaf open time portion of the multiple leaf open time portions during the discrete time interval corresponding to the range of radiation beam positions while the radiation beam of the radiation therapy system is active. In one embodiment, the treatment beam is active during the entire discrete time interval (e.g., when the LINAC passes through the position section).

[0058] In one embodiment, the open time portions of the multiple leaves create overlapping radiation fields of different intensities that combine to provide an intensity-modulated fluence field that is delivered to the treatment target. Advantageously, the above operations allow the radiation therapy delivery system to effectively time modulate the radiation therapy beam while precisely conforming to the contours of the target site.

[0059] 6 illustrates an example of a system 600 capable of executing a set of instructions to cause the system to perform any one or more of the methods discussed herein. In alternative implementations, the machine may be connected (e.g., networked) to other machines in a LAN, an intranet, an extranet, and / or the Internet. Each of the systems may operate in the capacity of a server or a client machine in a client / server network environment, as a peer machine in a peer-to-peer (or distributed) network environment, or as a server or client machine in a cloud computing infrastructure or environment.

[0060] A system is a machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be performed by the machine. Moreover, although a single machine is illustrated, the term "machine" shall be interpreted to include a collection of machines that individually or collectively execute a set (or sets) of instructions to perform any one or more of the methods discussed herein.

[0061] As described below and shown in FIG. 6, the system 600 may include an imaging system 605, a treatment planning system 610, and a treatment delivery system 615. The imaging system 605 may be any system capable of generating medical diagnostic images of a patient that can be used for subsequent medical diagnosis, treatment planning, treatment simulation, and / or treatment delivery. For example, the imaging system 605 may be a computed tomography (CT) system, a magnetic resonance imaging (MRI) system, a positron emission tomography (PET) system, a combination of such systems, or the like. For ease of explanation, the imaging system 605 may be described below in relation to an X-ray imaging modality. In other embodiments, other imaging modalities may be used, such as those discussed above.

[0062] In one embodiment, the imaging diagnostic system 605 includes an imaging source 620 for generating an imaging beam (e.g., X-rays) and an imaging detector 630 for detecting and receiving the beam generated by the imaging source 620 or a secondary beam or emission stimulated by the beam from the imaging source (such as an MRI or PET scan).

[0063] In one embodiment, the imaging source 620 and the imaging detector 630 can be coupled to a digital processing system 625 to control the imaging operations and process the image data. In one embodiment, the diagnostic imaging system 605 can receive imaging commands from the treatment delivery system 615 and / or the treatment planning system 610.

[0064] The imaging diagnostic system 605 includes a bus or other means 680 for transferring data and commands between the digital processing system 625, the imaging source 620, and the image detector 630. The digital processing system 625 can include one or more general-purpose processors (e.g., microprocessors), special-purpose processors such as digital signal processors (DSPs), or other types of processing devices such as controllers or field programmable gate arrays (FPGAs). The digital processing system 625 can also include other components (not shown), such as memory, storage, network adapters, and the like. The digital processing system 625 can be configured to generate digital diagnostic images in a standard format, such as, for example, the Digital Imaging and Communications in Medicine (DICOM) format. In other embodiments, the digital processing system 625 can generate other standard or non-standard digital image formats. The digital processing system 625 can transmit the diagnostic image files (e.g., the DICOM formatted files mentioned above) to the therapy delivery system 615 via a data link 683, which can be, for example, a direct link, a local area network (LAN) link, or a wide area network (WAN) link such as the Internet. Additionally, information transferred between systems can be pulled or pushed over the communications medium connecting the systems, such as in remote diagnosis or treatment planning configuration, in which a user can utilize embodiments of the present disclosure to diagnose or treat a patient despite the existence of a physical separation between the system user and the patient.

[0065] In one embodiment, the treatment delivery system 615 includes a therapeutic and / or surgical radiation source 660 for administering a prescribed radiation dose to a target volume according to a treatment plan. The treatment delivery system 615 may also include an imaging system 665 performing computed tomography (CT), such as cone beam CT, and the images generated by the imaging system 665 may be two-dimensional (2D) or three-dimensional (3D).

[0066] The treatment delivery system 615 may also include a digital processing system 670 for controlling the radiation source 660, receiving and processing data from the diagnostic imaging system 605 and / or the treatment planning system 610, and controlling a patient support device such as a treatment couch 675. The digital processing system 670 may be connected to or part of a camera feedback system. The digital processing system 670 may be configured to perform any of the operations described herein. The digital processing system 670 may include a processing device representing one or more general purpose processors (e.g., microprocessors), special purpose processors such as digital signal processors (DSPs), or other types of devices such as controllers or field programmable gate arrays (FPGAs). The processing devices of the digital processing system 670 may be configured to execute instructions to perform the operations described herein.

[0067] In one embodiment, the digital processing system 670 includes a system memory, which may include random access memory (RAM) or other dynamic storage device coupled to the processing device for storing information and instructions executed by the processing device. The system memory may also be used to store temporary variables or other intermediate information during execution of instructions by the processing device. The system memory may include read only memory (ROM) and / or other static storage device for storing static information and instructions for the processing device.

[0068] The digital processing system 670 may also include a storage device, which represents one or more storage devices (e.g., magnetic disk drives or optical disk drives) for storing information and instructions. The storage devices may be used to store instructions for performing the treatment delivery steps discussed herein. The digital processing system 670 may be coupled to the radiation source 660 and the treatment couch 675 by a bus 692 or other type of control and communication interface.

[0069] In one embodiment, the treatment delivery system 615 includes an input device 678 and a display 677 connected to the digital processing system 670 via bus 692. The display 677 can display trend data identifying the rate of target motion (e.g., the rate of motion of the target volume during treatment). The display can also display the patient's current radiation exposure and the patient's projected radiation exposure. The input device 678 can allow the clinician to adjust parameters of the treatment implementation plan during treatment.

[0070] Treatment planning system 610 includes a processing device 640 for generating and modifying treatment plans and / or simulation plans. Processing device 640 may represent one or more general-purpose processors (e.g., microprocessors), special-purpose processors such as digital signal processors (DSPs), or other types of devices such as controllers or field programmable gate arrays (FPGAs). Processing device 640 may be configured to execute instructions for performing the simulation generation and / or treatment planning operations discussed herein.

[0071] The treatment planning system 610 can also include a system memory 635, which can include random access memory (RAM) or other dynamic storage device coupled to the processing device 640 by the bus 686 for storing information and instructions executed by the processing device 640. The system memory 635 can also be used to store temporary variables or other intermediate information during execution of instructions by the processing device 640. The system memory 635 can also include a read only memory (ROM) and / or other static storage device coupled to the bus 686 for storing static information and instructions for the processing device 640.

[0072] Treatment planning system 610 may also include storage 645, which represents one or more storage devices (e.g., magnetic disk drives or optical disk drives) coupled to bus 686 for storing information and instructions. Storage 645 may be used to store instructions for performing the treatment planning steps discussed herein.

[0073] The processing device 640 may also be coupled to a display device 650, such as a cathode ray tube (CRT) or liquid crystal display (LDC), for displaying information (e.g., a 2D or 3D representation of the VOI) to a user. An input device 655, such as a keyboard, may be coupled to the processing device 640 for communicating information and / or command selections to the processing device 640. One or more other user input devices (e.g., a mouse, trackball, or cursor direction keys) may also be used to communicate directional information and select commands for processing device 640 and to control cursor movement on the display 650.

[0074] The treatment planning system 610 can share a database (e.g., data stored in storage 645) with a treatment delivery system, such as treatment delivery system 615, so that it does not need to be exported from the treatment planning system prior to treatment delivery. The treatment planning system 610 can be linked to the treatment delivery system 615 via a data link 690, which in one embodiment can be a direct link, a LAN link, or a WAN link.

[0075] It should be noted that if the data links 683, 686, and 690 are implemented as LAN or WAN connections, any of the diagnostic imaging system 605, the treatment planning system 610, and / or the treatment delivery system 615 may be in distributed locations such that the systems may be physically separate from one another, or any of the diagnostic imaging system 605, the treatment planning system 610, and / or the treatment delivery system 615 may be integrated with one or more other systems.

[0076] From the foregoing description, it will be apparent that aspects of the present disclosure may be embodied at least in part in software. That is, the techniques may be executed in a computer system or other data processing system in response to, for example, a processing device 625, 640, or 670 (see FIG. 6) executing sequences of instructions contained in a memory. In various implementations, hardware circuitry may be used in combination with software instructions to implement the present disclosure. Thus, the techniques are not limited to any specific combination of hardware circuitry and software, or to any particular source of instructions executed by a data processing system. Additionally, throughout this specification, various functions and operations may be described as being performed or caused by software code for ease of explanation. However, those skilled in the art will recognize that such expressions mean that the functions result from execution of the code by the processing device 625, 640, or 670.

[0077] A machine-readable medium can be used to store software and data that, when executed by a general-purpose or special-purpose data processing system, causes the system to perform various methods of the present disclosure. The executable software and data can be stored in various locations, including, for example, system memory and storage, or any other device capable of storing at least one of a software program or data. Thus, a machine-readable medium can include any mechanism that provides (i.e., stores) information in a form accessible by a machine (e.g., a computer, a network device, a personal digital assistant, a manufacturing tool, any device having a set of one or more processors, etc.). For example, a machine-readable medium includes a read-only memory (ROM), a random access memory (RAM), a magnetic disk storage medium, an optical storage medium, a flash memory device, and other recordable / non-recordable media. A machine-readable medium can be a non-transitory computer-readable storage medium.

[0078] As is clear from the above discussion, unless otherwise stated, terms such as "receive," "place," "execute," "emit," "cause," or the like, may refer to the operations and processes of a computer system or similar electronic computing device that manipulates and converts data represented as physical (e.g., electronic) quantities in the registers and memory of the computer system into other data similarly represented as physical quantities in the memory or registers of the computer system or other such information storage or display devices. Implementations of the methods described herein may be implemented using computer software. When written in a programming language that conforms to an approved standard, instruction sequences designed to implement the methods may be compiled to run on a variety of hardware platforms and to interface with a variety of operating systems. Furthermore, embodiments of the present invention are not described with reference to any particular programming language. It will be understood that a variety of programming languages ​​may be used to implement embodiments of the present invention.

[0079] It should be noted that the methods and apparatus described herein are not limited to use in medical diagnostic imaging and therapy. In another embodiment, the methods and apparatus described herein can be used in applications outside the medical technology field, such as industrial imaging and non-destructive testing of materials. In such applications, for example, "treatment" can generally refer to the performance of actions controlled by a treatment planning system, such as the application of a beam (e.g., radiation, sound, etc.), and "target" can refer to a non-anatomical object or region.

[0080] In the foregoing specification, embodiments of the invention have been described with respect to specific examples. It will be apparent, however, that various modifications and changes can be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. 1. A method of operating a radiation therapy system to deliver a radiation dose, comprising: shaping a radiation beam directed at a target through an aperture between a leaf pair of complementary leaves of a collimator mounted on the gantry while a gantry of the radiation therapy system moves sequentially through a series of position sections; modulating, by a processing device, sub-beam intensities of the radiation beam across a plurality of sub-beams that subdivide a fluence field into a two-dimensional (2D) grid, the modulating of the sub-beam intensities comprising: each of said leaf pairs moving together in a first direction in a first position section of said series of position sections; each of the leaf pairs moving together in a second direction opposite to the first direction in a second position section contiguous to the first position section; and modulating the movement of the leaf pairs to alternate between: delivering a two-dimensional (2D) sub-beam intensity pattern while the gantry moves sequentially through the series of position sections; A method of operating a radiation therapy system, comprising:

2. 2. The method of claim 1 , further comprising the step of continuously rotating the gantry, wherein the 2D sub-beam intensity pattern for a particular gantry angle is approximated by delivering the 2D sub-beam intensity pattern onto a particular position section that includes the particular gantry angle.

3. 2. The method of claim 1 , wherein the collimator is a multi-leaf collimator (MLC) including multiple leaf pairs, a first axis of the 2D grid is along a direction perpendicular to a line of movement of the leaf pairs and a second axis of the 2D grid is along the line of movement of the leaf pairs, and modulating the sub-beam intensities includes modulating a speed of movement of the leaf pairs as they move in a single pass from one end of the line of movement to the other end of the line of movement.

4. The method of claim 3 , wherein each of the plurality of leaf pairs changes its direction of movement in each successive position section.

5. The method of claim 1, further comprising the step of: the gantry moving through a first position section of the series of position sections over a first discrete time interval, and constraining movement of the leaf pair during the first position section such that the 2D sub-beam intensity pattern is delivered within the first discrete time interval.

6. 10. The method of claim 1, further comprising axially moving the target through a center of the gantry via an axial support, the gantry and the axial support moving simultaneously during irradiation of the target to perform helical delivery.

7. The method of claim 6 , wherein the helical pitch is greater than 0.

5.

8. 1. A system for delivering a radiation dose, comprising: a gantry that moves continuously through a series of position sections around the target to be irradiated; a radiation source mounted to the gantry and directed inwardly toward the target; a collimator mounted to the gantry in front of the radiation source, the collimator shaping a radiation beam directed at the target through an opening between a pair of complementary leaves of the collimator; Equipped with The collimator modulates sub-beam intensities of the radiation beam across a plurality of sub-beams that subdivide a fluence field into a two-dimensional (2D) grid, and modulating the sub-beam intensities comprises: each of said leaf pairs moving together in a first direction in a first position section of said series of position sections; each of the leaf pairs moving together in a second direction opposite to the first direction in a second position section contiguous to the first position section; and modulating the movement of the leaf pairs to alternate between: two-dimensional (2D) sub-beam intensity patterns are delivered while the gantry moves sequentially through the series of position sections; the collimator is a multi-leaf collimator (MLC) including a plurality of the leaf pairs, a first axis of the 2D grid is aligned orthogonal to a line of motion of the leaf pairs, and a second axis of the 2D grid is aligned along the line of motion of the leaf pairs; The system, wherein modulating the sub-beam intensities includes modulating a speed of movement of the leaf pair as the leaf pair moves in a single pass from one end of the line of movement to the other end of the line of movement.

9. The gantry rotates continuously and the 2D sub-beams for a particular gantry angle are The intensity pattern is determined by the 2D sub-scan over a particular position section that includes the particular gantry angle.

9. The system of claim 8, wherein the beam intensity pattern is approximated by transmitting a beam intensity pattern.

10. The system described in claim 8, wherein the gantry moves through a first position section of the series of position sections over a first discrete time interval, and the system constrains movement of the leaf pair during the first position section such that the 2D sub-beam intensity pattern is delivered within the first discrete time interval.

11. The system described in claim 8, wherein each of the plurality of leaf pairs changes the direction of movement of each successive position section.

12. 10. The system of claim 8, further comprising an axial support that moves the target axially through a center of the gantry, the gantry and the axial support moving simultaneously during irradiation of the target to perform helical delivery.

13. The system of claim 12 , wherein the helical pitch is greater than 0.

5.

14. The system of claim 8 , wherein the system is a helical radiotherapy delivery system.

15. The system of claim 8 , wherein the system is a robot-based LINAC radiation therapy system.

16. The system of claim 8 , wherein the system is a gantry-based radiation therapy delivery system.

17. when executed by a processing device of a radiation therapy delivery system, shaping a radiation beam directed at a target through an aperture of a leaf pair of complementary leaves of a collimator mounted on the gantry while a gantry of the radiation therapy system moves sequentially through a series of position sections; Modulating, by the processing device, sub-beam intensities of the radiation beam across a plurality of sub-beams that subdivide a fluence field into a two-dimensional (2D) grid, the modulating of the sub-beam intensities comprising: each of said leaf pairs moving together in a first direction in a first position section of said series of position sections; each of the leaf pairs moving together in a second direction opposite to the first direction in a second position section contiguous to the first position section; and modulating the movement of complementary leaves of said leaf pairs to alternate between: delivering a two-dimensional (2D) sub-beam intensity pattern while the gantry moves sequentially through the series of position sections; and instructions for causing the processing device to: a first axis of the 2D grid is along a direction perpendicular to a line of movement of the leaf pairs and a second axis of the 2D grid is along the line of movement of the leaf pairs, and modulating the sub-beam intensities includes modulating a speed of movement of the leaf pairs as the leaf pairs move in a single pass from one end of a line of movement to the other end of the line of movement.

18. 20. The non-transitory computer-readable medium of claim 17, wherein the processing device further further continuously rotates the gantry such that the 2D sub-beam intensity pattern for a particular gantry angle is approximated by delivering the 2D sub-beam intensity pattern onto a particular position section that includes the particular gantry angle.

19. A non-transitory computer-readable medium as described in claim 17, wherein each of the plurality of leaf pairs changes its respective direction of movement in each successive position section.

20. A non-transitory computer-readable medium as described in claim 17, wherein the gantry moves through a first position section of the series of position sections over a first discrete time interval, and the processing device further constrains movement of the leaf pair during the first position section such that the 2D sub-beam intensity pattern is delivered within the first discrete time interval.

21. 20. The non-transitory computer readable medium of claim 17, further comprising: moving the target axially through a center of the gantry via an axial support, the gantry and the axial support moving simultaneously during irradiation of the target to perform helical delivery.

22. 22. The non-transitory computer readable medium of claim 21, wherein the helical pitch is greater than 0.5.

Images