Multi-energy spectral imaging for adaptive radiotherapy

Abstract

A radiotherapy treatment apparatus for imaging and treating a patient, comprising: a radiotherapy system comprising a treatment radiation source configured to perform radiotherapy treatment of a patient by directing treatment radiation towards the patient, wherein the patient is located substantially within a treatment region defining a longitudinal axis, wherein the treatment radiation source is moveable with respect to the longitudinal axis to thereby enable a selection of a treatment direction in preparation for radiotherapy treatment of the patient; an imaging system comprising an imaging radiation source and a radiation detector, wherein the imaging radiation source is moveable with respect to the longitudinal axis and is arranged to direct imaging radiation towards the patient in an imaging direction, and wherein the radiation detector is arranged to measure the imaging radiation after interaction of the imaging radiation with the patient, wherein the radiation detector comprises one or more photon counting detector arrays defining a sensitive area of the radiation detector, and wherein the imaging system is configured to generate multi-spectral images of the patient based on measurements of the imaging radiation by the one or more photon counting detector arrays.

Description

MULTI-ENERGY SPECTRAL IMAGING FOR ADAPTIVE RADIOTHERAPYField of the Invention

[0001] The present invention is generally directed to adaptive radiotherapy utilising photon counting detectors, which can enable multi-energy spectral tissue imaging.Background to the Invention

[0002] A critical challenge of modem radiotherapy is the lack of accessible, and cutting-edge imaging technology both before and at the time of treatment. Radiotherapy is a form of localised cancer therapy that is used to treat up to 50% of all cancer patients; in 2018-19, 74,200 courses of radiotherapy were delivered in Australia. Modern radiotherapy demonstrates an exquisite ability to conform radiation dose to the tumour shape, minimising delivery of dose to adjacent organs, thus reducing treatment side effects. This dose shaping relies on imaging typically acquired 5-10 days before treatment, including information from Computed Tomography (CT), augmented by nuclear medicine and / or magnetic resonance (MR) imaging. Patients, however, breathe, their hearts beat, their bowels digest, and over the course of treatment, tumours change (e.g., shape, size, and / or position). This continuous variation in internal anatomy hampers the ability to realise the exquisitely planned conformal dose delivery. As such, imaging is required at the time of treatment to “see” where radiation is to be delivered (tumour) and where to avoid (surrounding organs).

[0003] Standard linear accelerators (Linacs) delivering radiotherapy employ various implementations of X-ray imaging to guide radiation. Typically X-ray imaging uses cone-beam computed tomography (CBCT) to acquire a volumetric image of the patient's anatomy and density. CBCT can sometimes identify tumours and organs, however CBCT typically suffers from poor image quality and is only sufficient for aligning the patient to the correct position. Due to the typical quality of information provided by CBCT, it may not be possible to adapt the treatment plan to the individual deformations of the tumour and organs occurring over the course of treatment. Poor image quality lessens the ability to distinguish and target the tumour cells from adjacent healthy structures with similar density and causes inaccurate identification of critical organs. This targeting uncertainty leads to increased treatment margins (larger treatment volume) to account for anatomical variations and ensures tumour control at the expense of an increased probability of treatment side effects. These side-effects significantly impact patient quality of life and can include damage to healthy organs, tumour recurrence,organ dysfunction, internal bleeding, secondary cancers4, shorter lifespan and in rare cases, patient death.

[0004] In addition to ‘standard’ Linacs, there are currently four ‘MR-Linacs’ in Australia. These machines combine an MR imaging system with a Linac and provide the highest quality anatomical imaging of the tumour and adjacent organs in a treated region. Such image quality facilitates shaping the delivered radiation dose according to the daily position and shape of the tumour and adjacent organs. This ensures the targeted dose to the tumour is achieved while minimising adjacent organ dose. Such technology has enabled the treatment of cancers surrounded by critical organs that traditionally could not be aggressively treated with standard Linacs, such as pancreatic cancers, however, MR-Linacs are very expensive (A$10M), highly complex, require specialist staffing, and will likely remain a niche device in Australia. For most patients receiving radiotherapy in Australia, and globally, there is a fundamental need to improve image quality on all standard Linacs.

[0005] Radiotherapy demands stringent control of geometric uncertainties, which are dominated by tumour outlining at planning and target localisation at the time of treatment delivery. In the treatment planning phase, typically 5-10 days before the start of treatment, diagnostic and contrast-enhanced CTs, MRI, and Positron Emission Tomography (PET) are all used to ensure accurate identification of the tumour and adjacent critical organs. A treatment plan is created based on this mapping, and the patient returns for treatment. At treatment, and over the radiotherapy course (up to 7-weeks), patients breathe, twitch and swallow which moves their tumours and nearby organs, tumours grow and shrink, and patients lose weight. Contemporary radiotherapy involves radiation doses that are highly conformal to the tumour shape and size; with a rapid fall-off in dose outside the target, it is essential that daily patient anatomical variations can be visualised at the time of treatment. Integration of various imaging modalities within the treatment room performs the primary role of aligning the tumour with the radiation beam but is also used to monitor anatomical changes. Image-guided radiation therapy thus aims to maintain consistency between planned and actual treatment geometry, including potential adaptation to anatomical variations over the course of treatment, resulting in improved dose delivery.

[0006] Imaging available at treatment however is typically limited to simple planar X-rays, and CBCT, which simply measure how much of the X-rays are stopped (attenuated) by the patient's anatomy. Often organs and tumours have similar X-ray attenuation properties, whichlimits the ability to distinguish between tumours and organs. Image quality from conventional CBCT on radiotherapy treatment systems is significantly inferior to diagnostic / planning CT machines, or MR-Linacs. This often results in a difficult decision to be made on what is tumour and, in contrast, that is an organ. Poor image quality makes it extremely difficult to localise the treatment site and the critical organs, leading to sub-optimal tumour control. Conventional CBCT image quality suffers due to the cone-beam X-ray shape, causing significant scattering and reducing the ability to visualise soft-tissue structures (tumours and organs). Further, Conventional CBCTs typically take 60-seconds to acquire, during which organs move; this further erodes soft-tissue contrast making it very challenging to localise the target. Low- contrast soft tissue structures such as the prostate, seminal vesicles, duodenum, spleen, spinal cord and the liver are very problematic for visualisation. Figure 1 shows the difference in contrast when assessing images of a tumour between conventional CBCT (A) and avaiabel from MR-linacs (B).

[0007] Dual Energy CT (DECT) systems have gained significant traction over the past two decades as a means to enhance the contrast of anatomical regions of interest. The concept involves imaging a patient using two X-ray energy spectrums; the interaction within the body of the radiation spectrums differs based on the density of the anatomy. The premise allows differentiating between materials, enhancing the image contrast and allowing visualisation of anatomy that otherwise would be difficult to visualise using conventional CT. The separation of materials enables the generation of material decomposition maps which help enhance characteristics of a single material of interest. Major challenges with DECT are the specialised hardware required for their operation, and the additional imaging dose delivered to the patient. DECT systems demand two X-ray systems with additional imaging detectors. Due to the specialised hardware of DECT systems, they have not found their way into radiotherapy imaging. DECT applied in radiotherapy imaging has the potential to transform the accuracy of treatment deliveries. Introducing dual-energy CBCT (DC-CBCT) in conjunction with contrast injection has the potential to enable image-guided radiation therapy. Many studies are investigating ways of bringing DC-CBCT-based technologies into radiotherapy practice. A recent study has found that DC-CBCT for image-guided radiotherapy to track lung tumour motion can be performed without surgically implanting invasive fiducial markers due to the improved image quality. The study showed that DC-CBCT imaging improved the tumour tracking accuracy, relative to standard imaging, for all tumour targets tested.

[0008] Siemens Healthineers has developed a radiotherapy treatment machine named Ethos30. The Ethos system is an X-ray-based imager that allows for online adaptive treatments through the utilisation of artificial intelligence (Al) and deformable image registration which automates large parts of the anatomical contouring and plan optimisation process. The technology utilises existing detector technology with fast CBCT scanning in a closed-bore arrangement. HyperSight is a new technology developed by Siemens Healthineers that reached the market in 2023. This technology utilises charge-integrating detectors (amorphous silicon scintillator flat panel) with a larger field of view and fast CBCT scan times to improve image contrast by removing motion artifacts.

[0009] It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.Summary of the Invention

[0010] According to an aspect of the present invention, there is provided a radiotherapy treatment apparatus for imaging and treating a patient, comprising: a radiotherapy system comprising a treatment radiation source configured to perform radiotherapy treatment of a patient by directing treatment radiation towards the patient, wherein the patient is located substantially within a treatment region defining a longitudinal axis, wherein the treatment radiation source is moveable with respect to the longitudinal axis to thereby enable a selection of a treatment direction in preparation for radiotherapy treatment of the patient; an imaging system comprising an imaging radiation source and a radiation detector, wherein the imaging radiation source is moveable with respect to the longitudinal axis and is arranged to direct imaging radiation towards the patient in an imaging direction, and wherein the radiation detector is arranged to measure the imaging radiation after interaction of the imaging radiation with the patient, wherein the radiation detector comprises one or more photon counting detector arrays defining a sensitive area of the radiation detector, and wherein the imaging system is configured to generate multi-spectral images of the patient based on measurements of the imaging radiation by the one or more photon counting detector arrays.

[0011] Optionally, the treatment direction is substantially perpendicular to the longitudinal axis and / or the imaging direction is substantially perpendicular to the longitudinal axis.

[0012] In an embodiment, the radiotherapy treatment apparatus comprises a rotatable body portion rotatably mounted to a main body portion, and the treatment radiation source, imaging radiation source, and radiation detector are each mounted to the rotatable body portion. An axis of rotation of the rotatable body portion may correspond to the longitudinal axis. The imaging radiation source may be mounted to a first arm extending from the rotatable body portion, and the first arm may be hinged with respect to the rotatable body portion such that the imaging radiation source is moveable between an in-use position and a stowed position; and / or the radiation detector may be mounted to a second arm extending from the rotatable body portion, and the second arm may be hinged with respect to the rotatable body portion such that the radiation detector is moveable between an in-use position and a stowed position. The rotatable body portion may be in a closed bore configuration and both the imaging radiation source and the radiation detector may be mounted to a cylindrical portion of the rotatable body portion.

[0013] Optionally, the relative positions of the imaging radiation source, radiation detector, and optionally treatment radiation source to one another are fixed with respect to the longitudinal axis.

[0014] In an embodiment, the imaging radiation source, the radiation detector, or both, is or are mounted separate to the radiotherapy system.

[0015] Optionally, one of the imaging radiation source and the radiation detector is positioned to be, in use, above the patient, and the other one of the imaging radiation source and the radiation detector is positioned to be, in use, below the patient.

[0016] Optionally, one of the imaging radiation source and the radiation detector is ceiling mounted in a room in which the radiotherapy system, and the other one of the imaging radiation source and the radiation detector is floor mounted.

[0017] In an embodiment, the imaging system comprising two or more sets of imaging radiation sources and radiation detectors, the sets being positioned to, in use, image the patient from different perspectives.

[0018] Optionally, two of the sets are configured to provide stereoscopic imaging of the patient, and the imaging system is configured to general a three-dimensional image of the patient based on imaging radiation measurements by the radiation detectors of the two sets.

[0019] In an embodiment, the radiotherapy treatment apparatus further comprises a patient support, wherein the patient is positioned on the patient support such as to be aligned with thelongitudinal axis. The patient support may have an axis which is generally aligned with the longitudinal axis A relative location of the patient support with respect to the longitudinal axis may be controllable.

[0020] In an embodiment, the radiation detector comprises two or more photon counting detector arrays arranged on a planar surface of the radiation detector arranged facing the imaging radiation source. The sensitive area may correspond to the extent of the two or more photon counting detector arrays over the planar surface.

[0021] In an embodiment, each photon counting detector array comprises an arrangement of photo counting pixels each configured to enable a determination of received photon energy in response to imaging radiation passing through the patient and interacting with the photo counting pixels.

[0022] Optionally, the imaging radiation is emitted as cone with a central vertex substantially located at the imaging radiation source.

[0023] In an embodiment, the radiation treatment apparatus is configured to generate one or more multi-spectral images during radiotherapy treatment of the patient by the radiotherapy system. The radiotherapy treatment apparatus may be configured to process an output of the one or more photon counting detector arrays based on one or more contrast agents present within the patient when generating the one or more multi-spectral images.

[0024] According to another aspect of the present invention, there is provided a method of imaging for use in radiotherapy treatment using the radiation treatment apparatus of the first aspect, comprising the steps of: providing a radiotherapy treatment dose plan for a patient; undertaking an instance of treatment of the patient by: positioning the patient on a patient support; imaging the patient using the imaging system of the radiation treatment apparatus to generate one or more multi-spectral images of the patient; determining that a modification to the radiation treatment plan is required based on the one or more multi-spectral images of the patient and modifying the radiotherapy treatment dose plan accordingly; and performing treatment of the patient by operating the radiotherapy system of the radiation treatment apparatus according to the modified the radiotherapy treatment dose plan.

[0025] According to yet another aspect of the present invention, there is provided a method of imaging for use in radiotherapy treatment using the radiation treatment apparatus of the first aspect, comprising the steps of: providing a radiotherapy treatment dose plan for a patient;undertaking an instance of treatment of the patient by: positioning the patient on a patient support; performing treatment of the patient by operating the radiotherapy system of the radiation treatment apparatus according to the modified the radiotherapy treatment dose plan; during treatment, imaging the patient using the imaging system of the radiation treatment apparatus to generate one or more multi-spectral images of the patient; modifying the operation of the radiotherapy system based on the generated one or more multi-spectral images during treatment.

[0026] Optionally, the radiotherapy treatment dose plan is generated at least in part by using the imaging system of the radiation treatment apparatus.

[0027] According to still another aspect of the present invention, there is provided a method of controlling a patient bed of a radiotherapy treatment system. The method comprises: providing planning images in respect of a radiotherapy treatment dose plan for a patient; positioning the patient on a patient support; imaging the patient using the imaging system of the radiation treatment system to generate one or more multi-spectral images of the patient; determining a required movement of the patient support to align the patient with treatment beam(s), based on the planning images and the one or more multi-spectral images; move the patient support based on the determined required movement.Brief Description of the Drawings

[0028] In order that the invention may be more clearly understood, embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:Figure 1 shows a comparison between images generated by prior art systems;Figure 2 shows a schematic representation of a radiotherapy treatment system, according to an embodiment of the present invention;Figure 3 shows the embodiment of Figure 2, except the radiation detector and the imaging radiation source are not mounted on the main body portion of the radiotherapy system;Figure 4 shows an embodiment in which the imaging radiation source generates a cone- shaped beam of imaging radiation and the radiation detector comprises a plurality of photon counting detector arrays;Figure 5 shows a method of imaging for use in radiotherapy treatment of a patient is shown, according to an embodiment; andFigure 6 depicts a method of controlling the movement of the patient support, in accordance with an embodiment of the present invention.Description of Embodiments

[0029] Figure 2 shows a schematic representation of a radiotherapy treatment system 10 according to an embodiment.

[0030] The radiotherapy treatment system 10 comprises a radiotherapy system 11 and an imaging system 12. The radiotherapy system 11 comprises a radiation treatment linear accelerator (“linac”) 20 mounted to a rotatable body portion 21, which is itself rotatably mounted to a main body portion 22 and is also known as a “gantry”. In use, actuators associated with the rotatable body portion 21 and the main body portion 22 are controllably activated in order to rotate the rotatable body portion 21 such as to position the linac 20 at a desired angle before irradiation of the patient by the linac 20. The radiotherapy treatment system 10 also comprises a moveable patient support 23 configured for supporting the patient (for example, providing a flat surface onto which a patient can lay flat) during an irradiation procedure. Generally, these features of the radiotherapy system 11 are known in the art.

[0031] A controller 13 is shown interfaced with the radiotherapy system 11 and the imaging system 12. The controller 13 is conceptually represented by box 13, and can be positioned as chosen by the designer of the system 10, subject to constraints such as the suitability of the physical space(s) to accommodate the controller 13, and / or components required for the data communication to occur to enable the interfacing. The controller 13 is representative of computerised control of both the radiotherapy system 11 and the imaging system 12, however, the single controller 13 shown is not intended to be limiting. For example, the controller 13 can represent a number of controller sub-systems operating as logically distinct units, or in fact, physical distinct units. The controller 13 can represent a controller sub-system for controlling the radiotherapy system 11, another controller sub-system for controlling the imaging system 12, and yet another controller sub-system for controlling interactions between the radiotherapy system 11 and the imaging system 12. In addition, the controller 13 can represent computerised control of other features described herein, where appropriate. At least a portion of the controller 13 functionality can be controlled by a user via suitable user input(not shown), which can include human interface devices such as keyboards, mice, displays, and touchscreens (which can include touchscreen displays). A user can also be provided with control via a separate computer device (“user device”) configured for data communication (wired and / or wirelessly) with the controller 13, such as a smartphone or tablet.

[0032] Figure 2 also shows a longitudinal axis Z parallel to an elongate axis of the patient support 23. The rotatable body portion 21 is arranged to rotate around the longitudinal axis Z, such that the longitudinal axis corresponds to the axis of rotation of the rotatable body portion 21. In an embodiment, the patient support 23 is moveable in a direction of the longitudinal axis Z, for example, via a computer-controlled actuation of the patient support 23 (for example, controllable by controller 13). In an embodiment, the patient support 23 is manually moveable in the direction of the longitudinal axis Z and can include a locking mechanism to enable a user to selectively lock the patient support 23 against further such movement.

[0033] The imaging system 12 comprises a first arm 30 extending, from a proximal end of the first arm 30, from the rotatable body portion 21. Optionally, the first arm 30 is moveably attached at its proximal end to the rotatable body portion 21 such that the first arm 30 can be moved between an in-use position and a stowed position, for example, via a hinge mechanism connecting the first arm 30 to the rotatable body portion 21.

[0034] An imaging radiation source 24 for generating imaging radiation is located at a distal end of the first arm 30. The imaging radiation source 24 typically comprises an x-ray source, for example, comprising an x-ray tube electrically coupled to a kV generator (the kV generator can be located separately to the first arm 30). In the in-use position of the first arm 30, the imaging radiation source 24 is positioned such as to emit imaging radiation such as to be directed towards the patient.

[0035] The imaging system 12 comprises a second arm 31 extending, from a proximal end of the second arm 31, from the rotatable body portion 21. The second arm 31 is positioned substantially opposite the first arm 30. Typically, the second arm 31 is moveably attached at its proximal end to the rotatable body portion 21 such that the second arm 31 can be moved between an in-use position and a stowed position, for example, via a hinge mechanism connecting the second arm 31 to the rotatable body portion 21.

[0036] A radiation detector 25 for measuring received imaging radiation is located at a distal end of the second arm 31. The radiation detector 25 comprises a substantially planar receivingface 35 arranged, when in the in-use position, to face the radiation beam emitted by the imaging radiation source 24. That is, the receiving face has a normal axis parallel to a central axis of the emitted imaging radiation. The radiation detector 25 and the radiation source 24 are positioned, so that at least a portion of the imaging radiation is arranged to pass through the patient before impinging on the radiation detector 25.

[0037] In the embodiment shown in Figure 2, the imaging radiation source 24 and the imaging radiation detector 25 are mounted on the rotatable body portion 21. Therefore, it is possible to rotate the body portion 21 by at least a partial rotation, to also rotate the imaging system 12 with respect to the patient. This can allow the construction of a three-dimensional image from the measurements, or the acquisition of static images from different angles. The amount of rotation may be determined based on the quality of the image which is required.

[0038] Whether the radiation detector 25 and the radiation source 24 are mounted as shown on the first and second arms 30, 31, or by another arrangement, is not a general limiting factor of the working of the broadest embodiments of the imaging system 12.

[0039] For example, the radiotherapy system 11 shown in Figure 2 can be considered a “C- arm” type system. Another available type of radiotherapy system is an O-ring type system. In accordance with the present disclosure, if the radiotherapy system 11 used is an O-ring system, the imaging radiation source 24 and imaging radiation detector 25 may be mounted within the O-ring.

[0040] For another example, referring to Figure 3, the radiation source 24 and the radiation detector 25 are not attached to the radiotherapy system 11 via the supporting arms 30, 31. Instead, they are mounted on fixtures or installations which are provided adjacent to the radiotherapy system 11. For example, the radiation source 24 is floor mounted, and thus below the plane of the patient support 23. It can be mounted on a support 27 installed on the floor at a location adjacent the radiotherapy system 11, and located so that in use at least a portion of its imaging rays will pass through the patient. In the embodiment, the radiation detector 25 is provided above the plane of the patient support 25, e.g., it may be ceiling mounted. For instance it may be mounted on a support (not shown) installed on the ceiling. The locations of the radiation source 24 and detector 25 may be reversed in that the radiation source 24 may be mounted above patient support 23 (e.g., ceiling mounted) and the radiation detector 25 below (e.g. floor mounted). Also, similar to the first and second arms 30, 31 in the embodiment shown in Figure 2, the floor support 27 and the ceiling support (not shown) may be configured to bepivotable, translatable, or both, to allow the positioning and / or orientation of the radiation source 24 to be adjusted. This can be done using available hardware such as actuators and movement tracks, and is not a limitation on the general scope of the present disclosure. Embodiments of the type shown in Figure 3 may be particularly suited for imaging patients undergoing isocentre rotation during therapy.

[0041] As the skilled person would understand, the working of the imaging system 12 does not limit the imaging system 12 to having only one set of radiation sources 24 and detectors 25. Multiple sets of radiation sources 24 and detectors 25 may be provided in an imaging system 12 described herein, subject to constraints such as the availability of the space where the sets can be mounted so that they can be used to image the patient during operation, and the availability of connectivity components to control the different sets of imaging radiation sources and detectors in the imaging system 12 and to receive the measurements from the imaging system 12. The sets may be positioned so as to image the patient from different perspectives. That is, different radiation sources 24 may be positioned so that their imaging rays (or portions thereof) will pass through the patient from the different perspectives. The detectors 25 will be correspondingly positioned so that each detector 25 will receive and detect the imaging rays from a respective source 24. This can be useful in the construction of a three- dimensional image. For example, at least two of the sets may be configured to acquire images at the same time, and positioned so that their resulting images can be used for stereoscopic imaging. Given a plurality of sets of radiation sources 24 and detectors 25, optionally, the system may be configured to enable the operator to select which set or sets will be activated to pass the imaging rays through the patient, so as to obtain images that show the region of interest from the desired perspective(s).

[0042] Figure 3 depicts an example where the imaging system 12 includes two sets of radiation sources and detectors. Two radiation sources 24a, 24b (24b not shown), one on each side of the longitudinal axis Z of the patient support 23, are provided. A corresponding number of radiation detectors 25a, 25b are provided, each being on an opposite side of the longitudinal axis Z from its corresponding radiation source 24a, 24b. The radiation detector 25a is positioned to detect rays from the radiation source 24a, and the radiation detector 25b is positioned to detect rays from the radiation source 24b (not shown). Such an imaging system 12 can be operated to provide stereoscopic imaging, by configuring the imaging performed by the sets of radiation sources and radiation detectors to occur at the same time and thenconstructing the three-dimensional image. The three-dimensional image may be generated on the fly (if the processing capability within or accessible by the imaging system allows) or in post processing. As the skilled person will understand, it would also be possible to provide multiple sets of radiation sources and detectors in embodiments where the imaging system 12 is mounted onto the radiotherapy system - again this is subject to the availability of space and connectivity to accommodate the sets.

[0043] Referring to Figure 4, in an embodiment, a radiation detector 25 of the imaging system 12 comprises one or more photon counting detector arrays 36 defining a sensitive region 37 typically of rectangular extent across the receiving face 35. In an embodiment, a plurality (in the example, four) of photon counting detector arrays 36a-36d are arranged over the receiving face 35, such that the sensitive region 37 corresponds to the total surface area of the plurality of photon counting detector arrays 36a-36h. A different number of photon counting detector arrays may be provided. In another embodiment (not shown), a single photo counting detector array 36 is utilised and thereby defines the entire sensitive region 37..

[0044] With reference to Figure 4, in an embodiment, the imaging radiation source 24 is configured to generate “cone-beam” imaging radiation. That is, the emitted imaging radiation fans out from a central vertex proximal to the imaging radiation source 24 in a cone-like manner. Notably, the cone-like shape of the imaging radiation can be understood as defining a central radiation axis 40 extending away from the imaging radiation source 24. The central radiation axis 40 can be arranged to bisect the planar receiving face 35. For example, in the absence of any interference with the path of the imaging radiation (e.g., when a patient is not positioned such as to receive the imaging radiation), the central radiation axis 40 can be arranged to pass substantially perpendicularly through the planer receiving face 35. Therefore, in an embodiment, the central radiation axis 40 can be arranged to substantially intersect the longitudinal axis Z of the rotatable body portion 21. In available radiotherapy systems, the treatment beam is typically controlled to be provided from a direction which is perpendicular to the longitudinal axis Z. Therefore, the imaging radiation source 24 can be arranged to image the patient where the imaging direction is generally orthogonal to the treatment radiation direction, as generally shown in Figure 2.

[0045] In an embodiment, the imaging system 12 is configured so that the radiation detector 25 is moveable perpendicularly with respect to the central radiation axis 40. This can enable the radiation detector 25 to sweep through an imaging plane larger than the sensitive region37. In an embodiment, the radiation detector 25 is moveable in one axis (for example, substantially parallel the longitudinal axis Z about which the rotatable body portion 21 is configured to rotate). In another embodiment, the radiation detector 25 is moveable in two axes (for example, substantially parallel to the longitudinal axis Z of the rotatable body portion 21 as well as substantially perpendicular to both the longitudinal axis Z and the central radiation axis 40). Movement of the radiation detector 25 can be computer controlled via suitably arranged computer controllable translation actuators.

[0046] A particular photo counting detector array 36, generally, comprises an array of CMOSbased pixels (e.g., formed on a semiconductor chip) defining a first layer of the photo counting detector array 36. Overlaid and bonded to the first layer is a second layer comprising a detector material, such as Si (Silicon), CdTe (Cadmium telluride), Lead Halide Perovskites, and CZT (Cadmium zinc telluride). Each pixel is arranged to accurately count the number of photons that reach it. In addition, pixel counting can be on the basis of two or more different “energy bins”, such that a photo count for each energy bin can be determined from the pixel. Each photon making up the imaging radiation can be understood to undergo a varying level of energy loss as it passes through the patient, in dependence on the particular material in the path of the photon.

[0047] Commercially available linac radiotherapy systems can utilise an imaging radiation source 24 configured to produce a “cone-shaped” x-ray beam. For such imaging radiation sources 24, a problem exists in that a relatively large sensitive region 37 of the radiation detector 25 is required in order to provide a sufficient field-of-view (FOV) for patient imaging. This is to be contrasted with other medical imaging systems that utilise “fan-shaped” x-rays for patient imaging, such as CT-scanners. Fan-shaped x-rays provide high spatial resolution on the basis that the imaging radiation source 24 and the radiation detector 25 can be rotated about an imaging axis (e.g., such as axis Z of Figure 2 and Figure 3) relatively quickly. For practical reasons, the rotation rate of commercially available linac systems is often too slow to enable imaging with fan-shaped x-rays. Therefore, cone-shaped x-rays are utilised such that a sufficiently large volume of the patient can be imaged without requiring movement of the imaging radiation source 24 and the radiation detector 25 about the Z axis during imaging. Additionally, in commercial linac systems, the patient support 23 does not have a sufficient range of motion to cover the sensitive region 37.

[0048] Therefore, in an embodiment, a relatively large sensitive region 37 is required. The inventors have found that it is generally not practical to manufacture single photon counting detector arrays 36, suitable for use in the embodiments herein described, with a sufficient surface area to correspond to the required size of the sensitive region 37. For example, a photo counting detector array 36 typically comprises a semiconductor sensor layer overlaying a pulse electronics layer. Example materials making up the semiconductor sensor layer include: Si (Silicon), CdTe (Cadmium telluride), and Lead Halide Perovskites, CZT (Cadmium zinc telluride). In the case particular of CdTe and CZT-based sensors, manufacturing techniques can limit single photon counting detector array 36 sizes to be of the order of 1.4 x 1.4 cm2to 2.5 x 2.5 cm2whereas the sensitive region 37 can be of the order of 40 x 40 cm2. One example of a photon counting detector array 36 is the Medipix3RX 34 custom photon counting detector manufactured by MBI.

[0049] In order to facilitate the use of photon detector arrays 36 while retaining existing linac imaging radiation sources 24 having cone-shaped x-rays, an embodiment comprises an arrangement of a plurality of photon counting detector arrays 36 in order to provide a sufficient FOV for use with the existing imaging radiation sources 24. This may be particularly advantageous for CdTe and CZT-based sensors (more generally, any photo counter limited in surface area as described). Linacs in particular may be limited to the use of cone-beam x-rays as the imaging radiation source 24; for example, the primary radiation treatment linear accelerator (“linac”) 20 may impede having the imaging radiation source 24 and the radiation detector 25 rotate about the imaging axis Z sufficiently quickly to enable the use of a fanshaped x-ray beam (as is possible with medical CT-scanners).

[0050] Typically, the radiation detector 25 is in data communication with the controller 13, allowing the controller 13 to receive data representing measurements of the imaging radiation made by the radiation detector 25. The controller 13 is also typically arranged to control operation of the radiation detector 25, for example, by sending commands to the radiation detector 25. The controller 13 can control the radiation detector 25 to cause it to switch to a measurement mode (where measurements are made of the incident imaging radiation) and at another time to a read-out mode (where previously made measurements are communicated to the controller 13).

[0051] In an embodiment, the radiation detector 25 is electrically coupled to a signal processor 26 configured to receive measurement signals from the radiation detector 25 (depending on theembodiment, when in the read-out mode), the measurement signals indicative of the measurements of the imaging radiation. The signal processor 26 is configured to process the measurement signals into a suitable format for the controller 13, for example, this can include digitisation in a case where the radiation detector 25 outputs analogue signals.

[0052] The signal processor 26 and controller 13 are depicted conceptually in Figure 2. The location of the processor 26 and / or controller 13 as depicted should not be taken to be a limiting disclosure. For example, for embodiments where the radiation source(s) 24 and detector(s) 25 are not mounted to the radiotherapy system 11, the processed measurement signals may be provided either wirelessly or over a physical connector to the controller 13, and system may be configured for the control signals to be provided wirelessly or over a physical connector to the radiation sources 24. The controller 13 may be located separate to the radiation detectors 25 and the radiation sources 24. Connectivity solutions such as but not limited to C-Bus, virtual private networks (VPNs), wireless networks, near field communication or Bluetooth®, may be used to facilitate the required data communication.

[0053] In the embodiment comprising two or more photon detector arrays 36 as the radiation detector 25, the signal processor 26 can include combining the measurement signals of each of the photon detector arrays 36 into a single measurement representing the photon counting measurements made over the entire sensitive region 37 (i.e., accounting for the relative position of each photon detector array 36 with respect to the one or more other photo detector arrays 36). In an embodiment, the photon counting measurements are received from each photon detector array 36 substantially in parallel. The signal processor 26 therefore may advantageously allow for relatively fast read-out of the two or more photo detector arrays 26 due to receiving measurement signals in parallel, while avoiding said combination needing to be performed by the controller 13. The signal processor 26 can comprise suitable processing means for combining the measurement signals, and can in an embodiment comprise one or more of field-programmable gate arrays (FPGA), microcontrollers, microprocessors, and the like.

[0054] Referring to Figure 5, a method of imaging for use in radiotherapy treatment of a patient is shown, according to an embodiment. The method can utilise the radiotherapy treatment system 10 according to at least one embodiment described herein.

[0055] At step SI 00, a radiotherapy treatment dose plan for the patient is created based on one or more reference images. The purpose of the reference image(s) is to is identify the locationwithin the patient requiring radiotherapy (e.g., the location of a tumour). Therefore, the reference image(s) can be created, at least in part, using known techniques utilising CT, positron emission tomography (PET), and / or magnetic resonance imaging (MRI) in order to identify the location, shape, and size of the treatment location (e.g., the location, shape, and size of the tumour).

[0056] Alternatively, or in addition, in an embodiment, the imaging system 12 described herein can be utilised in the creation (at least in part) of the treatment plan. For example, a treatment plan can be created using the imaging system 12 of the radiotherapy treatment system 10 shortly before initial treatment of the patient using the radiotherapy system 11 while the patient remains supported by the patient support 23.

[0057] Optionally, the radiotherapy treatment dose plan also defines the number of instances of radiation therapy treatment for the patient and the intended dose for each treatment instance (although this may be modified based on the response of the patient to the treatment).

[0058] Steps S101-S104 relates to a particular treatment instance of a patient using the radiotherapy treatment system 10. Control of one or more of these various steps can be implemented by the controller 13. The particular treatment instance may be one of a planned series of treatment instances as per the radiotherapy treatment dose plan. At step S 101, the patient is positioned on the patient support 23 in a position suitable for radiation treatment using the radiotherapy system 11.

[0059] Next, at step S102, the imaging system 12 is utilised to image the patient — for example, the general location of radiotherapy treatment (e.g., the location of the tumour) — to thereby generate one or more treatment images.

[0060] Then, at step S103, the one or more treatment images are utilised in conjunction with the reference images and radiotherapy treatment dose plan of step SI 00 in order to determine whether the radiotherapy treatment dose plan requires modification. The radiotherapy treatment dose plan can require modification where the location, shape, and / or size of the tumour has changed since the radiotherapy treatment dose plan was created or most recently modified. It may be that the radiotherapy treatment dose plan accounts for expected changes to the location, shape, and / or size of the tumour yet the one or more treatment images reveals a sufficiently different change to the location, shape, and / or size of the tumour to require modification to the radiotherapy treatment dose plan. For example, the radiotherapy treatmentmay need to be directed towards a different location or the dose of radiation received by the patient may be changed. The radiotherapy treatment dose plan can require modification due to changes in the patient’s anatomy, for example, relative changes in location, shape, and / or size of sensitive organs with respect to the tumour.

[0061] Whether the radiotherapy treatment dose plan is modified or not, the method then proceeds to patient treatment step SI 04, where the radiotherapy system 11 is operated to treat the patient according to known techniques.

[0062] Typically, steps S101-S103 are implemented several times over a period of time (e.g., weekly, fortnightly, monthly) in order to complete treatment of the patient according to the radiotherapy treatment dose plan. Step SI 03 can be referred to as adaptive radiotherapy between fractions.

[0063] In an embodiment, the imaging system 12 is also (or alternatively) utilised during treatment with the radiotherapy system 11 (i.e., a modification to step S104 described above). This modification of step SI 04 can be termed intra-fraction motion monitoring or real-time adaptive radiotherapy. Imaging using the imaging system 12 is performed during treatment delivery using the radiotherapy system 11 using the one or more photon counting detector arrays 36 to monitor the motion of a surrogate. This may include imaging the treatment volume of interest and / or neighbouring regions of the patient, such as organs, that may be at risk of damage from the radiotherapy treatment.

[0064] For example, motion of the prostate can be monitored during treatment of prostate cancer. The prostate can move due to bladder filling up, gas build up in the bowel, and rectum filling. In another example, in treatment of lung cancer, the patient’s lung(s) can have significant movement due to breathing. The existing solution is to get the patient to hold their breath but this can be hard to reproduce accuracy since the tumour might be in a different location depending on the breath hold technique. In another example, the location of liver and pancreatic cancers can change during treatment due to motion from the patient’s lungs pushing on these organs. In another example, gas build up in the patient’s intestine can push a closely located tumour down and up.

[0065] There are imaging technologies that are available that use gold makers that are implanted into the tumour and can be visible by the X-ray imaging on the linac. These markers are then tracked to work out where the tumour is in real-time. However, a problem with this isthe invasive nature of implanting markers in the patient; the lung is an example, it is very hard and uncomfortable for the patient. Also, the marks may drift in the body between fractions.

[0066] According to the present embodiment, by providing real-time tracking of the tumour during treatment, treatment can be adaptive to mitigate against these movements which can advantageously allow for improved treatment of the tumour while reducing unwanted radiation dosage in surrounding tissue and organs. Advantageously, the present embodiment may avoid the need to utilise implants such as gold markers.

[0067] Real-time information from the spectral images generated by the one or more photon detector arrays 36 is then processed to track the motion of the target, user-defined motion thresholds can be set to trigger the termination or adaptation of the treatment beam. The motion information extracted from the multi-spectral images generated from the measurement signals output by the one or more photon counting detector arrays 36 can be used to adapt the treatment beam or patient position during treatment.

[0068] The one or more photon detector arrays 36 enable multi-energy spectral imaging. Each energy bin of the plurality of energy bins is assigned a range of photon energies according to expected features of the images. For example, energy bin 1 can be placed above the noise floor to improve the signal to noise, energy bins 2, 3, 4...n and so on can be user-defined (or otherwise predefined) to target specific material composition such as water (soft tissue), lipids (fats), muscle, and so forth to enable better target or organs at risk localisation before, during, or between fractions of radiotherapy delivery. The use of plural energy bins takes advantage of the different photo energy losses due to the various different materials associated with the patient. Therefore, the plural energy bins can advantageously enable improvements in localisations by improving contrast when compared to existing imaging sensors without energy bin discrimination capability. In an embodiment, at least three energy bins are utilised; these are selected according to expected photo energies associated with each of soft tissue, fats, and muscle.

[0069] Regarding step SI 04, in order to improve image quality during intrafraction imaging, the selection of energy bins or thresholds can be such as to filter out the radiation scatter from the treatment beam of the radiotherapy system 11, this scatter rejection technique utilises the photon counting detectors capability to measure the Compton scatter radiation from the treatment radiation generated by the radiotherapy system 11 in real-time and remove this effect in the resulting multi-spectral images.

[0070] Figure 6 depicts a method of controlling the movement of the patient support, applicable when the imaging system 12 is capable of providing a three-dimensional image of the treatment region in the patient. This may be provided by rotating the body portion 21 in the configuration shown in Figure 2 or by rotating the imaging system 12 in a closed-bore configuration, or by using the configuration of the type shown in Figure 3 where multiple imaging radiation source / detector pairs enable stereoscopic imaging.

[0071] As shown in Figure 6, at step S200, planning images used to determine a radiotherapy treatment dose plan for the patient is obtained. The planning images may be loaded with, or provided as part of, the radiotherapy treatment dose plan. At step S201, the patient is positioned on the patient support 23 in a position suitable for radiation treatment using the radiotherapy system 11. At step S202, the imaging system 12 is utilised to image the patient to thereby generate one or more images. The images may be treatment images acquired when the patient is undergoing treatment.

[0072] At step S203, the one or more generated images are utilised in conjunction with the planning images, in order to determine whether the position of the support bed needs to be modified, in order to correctly position the patient to receive the treatment. For example, this can involve using markers on the head frame or similar devices on the radiotherapy device for positioning the patient, and / or the bony anatomy of the head, as reference points, to determine if there is any mis-alignment between the patent and the location(s) of the treatment radiation beam(s). At step s204, the system may determine coordinates based on the reference points, for shifting the patient support 23, if needed, to make sure the patent is in the right spot to receive radiotherapy. At step S205, the patient support 23 is moved accordingly. Optionally, at step s206, a verification stereo image is performed to validate the patent is in the right spot. Steps s203-206 (or simply steps s205-206) may be performed until the validation process confirms the patient is in the right spot. More steps of the process described may be repeated until the validation confirms the patient is in the right spot.

[0073] It will be appreciated that, as some of the steps involved in relation to Figure 6 have parallels in the method described with reference to Figure 5, the variations or alternatives which are applicable to the method referenced by Figure 5 may also be applicable to the method described with reference to Figure 6, where appropriate.

[0074] In an embodiment, the imaging system 12 is adapted for imaging a patient having received injection of a contrast agent (or plural contrast agents). At least one contrast agent canutilise suitable nanoparticles. In this case, one or more of the energy bins can be configured to target the associated K-edge of the injected contrast agent. The contrast agent can be selected to localise organs at risk to help avoid radiation to critical structures or to target the treatment volume such as a tumour to help improve the accuracy in delivering radiotherapy to the intended volume. Multi -contrast injection can also be utilised with two different K-edge characteristics enabling multi-energy spectral distinction between two regions of interest such as the treatment volume and any organs at risk where radiation needs to be avoided.

[0075] Further modifications can be made without departing from the spirit and scope of the specification. For example, as alluded above, the radiotherapy treatment system 10 can be implemented in a closed bore configuration such that the rotatable body portion 21 has a substantially annular shape (“O-ring”) with the patient being positioned within a cylindrical bore of the rotatable body portion 21. The rotatable body portion 21 is itself located substantially within the main body portion 22 such that it is rotatable in place around the central longitudinal axis. In this variation, the linac 20, imaging radiation source 24, and radiation detector 25 can be mounted directly to or within the rotatable body portion 21 rather than to arms 30, 31. Other features described in relation to a radiotherapy treatment system 10 utilizing a C-arm type radiotherapy system 11 may also be applied in relation to a radiotherapy treatment system 10 utilizing an O-ring type radiotherapy system 11.

[0076] The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of the inventors’ contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art

[0077] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

Claims:

1. A radiotherapy treatment system for imaging and treating a patient, comprising: a radiotherapy system comprising a treatment radiation source configured to perform radiotherapy treatment of a patient by directing treatment radiation towards the patient, wherein the patient is located substantially within a treatment region defining a longitudinal axis, wherein the treatment radiation source is moveable with respect to the longitudinal axis to thereby enable a selection of a treatment direction in preparation for radiotherapy treatment of the patient; an imaging system comprising an imaging radiation source and a radiation detector, wherein the imaging radiation source is arranged to direct imaging radiation towards the patient in an imaging direction, and wherein the radiation detector is arranged to measure the imaging radiation after interaction of the imaging radiation with the patient, wherein the radiation detector comprises one or more photon counting detector arrays defining a sensitive area of the radiation detector, and wherein the imaging system is configured to generate multi-spectral images of the patient based on measurements of the imaging radiation by the one or more photon counting detector arrays.

2. The radiotherapy treatment system of claim 1, wherein the treatment direction is substantially perpendicular to the longitudinal axis and / or the imaging direction is substantially perpendicular to the longitudinal axis.

3. The radiotherapy treatment system of claim 1 or claim 2, wherein the radiotherapy treatment apparatus comprises a rotatable body portion rotatably mounted to a main body portion, and wherein the treatment radiation source, imaging radiation source, and radiation detector are each mounted to the rotatable body portion.

4. The radiotherapy treatment system of claim 3, wherein an axis of rotation of the rotatable body portion corresponds to the longitudinal axis.

5. The radiotherapy treatment system of claim 3 or claim 4, wherein: the imaging radiation source is mounted to a first arm extending from the rotatable body portion, wherein the first arm is hinged with respect to the rotatable body portion suchthat the imaging radiation source is moveable between an in-use position and a stowed position; and / or the radiation detector is mounted to a second arm extending from the rotatable body portion, wherein the second arm is hinged with respect to the rotatable body portion such that the radiation detector is moveable between an in-use position and a stowed position.

6. The radiotherapy treatment system of claim 3 or claim 4, wherein the rotatable body portion is in a closed bore configuration and wherein both the imaging radiation source and the radiation detector are mounted to a cylindrical portion of the rotatable body portion.

7. The radiotherapy treatment system of claim 1 or claim 2, wherein the imaging radiation source, the radiation detector, or both, is or are mounted separate to the radiotherapy system.

8. The radiotherapy treatment system of claim 7, wherein one of the imaging radiation source and the radiation detector is positioned to be, in use, above the patient, and the other one of the imaging radiation source and the radiation detector is positioned to be, in use, below the patient.

9. The radiotherapy treatment system of claim 8, wherein one of the imaging radiation source and the radiation detector is ceiling mounted in a room in which the radiotherapy system, and the other one of the imaging radiation source and the radiation detector is floor mounted.

10. The radiotherapy treatment system of any one of claims 1 to 9, the imaging system comprising two or more sets of imaging radiation sources and radiation detectors, the sets being positioned to, in use, image the patient from different perspectives.

11. The radiotherapy treatment system of claim 10, wherein two of the sets are configured to provide stereoscopic imaging of the patient, and the imaging system is configured to general a three-dimensional image of the patient based on imaging radiation measurements by the radiation detectors of the two sets.

12. The radiotherapy treatment system of any one of claims 1 to 11, wherein the relative positions of the or each imaging radiation source, radiation detector, and optionally treatment radiation source to one another are fixed with respect to the longitudinal axis.

13. The radiotherapy treatment system of any one of claims 1 to 12, further comprising a patient support, wherein the patient is positioned on the patient support such as to be aligned with the longitudinal axis.

14. The radiotherapy treatment system of claim 13, wherein a relative location of the patient support with respect to the longitudinal axis is controllable.

13. The radiotherapy treatment system of any one of claims 1 to 12, wherein the radiation detector comprises two or more photon counting detector arrays arranged on a planar surface of the radiation detector arranged facing the imaging radiation source.

14. The radiation treatment system of claim 13, wherein the sensitive area corresponds to the extent of the two or more photon counting detector arrays over the planar surface.

15. The radiation treatment system of any one of claims 1 to 14, wherein each photon counting detector array comprises an arrangement of photo counting pixels each configured to enable a determination of received photon energy in response to imaging radiation passing through the patient and interacting with the photo counting pixels.

16. The radiation treatment system of any one of claims 1 to 15, wherein the imaging radiation is emitted as cone with a central vertex substantially located at the imaging radiation source.

17. The radiation treatment system of any one of claims 1 to 16, configured to generate one or more multi-spectral images during radiotherapy treatment of the patient by the radiotherapy system.

18. The radiation treatment system of claim 17, configured to process an output of the one or more photon counting detector arrays based on one or more contrast agents present within the patient when generating the one or more multi-spectral images.

19. A method of imaging for use in radiotherapy treatment using the radiation treatment system of any one of claims 1 to 18, comprising the steps of: providing a radiotherapy treatment dose plan for a patient; undertaking an instance of treatment of the patient by: positioning the patient on a patient support; imaging the patient using the imaging system of the radiation treatment apparatus to generate one or more multi-spectral images of the patient; determining that a modification to the radiation treatment plan is required based on the one or more multi-spectral images of the patient and modifying the radiotherapy treatment dose plan accordingly; and performing treatment of the patient by operating the radiotherapy system of the radiation treatment apparatus according to the modified the radiotherapy treatment dose plan.20 A method of imaging for use in radiotherapy treatment, using the radiation treatment system of any one of claims 1 to 18, comprising the steps of: providing a radiotherapy treatment dose plan for a patient; undertaking an instance of treatment of the patient by: positioning the patient on a patient support; performing treatment of the patient by operating the radiotherapy system of the radiation treatment system according to the modified the radiotherapy treatment dose plan; during treatment, imaging the patient using the imaging system of the radiation treatment system to generate one or more multi-spectral images of the patient; modifying the operation of the radiotherapy system based on the generated one or more multi-spectral images during treatment.

21. The method of claim 19 or claim 20, wherein the radiotherapy treatment dose plan is generated at least in part by using the imaging system of the radiation treatment apparatus.

22. A method of controlling a patient bed of a radiotherapy treatment system of any one of claims 1 to 18, comprising the steps of: providing planning images in respect of a radiotherapy treatment dose plan for a patient; positioning the patient on a patient support; imaging the patient using the imaging system of the radiation treatment system to generate one or more multi-spectral images of the patient; determining a required movement of the patient support to align the patient with treatment beam(s), based on the planning images and the one or more multi-spectral images; move the patient support based on the determined required movement.

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