Time Domain Interleaving of Imaging and Therapeutic X-Rays in Radiotherapy Systems

Abstract

Temporal interleaving of therapeutic X-rays and imaging X-rays during an image guided radiation therapy (IGRT) procedure in a radiation therapy system prevents scatter of the therapeutic X-rays from degrading the quality of an X-ray image used to generate volumetric image data of a target volume. Imaging X-rays are delivered to the target volume during one or more imaging intervals, and one or more pulses of therapeutic X-rays are delivered to the target volume between the imaging intervals. Where a pulse of X-ray therapy is timed to occur during an imaging interval, the pulse of therapeutic X-ray is inhibited from occurring during the imaging interval and is rescheduled to occur at a later time that does not coincide with the imaging interval or a subsequent imaging interval.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 711,483, filed on July 28, 2018. Background Art

[0003] Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.

[0004] Radiation therapy is a localized treatment directed at a specific target tissue (planned target volume), such as a cancerous tumor. Ideally, radiation therapy is performed on the planned target volume so that the surrounding normal tissue is spared from receiving a dose exceeding a specified tolerance, thereby minimizing the risk of damage to healthy tissue. Prior to performing radiation therapy, an imaging system is typically used to provide a three-dimensional image of the target tissue and surrounding area. Based on such imaging, the size and mass of the target tissue can be estimated, and an appropriate treatment plan can be generated, and the planned target volume can be determined.

[0005] In order to correctly deliver the prescribed dose to the planned target volume (i.e., target tissue) during radiotherapy, the patient should be correctly positioned relative to the linear accelerator that delivers the radiotherapy. Typically, dose and geometric data are checked before and during treatment to ensure that the patient is correctly positioned and that the radiotherapy treatment delivered matches the previously planned treatment. This process is called image-guided radiation therapy (IGRT) and involves using an imaging system to view the target tissue while the radiotherapy is being delivered to the planned target volume. IGRT incorporates the imaging coordinates from the treatment plan to ensure that the patient is correctly aligned in the radiotherapy device for treatment. Summary of the invention

[0006] According to at least some embodiments of the present disclosure, a radiotherapy system is configured to generate volumetric image data for a target volume during treatment, wherein the volumetric image data is not degraded by X-ray image noise caused by scattering of therapeutic X-rays. As a result, the volumetric image data so generated can be used to more accurately detect intra-fractional motion that occurs during application of therapeutic X-rays. For example, using such higher quality volumetric image data of the target volume, intra-fractional motion of the target volume caused by loss of breath holding and / or anatomical changes caused by peristalsis can be more easily detected. Therefore, the radiotherapy system can perform image-guided radiotherapy (IGRT), which uses X-ray imaging rather than magnetic resonance imaging (MRI) to monitor intra-fractional motion. The detected anatomical changes can then be compensated via patient repositioning and / or treatment modifications, or the current treatment can be terminated.

[0007] In some embodiments, during the IGRT process, the temporal interleaving of the therapeutic X-rays and the imaging X-rays prevents scattering of the therapeutic X-rays from degrading the quality of the X-ray images used to generate volumetric image data of the target volume. In such embodiments, during one or more imaging intervals, the imaging X-rays are delivered to the target volume, and between the imaging intervals, one or more pulses of the therapeutic X-rays are delivered to the target volume. Where the pulses of the therapeutic X-rays are timed to occur during the imaging intervals, the pulses of the therapeutic X-rays are inhibited from occurring during the imaging intervals and are rescheduled to occur at a later time that does not coincide with the imaging interval or a subsequent imaging interval.

[0008] In some embodiments, therapeutic X-rays are delivered to the target volume while imaging X-rays are also delivered to the target volume to generate volumetric image data of the target volume. That is, during an imaging interval in which imaging X-rays are delivered to the target volume, one or more pulses of therapeutic X-rays are also delivered to the target volume. In such embodiments, in each pixel of the X-ray imaging device, image signals are accumulated in portions of the imaging interval in which only therapeutic X-rays are delivered to the target volume; and during pulses of therapeutic X-rays, image signals are prevented from accumulating in each pixel.

[0009] The foregoing summary is merely illustrative and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The foregoing and other features of the present disclosure will become more apparent through the following description and the appended claims in conjunction with the accompanying drawings. These drawings depict only several embodiments according to the present disclosure and therefore should not be considered as limiting the scope thereof. Through the use of the accompanying drawings, the present disclosure will be described with additional specificity and detail.

[0011] Figure 1 is a perspective view of a radiation therapy system in which various aspects of the present disclosure may be beneficially implemented.

[0012] Figure 2 Schematically illustrates various embodiments of the present disclosure. Figure 1 Drive table and frame of the radiation system.

[0013] Figure 3 A cross-sectional view of an X-ray imager according to an embodiment of the present disclosure is schematically illustrated.

[0014] Figure 4 Schematically illustrates various embodiments of the present disclosure. Figure 1 Drive table and frame of the radiation system.

[0015] Figure 5 Schematically illustrates various embodiments of the present disclosure based on Figure 1 A digital volume is constructed from projection images generated by one or more X-ray imagers included in a radiation therapy system.

[0016] Fig. 6A is a circuit diagram of a pixel detector element according to one embodiment of the present disclosure.

[0017] Figure 6B is a circuit diagram of a pixel detector element according to another embodiment of the present disclosure.

[0018] Fig. 7A is a schematic timing diagram illustrating application of treatment beam pulses during treatment intervals and application of imaging beam pulses during imaging intervals according to one embodiment of the present disclosure.

[0019] Figure 7B is a schematic timing diagram illustrating application of treatment beam pulses during treatment intervals and application of imaging beam pulses during imaging intervals according to another embodiment of the present disclosure.

[0020] Figure 8 A flow chart of a radiation therapy process according to one or more embodiments of the present disclosure is set forth.

[0021] Fig. 9 is a schematic timing diagram illustrating the timing of imaging beam pulses during an imaging interval, the duration of which is shorter than the time interval between two therapy beam pulses, according to one embodiment of the present disclosure.

[0022] Fig.10 is a circuit diagram of a pixel detector element including an electronic shutter according to one embodiment of the present disclosure.

[0023] Fig.11 is a schematic timing diagram illustrating application of treatment beam pulses and imaging beam pulses during an imaging interval according to one embodiment of the present disclosure.

[0024] Fig.12 A flow chart of a radiation therapy process according to one or more embodiments of the present disclosure is set forth. DETAILED DESCRIPTION

[0025] In the following detailed description, reference is made to the accompanying drawings which form a part thereof. In the accompanying drawings, the same symbols generally identify the same components unless the context indicates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized and other changes may be made without departing from the spirit or scope of the subject matter presented herein. It is readily understood that the various aspects of the present disclosure as generally described herein and illustrated in the accompanying drawings may be arranged, substituted, combined, and designed in a variety of different configurations, all of which are expressly contemplated and form a part of the present disclosure.

[0026] Introduction

[0027] Image guided radiation therapy (IGRT) is used to treat tumors in body regions that are subject to autonomous movement (such as the lungs) or in body regions that are subject to involuntary movement (such as organs affected by peristalsis). IGRT involves using an imaging system to view target tissue (also referred to as a "target volume") while applying radiation therapy to it. In IGRT, image-based coordinates of a target volume from a previously determined treatment plan are compared with image-based coordinates of a target volume determined during the application of a treatment beam. In this way, changes in surrounding organs at risk and / or movement or deformation of the target volume relative to the radiation therapy system can be detected. Therefore, based on daily position and shape, dose limits for organs at risk can be accurately implemented, and the position of the patient and / or the treatment beam can be adjusted to more accurately target the radiation dose to the tumor. For example, in pancreatic tumor treatment, organs at risk include the duodenum and stomach. The shape and relative position of these organs at risk relative to the target volume may change significantly every day. Therefore, accurately adapting to the shape and relative position of such organs at risk enables the dose to be gradually increased to the target volume and a better treatment effect is obtained.

[0028] In some conventional IGRT radiation systems, soft tissue motion is detected during application of the treatment beam via fiducial markers such as gold seeds. However, the use of fiducial markers, and in particular the invasive surgical procedures required to place the markers, has many disadvantages. Specifically, laparoscopic insertion of fiducial markers requires additional time and clinical resources, such as an operating room, anesthesia, antibiotics, and the involvement of numerous other medical specialists.

[0029] Alternatively, in some conventional IGRT radiation systems, the movement of soft tissue is detected during the application of the treatment beam via magnetic resonance imaging (MR1). However, MRI-based IGRT also has disadvantages. First, MRI-based IGRT systems are generally larger, more complex and more expensive than radiotherapy systems that use X-ray imaging. Secondly, detecting the movement or deformation of the target volume via MRI generally involves monitoring images associated with 2D slices passing through the target volume. As a result, target volume movement or deformation occurring anywhere outside (or perpendicular to) the monitored 2D slice is difficult to detect, which may seriously affect the accuracy of the applied radiation dose.

[0030] Alternatively, in some conventional IGRT radiation systems, the movement of soft tissue is detected during the application of treatment X-rays via imaging X-rays that also directly pass through the target volume. For example, volumetric image data for the target volume can be reconstructed based on X-ray projection images of the target volume, which are generated using a computed tomography (CT) or cone beam CT (CBCT) process. In the CT or CBCT process, multiple X-ray projection images are generated by imaging X-rays that pass through the target volume and reach the X-ray imaging device. Because there is a time interval when the X-rays are applied to the target volume and the imaging X-rays are received by the X-ray imaging device, the X-ray projection images generated during such time intervals may include significant image noise caused by scattered treatment X-rays, which are captured by the X-ray imaging device. For example, when typical megavoltage (MV) treatment X-rays and kilovoltage (kV) imaging X-rays are used, the amplitude of scattered MV radiation from the patient, treatment table, and machine components may exceed all other image noise. Because the Poisson distribution component of such image noise cannot be filtered out, the image quality of the X-ray projection image is reduced. Therefore, the detection of intra-fraction motion based on such X-ray images is negatively impacted.

[0031] In view of the foregoing, there is a need in the art for improved systems and techniques to ensure that a target volume remains properly positioned for treatment in a radiation therapy system while a treatment beam is delivered to the target volume. According to various embodiments described herein, a radiation system is configured to generate a high quality X-ray image of a target volume that is not degraded by image noise from scattered treatment X-rays. Figure 1 One such embodiment is illustrated in FIG.

[0032] System Overview

[0033] Figure 1is a perspective view of a radiation therapy system 100 that can beneficially implement various aspects of the present disclosure. The radiation therapy (RT) system 100 is a radiation system configured to detect intra-fraction motion in near real time using X-ray imaging technology. Therefore, the RT system 100 is configured to provide stereotactic radiosurgery and precision radiation therapy for lesions, tumors, and conditions anywhere in the body where radiation therapy is indicated. In this way, the RT system 100 may include one or more linear accelerators (LINACs) that generate megavolt (MV) treatment beams of high-energy X-rays, kilovolt (kV) X-ray sources, X-ray imagers, and in some embodiments, MV electronic access control imaging devices (EPIDs). For example, a radiation therapy system 100 configured with a circular gantry is described herein. In other embodiments, the radiation therapy system 100 may be configured with a C-shaped gantry that can be infinitely rotated via a slip ring connection.

[0034] Typically, the RT system 100 is capable of kV imaging of the target volume during application of the MV treatment beam, so that the IGRT process can be performed using X-ray imaging rather than MRI. The RT system 100 may include one or more touch screens 101, a couch motion control device 102, an aperture 103, a base positioning assembly 105, a couch 107 disposed on the base positioning assembly 105, and an image acquisition and treatment control computer 106, all of which are disposed within the treatment room. The RT system 100 also includes a remote control console 110, which is disposed outside the treatment room and enables treatment delivery and patient monitoring from a remote location. The base positioning assembly 105 is configured to accurately position the couch 107 relative to the aperture 103, and the motion control device 102 includes an input device such as a button and / or switch that enables a user to operate the base positioning assembly 105 to automatically and accurately position the couch 107 to a predetermined position relative to the aperture 103. The motion control device 102 also enables a user to manually position the couch 107 to a predetermined position. In some embodiments, RT system 100 also includes one or more cameras (not shown) for patient monitoring in the treatment room.

[0035] Figure 2 The drive stage 200 and the frame 210 of the RT system 100 according to various embodiments of the present disclosure are schematically illustrated. For clarity, Figure 2The cover, base positioning assembly 105, couch 107, and other components of the RT system 100 are omitted. The drive table 200 is a fixed support structure for the components of the RT treatment system 110, including a gantry 210 and a drive system 201 for rotatably moving the gantry 210. The drive table 200 rests on and / or is fixed to a support surface outside the RT treatment system 110, such as the floor of an RT treatment facility. The gantry 210 is rotationally coupled to the drive table 200 and is a support structure to which various components of the RT system 100 are mounted, including a linear accelerator (LINAC) 204, an MV electronic access control imaging device (EPID) 205, an imaging X-ray source 206, and an X-ray imager 207. During operation of the RT treatment system 110, the gantry 210 rotates around the hole 103 when actuated by the drive system 201.

[0036] The drive system 201 rotationally actuates the gantry 210. In some embodiments, the drive system 201 includes a linear motor that can be fixed to the drive table 200 and interacts with a magnetic track (not shown) mounted on the gantry 210. In other embodiments, the drive system 201 includes another suitable drive mechanism for causing the gantry 210 to rotate precisely about the aperture 201. The LINAC 204 generates an MV treatment beam 230 of high energy X-rays (or electrons in some embodiments), and the EPID 205 is configured to acquire X-ray images using the treatment beam 230. The imaging X-ray source 206 is configured to direct a cone-shaped X-ray beam (referred to herein as imaging X-rays 231) through the isocenter 203 of the RT system 100 to the X-ray imager 207, and the isocenter 203 generally corresponds to the location of the target volume 209 to be treated. Figure 2 In the illustrated embodiment, the X-ray imager 207 is depicted as a planar device, while in other embodiments, the X-ray imager 207 may have a curved configuration.

[0037] The X-ray imager 207 receives the imaging X-rays 231 and generates a suitable projection image therefrom. According to certain embodiments, such projection images can then be used to construct or update portions of the imaging data for a digital volume, which corresponds to a three-dimensional (3D) region including the target volume 209. That is, a 3D image of such a 3D region is reconstructed based on the projection image. In an embodiment, cone beam computed tomography (CBCT) and / or digital tomosynthesis (DTS) can be used to process the projection images generated by the X-ray imager 207. CBCT is typically used to acquire projection images over a relatively long acquisition arc, for example, when the gantry 210 rotates 180° or more. As a result, a high-quality 3D reconstruction of the imaging volume can be generated. CBCT is typically used at the beginning of a radiotherapy session to generate a set 3D reconstruction. For example, CBCT can be used to generate a 3D reconstruction immediately before applying the treatment beam 230, thereby confirming that the target volume 209 has not moved or changed shape.

[0038] Instead, during portions of the IGRT procedure, partial data reconstruction is performed by the RT system 100, wherein partial image data is used to generate a 3D reconstruction of the target volume 209. For example, while the gantry 210 is rotated through the treatment arc while the treatment beam 230 is directed to the isocenter 203, DTS image acquisition can be performed to generate image data of the target volume 209. Because DTS image acquisition is performed over a relatively short acquisition arc, e.g., between about 10° and 60°, near real-time feedback of the shape and position of the target volume 209 can be provided by DTS imaging during the IGRT procedure.

[0039] In some embodiments, the X-ray imager 207 includes a glass plate having a matrix or array of pixel detector elements formed thereon, each of which converts incident X-ray photons into an electrical charge. In an embodiment where the X-ray imager 207 is configured as an indirect flat panel detector, a scintillator material in the X-ray imager 207 is excited by incident X-rays and emits light, which is detected by a plurality of photodiodes. Each photodiode generates a signal (e.g., an electrical charge proportional to the intensity of the incident light) for a different pixel that will ultimately become a digital image. An encoder included in the X-ray imager 207 then interprets each of these signals and assigns each signal a value proportional to the signal. One such embodiment of the X-ray imager 207 is Figure 3 Medium picture.

[0040] Figure 3A cross-sectional view of an X-ray imager 207 according to one embodiment of the present disclosure is schematically illustrated. As shown, the X-ray imager 207 includes a photosensitive element and a detector circuit device layer 301 formed on a substrate 302. Additionally, the X-ray imager 207 includes a layer of scintillator material 303 formed on the photosensitive element and the detector circuit device layer 301. Also shown is an incident X-ray 309, which is incident on the imaging X-ray source 206 ( Figure 2 After being generated (as shown), the X-ray imaging array 305 passes through a patient, sample, or other object of interest. The photosensitive element and detector circuit device layer 301, the substrate 302, and the scintillator material 303 together form an X-ray imaging array 305. Note that the photosensitive element and detector circuit device layer 301 is generally formed of multiple processing layers, and the X-ray imaging array 305 may include Figure 3 Additional material layers not shown in the figure.

[0041] The photosensitive element and detector circuit device layer 301 generally includes a plurality of pixel detector elements 310. Each pixel detector element 310 includes a photosensitive element, such as a photodiode, a photogate, or a phototransistor, and any other circuitry suitable for operating as a pixel detector element in the x-ray imager 207. For example, the photosensitive element and detector circuit device layer 301 may also include a thin film transistor (TFT) for reading out a digital signal from the pixel detector element. The scintillator material 303 may include one or more material layers, including but not limited to gadolinium oxysulfide (Gd2O2S:Tb), cadmium tungstate (CdWO4), bismuth germanate (Bi4Ge3O12 or BGO), cesium iodide (CsI) or cesium thallium iodide (CsI:Tl), etc.

[0042] In some embodiments, the TFTs included in the detector circuitry layer 301 include one or more specific semiconductor materials, such as indium gallium zinc oxide (IGZO), low temperature polysilicon semiconductor materials, and polysilicon materials, which enable more transistors to be incorporated into the pixel detector element 310. Alternatively, in some embodiments, the transistors included in the detector circuitry layer 301 may be based on complementary metal oxide semiconductor (CMOS) technology, which enables more complex circuits to be included in a single pixel detector element 310. Since the charge carrier mobility in CMOS is very high, transistors can be made very small, and thus switching-induced charge injection can be significantly reduced compared to other technologies.

[0043] exist Figure 3In the illustrated embodiment, the X-ray imager 207 is depicted as an indirect flat panel detector, wherein X-ray photons are converted into other photons, which in turn are detected and converted into electrical charge. In other embodiments, the X-ray imager 207 may be a direct flat panel detector (FPD). In a direct FPD, incident X-ray photons are directly converted into electrical charge in the amorphous selenium layer, and wherein the resulting charge pattern is read out by suitable hardware (such as a thin film transistor (TFT) array, an active matrix array, micro plasma line addressing, etc.).

[0044] exist Figure 2 In the illustrated embodiment, the RT system 100 includes a single X-ray imager and a single corresponding imaging X-ray source. In other embodiments, the RT system 100 may include two or more X-ray imagers, each having a corresponding imaging X-ray source. Figure 4 One such embodiment is illustrated in FIG.

[0045] Figure 4 The driving stage 400 and the frame 410 of the RT system 100 according to various embodiments of the present disclosure are schematically shown. The driving stage 400 and the frame 410 are similar in configuration to Figure 2 The drive table 200 and the gantry 200 in the embodiment are substantially similar, except that the components of the RT system 100 mounted on the gantry 410 include a first imaging X-ray source 406, a first X-ray imager 407, a second imaging X-ray source 408, and a second X-ray imager 409. In such an embodiment, including multiple X-ray imagers in the RT system 100 facilitates generating projection images (for reconstructing the target volume) over a shorter image acquisition arc. For example, when the RT system 100 includes two X-ray imagers and corresponding X-ray sources, the image acquisition arc for acquiring a projection image of a certain image quality can be approximately half of the image acquisition arc for acquiring a projection image of similar image quality using a single X-ray imager and X-ray source.

[0046] The projection images generated by the X-ray imager 207 (or by the first X-ray imager 407 and the second X-ray imager 409) are used to construct imaging data for a digital volume of the patient's anatomy including the target volume within the 3D region. Alternatively or additionally, such projection images may be used to update portions of existing imaging data of the digital volume corresponding to the 3D region. Figure 5 An embodiment of such a digital volume is described below.

[0047] Figure 5A digital volume 500 according to various embodiments of the present disclosure is schematically illustrated, and the digital volume 500 is constructed based on projection images generated by one or more X-ray imagers included in the RT system 100. For example, in some embodiments, the projection images may be generated by a single X-ray imager (such as the X-ray imager 207), and in other embodiments, the projection images may be generated by multiple X-ray imagers (such as the first X-ray imager 407 and the second X-ray imager 409).

[0048] The digital volume 500 includes a plurality of voxels 501 (dashed lines) of anatomical image data, wherein each voxel 501 corresponds to a different location within the digital volume 500. For clarity, Figure 5 Only a single voxel 501 is shown in FIG. 5 . The digital volume 500 corresponds to a 3D region including a target volume 510. Figure 5 In FIG. 5 , the digital volume 500 is depicted as an 8×8×8 voxel cube, but in reality, the digital volume 500 typically includes more voxels, such as Figure 5 The magnitude shown is orders of magnitude larger.

[0049] For the purposes of discussion, the target volume 510 may refer to the gross tumor volume (GTV), clinical target volume (CTV), or planning target volume (PTV) for a particular treatment. The GTV depicts the location and extent of the gross tumor that can be seen or imaged; the CTV includes the GTV and an additional margin for subclinical disease spread that is typically not imaged; and the PTV is a geometric concept designed to ensure that the appropriate radiation therapy dose is actually delivered to the CTV without adversely affecting nearby organs at risk. Therefore, the PTV is typically larger than the CTV, but in some cases may also be reduced in certain portions to provide a safety margin around organs at risk. The PTV is typically determined based on imaging performed prior to treatment time, and embodiments of the present disclosure facilitate alignment of the PTV with the current position of the patient's anatomy at the time of treatment.

[0050] According to various embodiments described below, image information associated with each voxel 501 of the digital volume 500 is constructed by projection images generated by a single or multiple X-ray imagers, for example, via a CBCT process. In some embodiments, image information associated with some or all of the voxels 501 of the digital volume 500 is updated by projection images generated by a single or multiple X-ray imagers via a DTS process. For example, such a DTS process can be employed after a portion of a planned treatment begins and before the planned treatment is completed. In this way, the position and shape of the target volume 510 can be confirmed while the treatment is being performed. Therefore, if a sufficient portion of the target volume 510 is detected to extend outside the threshold area, the treatment can be suspended or modified. In this case, the modification of the treatment can be achieved by adjusting the patient position and / or the treatment beam.

[0051] Time-domain interleaving of imaging and therapeutic X-rays

[0052] During use, the treatment beam typically generates a large amount of scattered radiation in all directions, including scattered radiation emanating from the patient, the treatment table, and machine components. As a result, a large amount of MV scatter may be incident on the X-ray imager (e.g., Figure 2 X-ray imager 207 or Figure 4 In some cases, such X-ray scatter may even exceed the amplitude of the imaging X-ray. Therefore, in some embodiments, the temporal interleaving of the treatment beam and the imaging X-ray can be used to reduce or eliminate the interference of the X-ray scatter of the treatment beam on the detection of the imaging X-ray. That is, in such embodiments, the imaging X-ray (e.g., Figure 2 The imaging X-rays 231 in the target volume 510 and the treatment beam (e.g., Figure 2 In such an embodiment, the timing of delivery of the treatment beam 230 in the target volume 510 is optimized. In such an embodiment, the imaging X-rays and the treatment beam are pulsed or otherwise activated intermittently so that the treatment beam is not delivered to the target volume 510 when the imaging X-rays are received by the X-ray imager.

[0053] Fig. 6A 6 is a circuit diagram 600 of a pixel detector element 310 according to one embodiment of the present disclosure. The embodiment of the pixel detector element 310 illustrated by the circuit diagram 600 is included in an X-ray imager that enables time-domain interleaving of a treatment beam with imaging X-rays. The pixel detector element 310 may be included in an X-ray imager of the RT system 100, such as Figure 2 X-ray imager 207 or Figure 4The pixel detector element 310 includes a photodiode 601, a reset switch 602, a readout switch 603, and a voltage follower 604 in some embodiments. As shown, the photodiode 601 is communicatively coupled to a reference voltage V via the reset switch 602. ref , and is communicatively coupled to the data line 610 via the readout switch 603 and the voltage follower 604. Alternatively, in some embodiments, the reference voltage V ref The positions of the bias voltage 606 (eg, ground) are reversed. In such an embodiment, when the reset switch 602 is closed, one side of the photodiode 601 is connected to the bias voltage 606.

[0054] In operation, when Figure 3 When photons generated by the scintillator material 303 in the pixel detector element 310 are incident on the photodiode 601, the photodiode 601 generates charge. When the readout switch 603 is closed, the charge accumulated by the photodiode 601 is read out to the data line 610 and converted into a digital signal by an analog-to-digital converter (ADC) 611, which is external to the pixel detector element 310 and coupled to the data line 610. In an embodiment where the pixel detector element 310 includes a voltage follower 604, the charge accumulated by the photodiode 601 is reset when the reset switch 602 is closed.

[0055] Figure 6B is a circuit diagram 620 of a pixel detector element 310 according to another embodiment of the present disclosure. Figure 6B The embodiment of the pixel detector element 310 shown in FIG. Fig. 6A The embodiment of the pixel detector element 310 shown in FIG. 1 is substantially similar, except for the following. First, the pixel detector element 310 does not include a voltage follower 604. Second, the photodiode 601 is not directly coupled to the reference voltage V via the reset switch 602. ref Instead, the photodiode 601 is coupled to a reference voltage V via a reset switch 622 and a data line 610 as shown. ref Alternatively, in some embodiments, reset switch 622 is integrated into ADC 611. In either case, in such embodiments, readout switch 603 is closed whenever reset switch 602 is closed, so that signal accumulation in the photodiode during that time is avoided.

[0056] according to Fig. 6A and Figure 6B In the illustrated embodiment, application of treatment beam pulses is limited to treatment intervals, while application of imaging beam pulses is limited to imaging intervals, so that noise generated by the treatment beam pulses is prevented from being captured by the photodiode 601. Fig. 7A and Figure 7B Such an embodiment is illustrated in FIG.

[0057] Fig. 7A 7 is a schematic timing diagram 700 illustrating application of treatment beam pulses 721 during treatment intervals 720 and application of imaging beam pulses 731 during imaging intervals 730 according to one embodiment of the present disclosure. Specifically, Fig. 7A Applies to Fig. 6A An embodiment of a pixel detector element 310 is shown. Fig. 7A Also depicted in FIG. 6 is the timing of treatment beam pulses 721 and imaging beam pulses 731 relative to the opening and closing of reset switch 602 , readout switch 603 , and activation of ADC 611 .

[0058] During treatment interval 720, one or more treatment beam pulses 721 are directed to the target volume. Fig. 7A In the illustrated embodiment, the treatment interval 720 is shown as having three treatment beam pulses 721, but in practice, the treatment interval 720 may include up to one hundred or more treatment beam pulses. In some embodiments, a typical treatment beam pulse 721 (e.g., Figure 2 The duration of the treatment beam 230 pulses (in the embodiment) is about 5 microseconds (μs) and is delivered approximately every 1 to 10 milliseconds (ms). In such an embodiment, the duration of the treatment beam pulses 721 is significantly shorter than the duration of the imaging beam pulses 731 occurring during the imaging interval 730. Additionally, during the treatment interval 720, the reset switch 602 is closed so that the photodiode 601 is coupled to the reference voltage V ref Therefore, even if the scattered X-rays from the treatment beam pulse 721 hit Figure 5 The photodiode 601 also cannot accumulate such potential image noise as charges generated by the scintillator layer 503 that generate photons incident on the photodiode 601.

[0059] During each imaging interval 730, one or more imaging beam pulses 731 are directed to the target volume. In the embodiment shown in FIG. 7, a single imaging beam pulse 731 is illustrated. In some embodiments, a typical imaging beam pulse 731 (e.g., Figure 2The duration of the imaging beam pulse 731) is about 10 ms and is used to generate a single projection image of the target volume. In such an embodiment, one such image is acquired approximately every 30 ms-50 ms. One or more imaging beam pulses 731 occur during the illumination portion 732 of each imaging interval 730, and the signal accumulated in each pixel detector element 310 is read out from each pixel in the readout portion 733 of each imaging interval 730. As shown, the reset switch 602 is opened during the imaging interval 730, so that the photons generated by the imaging beam pulse 731 and incident on the photodiode 601 accumulate the image signal in the photodiode 601. In addition, the readout switch 603 is closed during each imaging interval 730, for example, in synchronization with other photodiodes (not shown) of the x-ray imager and activating the ADC 611. In this way, the image signal is read out from each photodiode 601 of the x-ray imager during the readout portion 733 of each imaging interval 730.

[0060] As shown, the treatment interval 720 and the imaging interval 730 do not overlap in time, but are interleaved in the time domain. Therefore, scattered X-rays occurring during the treatment interval 720 cannot be registered as charge by the photodiode 601. Fig. 7A In the illustrated embodiment, the duration 735 of the imaging interval 730 is greater than the time interval 725 between two treatment beam pulses 721. As a result, in embodiments in which treatment beam pulses 721 are directed through the target volume at regular intervals, one or more treatment beam pulses 721 must be timed to occur during each imaging interval 730. In such embodiments, such treatment beam pulses 721 are inhibited from being directed through the target volume so that the photodiode 601 does not accumulate charge caused by scattered x-rays. The inhibited treatment beam pulses 721 are indicated using dashed lines. Fig. 7A In the illustrated embodiment, the imaging interval 730 is shown as including a single treatment beam pulse 721 that is prohibited. In practice, depending on the duration 735 of the imaging interval 730 and the time interval 725 between two treatment beam pulses 721, a single imaging interval 730 may include any value from 0 treatment beam pulses 721 that are prohibited to 100 or more treatment beam pulses 721 that are prohibited.

[0061] In some embodiments, the treatment control computer 106 ( Figure 16 (shown) performs a logic operation for determining whether the reset switch 602 of the photodiode 601 is open, thereby indicating that the imaging interval 730 is in progress. In such an embodiment, the treatment control computer 106 then prevents the LINAC 204 from generating the one or more treatment beam pulses 721 that were prohibited. In addition, in some embodiments, the dose logic included in the treatment control computer 106 can cause additional treatment beam pulses 721 to be applied to the target volume at the end of the treatment fraction to recover the dose lost due to the elimination of the prohibited treatment beam pulses 721.

[0062] exist Fig. 7A In the illustrated embodiment, the duration 735 of the imaging interval 730 is greater than the time interval 725 between two treatment beam pulses 721, and one or more treatment beam pulses 721 are timed to occur during each imaging interval 730. By reducing the duration 735 of the imaging interval 730, the number of treatment beam pulses 721 that need to be inhibited can be reduced or eliminated, thereby preventing or reducing dose loss due to the inhibited treatment beam pulses 721. In some embodiments, the duration 736 of each irradiation portion 732 is reduced by delivering a higher power imaging beam pulse 731 during the irradiation portion 732. Therefore, in such an embodiment, the X-ray imager of the RT system 100 includes an X-ray tube having a power of up to about 10 kW.

[0063] Alternatively or additionally, in some embodiments, the duration 737 of each readout portion 733 is reduced by performing the readout operation of the photodiode 601 more quickly. For example, including a voltage follower 604 in each pixel detector element 310 enables very fast readout of the photodiode 601 because the circuitry of the pixel detector element 310 is not limited by the resistor-capacitor (RC) time constant of the circuit.

[0064] Figure 7B 7 is a schematic timing diagram 750 illustrating application of treatment beam pulses 721 during treatment intervals 720 and application of imaging beam pulses 731 during imaging intervals 730 according to another embodiment of the present disclosure. Specifically, Figure 7B Applies to Fig. 6A The timing diagram 750 is similar to the embodiment of the pixel detector element 310 shown in FIG. Fig. 7A The timing diagram 700 in FIG. 7 is substantially similar, except that in such a configuration, whenever the reset switch 602 is closed, the readout switch 603 is closed, so that signal accumulation in the photodiode 601 is prevented during that time.

[0065] Figure 8A flow chart of a radiation therapy process according to one or more embodiments of the present disclosure is set forth. The method may include one or more operations, functions, or actions as illustrated by one or more of blocks 801-840. Although the blocks are illustrated in a sequence, the blocks may be executed in parallel and / or in a sequence different from that described herein. Moreover, individual blocks may be combined into fewer blocks, divided into additional blocks, and / or removed based on the desired implementation. Although combined Figure 1 The method is described with reference to the system of FIG. 7 , but those skilled in the art will appreciate that any suitably configured radiation therapy system is within the scope of the present disclosure.

[0066] Prior to the method steps, volumetric (3D) image data set for the digital volume 500 including the target volume 510 is acquired. For example, the patient is positioned on the couch 107 of the RT system 100, and the set volumetric image data is generated by, for example, CBCT image acquisition. The set volumetric image data includes image information for each voxel 501 in the digital volume 500. When generated by CBCT processing, the set volumetric image data may include hundreds of different digital X-ray projection images of the digital volume 500. Automatic segmentation and deformable registration of the digital volume are then performed, followed by patient position adjustment. Automatic segmentation includes delineating the target volume and organs at risk in the digital volume 500. Deformable registration adjusts the contours generated for the target volume 510 and any organs at risk in the earlier planning stages. The deformable registration process compensates for changes in the shape and relative position of the target volume 510 and the organs at risk, such as due to filling of the stomach, colon and bladder, tumor shrinkage and other factors. When applicable, the patient's current position is also adjusted to precisely align the target volume 510 with the now modified planning target volume.For example, the position of the couch 107 may be automatically and / or manually adjusted to align the target volume 510 with the modified planning target volume.

[0067] When a treatment arc of the current RT fraction is initiated, method 800 starts from step 801. In step 801, the patient starts with a breath hold. In some embodiments, the RT treatment includes multiple fractions (ie, multiple treatment arcs). Alternatively, in other embodiments, the RT treatment consists of a single treatment arc.

[0068] In step 802, the treatment control computer 106 causes the gantry 210 to continuously rotate in a first direction through a treatment arc.

[0069] In step 803 , the treatment control computer 106 begins directing a series of treatment X-ray pulses, such as treatment beam pulses 721 or 821 , to the target volume 510 while the gantry 210 continues to rotate in a first direction.

[0070] In step 804 , the treatment control computer 106 selects the next treatment beam pulse to be directed to the target volume 510 .

[0071] In step 805, the treatment control computer 106 determines whether the next imaging interval 730 is timed to begin before the next selected treatment beam pulse. If so, the method 800 proceeds to step 820; if not, the method 800 proceeds to step 806.

[0072] In step 806, the treatment control computer 106 determines whether the selected next treatment beam pulse is timed to occur during the imaging interval 730. If so, the method 800 proceeds to step 830; if not, the method 800 proceeds to step 807.

[0073] In step 807 , the treatment control computer 106 causes the next selected treatment beam pulse to be directed to the target volume 510 .

[0074] In step 808, the treatment control computer 106 determines whether there are any remaining treatment intervals 720 or imaging intervals 730 in the treatment arc. If so, the method 800 returns to step 804 and the next treatment beam pulse is selected; if not, the method 800 proceeds to step 840 and the method 800 terminates.

[0075] Step 820 is performed in response to the treatment control computer 106 determining that the next imaging interval 730 is timed to begin before the selected next treatment beam pulse. In step 820, the treatment control computer 106 causes the next imaging interval 730 to begin. Specifically, the reset switch 602 is opened during the imaging interval 730 so that each photodiode 601 in the x-ray imager can accumulate charge, and the readout switch 603 is closed so that the image signal is read out from the photodiode 601. When step 820 is performed, the method 800 proceeds to step 806.

[0076] Step 830 is performed in response to the treatment control computer 106 determining that the selected next treatment beam pulse is timed to occur during the imaging interval 730. In step 830, the treatment control computer 106 prohibits one or more treatment beam pulses 721 from being directed through the target volume during the current imaging interval 730.

[0077] In optional step 831 , the treatment control computer 106 updates the series of treatment beam pulses 721 directed to the target volume 510 .

[0078] In some embodiments, the imaging interval is between a series of multiple therapy beam pulses, and as a result, inhibition of therapy beam pulses is not performed. Fig. 9One such embodiment is illustrated in FIG.

[0079] Fig. 9 9 is a schematic timing diagram 900 illustrating the timing of imaging beam pulses 931 during an imaging interval 930, the duration 935 of the imaging interval 930 being shorter than the time interval 925 between two treatment beam pulses 921, according to one embodiment of the present disclosure. Fig. 9 9, the timing of treatment beam pulses 921 during treatment interval 930, the opening and closing of reset switch 602 and readout switch 603, and the activation of ADC 611 are also depicted. As shown, time interval 925 is longer in duration than imaging interval 930. Therefore, inhibition of treatment beam pulses 921 is not performed.

[0080] In some embodiments, the duration of the imaging interval 930 can be shortened to less than the time interval 925 due to the brief readout portion 933 enabled by the voltage follower 604. Alternatively or additionally, the duration of the imaging interval 930 can be shortened to less than the time interval 925 due to the brief irradiation portion 932 enabled by a sufficiently high power imaging X-ray source. Alternatively or additionally, the time interval 925 separating each treatment beam pulse 921 can be extended, for example up to about 10 ms. Thus, in one example embodiment, an X-ray image is acquired in about 1 ms to 5 ms, and a treatment beam pulse 921 is directed to the target volume every 6 ms (or longer). Thus, each imaging interval 930 can be performed between each treatment beam pulse 921.

[0081] Electronic shutter

[0082] In some embodiments, therapeutic X-rays are delivered to the target volume while imaging X-rays are also delivered to the target volume to generate volumetric image data of the target volume. That is, during an imaging interval in which imaging X-rays are received by the X-ray imaging device, one or more pulses of therapeutic X-rays are also directed to the target volume. However, in such embodiments, an electronic shutter included in each pixel of the X-ray imaging device prevents image signals from accumulating during portions of the imaging interval in which pulses of therapeutic X-rays are directed to the target volume. Figures 10 to 12 One such embodiment is described below.

[0083] Fig.101 is a circuit diagram 1000 of a pixel detector element 310 including an electronic shutter 1002 according to one embodiment of the present disclosure. In this embodiment, the pixel detector element 310 enables an X-ray imager to receive imaging X-rays during an imaging interval in which pulses of therapeutic X-rays are also directed to a target volume. Specifically, the electronic shutter 1002 prevents charge from accumulating in a signal integrator 1004 associated with the pixel detector element 310 when therapeutic X-rays are directed to the target volume.

[0084] The pixel detector element 310 includes a photodiode 1001, an electronic shutter 1002, a readout / reset switch 1003, and a signal integrator 1004. In some embodiments, the pixel detector element 310 also includes a capacitor reset switch 1005. Fig.10 The illustrated embodiment of the pixel detector element 310 may be included in an X-ray imager of the RT system 100, such as included in Figure 2 X-ray imager 207 or Figure 4 In the first X-ray imager 407 or the second X-ray imager 409. As shown in the figure, the photodiode 1001 is communicatively coupled to the reference voltage V via the electronic shutter 1002. ref , and is communicatively coupled to data line 1010 via signal integrator 1004 and readout / reset switch 1003. In some embodiments, V ref Can be any suitable reference voltage, for example, ground or 0V. Photodiode 1001 is a diode that does need to store enough charge to generate an image signal. For example, in some embodiments, photodiode 1001 is configured as a PN diode that does not include an intrinsic semiconductor region for storing charge. Alternatively, in some embodiments, photodiode 1001 is configured as a PIN diode that can store significantly more charge than a PN diode. Pixel detector elements in conventional X-ray imagers are typically configured as PIN diodes. In some embodiments, signal integrator 1004 is a voltage integrator, a current integrator, or a charge integrator. In some embodiments, signal integrator 1004 is formed by a single transistor 1004A and a single capacitor 1004B as shown. Alternatively, in other embodiments, any other technically feasible charge integration device can be used as signal integrator 1004.

[0085] In operation, when Figure 5When photons generated by the scintillator material 503 in the target volume 510 are incident on the photodiode 1001, the photodiode 1001 generates a charge or image signal. The charge is accumulated in a signal integrator 1004, which is included in the pixel detector element 310 and is external to the photodiode 1001. When the readout / reset switch 1003 is closed, the charge accumulated by the photodiode 1001 is then read out to the data line 1010 and converted into a digital signal by the ADC 1011, which is external to the pixel detector element 310 and coupled to the data line 1010. In some embodiments, the capacitor reset switch 1005 is also closed to reset the signal integrator 1004. According to various embodiments, during the time interval when the treatment beam pulse is directed to the target volume 510, the electronic shutter 1002 is closed so that the signal integrator 1004 does not receive additional image signals caused by the scattered treatment beam pulse. Therefore, the noise generated by the treatment beam pulse is prevented from being captured by the photodiode 1001. Fig.11 One such embodiment is illustrated in FIG.

[0086] Fig.11 1 is a schematic timing diagram 1100 illustrating application of treatment beam pulses 1121 and imaging beam pulses 1131 during an imaging interval 1130 according to one embodiment of the present disclosure. Fig.11 Also depicted in FIG. 1 are the opening and closing timing of the activation of the electronic shutter 1002 , the readout / reset switch 1003 , and the ADC 1011 relative to the treatment beam pulse 1121 and the imaging beam pulse 1131 .

[0087] Imaging interval 1130 includes an irradiation portion 1132 and a readout portion 1133. During irradiation portion 1132, at least one imaging beam pulse 1131 is directed to the target volume and received by an X-ray imager of RT system 100. In some embodiments, a typical imaging beam pulse 1131 (e.g., Figure 2 The duration of the imaging beam pulse of the imaging X-ray 231 in the X-ray imager is approximately 10 ms and is used to generate a single projection image of the target volume. In such an embodiment, one such image is acquired approximately every 30 ms-50 ms. During the readout portion 1133, for each pixel detector element 310 included in the X-ray imager, the image signal stored in the signal integrator 1004 of the pixel detector element 310 is read out to the ADC 1011. Specifically, the readout / reset switch 1003 is closed during the readout portion 1133, for example, synchronized with other pixel detector elements 310 (not shown) of the X-ray imager and synchronized with the activation of the ADC 1011. In this way, during the readout portion 1133 of each imaging interval 1130, the image signal is read out from each signal integrator 1004 of the X-ray imager.

[0088] As shown, one or more treatment beam pulses 1121 are directed to the target volume before, during, and after imaging interval 1130. In some embodiments, a typical treatment beam pulse 1121 (e.g., Figure 2 The duration of the pulses of the treatment beam 230 in the embodiment is about 5 μs and is delivered approximately every 1 ms-10 ms. Fig.11 In the illustrated embodiment, the electronic shutter 1002 is closed when the treatment beam pulse 1121 is directed to the target volume 510. Therefore, when the electronic shutter 1002 is closed, the output of the photodiode 1001 is coupled to ground, and the signal integrator 1004 cannot receive additional image signals from the photodiode 1001. Therefore, even if scattered X-rays from the treatment beam pulse 1121 strike the target volume 510, the output of the photodiode 1001 is coupled to ground, and the signal integrator 1004 cannot receive additional image signals from the photodiode 1001. Figure 5 The signal integrator 1004 also cannot accumulate this potential image noise as charge even though the scintillator layer 503 in the photodiode 1001 generates photons incident on the photodiode 1001.

[0089] Fig.12 A flow chart of a radiation therapy process according to one or more embodiments of the present disclosure is set forth. The method may include one or more operations, functions, or actions shown in one or more of blocks 1201-1230. Although the blocks are illustrated in a sequential order, the blocks may be executed in parallel and / or in an order different from that described herein. Moreover, various blocks may be combined into fewer blocks, divided into additional blocks, and / or eliminated based on the desired implementation. Although combined Figures 1 to 5 , Fig.10 and Fig.11 The method is described with reference to a system of the invention, but those skilled in the art will appreciate that any suitably configured radiation therapy system is within the scope of the present disclosure.

[0090] Prior to the method steps, a similar setup process is performed as described above in connection with method 800, including acquiring volumetric image data for the digital volume 500, performing automatic segmentation and deformable registration, and positioning the patient prior to RT treatment.

[0091] When a treatment arc is initiated to perform the current RT fraction, method 1200 starts at step 1201. In step 1201, the patient starts with a breath hold. In some embodiments, the RT treatment includes multiple fractions. Alternatively, in other embodiments, the RT treatment consists of a single treatment arc.

[0092] In step 1202, the treatment control computer 106 causes the gantry 210 to continuously rotate in a first direction through a treatment arc.

[0093] In step 1203 , the treatment control computer 106 begins directing a series of treatment X-ray pulses, such as treatment beam pulses 721 or 821 , to the target volume 510 while the gantry 210 continues to rotate in a first direction.

[0094] In step 1204 , the treatment control computer 106 selects the next treatment beam pulse to be directed to the target volume 510 .

[0095] In step 1205, the treatment control computer 106 determines whether the selected next treatment beam pulse is timed to occur during the imaging interval 1130. If so, the method 1200 proceeds to step 1206; if not, the method 1200 proceeds to step 1210.

[0096] In step 1206, the treatment control computer 106 causes the electronic shutter 1002 in each pixel detector element 310 to close before directing the selected next treatment beam pulse to the target volume 510. For example, in some embodiments, the treatment control computer 106 causes the output of the photodetector 10001 to be communicatively coupled to ground. Thus, the treatment control computer 106 prevents image signals from accumulating in each signal integrator 1004 of the x-ray imager.

[0097] In step 1207 , the treatment control computer 106 causes the selected next treatment beam pulse to be directed to the target volume 510 .

[0098] In step 1208, the treatment control computer 106 causes the electronic shutter 1002 in each pixel detector element 310 to open. For example, in some embodiments, the treatment control computer 106 causes the output from the photodetector 10001 to be decoupled from the ground communication ground. Thus, the treatment control computer 106 enables the image signal to be accumulated again in each signal integrator 1004 of the X-ray imager.

[0099] In step 1210, the treatment control computer 106 determines whether there are any remaining treatment beam pulses in the treatment arc. If so, the method 1200 returns to step 1204 and the next treatment beam pulse is selected; if not, the method 1200 proceeds to step 820 and the method 800 terminates.

[0100] In step 1210 , the treatment control computer 106 directs the selected next treatment beam pulse to the target volume 510 , and the method 1200 proceeds to step 1210 .

[0101] As an example, embodiments of the present disclosure have been described with respect to an RT system that includes a circular gantry and generates volumetric image data of a target volume. However, the various embodiments described herein may also be advantageously implemented in RT systems having other configurations and / or that perform two-dimensional imaging of a target volume. For example, various embodiments of the present disclosure may be advantageously applied to a radiation system configured to perform fluoroscopy, serial imaging, or triggered imaging. In such embodiments, the x-ray imager, treatment beam generator, and / or imaging x-ray source may not be coupled to the rotating gantry, or may be used when the gantry is stationary.

[0102] The implementation of the above-described embodiments enables an X-ray imager to collect imaging data of a target volume during IGRT without image noise due to treatment beam scatter. Advantageously, movement or deformation of the target volume relative to the radiotherapy system and / or changes in surrounding organs at risk can be more reliably detected and compensated. Thus, the shape and relative position of the organs at risk and the target volume can be more accurately adapted, thereby contributing to a better treatment effect.

[0103] Descriptions of various embodiments have been given for purposes of illustration, but are not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

[0104] The various aspects of the present embodiment may be embodied as a system, method or computer program product. Therefore, the various aspects of the present disclosure may take the form of a complete hardware embodiment, a complete software embodiment (including firmware, resident software, microcode, etc.) or a combination of software and hardware embodiments that may be generally referred to as a "circuit", "module" or "system" as a whole. In addition, the various aspects of the present disclosure may take the form of a computer program product embodied in one or more computer-readable media on which a computer-readable program code is embodied.

[0105] Any combination of one or more computer-readable media may be utilized. A computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or apparatus, or any suitable combination of the foregoing. More specific examples (non-exhaustive list) of computer-readable storage media would include the following: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any other suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or apparatus.

[0106] Although various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

1. A radiotherapy system, comprising: X-ray imager; a treatment delivery X-ray source configured to direct treatment X-rays toward a target volume; an imaging X-ray source configured to direct imaging X-rays through the target volume and toward the X-ray imager; as well as The controller is configured as: directing a first pulse from a series of therapeutic X-ray pulses toward the target volume; directing first imaging X-rays through the target volume after directing the first pulse of therapeutic X-rays to the target volume and during a first imaging interval in which no therapeutic X-rays are directed to the target volume; as well as directing a second pulse from the series of therapeutic X-ray pulses toward the target volume after directing the first imaging X-ray through the target volume, the time interval between two therapeutic beam pulses separating each therapeutic beam pulse; in: The radiotherapy system is configured to: shorten the duration of an imaging interval to less than the time interval between two treatment beam pulses by means of a voltage follower communicatively coupled to the output of a photodiode in a pixel detector element of the X-ray imager; wherein the photodiode is communicatively coupled to a data line via a readout switch and the voltage follower, wherein the voltage follower is included in each pixel detector element such that the circuit of the pixel detector element is not limited by the resistor-capacitor time constant of the circuit, the voltage follower enabling a brief readout portion that shortens the duration of an imaging interval; and Wherein the controller is further configured to: communicatively connect the voltage follower to a data line during the readout portion of the first imaging interval.

2. The radiation therapy system of claim 1 , wherein the controller is further configured to: determining that a third pulse from the series of therapeutic X-ray pulses is timed to be directed to the target volume during the first imaging interval; and The third pulse of therapeutic X-rays is inhibited from being directed through the target volume during the first imaging interval.

3. The radiation therapy system of claim 2 , wherein the controller is further configured to prohibit the third pulse of therapeutic X-rays from being directed through the target volume during the first imaging interval by directing the third pulse of therapeutic X-rays toward the target volume during a time interval occurring after the first imaging interval.

4. The radiation therapy system of claim 2, wherein the first imaging interval comprises an illumination portion and a readout portion.

5. The radiation therapy system of claim 1 , wherein the controller is further configured to: determining that a fourth pulse from the series of therapeutic X-ray pulses is timed to be directed to the target volume during the first imaging interval; and The fourth pulse of therapeutic X-rays is prohibited from being directed through the target volume during the first imaging interval.

6. The radiation therapy system of claim 1, wherein: The first imaging interval includes an illumination portion and a readout portion; and The controller is also configured to direct the first imaging X-rays through the target volume during the irradiation portion.

7. The radiation therapy system of claim 6 , wherein the first imaging X-ray comprises a single pulse of imaging X-rays that begins at a start time of the irradiation portion of the first imaging interval and ends at an end time of the irradiation portion of the first imaging interval.

8. The radiation therapy system of claim 1 , wherein the controller is further configured to direct a third pulse of therapeutic X-rays toward the target volume after directing the second pulse of therapeutic X-rays to the target volume and before a second imaging interval in which the second imaging X-rays are directed through the target volume.

9. The radiation therapy system of claim 1, wherein the pixel comprises one of: an indium gallium zinc oxide (IGZO) semiconductor material, a low temperature polysilicon semiconductor material, and a polysilicon semiconductor material.

10. The radiation therapy system of Claim 1, further comprising a reset switch communicatively coupled to the photodiode.

11. The radiation therapy system of claim 10, wherein the controller is further configured to communicatively couple the photodiode to a reference voltage during treatment intervals.

12. The radiation therapy system of claim 11, wherein the treatment interval does not overlap in time with the imaging interval.

13. The radiation therapy system of claim 1 , further comprising a gantry configured to rotate about a bore of the radiation therapy system, wherein the target volume is disposed in the bore, and wherein the controller is further configured to continuously rotate the gantry in a first direction through a treatment arc while directing the first pulse of therapeutic x-rays, the first imaging x-rays, and the second pulse of therapeutic x-rays toward the target volume.

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