Method for saturation correction and dynamic gain configuration, and device for implementing the same

Abstract

To address the necessity of an alternative system and method for operating a dual energy ST system for overcoming a narrow dynamic range of the conventional flat panel detector.SOLUTION: Saturation in at least one saturated ray is corrected by a method including the steps of: identifying a saturated ray corresponding to a first ray of a radiation source received at a radiation detector after passing through a reference point during a current view of the radiation detector; identifying at least one non-saturated ray corresponding to a second ray of the radiation source received at the radiation detector; and responsive to the identifying step, adjusting a value for the saturated ray based on a value of the at least one non-saturated ray. The non-saturated ray can be a ray from an adjacent view of a current rotation, an adjacent view of a previous or subsequent rotation, or a conjugate ray. Methods of selecting a gain level to avoid saturation are also disclosed.

Description

Technical Field

[0005] , , ,

[0004] , ,

[0001] The present disclosure relates to imaging that utilizes a combination of low-energy radiation (e.g., kilovolts (kV)) and high-energy radiation (e.g., megavolts (MV)) for improved imaging including computed tomography (CT) scans.

Background Art

[0002] In dual-energy CT scans, radiation beams having different energies are used for the scan. In a kilovolt (kV) switching imaging protocol, the radiation voltage is rapidly alternated between low energy (e.g., 80 kV) and high energy (e.g., 140 kV). As a result, dual-energy data registered almost simultaneously can be decomposed, and high-quality images can be generated.

[0003] Various dual-energy CT systems include flat panel detectors configured to detect radiation beams. However, such flat panel detectors may have a narrow dynamic range. For example, conventional flat panel detectors have 16 bits compared to 20 or 24 bits commonly used in CT detectors. As a result of the narrow dynamic range, the detector may saturate in a low-attenuation path by a high-energy pulse or a low-energy pulse.

[0004] Therefore, there may be a need for alternative systems and methods for operating dual-energy CT systems to overcome the narrow dynamic range of flat panel detectors.

Summary of the Invention

[0005] In the first embodiment, a method for correcting the saturation of at least one saturation ray includes the steps of: identifying a saturation ray corresponding to a first ray of a radiation source received by the radiation detector after passing a reference point during the current view of the radiation detector; identifying at least one unsaturated ray corresponding to a second ray of the radiation source received by the radiation detector after passing a reference point during the previous view of the radiation detector, or a third ray of the radiation source received by the radiation detector after passing a reference point during the next view of the radiation detector; and adjusting the value of the saturation ray based on the value of at least one unsaturated ray in response to the identifying step. Each of the previous view and the next view of the radiation detector is adjacent to the current view, and the radiation source has a first energy for the current view and a second energy for the previous and next views, the second energy being different from the first energy.

[0006] In another embodiment, a method for correcting the saturation of at least one saturated ray includes the steps of: identifying a saturated ray corresponding to a first ray of a radiation source received by the radiation detector after passing a reference point during the current view of the radiation detector; identifying at least one unsaturated ray corresponding to a second ray of a radiation source received by the radiation detector after passing a reference point during the conjugate view; and adjusting the value of the saturated ray based on the value of the at least one unsaturated ray in response to the identifying step. The second ray is adjacent to a third ray rotated 180° with respect to the first ray.

[0007] According to another embodiment, a method for operating a dual-energy imaging system includes the steps of: emitting a first plurality of photons from a radiation source at a first energy level; receiving at least a portion of the first plurality of photons with a radiation detector; amplifying a first signal indicating a first quantity of at least a portion of the first plurality of photons received by the radiation detector by a first gain level of the radiation detector and outputting it from the radiation detector; emitting a second plurality of photons from a radiation source at a second energy level; receiving at least a portion of the second plurality of photons with a radiation detector; and amplifying a second signal indicating at least a portion of the second plurality of photons received by the radiation detector by a second gain level of the radiation detector and outputting it from the radiation detector. The first and second gain levels are selected to avoid saturation of the first signal corresponding to the first plurality of photons and the second signal corresponding to the second plurality of photons.

[0008] Features described and / or illustrated in reference to one embodiment may be used in the same or similar manner, and / or in combination with, or instead of, features of the other embodiments in one or more other embodiments.

[0009] This description of the present invention does not limit in any way the words used in the claims or the claims or the scope of the invention. The words used in the claims have all of their full, ordinary meanings.

[0010] The accompanying drawings incorporated herein and constituting part thereof illustrate embodiments of the present invention and, together with the above general description of the invention and the following detailed description, are useful in illustrating embodiments of the invention. It will be understood that the element boundaries shown in the drawings (e.g., boxes, groups of boxes, or other shapes) represent one embodiment of the boundary. In some embodiments, one element may be designed as multiple elements, and multiple elements may be designed as one element. In some embodiments, an element shown as an internal component of another element may be implemented as an external component, and vice versa. Furthermore, elements may not be drawn to scale. [Brief explanation of the drawing]

[0011] [Figure 1] This specification describes an exemplary radiotherapy device according to one or more embodiments. [Figure 2] This is an illustrative diagram of a radiotherapy delivery device according to one or more embodiments described herein. [Figure 3] This is an exemplary device configuration according to one or more embodiments described herein. [Figure 4] This is a flowchart illustrating an exemplary method for performing saturation correction in a saturated ray according to one or more embodiments shown and described herein. [Figure 5] Another exemplary device configuration according to one or more embodiments described herein. [Figure 6] This is a flowchart of another exemplary method for performing saturation correction in a saturated ray according to one or more embodiments shown and described herein. [Figure 7] Another exemplary device configuration according to one or more embodiments described herein. [Modes for carrying out the invention]

[0012] The following includes definitions of exemplary terms used throughout this disclosure. The singular and plural forms of all terms correspond to their respective meanings.

[0013] As used herein, “components” may be defined as parts of hardware, parts of software, or a combination thereof. Parts of hardware may include at least a processor and parts of memory, where memory includes instructions to be executed. Components may be associated with a device.

[0014] Although described in various embodiments as “dual scan” or “first scan” and “second scan,” the image acquisition methods described herein may include or be used in other ways, such as a continuous scan (e.g., the patient support moves longitudinally through the gantry bore while the source traces a helical trajectory around the central axis), a discontinuous stop-and-reverse circular scan with incremental longitudinal movement of the patient support, or a step-and-shoot circular scan. Therefore, as used herein, the term “dual scan” refers to a scan that includes multiple rotations, which may be continuous or discontinuous.

[0015] As used herein, “logic” is synonymous with “circuit” and includes, but is not limited to, hardware, firmware, software, and / or combinations thereof for performing a function or operation. For example, depending on the desired application or need, logic may include software-controlled microprocessors, application-specific integrated circuits (ASICs), or other programmed logic devices and / or controllers. Logic may also be fully embodied as software.

[0016] As used herein, “processor” includes, but is not limited to, one or more substantially any number of processor systems or standalone processors, such as microprocessors, microcontrollers, central processing units (CPUs), and digital signal processors (DSPs), in any combination. A processor may be associated with various other circuits that support the operation of the processor, such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), clocks, decoders, memory controllers, or interrupt controllers. These support circuits may be inside or outside the processor or its associated electronic package. The support circuits communicate operationally with the processor. Note that the support circuits do not necessarily need to be shown separately from the processor in block diagrams or other drawings.

[0017] As used herein, “signal” includes, but is not limited to, analog or digital signals, one or more computer instructions, or one or more electrical signals including bits or bitstreams.

[0018] As used herein, “software” includes, but is not limited to, one or more computer-readable and / or executable instructions that cause a computer, processor, logic, and / or other electronic device to function, operate, and / or perform in a desired manner. Instructions may be embodied in various forms, such as routines, algorithms, modules, or programs, which may include separate applications or code from dynamically linked sources or libraries.

[0019] While illustrative definitions have been provided above, the applicant intends that the broadest and most reasonable interpretation consistent with this specification be used for these and other terms.

[0020] According to one or more embodiments, the saturation of at least one saturated ray in the current view is corrected by identifying at least one unsaturated ray corresponding to a subsequent ray of a radiation source received by the radiation detector after passing a reference point, and adjusting the value of the saturated ray based on the value of at least one unsaturated ray. The subsequent ray may be, for example, a ray received by the radiation detector after passing a reference point during the previous view of the radiation detector, during the next view of the radiation detector, or during the conjugate view of the radiation detector, or during the previous or upcoming rotation (at the same or similar angle). In some embodiments, the radiation source has a first energy for the current view and a second energy for the previous view, next view, or conjugate view, where the second energy is different from the first energy. Thus, the value of the saturated ray can be adjusted using data from the adjacent or conjugate view of the unsaturated ray, and a flat panel detector can be used in a dual-energy imaging system despite a narrow dynamic range.

[0021] Furthermore, according to one or more embodiments, the gain value of the radiation detector can be switched in conjunction with the energy switching of the radiation source. In one embodiment, photons are emitted from the radiation source at a first energy level, at least a portion of these photons are received by the radiation detector, and a first signal is output indicating the amount of received photons amplified at the first gain level. The radiation source emits photons at a second energy level, at least a portion of these photons are received by the radiation detector, and a second signal is output indicating the amount of received photons amplified at the second gain level. The first gain level is lower than the second gain level. In one embodiment, the first energy level is lower than the second energy level so that high-energy pulses are detected using a lower gain level compared to low-energy pulses. Thus, the gain level of the detector can be dynamically adjusted based on the expected amount of energy stored in the detector, and can be used in dual-energy imaging systems despite the narrow dynamic range of flat-panel detectors.

[0022] Referring now to FIGS. 1 and 2, a multimodal device 10 is shown. The multimodal device 10 can be associated with and / or integrated into a radiation therapy device (such as that shown in FIG. 2) for various applications, not limited to IGRT, and can be used, for example, as an IGRT providing system. The multimodal device 10 includes a rotatable gantry system called gantry 12, which is supported by a support unit or housing 14 or otherwise accommodated. As used herein, a gantry refers to a gantry system comprising one or more gantries (such as ring arms or C arms) capable of supporting one or more radiation sources and / or associated detectors while rotating around a target. The rotatable ring gantry 12 may be capable of rotating at 10 revolutions per minute (rpm) or more.

[0023] The rotatable gantry 12 defines a gantry bore 16 and is capable of moving and positioning a patient for imaging and / or treatment. According to one embodiment, the rotatable gantry 12 is configured as a slip ring gantry that provides continuous rotation of a radiation source and associated radiation detector(s), while providing sufficient bandwidth for high-quality imaging data received by the detector(s). A slip ring gantry does not require the gantry to be rotated in alternating directions for winding and unwinding cables that transmit power and signals associated with the device. Such a configuration enables continuous helical computed tomography including CBCT even when incorporated into an IGRT system.

[0024] The patient support 18 is disposed adjacent to the rotatable gantry 12 and is configured to support a patient, generally in a horizontal position, for longitudinal movement into and within the rotatable gantry 12. The patient support 18 can move the patient, for example, in a direction perpendicular to the rotation plane of the gantry 12 (along or parallel to the rotation axis of the gantry 12). The patient support 18 can be operatively coupled to a patient support controller for controlling the movement of the patient and the patient support 18. The patient support controller can be synchronized with the rotatable gantry 12 and the radiation source attached to the rotatable gantry to rotate about the longitudinal axis of the patient according to the indicated imaging plan and / or treatment plan. The patient support can also be moved within a limited range of up, down, left, and right when it enters the bore 16, and the position of the patient can be adjusted to enable optimal treatment. The axes x, y, and z are shown. As viewed from the front of the gantry 12, the x-axis is horizontal and points to the right, the y-axis points to the gantry plane, and the z-axis is vertical and points up. The x-axis, y-axis, and z-axis follow the right-hand rule.

[0025] As shown in FIG. 2, the multimodal device 10 includes a radiation source 30 coupled to or otherwise supported by the rotatable gantry 12. In this embodiment, the radiation source 30 is an imaging radiation source and emits a radiation beam (generally shown as 32) to generate a high-quality image. In this embodiment, the imaging radiation source is an x-ray source 30 configured as a kilovolt (kV) source (e.g., a clinical x-ray source having an energy level in the range of about 20 kV to about 150 kV). In one embodiment, the low-energy radiation source includes a maximum kiloelectron volt (keV) peak photon energy of 150 keV. The imaging radiation source can be any type of transmission source suitable for imaging. For example, the imaging radiation source can be, for example, an x-ray generation source. References to x-rays, x-ray imaging, x-ray imaging sources, etc. in this specification are illustrative of particular embodiments. Other imaging transmission sources can be used interchangeably in various other embodiments.

[0026] In various embodiments, the radiation source 30 is rapidly switched between a first voltage (e.g., about 80 kV) and a second voltage (e.g., about 140 kV) between projection views, thereby providing dual energy data registered almost simultaneously. In embodiments, the voltage of the radiation source 30 is switched from a first voltage to a second voltage between two consecutive projection views such that the current view at the first voltage has the previous adjacent view and the next adjacent view at the second voltage. In embodiments, the voltage of the radiation source 30 is switched according to a predetermined sequence (e.g., a repeating sequence such as three pulses at the first voltage followed by one pulse at the second voltage).

[0027] The X-ray detector 34 (e.g., a two-dimensional flat-panel detector) is coupled to or otherwise supported by the rotatable gantry 12. The X-ray detector 34 is positioned to receive radiation from the X-ray source 30 and can rotate with the X-ray source 30. It will be understood that the X-ray detector 34 can take on several configurations without departing from the scope of the disclosed art. As shown in Figures 1 and 2, the X-ray detector 34 can be configured as a flat-panel detector (e.g., a multi-row flat-panel detector). The detector 34 can detect or otherwise measure the amount of radiation that has not been attenuated and can therefore estimate the amount that has actually been attenuated by the patient or associated patient ROI (compared to the initially generated amount). The detector 34 can detect or collect attenuation data from different angles as the radiation source 30 rotates around the patient and radiates radiation toward the patient.

[0028] Figures 1 and 2 show a multimodal apparatus 10 in which a radiation source 30 is mounted on a ring gantry 12, but other embodiments may include other types of rotatable imaging devices, such as C-arm gantry and robotic arm-based systems. In a gantry-based system, the gantry rotates the imaging radiation source 30 around an axis passing through an isocenter. The gantry-based system includes a C-arm gantry, in which the imaging radiation source 30 is cantilevered over an axis passing through an isocenter and rotates around that axis. The gantry-based system further includes a ring gantry, e.g., a rotatable gantry 12, which has a generally toroidal shape through which the patient's body extends via a ring / toroidal bore, in which the imaging radiation source 30 is mounted on the outer circumference of the ring and rotates around an axis passing through an isocenter. In some embodiments, the gantry 12 rotates continuously. In other embodiments, the gantry 12 utilizes a cable-based system that repeatedly rotates and reverses.

[0029] A collimator or beamformer assembly (generally shown as 36) is positioned relative to an X-ray source 30 and selectively controls and adjusts the shape of the radiation beam 32 emitted by the X-ray source 30 to selectively expose a portion or region of the active area of ​​the X-ray detector 34. The beamformer can also control how the radiation beam 32 is positioned on the X-ray detector 34. In one embodiment, the beamformer 36 may have one degree of freedom / dimensional movement (e.g., to create thinner or thicker slits). In another embodiment, the beamformer 36 may have two degrees of freedom / dimensional movement (e.g., to create rectangles of varying sizes). In yet another embodiment, the beamformer 36 may be capable of various other dynamically controlled shapes, including, for example, parallelograms. All of these shapes can be dynamically adjusted during scanning. In some embodiments, the cutoff portion of the beamformer can be rotated and / or translated.

[0030] The beamformer 36 can be configured in various ways to adjust the shape of the radiation beam 32 emitted by the X-ray source 30. For example, the beamformer 36 can be configured to include a set of jaws or other suitable members that define and selectively adjust the size of the opening through which the radiation beam from the X-ray source 30 can pass parallel to each other. According to one exemplary configuration, the beamformer 36 may include an upper jaw and a lower jaw, which are movable in different directions (e.g., parallel directions) to adjust the size of the opening through which the radiation beam from the X-ray source 30 passes, and to adjust the position of the beam 32 relative to the patient so as to irradiate only the portion of the patient being imaged, for the purpose of optimizing imaging and minimizing the patient's radiation dose.

[0031] As shown in Figure 2, the multimodal apparatus 10 may be integrated with a radiotherapy device including a high-energy radiation source (e.g., MV) 20 coupled to a rotatable gantry 12 or otherwise supported. According to one embodiment, the high-energy radiation source 20 is configured as a therapeutic radiation source, such as a high-energy radiation source used to treat a tumor in a patient in a region of interest. In other embodiments, the high-energy radiation source 20 is also configured as an imaging radiation source, or at least used in that manner. It will be understood that the therapeutic radiation source may be a high-energy X-ray beam (e.g., an X-ray beam of MV), and / or a high-energy particle beam (e.g., an electron beam, a proton beam, or a heavy ion beam such as carbon), or another suitable form of high-energy radiation. In one embodiment, the high-energy radiation source 20 includes a megaelectron volt (MeV) peak photon energy of 1 MeV or greater. In one embodiment, the high-energy X-ray beam has an average energy greater than about 0.8 MeV. In another embodiment, the high-energy X-ray beam has an average energy greater than about 0.2 MeV. In another embodiment, the high-energy X-ray beam has an average energy of approximately 150 keV or more. Generally, the high-energy radiation source 20 has a higher energy level (peak and / or average, etc.) than the low-energy radiation source 30.

[0032] In one embodiment, the high-energy radiation source 20 is a LINAC that generates therapeutic radiation (e.g., MV), and the imaging system includes a separate low-energy radiation source 30 that generates relatively low-intensity, low-energy imaging radiation (e.g., kV). In other embodiments, the therapeutic radiation source 20 may be a radioisotope such as C0-60, which can generally have an energy greater than about 1 MeV. The high-energy radiation source 20 can emit one or more radiation beams (generally shown as 22) toward a region of interest (ROI) within the patient supported on a patient support 18 according to the treatment plan.

[0033] In various embodiments, the high-energy radiation source 20 is used as both a therapeutic radiation source and an imaging radiation source. As will be described in detail below, the radiation sources 20 and 30 can be used in combination to provide higher quality and more useful images. The reference to the therapeutic radiation source 20 herein is to distinguish it from the high-energy radiation source 20, which may be used solely for imaging. However, the reference to the therapeutic radiation source 20 includes embodiments in which the therapeutic radiation source 20 (high-energy radiation source) can be used for therapy and / or imaging. In other embodiments, at least one additional radiation source can be coupled to the rotatable gantry 12 and operated to acquire projection data at a peak photon energy different from the peak photon energies of the radiation sources 20 and 30.

[0034] The multimodal device 10 may include an operator / user interface 48, which the operator of the device 10 can interact with or otherwise control to provide input regarding scan or imaging parameters, etc. The operator interface 48 may include any suitable input device such as a keyboard, mouse, or voice-activated controller. The device 10 may also include a display 52 or other human-readable element to provide output to the operator of the device 10. For example, the display 52 allows the operator to observe reconstructed patient images and other information such as imaging or scan parameters related to the operation of the device 10.

[0035] As shown in Figure 2, the multimodal apparatus 10 includes a controller (generally referred to as 60) operably coupled to one or more components of the apparatus 10. The controller 60 controls the overall function and operation of the apparatus 10, including the supply of power and timing signals to the X-ray source 30 and / or therapeutic radiation source 20, the supply of gain signals to the detector 34, and a gantry motor controller that controls the rotational speed and position of the rotatable gantry 12. It will be understood that the controller 60 may encompass one or more of the following: a patient support controller, a gantry controller, a controller coupled to the therapeutic radiation source 20 and / or X-ray source 30, a beamformer controller, a controller coupled to the detector 24 and / or X-ray detector 34, etc. In one embodiment, the controller 60 is a system controller that can control other components, devices, and / or controllers.

[0036] In various embodiments, the reconfiguration processor 40, operator interface 48, display 52, controller 60, and / or other components can be combined into one or more components or devices.

[0037] The apparatus 10 may include various components, logic, and software. In one embodiment, the controller 60 comprises a processor, memory, and software. A multimodal apparatus and / or radiotherapy system may include various other devices and components (e.g., gantry, radiation source, collimator, detector, controller, power supply, patient support, etc.) that can perform one or more routines or steps related to imaging and / or IGRT for a particular application, where the routine may include imaging, image-based pre-delivery steps, and / or treatment delivery, including the respective device settings, configuration, and / or position (e.g., path / trajectory) that can be stored in memory. Furthermore, the controller(s) may directly or indirectly control one or more devices and / or components according to one or more routines or processes stored in memory. An example of direct control is setting various radiation source or collimator parameters (power, velocity, position, timing, modulation, etc.) related to imaging or treatment. An example of indirect control is transmitting position, path, velocity, etc. to a patient support controller or other peripheral equipment. A hierarchy of various controllers that may be associated with the device may be arranged in any suitable manner to transmit appropriate commands and / or information to the desired devices and components.

[0038] Furthermore, those skilled in the art will understand that the system and method can be implemented in other computer system configurations. Illustrated embodiments of the present invention may be implemented in a distributed computing environment in which specific tasks are performed by local or remote processing units linked via a communication network. For example, in one embodiment, the reconfiguration processor 40 may be associated with a separate system. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. For example, a remote database, a local database, a cloud computing platform, a cloud database, or a combination thereof may be utilized by the device 10.

[0039] The multimodal apparatus 10 can utilize exemplary environments for carrying out various aspects of the present invention, including a computer, which includes a controller 60 (for example, including a processor and memory 44) and a system bus. The system bus can connect system components, including but not limited to memory, to the processor and can communicate with other systems, controllers, components, devices, and the processor. The memory may include read-only memory (ROM), random access memory (RAM), hard drives, flash drives, and any other form of computer-readable media. The memory can store various software and data, including routines and parameters, which may include treatment plans.

[0040] The therapeutic radiation source 20 and / or X-ray source 30 can be operably coupled to a controller 60 configured to control the relative operation of the therapeutic radiation source 20 and the X-ray source 30. For example, the X-ray source 30 can be controlled and operated simultaneously with the therapeutic radiation source 20. In addition, or alternatively, the X-ray source 30 can be controlled and operated sequentially using the therapeutic radiation source 20, depending on the specific treatment plan and / or imaging plan being implemented. For example, in various embodiments, the radiation sources 20 and 30 can be operated so that measurement projection data from the radiation sources 20 and 30 are acquired simultaneously (or essentially / nearly simultaneously, e.g., within about 50 ms of each other) or sequentially (e.g., separated by seconds, minutes, etc.).

[0041] It will be understood that the radiation sources 20, 30 and detectors 24, 34 can be configured to rotate around the patient in several ways during imaging scans and / or therapeutic scans. In one embodiment, continuous helical imaging or helical scanning of patient images can be performed during treatment by synchronizing the movement and exposure of the radiation sources 20, 30 with the longitudinal movement of the patient support 18. In addition to the radiation sources 20, 30 and detectors 24, 34 (e.g., continuous and constant rotation of the gantry with a constant patient movement speed), it will be understood that other modifications can be adopted without departing from the scope of the disclosed art. For example, the rotatable gantry 12 and patient support can be controlled to rotate around the patient supported on the patient support in a "reciprocating" manner (e.g., alternating clockwise and counterclockwise rotations) (rather than continuously as described above), since the support is controlled to move relative to the rotatable gantry 12 (at a constant or variable speed). In another embodiment, a continuous step-and-shoot circular scan alternates between longitudinal movement (stepping) of the patient support 18 and scanning rotation (shooting) by the rotatable gantry 12 until a desired amount is captured. The multimodal device 10 is capable of volume-based and planar-based image acquisition. For example, in various embodiments, the multimodal device 10 can be used to acquire volume images and / or planar images and perform associated processing.

[0042] By utilizing the movement of various other types of radiation sources and / or patient supports, the relative motion between the radiation source and the patient can be realized and projection data can be generated. Discrete motion, continuous but variable / non-constant (including linear and non-linear) motion, velocity, and / or trajectory of the radiation source and / or patient support, and combinations thereof may be used, including in combination with various embodiments of the apparatus 10 described above.

[0043] In one embodiment, the rotation speed of the gantry 12, the speed of the patient support 18, the shape of the beamformer, and / or the detector readout may all be constant during image acquisition. In other embodiments, one or more of these variables may change dynamically during image acquisition and / or treatment.

[0044] In other embodiments, these features can be combined with one or more other image-based actions or procedures, including, for example, patient setup, adaptive treatment monitoring, and treatment planning.

[0045] During image data acquisition, both the radiation source (e.g., source 30) and the detector (e.g., 34) move along an angular path as the gantry 12 rotates. The radiation source 30 and the detector 34 can move synchronously along their respective paths. For example, as shown in Figure 3, if the detector 34 is positioned at positions 303, 305, and 307, data is collected at various positions along the angular path.

[0046] At each of the positions 303, 305, and 307, the detector 34 spends a certain amount of time collecting the appropriate type of data before proceeding to the next view. The data type may be image data I, which is data relating to the cross-section of X-rays passing from the source 30 through the object 26 (sometimes referred to herein as the “scanned object”), or background data B, which is data detected by the detector 34 when the source 30 is powered off. Image data I may be, for example, diagnostic data relating to a patient. However, other data may be obtained in the context of this disclosure. Image data I can be reconstructed using tomography to form a 3D representation of the patient. To detect image data I, the source 30 must be powered on and emit X-rays. Although referred to herein as “emitting X-rays”, it should be understood that the source 30 emits a stream of photons (e.g., light rays) which together are referred to as X-rays or light rays.

[0047] In this embodiment, the radiation source 30 is rapidly switched between a first voltage (e.g., approximately 140 kV) and a second voltage (e.g., approximately 80 kV) between projection views, as shown in Figure 3. In Figure 3, the positions of the radiation source 30 and X-ray detector 34 in the current view 304 are shown in dark gray, and the positions of the radiation source 30 and X-ray detector 34 in the previous and next views are shown with dashed lines. In particular, in the previous view, the radiation source is at position 306 and the X-ray detector is at position 307, and in the next view, the radiation source is at position 302 and the X-ray detector is at position 303. It should be understood that in each view, the radiation source 30 emits multiple rays and the X-ray detector 34 receives multiple rays, but in Figure 3, only a single ray emitted by the radiation source 30 at each position is shown, and other rays are omitted for clarity. Ray C is emitted during the current view, ray P is emitted during the previous view, and ray N is emitted during the next view.

[0048] Each of the illustrated rays C, N, and P passes through a reference point R within the object being scanned 26. In the embodiment shown in Figure 3, the reference point R is located in the peripheral region of the object being scanned 26. The location of the reference point R is not limited to the peripheral region, but it is thought that the attenuation of X-rays by the object being scanned is small and saturation is more likely to occur. Therefore, although the reference point R can be described in various embodiments as being located in the peripheral region, it is thought that the reference point R may be located anywhere in the view. Each of the rays C, N, and P is received by the radiation detector 34 after passing through the reference point R. In various embodiments, the reference point R is configured as the point on the ray closest to the isocenter.

[0049] In the embodiment shown in Figure 3, the voltage switching is interleaved, meaning that radiation at a certain view (e.g., the current view) at the first voltage is followed by radiation at the next view at the second voltage, and that radiation at a certain view at the first voltage precedes radiation at the previous view at the second voltage. In other words, radiation from the radiation source alternates between the first and second voltages. In various embodiments, saturation correction can be performed for at least one saturated ray using unsaturated rays or information from frames from the current and / or next or previous view. Although saturation correction is described herein as using unsaturated rays, it is conceivable that multiple unsaturated rays from the same frame (i.e., unsaturated frames) could be used (e.g., averaged) to correct for saturated rays.

[0050] Figure 4 is a flowchart illustrating exemplary methods of saturation correction using adjacent frames in various embodiments. In the following description of Figures 3 and 4, the current view is described as containing radiation at a first voltage (e.g., about 140 kV), and the previous and next views are described as containing radiation at a second voltage (e.g., about 80 kV). However, it should be understood that the voltages of the current view, previous view, and next view can be reversed depending on the “current view” being referred to. Furthermore, it is conceivable that unsaturated data can come from one or more unsaturated rays adjacent to (e.g., adjacent to) the saturated ray in three-dimensional space, regardless of whether they are located between the same or different rotations, provided that the unsaturated rays have substantially the same path length through the reference point as the saturated ray.

[0051] In this example, the amount of energy received by the X-ray detector 34 at position 305 as a result of ray C (block 500 in Figure 4) exceeds the dynamic range of the X-ray detector 34. As a result of receiving this energy, the controller associated with the X-ray detector 34 determines that the projected ray C is saturated (block 502 in Figure 4). However, the amount of energy received by the X-ray detector 34 as a result of rays P and N (in this example, about 1 / 3 of the amount of energy received by the X-ray detector as a result of ray C) does not exceed the dynamic range of the X-ray detector 34. In block 504 in Figure 4, the controller associated with the X-ray detector 34 identifies the corresponding projected ray from the view before the projection ray C passes through the reference point R (e.g., ray P) and the corresponding projected ray from the next view (e.g., ray N). Based on the amount of energy received by the X-ray detector 34 as a result of rays P and N, the controller determines that the projected rays P and N are not saturated (e.g., "No" in decision block 506). In other words, the controller identifies at least one unsaturated ray from either the front or the next view of the X-ray detector.

[0052] In various embodiments, the determination of whether a given projected ray is saturated may be the result of a controller comparing the output of an X-ray detector in response to the received energy for a given ray with a threshold output value of the X-ray detector. In one embodiment, the controller compares the signal output by the X-ray detector as a result of receiving ray C with the maximum signal output value, and determines that projected ray C is saturated if the controller determines that the signal output by the X-ray detector is equal to the maximum signal output value. Furthermore, the controller compares the signals output by the X-ray detector as a result of receiving ray P and / or ray N with the maximum signal output value, and determines that the corresponding projected ray P or N is not saturated if the controller determines that the signal output by the X-ray detector is less than the maximum signal output value (block 506). In various embodiments, if it is determined that projected ray P and / or N are not saturated (e.g., "no" in block 506), the saturated ray of the current ray C is corrected using data from the corresponding projected ray P and / or N (block 508).

[0053] In one embodiment, while the current ray C is saturated, both the ray P from the previous view and the ray N from the next view are not saturated, and therefore, saturation correction for ray C can be performed using data from both ray P and ray N. However, in another embodiment, the current ray C is saturated, and one of rays P and N is not saturated, while the other is. In such an embodiment, in block 508, data from the corresponding unsaturated projection ray is used for saturation correction, while data from the other corresponding projection ray is ignored for the purpose of saturation correction. For example, in an embodiment where the corresponding projection ray P from the previous view is not saturated and the corresponding projection ray N from the next view is saturated, data from ray P is used for saturation correction, and data from ray N is ignored for the purpose of saturation correction. As another example, in an embodiment where the corresponding projection ray N from the next view is not saturated and the corresponding projection ray P from the previous view is saturated, data from ray N is used for saturation correction, while data from ray P is ignored for the purpose of saturation correction.

[0054] In various embodiments, in block 508, adjacent unsaturated projection data is also used for saturation correction, in addition to data from any unsaturated data from adjacent (e.g., previous or next) views. Such adjacent unsaturated projection data may include adjacent unsaturated rays in the same frame, or corresponding rays in adjacent unsaturated frames of data. In embodiments, “adjacent” means having similar azimuth angles in consecutive rotations. In embodiments where both adjacent (e.g., previous or next) views are saturated (e.g., “yes” in block 506), adjacent unsaturated projection data is used for saturation correction without data from adjacent (e.g., previous or next) views (block 510). In embodiments, the controller takes adjacent unsaturated projection data and any corresponding unsaturated projection rays from the previous or next view as inputs and performs saturation correction using a linear interpolation method or an advanced interpolation method. The saturation correction performed by the controller is effective in adjusting the value of saturated rays based on the value of at least one unsaturated ray.

[0055] In embodiments where adjacent unsaturated rays from the same frame as the saturated ray are used for saturation correction, a simple linear interpolation method can be used. One exemplary linear interpolation method is to average the adjacent unsaturated rays (e.g., (ray 1 + ray 2) * 0.5). In other embodiments, for example, if corresponding rays from adjacent unsaturated frames are used and the rays are emitted at different voltages, a spectrally derived interpolation method with scaling can be used.

[0056] When correcting saturated rays from a different energy using unsaturated rays from a certain energy, the imaging chain, specifically the X-ray spectrum, can be considered, and the unsaturated measurements can be transformed using a correction factor. In one embodiment, the calibrated correction factor is generated by assuming that the projection data of adjacent unsaturated rays are associated with a specific material (e.g., water). Based on the unsaturated data of this assumed material, along with prior knowledge of the imaging chain (e.g., spectra of both high-energy and low-energy radiation), a calibration table can be generated. The adjacent unsaturated rays can then be adjusted based on the values ​​in the calibration table to determine the appropriate value for the saturated rays.

[0057] In another embodiment, the correction factor can be calculated using imaging chain information (e.g., spectrum) and system configuration, and using the image reconstructed in the first pass, virtually generating two projections, one for each energy. The correction factor can then be determined and applied to the values ​​of adjacent unsaturated rays to determine the appropriate values ​​for saturated rays. In various embodiments, the correction factor determination process can be performed several times to improve the accuracy of the correction factor.

[0058] In the embodiments described in Figures 3 and 4, high-voltage and low-voltage pulses are interleaved. This ensures that the energy for the current view is different from the energy for the previous and next views. However, in other embodiments, high-voltage and low-voltage pulses may or may not be interleaved. Therefore, in some such embodiments, saturation correction can be performed using conjugate frames instead of adjacent views.

[0059] In Figure 5, the positions of the radiation source 30 and X-ray detector 34 in the current view (602 and 608, respectively) are shown in dark gray, while the positions of the radiation source 30 and X-ray detector 34 in the conjugate view are shown with dashed lines. Specifically, in the first conjugate view, the radiation source is located at position 606 and the X-ray detector at position 612, and in the second conjugate view, the radiation source is located at position 604 and the X-ray detector at position 610. It should be understood that multiple rays are emitted by the radiation source 30 and received by the X-ray detector 34 in each view, but in Figure 5, only a single ray emitted by the radiation source 30 at each position is shown, and other rays are omitted for clarity. Ray C is emitted during the current view, and rays C1 and C2 are emitted between the conjugate views.

[0060] Each of the illustrated rays C, C1, and C2 passes through a reference point R within the object being scanned 26. In the embodiment shown in Figure 5, the reference point R is located in the peripheral region of the object being scanned 26. Each of the rays C, C1, and C2 is received by the radiation detector 34 after passing through the reference point R. In various embodiments, the reference point R is configured as the point on the ray closest to the isocenter.

[0061] In the embodiment shown in Figure 5, the voltage switching may or may not be interleaved. However, the radiation in the conjugate view is different from the radiation in the current view. The pulse width and tube current remain the same between the current view and the conjugate view. Figure 6 is a flowchart illustrating exemplary methods of saturation correction using conjugate frames according to various embodiments. In the following description of Figures 5 and 6, the current view is described as including radiation at a first voltage (e.g., about 140 kV), and the conjugate view is described as including radiation at a second voltage (e.g., about 80 kV). However, it should be understood that the voltages of the current view and the conjugate view can be reversed depending on the “current view” being referred to.

[0062] In this example, the amount of energy received by the X-ray detector 34 as a result of ray C (block 700 in Figure 6) exceeds the dynamic range of the X-ray detector 34. As a result of receiving this energy, the controller associated with the X-ray detector 34 determines that the ray corresponding to projected ray C is saturated (block 702 in Figure 6). However, the amount of energy received by the X-ray detector 34 as a result of each of the conjugate rays C1 and C2 (in this example, about 1 / 3 of the amount of energy received by the X-ray detector as a result of ray C) does not exceed the dynamic range of the X-ray detector 34. In block 704 in Figure 6, the controller associated with the X-ray detector 34 identifies the corresponding projected rays C1 and C2 from the conjugate view through the reference point R of projected ray C. In this embodiment, the corresponding projected rays are identified based on system placement trigger information, which includes X-ray source trajectory information and X-ray cone beam projection arrangement (e.g., information on how the detector is positioned relative to the source). Based on the amount of energy received by the X-ray detector 34 as a result of rays C1 and C2, the controller determines that the conjugate projection rays C1 and C2 are not saturated (e.g., "No" in decision block 706). In other words, the controller identifies at least one unsaturated ray.

[0063] In various embodiments, the determination of whether a given projection ray is saturated may be the result of a controller comparing the output of an X-ray detector in response to the received energy for a given ray with a threshold output value of the X-ray detector. In one embodiment, the controller compares the signal output by the X-ray detector as a result of receiving ray C with the maximum signal output value, and determines that the projection ray C is saturated if the controller determines that the signal output by the X-ray detector is equal to the maximum signal output value. Furthermore, the controller compares the signals output by the X-ray detector as a result of receiving ray C1 and / or ray C2 with the maximum signal output value, and determines that the corresponding projection ray C1 or C2 is not saturated if the controller determines that the signal output by the X-ray detector is less than the maximum signal output value (block 706). In various embodiments, if it is determined that the projected rays C1 and / or C2 are not saturated (for example, "No" in block 706), the saturated rays of the current ray C are corrected using data from the corresponding projected rays C1 and / or C2 (block 708).

[0064] In one embodiment, while the current ray C is saturated, both rays C1 and C2 are not saturated, and therefore, saturation correction for ray C can be performed using data from both conjugate rays C1 and C2. However, in another embodiment, the current ray C is saturated, and one of the conjugate rays C1 and C2 is not saturated, while the other is. In such an embodiment, in block 708, data from the corresponding unsaturated projection ray is used for saturation correction, while data from the other corresponding projection ray is ignored for the purpose of saturation correction. For example, in an embodiment where the corresponding projection ray C1 is not saturated and the corresponding projection ray C2 is saturated, data from ray C1 is used for saturation correction, and data from ray C2 is ignored for the purpose of saturation correction. As another example, in an embodiment where the corresponding projection ray C2 is not saturated and the corresponding projection ray C1 is saturated, data from ray C2 is used for saturation correction, and data from ray C1 is ignored for the purpose of saturation correction.

[0065] In various embodiments, in block 708, adjacent unsaturated projection data is also used for saturation correction, in addition to data from any unsaturated data from the conjugate view. In embodiments where both conjugate views are saturated (e.g., "yes" in block 706), adjacent unsaturated projection data is used for saturation correction without data from the conjugate view (block 710). In embodiments, the controller takes adjacent unsaturated projection data and any unsaturated corresponding projection rays from the conjugate view as inputs and performs saturation correction using a linear interpolation method or an advanced interpolation method. The saturation correction performed by the controller is effective in adjusting the value of saturated rays based on the value of at least one unsaturated ray.

[0066] Figure 7 shows an exemplary embodiment in which the dynamic gain setting is varied for high-voltage and low-voltage pulses. Unlike the embodiments described above, the dynamic gain setting can be varied in a configuration in which the tube current changes in addition to the voltage. Furthermore, such embodiments can be used to select an appropriate gain setting to reduce or eliminate saturation rays in subsequent scans.

[0067] In various embodiments, a first plurality of photons are emitted from the radiation source 30 at a first energy level, and a second plurality of photons are emitted from the radiation source 30 at a second energy level. As shown in Figure 7, the first pulse has a first voltage (e.g., 140 kV) and a first current (e.g., 80 mA) when the radiation source 30 is at a first position 800, and the second pulse has a second voltage (e.g., 80 kV) and a second current (e.g., 120 mA) when the radiation source 30 is at a second position 802. At least some of the first plurality of photons and at least some of the second plurality of photons are received by the X-ray detector 34. For example, when the radiation source 30 is at the first position 800, the X-ray detector 34 is at position 804, and when the radiation source 30 is at the second position 802, the X-ray detector is at position 806. It should be understood that the specific voltage and current of each pulse may vary depending on the particular embodiment.

[0068] Depending on the specific configuration, the energy the detector receives from high-energy pulses may be twice (or more) the energy it receives from low-energy pulses. Therefore, a first detector gain (e.g., a high detector gain) can be selected for a first pulse configuration, and a second detector gain (e.g., a low detector gain) can be selected for a second pulse configuration.

[0069] As a result of the photons received from each energy pulse, the X-ray detector outputs a signal indicating the amount of photons received. For example, upon receiving a portion of a first group of photons, the X-ray detector outputs a first signal indicating a first amount of the first group of photons received by the X-ray detector. In an embodiment, the first signal is an amplification of the first amount by a coefficient of a first gain level. Upon receiving a portion of a second group of photons, the X-ray detector outputs a second signal indicating a second amount of the second group of photons received by the X-ray detector. In an embodiment, the second signal is an amplification of the second amount by a coefficient of a second gain level. Thus, by changing the amplification factor for the amount of photons received as a result of each pulse, signals that can be used for image reconstruction can be generated. In particular, the first and second gain levels can be adjusted (e.g., increased or decreased depending on the value) to reduce or eliminate the number of saturation signals emitted between subsequent scans.

[0070] In various embodiments, the first and second gain levels are selected to avoid saturation of the first signal corresponding to the first plurality of photons and the second signal corresponding to the second plurality of photons. The selection of each gain level may be based, for example, on saturation information obtained during the previous scan (e.g., whether a saturation signal was output for a particular pulse configuration during the previous scan, the energy level and gain level used during the previous scan, etc.). For example, in one embodiment, the output of a saturation signal during the first scan allows the controller to adjust the gain level for the subsequent scan. The adjusted gain level may be determined based on the energy level and gain level of the previous scan at the time of the saturation signal output and the energy level of the subsequent scan.

[0071] While the disclosed technology has been shown and described in relation to specific aspects, embodiments, or multiple embodiments, it will be apparent to those skilled in the art, upon reading and understanding this specification and the accompanying drawings, that they will notice equivalent changes and modifications. In particular, with respect to the various functions performed by the elements described herein (such as components, assemblies, devices, members, compositions, etc.), the terms used to describe such elements (including references to “means”) are intended, unless otherwise indicated, to correspond to any element that performs a particular function of the described element (i.e., is functionally equivalent), even if it is not structurally equivalent to a disclosed structure that performs the function in an exemplary aspect, embodiment, or multiple embodiment of the disclosed technology shown herein. Furthermore, while certain features of the disclosed technology may have been described in relation to only one or more of the illustrated aspects or embodiments, such features may be combined with other features of one or more of the other embodiments so as to be desirable and advantageous for any given or particular use.

[0072] The embodiments described herein relate to the systems and methods described above, but these embodiments are intended to be illustrative and not to limit the applicability of these embodiments to the descriptions provided herein. While the present invention has been illustrated by the description of its embodiments, and embodiments have been described in some detail, it is not the applicant's intention to limit the appended claims to such detail or in any way. Further advantages and modifications will readily come to mind for those skilled in the art. Therefore, the present invention in its broader aspects is not limited to the specific details illustrated and described, representative apparatus and methods, and exemplary embodiments. Accordingly, deviations from such details can be made without departing from the spirit or scope of the applicant's general inventive concept. [Explanation of Symbols]

[0073] 10 equipment 12 rotatable gantry 14 Housing 16 Gantriboa 18 Patient support 20 Therapeutic radiation sources 22 Radiation beam 24 detectors 26. Items to be scanned 30 Radiation (x-ray) source 32 Radiation beam 34 X-ray (radiation) detector 36 Beamformer 40 Reconfiguration Processors 44 memory 48 Operator Interface 52 displays 60 Controllers Locations of radiation source 302, 304, and 306. 303, 305, 307 Position of X-ray detector 34 Locations of radiation source 30: 602, 604, 606 608, 610, 612 Position of X-ray detector 34 800 First location of radiation source 30 802 Second location of radiation source 30 804, 806 Position of X-ray detector 34 B Background data C Current view light rays C1 Conjugate View Ray C2 Conjugate View Rays Image data N The light rays of the next view P The light rays in the front view R reference point

Claims

1. 1. A method for correcting saturation in at least one saturating ray, comprising: identifying a saturated ray corresponding to a first ray of the radiation source received at the radiation detector after passing a reference point during a current view of the radiation detector; identifying at least one non-saturated ray corresponding to a second ray of the radiation source received at the radiation detector after passing the reference point during a previous view of the radiation detector, or a third ray of the radiation source received at the radiation detector after passing the reference point during a next view of the radiation detector; each of the previous view of the radiation detector and the next view of the radiation detector is adjacent to the current view; the radiation source has a first energy for the current view and a second energy for the previous view and the next view, the second energy being different from the first energy; adjusting the value of the saturating light ray based on the value of the at least one non-saturating light ray in response to the identifying step; A method comprising:

2. The method of claim 1 , wherein the non-saturating light beam is emitted during a current rotation of the radiation source.

3. The method of claim 1 , wherein the non-saturating light beam is emitted during a rotation of the radiation source that is different from a rotation of the radiation source during which the saturating light beam is emitted.

4. 2. The method of claim 1, wherein adjusting the value of the saturating light ray comprises adjusting the value of the saturating light ray based on the value of the at least one non-saturating light ray and information about the current view.

5. The method of claim 1 , wherein the non-saturating light ray corresponds to the second light ray.

6. The method of claim 1 , wherein the non-saturating light ray corresponds to the third light ray.

7. The method of claim 1 , wherein the value of the saturated ray is adjusted based on a value of a non-saturated ray corresponding to the second ray and a value of a non-saturated ray corresponding to the third ray.

8. 2. The method of claim 1, wherein adjusting the value of the saturating ray comprises adjusting the value of the saturating ray based on the value of the non-saturating ray and values ​​of non-saturating rays adjacent to the saturating ray from the current view of the radiation detector.

9. The method of claim 1 , wherein the first light beam passes through a region of the scanned object having a short path length.

Images