Methods and apparatus for improving scattering evaluation and scattering correction in imaging.

Abstract

SOLUTION: An X-ray imaging apparatus and associated method are provided that receive measured projection data from a wide aperture scan of a wide body-axis direction and a narrow aperture scan of a narrow body-axis direction within the wide body-axis direction and determine an estimated scatter in the wide body-axis direction using an optimized scatter estimation technique. The optimized scattering evaluation technique is based on the difference between the measured scattering in the narrow body-axis direction and the evaluated scattering in the narrow body-axis direction. The kernel-based scatter evaluation / scatter correction approach can be fitted to minimize scatter differences in a narrow body-axis direction. Thereafter, the fitted (optimized) kernel-based scatter evaluation / correction is applied to the wide body-axis direction region. Optimization may occur in the projection data domain or in the reconstruction domain. An iterative process is also utilized.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Cross-reference of related applications This application is a U.S. Provisional Patent Application No. 62 / 773,712 filed on November 30, 2018 (Agent Reference Number 38935 / 04001); a U.S. Provisional Patent Application No. 62 / 773,700 filed on November 30, 2018 (Agent Reference Number 38935 / 04002); and a U.S. Provisional Patent Application No. 62 / 796,831 filed on January 25, 2019 (Agent Reference Number 38935 / 04002). 38935 / 04004); U.S. Patent Provisional Application No. 62 / 800,287 filed on February 1, 2019 (Agent Reference Number 38935 / 04003); U.S. Patent Provisional Application No. 62 / 801,260 filed on February 5, 2019 (Agent Reference Number 38935 / 04006); U.S. Patent Provisional Application No. 62 / 813,335 filed on March 4, 2019 (Agent Reference Number U.S. Patent Provisional Application No. 62 / 821,116 filed March 20, 2019 (Agent Reference Number 38935 / 04009); U.S. Patent Provisional Application No. 62 / 836,357 filed April 19, 2019 (Agent Reference Number 38935 / 04016); U.S. Patent Provisional Application No. 62 / 836,352 filed April 19, 2019 The applicant claims interest in 11 U.S. provisional patent applications, including (Agent Reference Number 38935 / 04017); U.S. Provisional Patent Application No. 62 / 843,796 filed on May 6, 2019 (Agent Reference Number 38935 / 04005); and U.S. Provisional Patent Application No. 62 / 878,364 filed on July 25, 2019 (Agent Reference Number 38935 / 04008). This application is also referred to as Agent Reference No. 38935 / 04019, titled "MULTIMODAL RADIATION APPARATUS AND METHODS"; Agent Reference No. 38935 / 04020, titled "APPARATUS AND METHODS FOR SCALABLE FIELD OF VIEW IMAGING USING A MULTI-SOURCE SYSTEM"; and Agent Reference No. 38935 / 04011, titled "INTEGRATED HELICAL FAN-BEAM COMPUTED TOMOGRAPHY IN IMAGE-GUIDED RADIATION TREATMENT DEVICE";Agent reference number 38935 / 04010, titled "COMPUTED TOMOGRAPHY SYSTEM AND METHOD FOR IMAGE IMPROVEMENT USING PRIOR IMAGE"; Agent reference number 38935 / 04013, titled "OPTIMIZED SCANNING METHODS AND TOMOGRAPHY SYSTEM USING REGION OF INTEREST DATA"; Agent reference number 38935 / 04015, titled "HELICAL CONE-BEAM COMPUTED TOMOGRAPHY IMAGING WITH AN OFF-CENTERED DETECTOR"; Agent reference number 38935 / 04021, titled "MULTI-PASS COMPUTED TOMOGRAPHY SCANS FOR IMPROVED WORKFLOW AND PERFORMANCE"; "METHOD AND APPARATUS FOR SCATTER ESTIMATION IN CONE-BEAM COMPUTED This relates to ten non-provisional U.S. patent applications filed on the same day, including Agent Reference No. 38935 / 04012, titled "TOMOGRAPHY"; Agent Reference No. 38935 / 04014, titled "ASYMMETRIC SCATTER FITTING FOR OPTIMAL PANEL READOUT IN CONE-BEAM COMPUTED TOMOGRAPHY"; and Agent Reference No. 38935 / 04022, titled "METHOD AND APPARATUS FOR IMAGE RECONSTRUCTION AND CORRECTION USING INTER-FRACTIONAL INFORMATION." All of the contents of one or more patent applications and one or more patents identified above are incorporated fully by reference herein.

[0002] Aspects of the disclosed techniques relate to the evaluation of scatter in projection data, and more particularly to the use of narrow aperture scans for evaluating scatter in wide aperture scans, including X-ray, computed tomography (CT), and cone beam computed tomography (CBCT) scans, among various imaging techniques. BACKGROUND ART

[0003] Scatter in cone beam CT can occupy a significant portion of the detected photons. This is particularly the case when an anti-scatter grid is not used with a wide collimation aperture.Scatter can have a negative impact on image quality, including contrast and quantitative accuracy.As a result, scatter measurement, evaluation, and correction can be applied to the processing and image reconstruction of cone beam CT data, including in the context of image-guided radiation therapy (IGRT). IGRT can utilize medical imaging techniques such as CT to collect images of a patient before, during, and / or after treatment.

[0004] For flat-panel-based cone beam computed tomography (CBCT), a pair of high-attenuation blades is used as part of the collimator to form an aperture that restricts the axial range of the body illuminated by the X-ray beam within the patient / panel. A larger aperture enables an increase in the axial effective range of the patient during the scan. Therefore, when it is necessary to image a large axial range of the patient, the total scan time can be reduced by using a wider aperture. However, in exchange, although the amount of scatter increases with the aperture, the primary data remains similar. Without scatter correction, the increased scatter will have a negative impact on image quality and image quantity.

[0005] Hardware-based scattering reduction methods include the use of a scattering prevention grid on the detector panel surface, very narrow apertures, dose-compensating filters, and air separation between the patient and the detector. Conventional scattering prevention grids can significantly reduce X-ray scattering. A major drawback is that this system is more complex and also reduces a large amount of primary data. Using a very narrow aperture can significantly reduce scattering (even to an effective level of almost nothing). However, the effective range in the axial direction becomes very small, resulting in an overall scan time that is not practical.

[0006] Software-based scattering reduction / correction can evaluate scattering in data acquired using physical models. These methods can test both the data acquisition system and the interaction process between X-rays and matter. The former requires detailed knowledge of the key components of the overall imaging chain, and patient information that may be obtained from treatment planning CT or initial reconstruction without scattering correction. These methods can be achieved either probabilistically (e.g., Monte Carlo simulation-based approaches) or deterministically (e.g., radiation transfer equation-based approaches). The former are computationally expensive, while the latter are generally considered an unsolved problem in this field. Model-based methods are typically patient-specific and may be more accurate. However, these methods require a significant amount of prior information about the data acquisition system and the patient. This is because the effectiveness of these methods depends heavily on the accuracy of the modeling. Furthermore, these methods have high demands in terms of computational power and time, resulting in a significant negative impact on workflow and throughput. The evaluated scattering is then used to correct the data prior to or during image reconstruction.

[0007] Software-based scattering correction approaches include kernel-based scattering assessment and correction. In kernel-based approaches, scattering kernels are determined by physical measurements or Monte Carlo simulations that estimate the material's composite structure. For example, one typical method involves measuring scattering kernels with water layers of different thicknesses at a given X-ray spectrum and aperture. The aperture projected onto the detector surface is equivalent in size to the panel's axial dimension. Once kernels are measured / determined for different water layers, these kernels are used for scattering correction in patient scans to estimate that the patient's tissues correspond to water layers of different thicknesses. The application of kernels for scattering assessment and correction may include inverse superposition integration of scattering using kernels in either the spatial or frequency domain. Furthermore, it can be adapted to the local dispersion of an object. For example, measured scattering data may be considered as the superposition of primary and scattering kernels. By performing an inverse superposition process and using appropriate pre-built kernels, the primary and scattering can be separated.

[0008] Kernel-based scattering assessment / correction is widely used in CBCT due to its simplicity. However, a fundamental challenge with this type of approach is that its accuracy can degrade when the distribution of patient tissue is highly non-uniform, particularly in the thoracic and pelvic regions. Furthermore, with larger aperture sizes, the performance of the approach can degrade based on the increased scattering associated with the larger aperture. [Overview of the project]

[0009] In one embodiment, the imaging device includes a rotating imaging source for emitting a radiation beam, a detector positioned to receive radiation from the imaging source, and a beamformer configured to adjust the shape of the radiation beam emitted by the imaging source. The shape of this radiation beam is intended to be configured for a wide aperture scan of a wide axial region and a narrow aperture scan of a narrow axial region within the wide axial region, in which case the evaluated scattering in the wide axial region is based on projection data from the narrow axial region.

[0010] Features described and / or illustrated in relation to one embodiment may be used in a similar or analogous manner, and / or in combination with or instead of features of other embodiments, in one or more other embodiments.

[0011] 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. All terms used in the claims have their fully general meanings.

[0012] Embodiments of this specification are illustrated in the accompanying drawings incorporated herein and constituting part thereof, and these, together with the general description of the invention provided above and the detailed description provided below, contribute to illustrating embodiments of the invention. It will be understood that the range of elements illustrated in the figures (e.g., a box, a group of boxes, or other shapes) represents one embodiment of the range. In some embodiments, one element may be designed as multiple elements, or multiple elements may be designed as one element. In some embodiments, an element shown as an internal component of another component may be implemented as an external component, and vice versa. Furthermore, elements may not be drawn to scale. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view of an exemplary X-ray imaging apparatus relating to one aspect of the disclosed method. [Figure 2] This is a schematic diagram of an X-ray imaging device incorporated into an exemplary radiotherapy apparatus, relating to one aspect of the disclosed method. [Figure 3] This is a schematic diagram of an exemplary scan design for imaging the axial region of a target. [Figure 4] This flowchart illustrates an exemplary method for evaluating scattering in a domain of projection data, using a scan design with a narrow scan area within a wide scan area. [Figure 5] This flowchart illustrates another exemplary method of scattering evaluation in the domain of projection data, using a scan design with a narrow scan area within a wide scan area. [Figure 6] This flowchart illustrates an exemplary iterative method for evaluating scattering in the domain of projection data, using a scan design with a narrow scan area within a wide scan area. [Figure 7] This flowchart illustrates an exemplary method of scattering correction in a reconstruction domain using a scan design with a narrow scan area within a wide scan area. [Figure 8] This flowchart illustrates an exemplary iterative method for scattering correction in a reconstruction domain, using a scan design with a narrow scan area within a wide scan area. [Figure 9] This flowchart illustrates an exemplary method for determining a narrow scan from pre-image data intended for use in narrow / wide scan designs. [Figure 10] This flowchart illustrates an exemplary method for determining a narrow scan from wide scan data for use in a narrow / wide scan design. [Figure 11] This flowchart illustrates an example of IGRT using a radiotherapy device. [Figure 12]This is a block diagram representing an image-based, exemplary pre-supply step. [Figure 13] This is a block diagram representing an exemplary data source that may be used during imaging or image-based pre-feed steps. [Modes for carrying out the invention]

[0014] The following includes definitions of exemplary terms that may be used throughout this disclosure. Both singular and plural forms of all words are within the scope of their respective meanings.

[0015] As used herein, “Component” may be defined as part of hardware, part of software, or a combination thereof. Part of hardware includes at least a processor and part of memory, which contains instructions for execution. Component may be associated with a device.

[0016] As used herein, “logic,” synonymous with “circuit,” includes, but is not limited to, hardware, firmware, software, and / or combinations thereof for performing one or more functions or one or more operations. For example, based 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 entirely incorporated as software.

[0017] As used herein, "processor" includes, but is not limited to, one or more substantially arbitrary number of processor systems, either in any combination, such as a microprocessor, a microcontroller, a central processing unit (CPU), and a digital signal processor (DSP), or a stand-alone processor. The 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), a clock, a decoder, a memory controller, or an interrupt controller. These support circuits may be internal or external to the processor or its associated electronic package. The support circuits are in an operational communication state with the processor. The support circuits are not necessarily shown separately from the processor in a block diagram or other figure.

[0018] As used herein, "signal" includes, but is not limited to, one or more electrical signals, such as analog or digital signals, one or more computer instructions, bits, or bit streams.

[0019] As used herein, "software" includes, but is not limited to, one or more computer-readable instructions and / or executable instructions that cause a computer, processor, logic, and / or other electronic device to perform functions, operations, and / or operate in a desired manner. The instructions may be incorporated in various forms, such as routines, algorithms, modules, or programs that include individual applications. Or it may be coded from a dynamically linked source or library.

[0020] Although the above exemplary definitions are provided, it is the applicant's intention that the broadest reasonable interpretation consistent with this specification be applied to these and other terms.

[0021] As will be described in more detail below, embodiments of the disclosed methods relate to evaluating scattering in imaging of projection data, including using data from a narrow aperture scan within a wider aperture scan to evaluate scattering in data from a wider aperture scan, as well as during X-ray scans, CT scans, and CBCT scans. In some embodiments, radiotherapy delivery systems and methods can utilize an integrated low-energy radiation source of CT for use in conjunction with or as part of IGRT. In particular, for example, radiotherapy delivery systems and methods can use rotational (e.g., helical or step-and-shoot) imaging acquisition in conjunction with a high-energy radiation source for therapeutic procedures and combine it with a low-energy focused radiation source for imaging in the gantry.

[0022] Low-energy radiation sources (e.g., kilovolts (kV)) can produce higher-quality images for imaging than those produced by high-energy radiation sources (e.g., megavolts (MV)). Images produced with kV energy typically have better tissue contrast than those produced with MV energy. High-quality volume imaging may be required for visualization of target and risk organs (OARS) for adaptive treatment monitoring and treatment planning / replanning. In some embodiments, kV imaging systems may also be used for positioning, motion tracking, and / or characterization or correction capabilities.

[0023] Image acquisition techniques may include multiple rotational scans, but other methods may be used. These rotational scans may be, for example, continuous scans (e.g., with a helical source trajectory around the central axis along with the longitudinal movement of the patient support through the gantry bore), discontinuous stop-and-reverse full-circumference scans with gradual longitudinal movement of the patient support, or step-and-shoot full-circumference scans.

[0024] In relation to various embodiments, imaging equipment focuses a radiation source. This includes, for example, using a beamformer to focus the beam into a cone beam or a fan beam. In one embodiment, the focused beam is combined with a gantry that rotates continuously while the patient moves, thereby enabling helical imaging.

[0025] In some embodiments, to complete high-quality volumetric images, the time associated with increased scan rotation is reduced by high gantry rates / speeds (e.g., using high-speed slip-ring rotations, including up to 10 revolutions per minute (rpm), up to 20 rpm, up to 60 rpm, or higher rpms), high kV frame rates, and / or sparse data reconstruction techniques, enabling kV CT imaging on a radiotherapy supply platform. Detectors (having various column / slice sizes, configurations, dynamic ranges, etc.), scan pitch, and / or dynamic collimation are additional features in various embodiments. This includes selectively irradiating portions of the detector and selectively defining effective readout areas, as will be described in detail later. In particular, image quality can be improved by using adjustable beamformers / collimators on X-ray (low-energy) imaging sources and / or optimizing the detector readout range (by evaluating scattering as described below).

[0026] Imaging instruments and methods can provide selective and variable collimation of a radiation beam emitted from a radiation source. This involves adjusting the shape of the radiation beam to irradiate a smaller area than the entire effective area of ​​the associated radiation detector (e.g., a radiation detector positioned to receive radiation from an X-ray radiation source). For example, a beamformer of an imaging instrument can adjust the shape of the radiation beam in response to pitch variations during a helical scan. In another embodiment, the beam aperture can be adjusted by the beamformer for various aFOV requirements in the axial direction. In particular, the aFOV can be adjusted to scan areas with various axial (longitudinal) lengths, including narrow and wide areas. Furthermore, by directly irradiating only the primary region of the detector with radiation, the shadow region of the detector can receive only scattering. In some embodiments, scattering measurements in the shadow region of the detector (and in some embodiments, measurements in the peripheral region) can be used to evaluate scattering in the primary region of the detector receiving projection data.

[0027] The imaging instrument and method provide a selective and variable detector readout region and range. This includes adjusting the detector readout range to limit the effective area of ​​the detector in order to improve readout speed. For example, it is possible to read out less data than the available shadow area and use it for scattering evaluation. Combining selective readout with beamforming enables various optimizations of scattering fitting techniques.

[0028] Referring to Figures 1 and 2, an imaging device 10 (e.g., an X-ray imaging device) is shown. It will be understood that the imaging device 10 may be associated with and / or incorporated into a radiotherapy device (shown in Figure 2) which can be used for a variety of applications including but not limited to IGRT. The imaging device 10 includes a rotatable gantry system called a gantry 12, which is supported by or otherwise housed within a support unit or housing 14. In this specification, a gantry refers to a gantry system comprising one or more gantry (e.g., a ring or C-arm) capable of supporting one or more radiation sources and / or associated detectors as it rotates around a target. For example, in one embodiment, a first radiation source and its associated detector can be mounted on a first gantry of the gantry system, and a second radiation source and its coupled detector can be mounted on a second gantry of the gantry system. In another embodiment, multiple radiation sources and one or more associated detectors can be mounted on the same gantry of the gantry system. This includes, for example, the case where the gantry system consists of only one gantry. Various combinations of gantry, radiation source, and radiation detector may be combined into various gantry system configurations for imaging and / or processing the same volume within the same instrument. For example, kV and MV radiation sources can be mounted on the same or different gantry of the gantry system and may be selectively used for imaging and / or treatment as part of an IGRT system. When mounted on different gantry, the radiation sources are rotatable independently. However, it is still possible to image the same (or nearly the same) volume simultaneously. The rotatable ring gantry 12 may have a capability of 10 rpm or more as described above. The rotatable gantry 12 defines a gantry bore 16 into which a patient can move and position for imaging and / or treatment.According to one embodiment, the rotatable gantry 12 is configured as a slip-ring gantry, providing continuous rotation of the imaging radiation source (X-rays) and associated radiation detectors while offering sufficient bandwidth for high-quality imaging data received by the detector. The slip-ring gantry eliminates the need for alternating gantry rotations intended for winding and unwinding cables carrying power and signals associated with the device. Such a configuration enables continuous helical tomography, including CBCT, even when integrated into an IGRT system.

[0029] The patient support 18 is positioned adjacent to the rotatable gantry 12 and is typically configured in a horizontal position to support the patient during 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 plane of rotation of the gantry 12 (along or parallel to the axis of rotation of the gantry 12). The patient support 18 can be operably 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 radiation sources mounted on the rotating gantry for rotation around the patient's longitudinal axis, according to a commanded imaging and / or treatment plan. The patient support can also be moved up, down, left, and right within a limited range when the patient support is inside the bore 16, allowing for adjustment of the patient position for optimal treatment. When viewed from the front of the gantry 12, axes x, y, and z are indicated. The x-axis points horizontally to the right, the y-axis points to the gantry plane, and the z-axis points vertically upward. The x, y, and z axes follow the right-hand rule.

[0030] It will be understood that other modifications may be used without departing from the scope of the disclosed techniques. For example, the rotatable gantry 12 and patient support 18 may be controlled so that the gantry 12 rotates around the patient supported on the patient support in a “reciprocating” manner (e.g., alternating clockwise and counterclockwise rotations) (as opposed to the continuous manner as described above), while the support is controlled to move relative to the rotatable gantry 12 (at a constant or variable speed). In another embodiment, by using a continuous step-and-shoot circumferential scan, the longitudinal movement (steps) of the patient support 18 is alternating with the scanning rotation (shoots) of the rotatable gantry 12 until a desired volume is captured. The apparatus 10 has the capability to perform volume-based and planar-based image acquisition. For example, in various embodiments, the apparatus 10 may be used to acquire volume images and / or planar images and perform the relevant processing methods described below.

[0031] To generate projection data, the movement of various other types of radiation sources and / or patient supports may be utilized to obtain relative motion of the radiation source and / or patient. Discontinuous motion of the radiation source and / or patient support, continuous but variable / non-constant (including linear and non-linear) linear motion, velocity, and / or trajectory, as well as combinations thereof, may be used, including in combination with various embodiments of the radiotherapy apparatus 10 described above.

[0032] As shown in Figure 2, the X-ray imaging apparatus 10 includes an imaging radiation source 30 coupled to or otherwise supported by a rotatable gantry 12. The imaging radiation source 30 emits a radiation beam (generally indicated as 32) for producing high-quality images. In this embodiment, the imaging radiation source is an X-ray source 30, which is configured as a kiloelectron volt (kV) source (e.g., a medical X-ray source having an energy level in the range of about 20 kV to about 150 kV). In one embodiment, the kV radiation source includes a kiloelectron volt peak photon energy (keV) of up to 150 keV. The imaging radiation source can be any type of transmission source suitable for imaging. For example, the imaging radiation source may be, for instance, an X-ray source (including one for CT) or other methods, which generate photons using sufficient energy and beam (e.g., a gamma-ray source (e.g., cobalt-57, with an energy peak at 122 keV), an X-ray fluorescence source (e.g., a fluorescence source that passes through the Pb k-line, with two peaks at about 70 keV and about 82 keV)). References herein to X-rays, X-ray imaging, X-ray imaging sources, etc., are illustrative to specific embodiments. Other imaging transmission sources may be used interchangeably in various other embodiments.

[0033] The X-ray imaging apparatus 10 may also include another radiation source 20 coupled to or otherwise supported by a rotatable gantry 12. According to one embodiment, the radiation source 20 is configured as a therapeutic radiation source, such as a high-energy radiation source used to treat a tumor inside a patient within a region of interest. It will be understood that the therapeutic radiation source may be a high-energy X-ray beam (e.g., a mega-voltage (MV) X-ray beam) and / or a high-energy particle beam (e.g., an electron beam, a photon beam, or a beam of heavy ions such as carbon) or another suitable form of high-energy radiation without departing from the scope of the disclosed techniques. In one embodiment, the radiation source 20 includes a mega-electron-volt peak photon energy (MeV) of 1 MeV or greater. In one embodiment, the high-energy X-ray beam has an average energy greater than 0.8 MeV. In another embodiment, the high-energy X-ray beam has an average energy greater than 0.2 MeV. In another embodiment, the high-energy X-ray beam has an average energy greater than 150 keV. Generally, radiation source 20 has a higher energy level (peak and / or average, etc.) than imaging radiation source 30.

[0034] In one embodiment, the radiation source 20 is a LINAC that generates therapeutic radiation (e.g., MV), and the imaging system comprises an independent imaging radiation source 30 that generates relatively low-intensity, low-energy imaging radiation (e.g., kV). In other embodiments, the radiation source 20 may be a radioisotope that can generally have energies greater than 1 MeV, such as Co-60. The radiation source 20 is capable of emitting one or more radiation beams (generally indicated by 22) towards a region of interest (ROI) inside the patient supported on a patient support 18 according to the treatment plan.

[0035] In some embodiments, the radiation sources 20 and 30 are used in conjunction with each other to provide high-quality and better usable images. In other embodiments, at least one additional radiation source is connected to the rotatable gantry 12 and can be operated to acquire projection data at a peak photon energy different from the peak photon energies of the radiation sources 20 and 30.

[0036] Figures 1 and 2 show an X-ray imaging apparatus 10 having a radiation source 30 mounted on a ring gantry 12, but other embodiments may include other types of rotatable imaging apparatus, 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. A gantry-based system includes a C-arm gantry, in which the imaging radiation source 30 is mounted on top in a cantilever-like manner and rotates about an axis passing through an isocenter. A gantry-based system further includes a ring gantry, such as a rotatable gantry 12, which generally has an annular shape in which the patient's body is extended through a bore of the ring / troid. The imaging radiation source 30 is mounted on the circumference of the ring and rotates about 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 rotates repeatedly and in the opposite direction.

[0037] The detector 34 (e.g., a two-dimensional flat detector or a curved detector) can be coupled to or otherwise supported by the rotatable gantry 12. The detector 34 (e.g., an X-ray detector) is positioned to receive radiation from the X-ray source 30 and is rotatable in conjunction with the X-ray source 30. The detector 34 can detect or measure the unattenuated radiation dose. Thus, it is possible to estimate what has actually been attenuated by the patient or the ROI of the associated patient (compared to the initially generated one). The detector 34 can detect or otherwise collect attenuation data from different angles if the radiation source 30 rotates around the patient and emits radiation toward the patient.

[0038] It will be understood that the detector 34 can take on a large number of configurations without departing from the scope of the disclosed method. As illustrated in Figure 2, the detector 34 may be configured as a flat panel detector (e.g., a multi-slice flat panel detector). According to another exemplary embodiment, the detector 34 may be configured as a curved detector.

[0039] A collimator or beamformer assembly (typically indicated as 36) is positioned relative to an imaging (X-ray) source 30 to selectively control and adjust the shape of the radiation beam 32 emitted by the X-ray source 30, selectively illuminating a location or area of ​​the effective region of the detector 34. The beamformer can also control how the radiation beam 32 is positioned on the detector 34. In one embodiment, the beamformer 36 may have a single kinetic / motion dimension (e.g., to create thinner or thicker slits). In another embodiment, the beamformer 36 may have two kinetic / motion dimensions (e.g., to create rectangles sized to various sizes). In yet another embodiment, the beamformer 36 may have the ability to take on a variety of other dynamically controlled shapes, including, for example, a parallelogram. All of these shapes can be dynamically adjusted during scanning. In some embodiments, the cutoff portion of the beamformer can be rotated and translated.

[0040] The beamformer 36 can be controlled to dynamically adjust the shape of the radiation beam 32 emitted by the X-ray source 30 in many geometric shapes. These geometric shapes include, but are not limited to, fan beams or cone beams with low beam thickness (width) as well as those including single-row detector widths or multi-row detectors (which represent only a portion of the detector's effective area). In various embodiments, the beam thickness may irradiate several centimeters of the effective area of ​​a larger detector. For example, of a 5-6 centimeter detector, 3-4 centimeters (measured along the longitudinal direction of the detector surface) may be selectively irradiated to the imaging radiation 32. In this embodiment, the 3-4 centimeter projection image data may be captured using approximately 1-2 centimeters of the unirradiated detector area on one or each side, which can be used to capture scattering data using their respective readings, as described later.

[0041] In other embodiments, the majority of the effective detector may be selectively irradiated with imaging radiation. For example, in some embodiments, the beam thickness may be reduced to a range of about 2 centimeters, about 1 centimeter, less than 1 centimeter, or similar sizes. This includes the case of smaller detectors. In other embodiments, the beam thickness may be increased to a range of about 4 centimeters, about 5 centimeters, more than 5 centimeters, or similar sizes. This includes the case of larger detectors. In various embodiments, the irradiation-to-effective detector area ratio may be 30-90% or 50-75%. In other embodiments, the irradiation-to-effective detector area ratio may be 60-70%. However, in other embodiments, various other irradiation and effective area sizes or irradiation-to-effective detector area ratios may be suitable. The beam and detector may be configured such that the detector's shadowed area (effective but not directly irradiated with radiation) is sufficient to capture scattering data beyond the peripheral area.

[0042] Various embodiments may include optimization of features that control the selective irradiation of the detector (e.g., beam size, beam / aperture center, sighting, collimation, pitch, detector readout range, detector readout center, etc.) so that the measurement data is sufficient for the primary (irradiated) and shadow regions, but is also optimized for velocity and dose control. The shape / position of the beamformer 36 and the readout range of the detector 34 may be controlled so that the radiation beam 32 from the X-ray source 30 is brought into range of an equivalent or smaller X-ray detector 34 based on a specific imaging task and scattering evaluation process being performed, including, for example, a combination of narrow and wide aFOV scans.

[0043] The beamformer may be configured in various ways to adjust the shape of the radiation beam 32 emitted by the X-ray source 30. For example, the collimator 36 may be configured to include a series of jaws, or other suitable members for defining and selectively adjusting the size of the aperture through which the radiation beam from the X-ray source 30 can pass in a focused manner. According to one exemplary configuration, the collimator 36 may include upper and lower jaws. In this case, the upper and lower jaws move in different directions (e.g., parallel directions) to adjust the size of the aperture through which the radiation beam from the X-ray source 30 passes, and further adjust the beam position relative to the patient to irradiate only the portion of the patient being imaged, for the purpose of optimized imaging and minimized patient dose. For example, the collimator may be configured as a multi-leaf collimator (MLC). This may include a plurality of combined leaves that are operable to move to one or more positions between a minimum open or closed position and a maximum open position. It will be understood that the leaves can be moved to desired positions in order to obtain a desired shape of the radiation beam emitted by the radiation source. In one embodiment, MLC enables sub-millimeter target accuracy.

[0044] According to one embodiment, the shape of the radiation beam 32 from the X-ray source 30 may be changed during image acquisition. In other words, according to one exemplary embodiment, the leaf position and / or aperture width of the beamformer 36 may be adjusted before or during the scan. For example, according to one embodiment, the beamformer 36 may be selectively controlled and dynamically adjusted during the rotation of the X-ray source 30 so that the radiation beam 32 has a shape with sufficient primary / shadow regions and is adjusted to include only the object of interest (e.g., the prostate) during imaging. The shape of the radiation beam 32 emitted by the X-ray source 30 may be changed during or after the scan depending on the desired image acquisition. This may be based on imaging feedback and / or therapeutic feedback, as will be described in more detail later.

[0045] The detector 24 can be connected to, or otherwise supported by, a rotatable gantry 12 and positioned to receive radiation 22 from the therapeutic radiation source 20. The detector 24 can detect or measure the unattenuated radiation dose. Thus, it is possible to estimate what has actually been attenuated by the patient or associated patient's ROI (compared to the initially generated one). The detector 24 can detect or otherwise collect attenuation data from different angles if the therapeutic radiation source 20 rotates around the patient and emits radiation toward the patient.

[0046] It will be understood that the therapeutic radiation source 20 may include a beamformer or collimator, or otherwise be associated with one. The collimator / beamformer associated with the therapeutic radiation source 20 may be configured in many ways, as may the collimator / beamformer 36 associated with the imaging radiation source 30.

[0047] The therapeutic radiation source 20 may be mounted, configured, and / or moved to be on the same plane as the imaging radiation source 30, or to a different plane (offset). In some embodiments, scattering caused by the simultaneous activation of radiation sources 20 and 30 may be reduced by offsetting the radiation planes.

[0048] When integrated with a radiotherapy device, the imaging device 10 can provide images. These are used to set up (e.g., align and / or register), plan and / or manage the radiation delivery procedure (treatment). A typical setup is achieved by comparing current (in-treatment) images with pre-treatment image information. Pre-treatment image information may include, for example, X-ray, CT data, CBCT data, magnetic resonance imaging (MRI) data, positron emission tomography (PET) data or 3D rotational angiography (3DRA) data and / or any information obtained from the aforementioned devices or other imaging diagnostic means. In some embodiments, the imaging device 10 may track the movement of the patient, target, or ROI during treatment.

[0049] The reconstruction processor 40 may be operably coupled to the detector 24 and / or the X-ray detector 34. In one embodiment, the reconstruction processor 40 is configured to generate patient images based on radiation from the radiation sources 20 and 30, received by the detectors 24 and 34. It will be understood that the reconstruction processor 40 may be configured to be used to perform the method fully described below. The instrument 10 may also include a memory 44 suitable for storing information including, but not limited to, processing algorithms and reconstruction algorithms and software, imaging parameters, pre-images or image data from otherwise pre-acquired images (e.g., planning images), and treatment plans.

[0050] The X-ray imaging device 10 may include an operator / user interface 48. In this case, the operator of the X-ray imaging device 10 may interact with or otherwise control the X-ray imaging device 10 and provide inputs or imaging parameters related to scanning, etc. The operator interface 48 may include any suitable input device such as a keyboard, mouse, or voice-activated controller. The X-ray imaging device 10 may also include a display 52 or other human-readable elements to provide output to the operator of the imaging device 10. For example, the display 52 may allow the operator to view reconstructed patient images and other information related to the operation of the X-ray imaging device 10, such as imaging parameters or scan parameters.

[0051] As shown in Figure 2, the X-ray imaging apparatus 10 includes a controller (typically indicated 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 providing power and timing signals to the X-ray source 30 and / or therapeutic radiation source 20, and to the gantry motor controller which 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 36 controller, a controller coupled to the detector 24 and / or detector 34, etc. In one embodiment, the controller 60 is a system controller capable of controlling other components, devices and / or controllers.

[0052] In various embodiments, the reconfiguration processor 40, operator interface 48, display 52, controller 60, and / or other components may be combined with one or more components or devices.

[0053] The device 10 may include various components, logic, and software. In one embodiment, the controller 60 includes a processor, memory, and software. For example, but not limited to, an X-ray imaging device and / or radiotherapy system may include various other devices and components (e.g., particularly gantry, radiation source, collimator, detector, controller, power supply, patient support) capable of performing one or more routines or steps related to imaging and / or IGRT for a particular application. Routines may include imaging, image-based pre-delivery steps, and / or therapeutic delivery including setting, configuration, and / or positioning (e.g., path / trajectory) of individual devices, which may be stored in memory. Furthermore, one or more controllers may directly or indirectly control components according to one or more devices and / or routines or processes stored in memory. An example of direct control is setting various radiation source or collimator parameters related to imaging or treatment (e.g., power, velocity, position, timing, adjustment). An example of indirect control is communicating position, path, velocity, etc., to a patient support controller or other peripheral device. The hierarchy of various controllers that may be associated with imaging equipment can be arranged in any suitable manner, enabling the transmission of appropriate commands and / or information to the desired devices and components.

[0054] In addition, those skilled in the art will understand that this system and method may be implemented in other computer system configurations. Exemplary 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 connected 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 used with the X-ray imaging equipment 10.

[0055] The X-ray imaging apparatus 10 may utilize an exemplary environment for carrying out various aspects of the present invention, including a computer. This computer includes a controller 60 (which may include memory, e.g., a processor and memory 44) and a system bus. The system bus can be connected to system components, including but not limited to memory, to the processor, and can communicate with other systems, controllers, components, devices, and processors. The memory may include read-only memory (ROM), random access memory (RAM), hard drives, flash drives, and other forms of computer-readable media. The memory can store various software, including routines and parameters, and data, which may include, for example, treatment plans.

[0056] The therapeutic radiation source 20 and / or X-ray source 30 may be operably connected 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 by the therapeutic radiation source 20. In addition or alternatively, the X-ray source 30 can be controlled and sequentially operated by the therapeutic radiation source 20 depending on the specific treatment plan and / or imaging plan being implemented.

[0057] It will be understood that the X-ray source 30 and X-ray detector 34 can be configured in many ways to provide rotation around the patient during imaging scans. In one embodiment, continuous helical acquisition of patient images can be provided during the procedure by synchronizing the movement and irradiation of the X-ray source 30 with the longitudinal movement of the patient support 18. In addition to the continuous rotation of the radiation sources 20, 30 and one or more detectors 24, 34 (e.g., continuous rotation and constant rotation of the gantry with a continuous patient motion velocity), it will be understood that other modifications can be used without departing from the scope of the disclosed techniques. For example, the rotatable gantry 12 and patient support can be controlled so that the gantry 12 rotates around the patient supported on the patient support in a "reciprocating" manner (e.g., alternating clockwise and counterclockwise rotations) (as opposed to the continuous manner as described above), while the support is controlled to move relative to the rotatable gantry 12 (at a constant or variable speed). In another embodiment, by using a continuous step-and-shoot 360-degree scan, the longitudinal movement (step) of the patient support 18 is alternating with the scan rotation (shoot) of the rotatable gantry 12 until the desired volume is captured. The X-ray imaging instrument 10 has the capability to perform volume-based and planar-based image acquisition. For example, in various embodiments, the X-ray imaging instrument 10 can be used to acquire volume images and / or planar images (e.g., by using an X-ray source 30 and a detector 34) and perform related processing, including the scattering evaluation / scattering correction method described below.

[0058] To generate projection data, the movement of various other types of radiation sources and / or patient supports may be utilized to obtain relative motion of the radiation source and / or patient. Discrete motion of the radiation source and / or patient support, continuous but variable / non-constant (including linear and non-linear) motion, velocity, and / or trajectory, as well as combinations thereof, may be used, including in combination with various embodiments of the radiotherapy apparatus 10 described above.

[0059] In one embodiment, the rotation speed of the gantry 12, the speed of the patient support 18, the shape of the beamformer 36, and / or the reading of the detector 34 may all be constant during image acquisition. In other embodiments, one or more of these variables may change dynamically during image acquisition. The rotation speed of the gantry 12, the speed of the patient support 18, the shape of the beamformer 36, and / or the reading of the detector 34 may be changed to balance with different factors, including, for example, image quality and image acquisition time.

[0060] In other embodiments, these features are combined with one or more other image-based actions or procedures, such as patient setting, adaptable treatment monitoring, and treatment planning.

[0061] Image quality is influenced by many factors (e.g., X-ray source focal size, detector dynamic range, etc.). A limitation of kV CBCT image quality is scattering. Various approaches can be used to reduce scattering. One approach is to use a scattering prevention grid (to narrow the scattering). However, implementing a scattering grid on a kV imaging system, including motion tracking and correction, can be problematic. Accurate evaluation of scattering in projection data is essential for improving image data quality. In various embodiments, scattering in projection data acquired in a wide aFOV region of detector 34 can be evaluated based on projection data (relatively free of scattering) acquired in a narrow aFOV region within the wide aFOV region.

[0062] In particular, data may be acquired using a narrow aperture over a narrow area of ​​the target such that scattering is either minimal / negligible or can be accurately obtained using simple methods. For example, narrow aperture data may contain little to no scattering or correct for scattering itself, using kernel-based scattering correction, collimator shadow fitting evaluation, etc. The narrow aperture can be any size suitable for the particular application, including, for example in some embodiments, 2-3 mm, 1 cm, 2 cm, and / or any size smaller than the wide aperture. Data may also be acquired using a wide aperture over a wide area of ​​the target. In this case, the narrow area lies within the wide area. The wide aperture can also be any size suitable for the particular application, including, for example in some embodiments, 5 cm, 10 cm, 15 cm, 20 cm, and / or any size larger than the narrow aperture. In various embodiments, narrow aperture data can be used to improve kernel-based scattering evaluation and correction of CBCT data acquired over a wide area. The process of improving scattering evaluation by using a narrow scan within a wide scan can be completed in either the projection domain or reconstruction, as will be described in detail later. The process can also be executed in either a non-repeated or iterative manner.

[0063] In an exemplary embodiment, Figure 3 illustrates an exemplary scan design 300 for imaging the axial region of a target 310. A large / wide aFOV beam 312 is used to scan a wide region 314 of the target 310, shown with an axial length W. A small / narrow aFOV beam 316 is used to scan a narrow region 318, shown with an axial length N1. The narrow region 318 lies within the wide region 314, and the axial length N1 is less than the axial length W. In some embodiments, multiple narrow scans can be used to improve accuracy (scattering evaluation), particularly when a portion of the wide region 314 exhibits axial variation. For example, in one embodiment, another narrow aFOV beam 320 can be used to scan another narrow region 322, shown with an axial length N2. The narrow region 322 also lies within the wide region 314, and the axial length N2 is less than the axial length W. All of the exemplary beams 312, 316, and 320 are shown, which are projected from a (focused) source 330 through target 310 and incident on detector 334. Any number of narrow scans may be used within the wider area 314.

[0064] The axial length N1 is small enough that the projection data of the narrow scan for the narrow region 318 contains no scattering, has minimal scattering, and / or has easily obtainable / correctable scattering. Part of the projection data of the wide scan for the wide region 314 (which contains scattering due to the wide scan) overlaps with that of the narrow region 318. By comparing the projection data from the wide scan in the narrow region 318 (containing scattering) with the projection data from the narrow scan in the narrow region 318 (without scattering) (e.g., finding the difference between the two), an accurate assessment (essentially measurement) of the true scattering in the narrow region 318 is obtained. The comparison may be performed either in the projection domain or in reconstruction, as will be described in detail later. In this embodiment, the wide scan is a 360-degree scan; however, in other embodiments, helical orbits and / or other scan orbits may be utilized.

[0065] Following this comparison, the true scattering for the narrow region 318 can be used to optimize the scattering assessment method applied to the entire wide region 314 with high confidence. This is particularly effective when the target changes minimally across the wide region 314. The optimization can be performed either non-repeatedly or iteratively, as will be described in detail later. In some embodiments, multiple narrow aperture datasets (e.g., narrow regions 318, 322) can be acquired over the axial range of a wide aFOV CBCT scan (e.g., wide region 314) to improve scattering correction.

[0066] In one embodiment, the scattering evaluation method utilizes kernel-based scattering evaluation / scattering correction. For example, since the true scattering is known for the narrow region 318, the kernel-based scattering evaluation method applied to projection data from the wide scan in the narrow region 318 can be suppressed so that the scattering evaluation generated by the kernel-based scattering evaluation method obtains an accurate scattering evaluation determined for the narrow region 318. Thus, the suppressed (optimized) kernel-based scattering evaluation method can be applied to a reminder for the wide region 314 with improved results (e.g., for unsuppressed applications). The kernel-based method may improve accuracy based on patient-dependent and / or system-dependent factors.

[0067] In some embodiments, multiple broad aFOV regions (e.g., 314) may be scanned as part of a larger axial range. Each of these broad aFOV regions 314 may include one or more narrow aFOV regions (e.g., 318, 322).

[0068] As shown in Figure 3, one embodiment of scan design 300 may include a large aFOV CBCT scan of the patient's chest (314) and a complementary scan of a region having a narrow aperture (318). In some embodiments, for more optimal performance, multiple narrow aperture scans (318, 322) whose locations are distributed within the large aFOV (314) may be determined and acquired. One or more narrow aperture scans associated with regions 318, 322 can use medically appropriate protocols. This also allows for accurate reconstruction of the range covered by the narrow apertures 316, 320, which can also be used for medical applications. In some embodiments, when used to improve scattering correction, narrow aperture scans may use high-speed gantry rotation and sparse-angle sampling to minimize the impact on overall scan time and patient dose.

[0069] If the aperture created by the beamformer 36 is sufficiently narrow (for example, beams 316 and 320 associated with narrow regions 318 and 322, respectively), scattering in the projection data is essentially negligible. Therefore, in one embodiment, the narrow aperture data can be used as scattering-free data. In another embodiment, several simple techniques are effective and accurate and can evaluate small amounts of scattering in the projection data. Thus, the narrow aperture data is scattering corrected to be scattering-free data. For example, as described above, a simple and effective scattering correction approach for narrow aperture data may include fitting data in the shaded portion of the beamformer collimator that forms the aperture, kernel-based scattering correction, etc. A reference to narrow aperture data as scattering-free data may be the result of the initial scattering correction for the narrow aperture data.

[0070] The following flowcharts and block diagrams illustrate exemplary configurations and methodologies related to scattering evaluation and scattering correction, following the system described above. The exemplary methodologies may be implemented using logic, software, hardware, or a combination thereof. In addition, while the procedures and methods are presented sequentially, the blocks may be executed in different orders, including serial and / or parallel. Furthermore, additional or fewer steps may be used.

[0071] Figure 4 is a flowchart illustrating method 400 for exemplary scattering evaluation in the domain of projection data using a scan design having a narrow scan region within a wide scan region, as described above. Narrow scan data 410 from the narrow region and wide scan data 420 from the wide region are provided or received from data acquisition using, for example, the imaging equipment 10 described above. The narrow region is, for example, located within the wide region as described above in Figure 3. The narrow scan data 410 does not contain scattering, but the wide scan data 420 does. In this embodiment, step 412 separates the portion of the wide scan data 420 that overlaps with the narrow region. Next, in step 414, method 400 subtracts the narrow scan data 410 (without scattering) from the portion of the wide scan data 420 (with scattering) corresponding to the separated narrow region. The resulting data is the true (measured) scattering 416 in the narrow region.

[0072] In step 422, method 400 evaluates the scattering in the wide scan data 420 using a scattering evaluation method. This may include, for example, a kernel-based scattering evaluation method. Next, in step 424, the evaluated scattering in the narrow region is separated from the evaluated scattering over the wide region. The resulting data is the evaluated scattering in the narrow region 426 using the scattering evaluation method.

[0073] Next, in step 430, method 400 determines the difference between the true (measured) scattering 416 and the evaluated scattering 426 in a narrow area. This difference can be used to optimize the scattering evaluation method in step 432. For example, the scattering evaluation method may be optimized by minimizing the difference between the evaluated scattering 426 and the true scattering 416. Minimizing the difference may involve various types of fitting processes. In one non-repeated embodiment, the optimization process may involve a least-squares solution. Next, in step 434, the optimized (e.g., fitted kernel-based) scattering evaluation method can be used to re-evaluate the scattering in the remainder of the wide scan data 420 with improved accuracy. The scattering evaluation may be used during the reconstruction of the wide area.

[0074] Figure 5 is a flowchart representing another exemplary method 500 for evaluating scattering in the domain of projection data, using a scan design having a narrow scan region within a wide scan region, as described above. Method 500 is similar to Method 400, except that in this embodiment, step 522 excludes the fact that Method 500 first evaluates scattering in the isolated portion of the wide scan data 420 that overlaps with the narrow region on which the scattering evaluation method is used. This is computationally less independent than evaluating scattering in the entire wide scan data 420 before separating the narrow region, as in steps 422 and 424 of Method 400. In this embodiment, the isolated wide scan data may directly originate from step 412. The resulting data is the evaluated scattering 426 in the narrow region using the scattering evaluation method. Other steps are performed in Method 400, etc.

[0075] Figure 6 is a flowchart illustrating an exemplary iterative method 600 for scattering evaluation in the domain of projection data, using a scan design having a narrow scan region within a wide scan region, as described above. Method 600 is similar to method 500, except that, in this embodiment, after step 430, method 600 omits the optimization of the iterative scattering evaluation method. In particular, in step 632, method 600 determines whether the difference between the true (measured) scattering 416 and the evaluated scattering 426 in the narrow region requires further improvement or optimization. In various embodiments, the difference from step 430 (representing how close the evaluated scattering 426 by the scattering evaluation method is to the true scattering 416) may be subjected to various conditions / analyses to determine whether further improvement is required in step 632. This could include, for example, the difference being compared to a threshold, the difference between the current iteration and one or more prior iterations being compared to a threshold or rate (e.g., to determine the convergence rate of iteration / incremental improvements to the evaluation), the number of iterations (loopback to step 522) being compared to a threshold, the time and / or iteration process associated with the scan being compared to a threshold (e.g., to consider the overall workflow), and combinations of these factors and / or other factors including a weighted average.

[0076] If the analysis in step 632 determines that the difference from step 430 requires further improvement, method 600 proceeds to step 634 to optimize the scattering evaluation method, taking into account the difference from step 430. For example, the scattering evaluation method may be optimized by minimizing the difference between the evaluated scattering 426 and the true scattering 416. Minimizing the difference may involve various types of fitting processes. In the case of multiple iterations, step 634 may be for further optimization.

[0077] If the analysis in step 632 determines that the difference from step 430 does not require further refinement, method 600 proceeds to step 636 and applies an optimized (e.g., fitted kernel-based) scattering evaluation method to the remainder of the wide scan data 420 with improved accuracy.

[0078] In this way, the acquired narrow-aperture scan data can be used to improve the scattering evaluation of wide-aperture scan data in imaging diagnostic means, including in conjunction with kernel-based scattering evaluation. For example, imaging includes X-ray imaging, CT imaging, CBCT imaging, etc. Image quality and quantity can be improved using kernel-based scattering evaluation and scattering correction, including improved / optimized embodiments. A beamformer (e.g., having a set of collimators) can effectively block a portion of the beam to form an aperture for imaging. In this case, the aperture size can be changed to enable the acquisition of very narrow-aperture data. The aperture position relative to the patient can be changed relative to the patient. In various embodiments, kernel-based scattering evaluation of data from a large aFOV (wide area) scan is compared to measured scattering in a small aFOV (narrow area) at the same angle. The measured scattering is the result of subtracting the data without scattering from the data of a narrow-aperture scan, which includes scattering in a similar area at the same angle / viewpoint.

[0079] Kernel-based scattering assessments can be optimized by minimizing the difference between assessed and measured scattering. The optimized kernel-based scattering assessment can then be applied to the remainder of the large aFOV data to improve the accuracy of the scattering correction.

[0080] As described above, optimization of the scattering evaluation method can also occur in the reconstruction domain. An image reconstructed from narrow aperture scan data may be considered a scattering-free image. For example, reconstruction of a similar area from wide aperture scan data using a kernel-based scattering correction method can be compared to a scattering-free image. The scattering correction method can be optimized to minimize the difference. In some embodiments, for example for the intended medical application, the difference may be focused on only certain image planes. For example, when wide aFOV images are used for planning applicable to radiotherapy, quantitative accuracy is important for dose calculation, and low-contrast recovery is important for tumor detection and depiction for dose planning.

[0081] Figure 7 is a flowchart illustrating an exemplary method 700 for scattering correction in a reconstruction domain using a scan design having a narrow scan region within a wide scan region, as described above. Narrow scan data 410 from the narrow region and wide scan data 420 from the wide region are provided or received, for example, from data acquisition using the imaging device 10 described above. The narrow region is, for example, located within the wide region as described above in Figure 3. The narrow scan data 410 does not contain scattering, but the wide scan data 420 does. In this embodiment, step 712 reconstructs the narrow region using the narrow scan data 410. The resulting image is a narrow region image 714 that does not contain scattering.

[0082] In step 722, method 700 separates and reconstructs a narrow region using wide scan data 420 with a scattering correction technique. This may include, for example, a kernel-based scattering evaluation / scattering correction technique. The resulting image is a scattering-corrected narrow region image 724.

[0083] Next, in step 730, method 700 determines the difference between the narrow region image 714 without scattering and the scattering-corrected narrow region image 724. This difference can be used to optimize the scattering correction method in step 732. For example, the scattering correction method can be optimized by minimizing the difference between the narrow region image 714 without scattering and the scattering-corrected narrow region image 724. Minimizing the difference can involve various types of fitting processes. In one non-repeated embodiment, the optimization process may involve a least-squares solution. Next, in step 734, the optimized (e.g., fitted kernel-based) scattering correction method can be used to reconstruct the wide region using the wide scan data 420 with improved accuracy.

[0084] Figure 8 is a flowchart illustrating an exemplary iterative method 800 for scattering correction in a reconstruction domain using a scan design having a narrow scan region within a wide scan region, as described above. Method 800 is similar to method 700, except that, after step 730, method 800 performs optimization of the iteration of the scattering correction method. In particular, in step 832, method 800 determines whether the difference between the scattering-free narrow region image 714 and the scattering-corrected narrow region image 724 requires further improvement or optimization. In various embodiments, the difference from step 730 (representing how close the scattering-corrected narrow region image 724 using the scattering correction method is to the scattering-free narrow region image 714) may be subjected to various conditions / analyses to determine whether further improvement is required in step 832. This could include, for example, the difference being compared to a threshold, the difference between the current iteration and one or more prior iterations being compared to a threshold or rate (e.g., to determine the convergence rate of iteration / incremental improvements to an evaluation), the number of iterations (loopback to step 722) being compared to a threshold, the time and / or iteration process associated with the scan being compared to a threshold (e.g., to consider the overall workflow), and combinations of these factors and / or other factors including a weighted average.

[0085] If the analysis in step 832 determines that the difference from step 730 requires further refinement, method 800 proceeds to step 834 to optimize the scattering correction method, taking into account the difference from step 730. For example, the scattering correction method may be optimized by minimizing the difference between the scattering-corrected narrow-region image 724 and the scattering-free narrow-region image 714. Minimizing the difference may involve various types of fitting processes. In the case of multiple iterations, step 834 may involve further optimization.

[0086] If the analysis in step 832 determines that the differences from step 730 do not require further improvement, method 800 proceeds to step 836 to reconstruct the wide area by applying an optimized (e.g., fitted kernel-based) scattering correction technique to the remainder of the wide scan data 420 with improved accuracy.

[0087] As described above, narrow aperture data can be acquired using medically appropriate protocols. In these embodiments, the data can be used to accurately reconstruct an image of this portion of the patient. An image reconstructed from large aFOV data of the same portion of the patient can be compared to an image from the narrow aperture reconstruction. Kernel-based scattering correction for large aFOV data (wide area) can be optimized so that the reconstructed image matches the narrow aperture image (narrow area) of the same portion. Consequently, the reconstructed image of the remaining wide area is improved by the optimized kernel-based scattering correction. In one embodiment, kernel-based scattering correction can be optimized by matching the large aFOV (wide area) image with the narrow aperture image (narrow area) of the same portion of the patient using medically desired criteria. For example, one criterion is to match the recovery of low contrast for tumor detection and depiction. Another criterion is to match the quantitative accuracy for dose simulation and dose planning for the applied radiotherapy.

[0088] A decision may be made on whether to perform the above method in the projection data domain and / or reconstruction domain, taking into account various factors, including, for example, accuracy, time, workflow, and available data. In some situations, only one domain may be available, or one domain may be preferred. For example, referring to Figure 3, if the narrow region beam 320 is tilted as shown, accurate image reconstruction with narrow aperture data is not possible. Therefore, only narrow scan data related to the narrow region 322 may be used to improve the scattering evaluation in the projection domain.

[0089] In various embodiments, image reconstruction may be reconstruction for analysis and / or iterative reconstruction.

[0090] Details of one or more narrow scans (including number, axial position, angle, size, narrow / wide size ratio, etc.) for one or more narrow regions (e.g., 318, 322 shown in Figure 3) can be determined and / or optimized using various methods. In embodiments where one or more scans are not yet completed, the determination of the details of one or more narrow scans may include the determination of similar details of one or more wide scans, including, for example, number, size, ratio, etc. An optimization process is performed to determine the narrow and / or wide scan details (including number, axial position, angle, size, narrow / wide size ratio, etc.) and optimize the various factors described above, including overall scan time, workflow, etc. For example, in some embodiments, narrow scans may be determined from pre-images (e.g., planning CT images, CBCT images from pre-treatment subsessions, etc.). In some embodiments, narrow scans may be selected from a bank of pre-determined narrow scans suitable for a particular wide region, including those based on typical uniformity / variability and narrow areas suitable as a basis for a wider region. In other embodiments, for example, if pre-images are unavailable, a narrow scan can be determined on the fly by using images reconstructed from a scout scan and / or a wide-area scan.

[0091] For example, in one embodiment, after acquiring sufficient data for acceptable image reconstruction from a wide-area scan, a relatively fast reconstruction of the wide-area scan data can be initiated. Then, using the reconstructed wide-area image, one or more narrow scans can be identified based on, for example, uniformity (or its absence), axial length, and the use of a clinical protocol or a protocol solely for scattering correction. These may include slight projection angles, larger pitch for helical scans, etc. In some embodiments, other factors such as workflow may be considered in determining the number of narrow scans. In one embodiment, a computer algorithm / analysis can automatically determine the details of one or more narrow scans based on the reconstructed wide-area image. In another embodiment, a user can determine the details of one or more narrow scans based on an overview of the reconstructed wide-area image. The narrow-area information can then be fed back to the system to control the narrow scans.

[0092] For example, Figure 9 is a flowchart representing an exemplary method 900 for determining a narrow scan from pre-image data for use in a narrow / wide scan design, as described above. The patient's pre-image data 905 (e.g., pre-images, which may be pre-acquired planning images, including pre-CT images) is provided or received, for example, from another source or from data acquisition using the X-ray imaging equipment 10 described above. In step 910, method 900 determines the narrow scan details based on the pre-image data 905 described above. As described above, in this embodiment, the determination of one or more narrow scan details may include the determination of one or more wide scan details, including an optimization process. Next, in step 920, method 900 initiates a narrow-area scan and a wide-area scan, for example, using the imaging equipment 10 described above. The data obtained is narrow scan data 410 for one or more narrow areas and wide scan data 420 for wide areas. The scan data 410, 420 may be used according to the scattering evaluation method and scattering correction method described above.

[0093] In another embodiment, Figure 10 is a flowchart representing an exemplary method 1000 for determining a narrow scan from wide scan data for use in a narrow / wide scan design, as described above. In step 1010, method 1000 performs a wide area scan of the patient onto a support imaging and / or treatment target, for example, using the imaging instrument 10 described above. The data obtained is wide scan data 420 for the wide area. Next, in step 1020, method 1000 begins to reconstruct the wide scan data 420. In step 1030, based on at least a partial reconstructed image of the patient, method 1000 determines narrow scan details based on the reconstructed image, as described above. Next, in step 1040, method 1000 begins one or more narrow scans, for example, using the imaging instrument 10 described above. The data obtained is narrow scan data 410 for one or more narrow areas. The scan data 410, 420 may be used according to the scattering evaluation method and scattering correction method described above.

[0094] In this way, narrow aperture scans (including, for example, number, location, angle, size, etc.) can be determined using pre-images or on the fly, depending on the validity of the data / image information from wide aperture scans. For example, if the size and location of the narrow aperture scans, as well as the angle at which the narrow aperture data is acquired, are determined on the fly, the patient's image is first obtained from a wide-area scan. Then, the patient's image, including image reconstruction, is acquired using the location or all of the wide scan data, while the large aFOV data acquisition (wide-area scan) is still (simultaneous reconstruction / acquisition) or reconstruction is progressing after the large aFOV scan has been completed. Determining narrow aperture scan details can be done using algorithms / software that utilize the image heterogeneity determined from the acquired patient images.

[0095] When using the above apparatus and method for scattering correction in a projection domain, if each projection viewpoint is a planar image, scattering correction can be applied to each projection viewpoint. In one embodiment, one or more planar X-ray images (e.g., for motion tracking) may be used in conjunction with a kernel-based scattering evaluation method to evaluate scattering in the planar image for scattering correction (e.g., for contrast enhancement). The above method can use measured scattering in narrow aperture data to improve kernel-based scattering evaluation.

[0096] In another embodiment, a first planar image may be acquired by a wide aperture and a collimator shadow region. The collimator shadow region can then be used to evaluate scattering in the planar image using a shadow fitting technique. Next, narrow aperture data can be used to measure scattering in a narrow region. The results can then be used to refine the shadow fitting technique for wide aperture scattering evaluation.

[0097] The above-described apparatus and method offer several advantages over existing techniques. For example, the apparatus and method can improve the performance of conventional kernel-based scattering assessment and scattering correction approaches in CBCT. In particular, improvements can be seen in large axial scanning areas, especially in the context of patient scans in highly heterogeneous regions.

[0098] In one embodiment, the use of a kernel-based model for scattering evaluation / correction when optimizing a region within range of a narrow aperture is more accurate for the rest of the wider region than conventional kernel-based approaches. Narrow aperture data (without scattering) provides complementary information to optimize or suppress the kernel-based model. This improves the accuracy of the kernel-based model during scattering evaluation / correction. In this way, the optimization process can be very direct but highly effective.

[0099] As described above, narrow-area scans can utilize medically sound protocols that allow for accurate reconstruction of the narrow area brought into range by the aperture. Therefore, the dose and scan time associated with narrow scans are fully utilized and not wasted. In other embodiments, narrow-area scans may be solely for scattering correction purposes. In these embodiments, acquisition can utilize high-speed gantry rotation and / or acquire angularly sparse data. As a result, the impact of narrow-area scans on patient dose and scan time can be minimized.

[0100] Various embodiments can utilize different scan geometry shapes, detector positioning (including offset detectors), and / or beamformer window shapes. In some embodiments, narrow and / or wide scan trajectories can be 180 degrees when the detector is centrally positioned, and up to 360 degrees when the detector is offset.

[0101] As described above, the disclosed embodiments of the method can be used in conjunction with or as part of radiotherapy equipment and IGRT, utilizing an integrated kilovoltage (kV) CT. According to one embodiment, the image acquisition methodology includes, or otherwise utilizes, a helical source trajectory (e.g., continuous source rotation around a central axis, accompanied by longitudinal movement of the patient support through the gantry bore) or a 360-degree scan with kV beam collimation, accompanied by high-speed slip ring rotation, to provide kV CT imaging on a radiotherapy delivery platform. It will be understood that such embodiments can provide reduced scattering and improved scattering assessment, enabling higher quality kV images than conventional systems.

[0102] It will be further understood that any potential increase in scan time associated with multiple beam rotations to complete a volumetric image can be mitigated, or otherwise offset, by high kV frame rates, high gantry rates, and / or sparse data reconstruction techniques. It will be further understood that by providing selectively controllable collimators / beamformers as described above, it will be possible to enable a system in which the user can trade off image acquisition time for image quality, or otherwise modify it, depending on the specific application and / or medical needs. It will also be understood that it is possible to control the radiotherapy supply unit to provide half-rotation or single-rotation cone-beam CT scans with fast image acquisition times (e.g., for motion tracking) (which may reduce image quality due to scattering), and full-circumference or continuous helical acquisitions with narrow / slit fan beams that have longer acquisition times but improve image quality by reducing scattering. One or more optimization processes are also applicable to all of the above embodiments to determine beam positioning, determine readout range, evaluate scattering, etc.

[0103] Figure 11 is a flowchart representing an exemplary method 1100 of IGRT using a radiotherapy apparatus (e.g., including imaging equipment 10). Patient pre-image data 1105 is available for use (e.g., pre-images including the pre-CT images described above, which may be pre-acquired planned images). In some embodiments, the pre-image data 1105 is generated by a similar radiotherapy apparatus but in a shorter time. In step 1110, patient imaging is performed using a low-energy radiation source (e.g., kV radiation from X-ray source 30). In one embodiment, imaging includes a 360-degree scan with a fan-beam geometric shape or a cone-beam geometric shape. Step 1110 generates one or more high-quality (HQ) images or imaging data 1115 using the scattering evaluation and scattering correction techniques described above. In some embodiments, image quality may be adjusted to optimize the balance between image quality / resolution and dose. In other words, not all images need to be of the highest quality. Alternatively, image quality may be adjusted to optimize or trade off the balance between image quality / resolution and image acquisition time. The imaging step 1110 also includes image processing 1120, which can generate a patient image based on the imaging data / scan data (for example, according to the method described above). The image processing step 1120 is shown as part of the imaging step 1110. In some embodiments, the image processing step 1120 is a separate step, including cases where the image processing is performed by a separate device.

[0104] Next, in step 1130, one or more image-based pre-delivery steps described below are performed at least in part on the imaging data 1115 from step 1110. As will be described in more detail later, step 1130 may include determining various parameters related to the treatment procedure and (subsequent) imaging plan. In some embodiments, the image-based pre-delivery step (1130) may require more imaging (1110) before treatment delivery (1140). Step 1130 may include adapting the treatment plan based on the imaging data 1115 as part of an adaptable radiotherapy routine. In some embodiments, the image-based pre-delivery step 1130 may include real-time treatment planning. Embodiments may also include simultaneous, overlapping, and / or alternating activation of imaging and therapeutic radiation sources. Real-time treatment planning may involve any or all of these types of imaging and therapeutic radiation activation techniques (simultaneous, overlapping, and / or alternating).

[0105] Next, in step 1140, the therapeutic treatment is delivered using a source of high-energy radiation (e.g., MV radiation from the therapeutic radiation source 20). Step 1140 delivers the therapeutic dose 1145 to the patient according to the treatment plan. In some embodiments, the IGRT method 1100 may include returning to step 1110 for additional imaging at various intervals, and then, if necessary, image-based pre-delivery steps (1130) and / or therapeutic deliveries (1140). In this way, high-quality imaging data 1115 may be generated and utilized during IGRT using some instrument 10 capable of adaptable treatment. As described above, steps 1110, 1130 and / or 1140 may be performed simultaneously, overlapping, and / or alternately.

[0106] IGRT may include at least two general objectives: (i) to deliver a high-precision source dose distribution to the target volume, and (ii) to deliver the treatment beam with high precision throughout the entire treatment. A third objective may be to achieve the two general objectives in the shortest possible time per portion. Precise delivery of the treatment beam requires the ability to identify and / or track the position of the target volume using high-quality imaging. The ability to increase the delivery rate requires the ability to move the radiation source accurately, precisely, and rapidly according to the treatment plan.

[0107] Figure 12 is a block diagram 1200 representing an exemplary image-based pre-delivery step / option that may relate to step 1130 above. The imaging device 10 (e.g., as part of a radiotherapy apparatus) can generate kV images that can be used in various ways. This will be understood to include, without departing from the scope of the invention, an image-based pre-delivery step (1130). For example, an image 1115 generated by the radiotherapy apparatus can be used to perform pre-treatment patient positioning (1210). Patient positioning may include correlating or registering the current imaging data 1115 with imaging data related to the plan, including earlier pre-treatment scans and / or treatment plans. Patient positioning may also include feedback on the patient's physical position relative to the radiation source to confirm whether the patient is physically present within the range of the delivery system. If necessary, the patient may be adjusted to fit. In some embodiments, the imaging for patient positioning may be intentionally of lower quality to provide adequate positioning information, although the dose is minimized.

[0108] Images generated by the imaging device 10 may also be used for treatment planning or replanning (1220). In various embodiments, step 1220 may include reviewing the treatment plan, modifying the treatment plan, creating a new treatment plan, and / or selecting a treatment plan from a set of treatment plans (sometimes called a “daily plan”). For example, imaging data 1115 shows that the target volume or ROI is the same as that which would be if the treatment plan had been developed. It is then possible to review the treatment plan. However, if the target volume or ROI is not the same, replanning of the treatment procedure may be necessary. In the case of replanning, since the imaging data 1115 (generated by the X-ray imaging device 10 in step 1110) is of high quality, imaging data 1115 may be used for treatment planning or replanning (e.g., creating a new or modified treatment plan). In this way, pre-treatment CT imaging by different devices is not required. In some embodiments, review and / or replanning may be procedures in progress before and / or after various treatments.

[0109] According to another exemplary use case, the imaging dose (1230) can be calculated using images generated by the imaging device 10. This may be used to determine the total dose to the patient in progress and / or for subsequent imaging planning. The quality of subsequent imaging may also be determined as part of the treatment plan, for example, to balance quality and dose. According to another exemplary use case, the therapeutic dose (1240) can be calculated using images generated by the imaging device 10. This may be used to determine the total dose to the patient in progress and / or may be included as part of the treatment plan or treatment replanning.

[0110] In accordance with other exemplary use cases, images generated by the imaging device 10 may be used in conjunction with planning or adjusting other imaging (1250) and / or other treatment (1260) parameters or plans. This may be included, for example, as part of creating an adaptable treatment and / or treatment plan. In accordance with another exemplary use case, images generated by the imaging device 10 may be used in conjunction with adaptable treatment monitoring (1270). This may include monitoring and adapting treatment delivery as needed.

[0111] The image-based pre-delivery steps (1130) are not mutually exclusive. For example, in various embodiments, the calculated therapeutic dose (1240) may be a standalone step, as well as / or part of adaptable therapeutic monitoring (1270) and / or therapeutic planning (1220). In various embodiments, the image-based pre-delivery steps (1130) may be performed automatically and / or manually with human involvement.

[0112] The above apparatus and method, including adjustable collimation (aperture) of imaging radiation and scattering evaluation and scattering correction schemes, provides improved scattering evaluation. This results in higher quality kV-generated images than conventional intra-treatment imaging systems using CBCT.

[0113] Figure 13 is a block diagram 1300 representing exemplary data sources that may be used during imaging (1110) and / or during the subsequent image-based pre-feed step (1130). Detector data 1310 represents all data received by the image radiation detector 34. Projection data 1320 is data generated by radiation incident in a focused beam region, referred to above as the scan region. Peripheral data 1330 is data generated by radiation incident in a peripheral region. Scattering data 1340 is data generated by radiation incident in the peripheral region outside the peripheral region described above and / or with determined scattering. In another embodiment, when the two sources 20, 30 are operated simultaneously or interleaved, the scattering data 1340 can be used to determine the residual effect of scattering from the therapeutic radiation source 20 (e.g., MV).

[0114] In this way, peripheral data 1330 and / or scattered data 1340 may be used to improve the quality of the image generated by the imaging step 1110. In some embodiments, peripheral data 1330 and / or scattered data 1340 may be combined with projection data 1320 and / or analyzed in terms of applicable imaging settings 1350, treatment settings 1360 (e.g., simultaneous imaging and therapeutic radiation), and any other data 1370 related to the imaging instrument 10 during the data acquisition time at the imaging detector 34. In other embodiments, the data may be used for the treatment planning step 1130.

[0115] While the disclosed techniques have been shown and described in relation to specific aspects, embodiments, or embodiments, it will be apparent to those skilled in the art that equivalent changes and modifications will be conceivable upon reading and understanding this specification and the accompanying drawings. 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 specified function of the described element (i.e., one that is functionally equivalent), even if it is not structurally equivalent to a disclosed structure that performs a function in an exemplary aspect, embodiment, or embodiment of the disclosed technique shown herein. Furthermore, while certain features of the disclosed techniques may be described above in relation to only one or more of the several exemplary aspects or embodiments, such features can be combined with one or more other features of other embodiments so as may be desired and advantageous for any given or particular application.

[0116] 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, or ever limit, the appended claims to such detail. Further advantages and modifications will be readily apparent to those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details, exemplary apparatuses and methods, and exemplary examples illustrated and described. Thus, deviations from such details can be made without departing from the spirit or scope of the applicant's general inventive concept.

Claims

1. It is an imaging device, A rotating imaging source for emitting a radiation beam, A detector positioned to receive radiation from the aforementioned imaging source, A beamformer configured to adjust the shape of the radiation beam emitted by the imaging source such that the shape of the radiation beam is configured for wide-aperture scanning of a wide area in the axial direction and for narrow-aperture scanning of a narrow area in the axial direction within the wide area in the axial direction, A data processing system, The system receives projection data measured from a wide-aperture scan of a wide area in the axial direction of the body and from a narrow-aperture scan of a narrow area in the axial direction within the wide area in the axial direction of the body. Based on the projection data from the aforementioned narrow aperture scan, a narrow region image free from scattering is reconstructed. Using a scattering correction method, a scattering-corrected narrow region image is reconstructed based on the projection data of the wide aperture scan that overlaps with the narrow region in the axial direction of the body. The difference between the narrow region image without scattering and the scattering-corrected narrow region image is calculated. Based on the difference between the narrow region image without scattering and the scattering-corrected narrow region image, the scattering correction method is optimized. Using the optimized scattering correction method, a scattering-corrected wide-area image is reconstructed based on the projection data of the wide-aperture scan. An imaging device equipped with a data processing system.

2. The imaging device according to claim 1, wherein the wide aperture scan and the narrow aperture scan include a 360-degree scan.

3. A method for evaluating scattering in an image, Receiving projection data measured from a wide-aperture scan of a wide area in the axial direction of the body and from a narrow-aperture scan of a narrow area in the axial direction within the wide area in the axial direction of the body, Determining the scattering measured in the narrow region in the body axis direction based on the projection data of the narrow aperture scan and the projection data of the wide aperture scan that overlaps with the narrow region in the body axis direction, Using a scattering evaluation method, the scattering evaluated in the narrow region in the body axis direction is determined based on the projection data of the wide aperture scan that overlaps with the narrow region in the body axis direction. The difference between the measured scattering in the narrow region in the axial direction of the body and the evaluated scattering in the narrow region in the axial direction of the body is calculated. Optimizing the scattering evaluation method based on the difference between the measured scattering in the narrow region in the axial direction of the body and the evaluated scattering in the narrow region in the axial direction of the body, A method comprising determining evaluated scattering in a wide area in the body axis direction based on projection data of the wide aperture scan using the optimized scattering evaluation method.

4. The method according to claim 3, wherein determining the measured scattering in the narrow region in the axial direction includes subtracting projection data of the narrow aperture scan from projection data of the wide aperture scan that overlaps with the narrow region in the axial direction.

5. The method according to claim 3, further comprising separating the projection data of the wide aperture scan from the projection data of the wide aperture scan that overlaps with a narrow region in the body axis direction.

6. The method according to claim 3, further comprising separating the evaluated scattering in a broad region in the direction of the body axis from the evaluated scattering in a narrow region in the direction of the body axis.

7. The method according to claim 3, further comprising determining whether the scattering evaluation method needs to be improved based on the difference between the measured scattering in the narrow region in the direction of the body axis and the evaluated scattering in the narrow region in the direction of the body axis, wherein optimizing the scattering evaluation method includes an iterative improvement process.

8. The method according to claim 7, wherein determining whether the scattering evaluation method needs to be improved includes comparing the difference between the measured scattering in the narrow region in the axial direction and the evaluated scattering in the narrow region in the axial direction with a threshold.

9. The method according to claim 3, further comprising determining the position of the narrow region in the axial direction of the body based on a prior image.

10. The method according to claim 3, further comprising determining the position of the narrow region in the axial direction of the body based on the projection data from the wide aperture scan.

11. The method according to claim 3, wherein the narrow region in the axial direction of the body includes a plurality of narrow regions in the axial direction of the body within the wider region in the axial direction of the body.

12. A method for correcting scattering in an image, Receiving projection data measured from a wide-aperture scan of a wide area in the axial direction of the body and from a narrow-aperture scan of a narrow area in the axial direction within the wide area in the axial direction of the body, Reconstructing a narrow region image free from scattering based on projection data from the aforementioned narrow aperture scan, Using a scattering correction method, a scattering-corrected narrow region image is reconstructed based on projection data from the wide aperture scan that overlaps with the narrow region in the axial direction of the body. The difference between the narrow region image without scattering and the scattering-corrected narrow region image is calculated, Optimizing the scattering correction method based on the difference between the narrow region image without scattering and the scattering-corrected narrow region image, A method comprising: reconstructing a scattering-corrected wide-area image based on projection data of the wide-aperture scan using the optimized scattering correction method described above.

13. The method of claim 12, further comprising determining whether the scattering correction method should be improved based on the difference between the narrow region image without scattering and the scattering-corrected narrow region image, and optimizing the scattering correction method comprising an iterative improvement process.

14. The method according to claim 13, wherein determining whether the scattering correction method needs to be improved includes comparing the difference between the scattering-free narrow region image and the scattering-corrected narrow region image with a threshold.

15. The method according to claim 12, further comprising determining the position of the narrow region in the axial direction of the body based on a prior image.

16. The method of claim 12, further comprising determining the position of the narrow region in the axial direction of the body based on the reconstruction of the projection data from the wide aperture scan.

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