WO2024160339A1

WO2024160339A1 - Patient monitoring using grating-based phase-contrast x-ray imaging

Info

Publication number: WO2024160339A1
Application number: PCT/EP2023/052129
Authority: WO
Inventors: Kajetan Berlinger; Stephan UMKEHRER; Arne TAPFER; Claus Promberger
Original assignee: Brainlab Ag
Priority date: 2023-01-30
Filing date: 2023-01-30
Publication date: 2024-08-08

Abstract

Disclosed is a computer-implemented method of determining the position of an image rendering of a region of interest in medical image data which encompasses determination of the position of an anatomical region of interest (e.g. a treatment target) in contrast-enhanced medical image data. The contrast enhancement is due to using a specific imaging modality, namely grating-based phase contrast imaging (for example, dark-field contrast imaging). This allows to identify a sharper contour of soft tissue in the image than could be achieved with approaches known from the state of the art. The region of interest is identified in the grating-based phase contrast image by comparing it to a DRR generated from planning data using a known positional transformation between the image datasets. Such a procedure can be used in the framework of positioning a patient ready for radiation treatment.

Description

PATIENT MONITORING USING GRATING-BASED PHASE-CONTRAST X- RAY IMAGING

FIELD OF THE INVENTION

The present invention relates to a computer-implemented method of determining the position of an image rendering of a region of interest in medical image data, a corresponding computer program, a computer-readable storage medium storing such a program and a computer executing the program, as well as a medical system comprising an electronic data storage device and the aforementioned computer.

TECHNICAL BACKGROUND

Known radiation treatment devices use standard x-ray imaging for positioning and monitoring the position of a patient for example during radiotherapy. Standard x-ray imaging measures the attenuation of an x-ray beam when traversing the object of interest. This approach is suitable for detecting the position of bony parts, but when it comes to tracking soft tissue parts, e.g. a lung tumour that is moving with respiratory motion, the method often lacks contrast in soft tissue, thereby impeding reliable tracking.

The present invention has the object of providing means for improving image contrast when tracking motion of soft tissue.

The present invention can be used for planning procedures e.g. in connection with a system for image-guided radiotherapy such as ExacTrac®, a product of Brainlab AG.

Aspects of the present invention, examples and exemplary steps and their embodiments are disclosed in the following. Different exemplary features of the invention can be combined in accordance with the invention wherever technically expedient and feasible.

EXEMPLARY SHORT DESCRIPTION OF THE INVENTION

In the following, a short description of the specific features of the present invention is given which shall not be understood to limit the invention only to the features or a combination of the features described in this section.

The disclosed method encompasses determination of the position of an anatomical region of interest (e.g. a treatment target) in contrast-enhanced medical image data. The contrast enhancement is due to using a specific imaging modality, namely gratingbased phase contrast imaging (for example, dark-field contrast imaging). Specifically, grating-based phase-contrast imaging provides two additional and complementary contrast modalities to the conventional attenuation contrast. This generates information about the scattering (dark-field) and refraction (phase-contrast) properties of an object of interest. Therefore, for example, both (dark-field and phase-contrast) shows almost no (overlaying) bony structures, which might influence diagnostics on soft tissue. The region of interest is identified in the grating-based phase contrast image by comparing it to a DRR generated from planning data using a known positional transformation between the image datasets. Such a procedure can be used in the framework of positioning a patient ready for radiation treatment.

GENERAL DESCRIPTION OF THE INVENTION

In this section, a description of the general features of the present invention is given for example by referring to possible embodiments of the invention.

In general, the invention reaches the aforementioned object by providing, in a first aspect, a computer-implemented medical method of determining the position of an image rendering of a region of interest in medical image data. The method comprises executing, on at least one processor of at least one computer (for example at least one computer being part of a navigation system), the following exemplary steps which are executed by the at least one processor.

In a (for example first) exemplary step, first medical image data is acquired which describes a two-dimensional digital first image including image information, for example an image rendering, of a region of interest in a patient’s body, for example a region of interest in an anatomical body part of the patient. For example, the region of interest comprises or consists of a target of a medical procedure to be carried out on the patient. For example, the region of interest comprises or consists of soft tissue. For example, the region of interest comprises at least a part of the thorax, for example of the lung. Positions in the first image are defined in a first spatial reference system, and the position of the region of interest in the first image is predetermined, for example known. For example, the position of the region of interest in the first image has been determined by delineating, for example manually delineating, a contour of the region of interest in the first image. For example, the first medical image data has been or is generated by generating tomographic image data describing a digital tomographic image of the region of interest by applying a computed x-ray tomography imaging modality and generating, as the first image, a digitally reconstructed radiograph from the tomographic image data, wherein the tomographic image describes at least one of an absorption contrast computed x-ray tomography and an x-ray dark-field contrast computed tomography. For example, the first medical image data has been generated from or constitutes planning image data describing a digital planning image including an image rendering of the region of interest usable for planning a medical procedure on the region of interest, wherein the medical procedure comprises or consists of for example radiation therapy, for example radiotherapy or radiosurgery. For example, the medical device comprises or consists of a radiation therapy device. For example, the position determination is used for determining a shift of the position of the region compared to the planning of the procedure.

For example, the position of the region of interest in the first image corresponds to a planned position, and the method according to the first aspect comprises determining, based on the first medical image data and the region position data and the transformation data, position correspondence data describing whether the position of the region of interest in the second image corresponds to the planned position. If the position correspondence data describes that the position of the region of interest in the second image does not correspond to the planned position (i.e. that the aforementioned shift is present), medical device control data is determined based on the first medical image data and the second medical image data and the transformation data. The medical device control data describes a control command to be issued to a medical device for conducting a medical procedure in the region of interest. For example, the control command describes at least one of an adjustment of a trajectory of a radiation treatment beam and a position of the patient relative to the radiation therapy device, for example to account for a deviation between a planned trajectory and the position of the region of interest in the second image.

In a (for example second) exemplary step, second medical image data is acquired which describes a second two-dimensional digital second image including image information describing the region of interest. The second image has been generated using grating-based phase contrast imaging and positions in the second image are defined in a second spatial reference system. For example, the second image comprises at least one of an absorption contrast x-ray image and an x-ray dark-field image.

In a (for example third) exemplary step, transformation data is acquired which describes a spatial transformation between the first spatial reference system and the second spatial reference system. The transformation constitutes a mapping of positional information from the first spatial reference system to the second spatial reference system or vice versa. For example, the spatial transformation is predetermined (for example, known to the method) or has been or is determined based on the first medical image data and the second medical image data, for example by matching an image rendering in the first image describing bony tissue to an image rendering in the second image describing bony tissue.

In a (for example third) exemplary step, region position data is determined based on the first medical image data and the second medical image data and the transformation data. The region position data describes positional information associated with the image information describing the region of interest in the second image, for example the position of the image rendering of the region of interest in the second image. In an example of the method according to the first aspect, the first medical image data has been or is generated by generating tomographic image data describing a digital phase contrast computed x-ray tomographic image of the region of interest by applying a computed x-ray tomography imaging modality and generating, as the first image, a digitally reconstructed differential phase contrast radiograph from the tomographic image data, and the second image is a differential phase contrast x-ray image, wherein the region position data is determined by aligning the digitally reconstructed differential phase contrast radiograph with the differential phase contrast x-ray image. For example, the position of the region of interest in the first image has been determined by delineating, for example manually delineating, a contour of the region of interest in the first image, and wherein the region position data is determined by aligning the contour to a corresponding image rendering in the differential phase contrast x-ray image.

In an example of the method according to the first aspect, the first medical image data has been or is generated by generating tomographic image data describing a digital dark-field contrast computed x-ray tomographic image of the region of interest by applying a computed x-ray tomography imaging modality and generating, as the first image, a digitally reconstructed dark-field contrast radiograph from the tomographic image data, and the second image is a dark-field contrast x-ray image, wherein the region position data is determined by aligning the digitally reconstructed dark-field contrast radiograph with the dark-field contrast x-ray image. For example, the position of the region of interest in the first image has been determined by delineating, for example manually delineating, a contour of the region of interest in the first image, and wherein the region position data is determined by aligning the contour to a corresponding image rendering in the dark-field contrast x-ray image.

In an example of the method according to the first aspect, the first medical image data has been or is generated by generating tomographic image data describing a computed x-ray tomographic image of the region of interest by applying a computed x- ray tomography imaging modality and generating, as the first image, a digitally reconstructed radiograph from the tomographic image data, and the second image is a hybrid image generated from a differential phase contrast x-ray image and a dark- field contrast image. For example, the position of the region of interest in the first image has been determined by delineating, for example manually delineating, a contour of the region of interest in the first image, and the region position data is determined by aligning the contour to a corresponding image rendering in the second image.

In a second aspect, the invention is directed to a computer program comprising instructions which, when the program is executed by at least one computer, causes the at least one computer to carry out method according to the first aspect. The invention may alternatively or additionally relate to a (physical, for example electrical, for example technically generated) signal wave, for example a digital signal wave, such as an electromagnetic carrier wave carrying information which represents the program, for example the aforementioned program, which for example comprises code means which are adapted to perform any or all of the steps of the method according to the first aspect. The signal wave is in one example a data carrier signal carrying the aforementioned computer program. A computer program stored on a disc is a data file, and when the file is read out and transmitted it becomes a data stream for example in the form of a (physical, for example electrical, for example technically generated) signal. The signal can be implemented as the signal wave, for example as the electromagnetic carrier wave which is described herein. For example, the signal, for example the signal wave is constituted to be transmitted via a computer network, for example LAN, WLAN, WAN, mobile network, for example the internet. For example, the signal, for example the signal wave, is constituted to be transmitted by optic or acoustic data transmission. The invention according to the second aspect therefore may alternatively or additionally relate to a data stream representative of the aforementioned program, i.e. comprising the program.

In a third aspect, the invention is directed to a computer-readable storage medium on which the program according to the second aspect is stored. The program storage medium is for example non-transitory.

In a fourth aspect, the invention is directed to at least one computer (for example, a computer), comprising at least one processor (for example, a processor), wherein the program according to the second aspect is executed by the processor, or wherein the at least one computer comprises the computer-readable storage medium according to the third aspect.

In a fifth aspect, the invention is directed to a medical system, comprising: a) the at least one computer according to the fourth aspect; b) at least one electronic data storage device storing at least the patient data; c) an x-ray imaging device for generating the second medical image data; and d) a radiation treatment apparatus comprising a treatment beam source and a patient support unit for carrying out radiation therapy on the patient, wherein the at least one computer is operably coupled to

- the at least one electronic data storage device for acquiring, from the at least one data storage device, the first medical image data, and

- to the radiation treatment apparatus for issuing a control signal to the radiation treatment apparatus for controlling, on the basis of the region position data, at least one of

- the operation of the treatment beam source or

- the position of the patient support unit.

In an example of the system according to the fifth aspect, the x-ray imaging device is configured to generate grating-based phase contrast x-ray images.

In an example of the system according to the fifth aspect, the radiation treatment apparatus comprises a treatment beam source and a patient support unit (such as at least one of a patient bed or a headrest).

Alternatively or additionally, the invention according to the fifth aspect is directed to a for example non-transitory computer-readable program storage medium storing a program for causing the computer according to the fourth aspect to execute the data processing steps of the method according to the first aspect.

For example, the disclosed method is not a method for treatment of the human or animal body by surgery or therapy. For example, the invention does not involve or in particular comprise or encompass an invasive step which would represent a substantial physical interference with the body requiring professional medical expertise to be carried out and entailing a substantial health risk even when carried out with the required professional care and expertise.

For example, the invention does not comprise a step of irradiating a patient with treatment radiation. More particularly, the invention does not involve or in particular comprise or encompass any surgical or therapeutic activity. The invention is instead directed as applicable to treatment planning or controlling a radiation treatment apparatus, for example the radiation treatment apparatus. For this reason alone, no surgical or therapeutic activity and in particular no surgical or therapeutic step is necessitated or implied by carrying out the invention.

DEFINITIONS

In this section, definitions for specific terminology used in this disclosure are offered which also form part of the present disclosure.

The method in accordance with the invention is for example a computer-implemented method. For example, all the steps or merely some of the steps (i.e. less than the total number of steps) of the method in accordance with the invention can be executed by a computer (for example, at least one computer). An embodiment of the computer implemented method is a use of the computer for performing a data processing method. An embodiment of the computer implemented method is a method concerning the operation of the computer such that the computer is operated to perform one, more or all steps of the method.

The computer for example comprises at least one processor and for example at least one memory in order to (technically) process the data, for example electronically and/or optically. The processor being for example made of a substance or composition which is a semiconductor, for example at least partly n- and/or p-doped semiconductor, for example at least one of II-, III-, IV-, V-, Vl-sem iconductor material, for example (doped) silicon and/or gallium arsenide. The calculating or determining steps described are for example performed by a computer. Determining steps or calculating steps are for example steps of determining data within the framework of the technical method, for example within the framework of a program. A computer is for example any kind of data processing device, for example electronic data processing device. A computer can be a device which is generally thought of as such, for example desktop PCs, notebooks, netbooks, etc., but can also be any programmable apparatus, such as for example a mobile phone or an embedded processor. A computer can for example comprise a system (network) of "sub-computers", wherein each sub-computer represents a computer in its own right. The term "computer" includes a cloud computer, for example a cloud server. The term computer includes a server resource. The term "cloud computer" includes a cloud computer system which for example comprises a system of at least one cloud computer and for example a plurality of operatively interconnected cloud computers such as a server farm. Such a cloud computer is preferably connected to a wide area network such as the world wide web (WWW) and located in a so-called cloud of computers which are all connected to the world wide web. Such an infrastructure is used for "cloud computing", which describes computation, software, data access and storage services which do not require the end user to know the physical location and/or configuration of the computer delivering a specific service. For example, the term "cloud" is used in this respect as a metaphor for the Internet (world wide web). For example, the cloud provides computing infrastructure as a service (laaS). The cloud computer can function as a virtual host for an operating system and/or data processing application which is used to execute the method of the invention. The cloud computer is for example an elastic compute cloud (EC2) as provided by Amazon Web Services™. A computer for example comprises interfaces in order to receive or output data and/or perform an analogue-to-digital conversion. The data are for example data which represent physical properties and/or which are generated from technical signals. The technical signals are for example generated by means of (technical) detection devices (such as for example devices for detecting marker devices) and/or (technical) analytical devices (such as for example devices for performing (medical) imaging methods), wherein the technical signals are for example electrical or optical signals. The technical signals for example represent the data received or outputted by the computer. The computer is preferably operatively coupled to a display device which allows information outputted by the computer to be displayed, for example to a user. One example of a display device is a virtual reality device or an augmented reality device (also referred to as virtual reality glasses or augmented reality glasses) which can be used as "goggles" for navigating. A specific example of such augmented reality glasses is Google Glass (a trademark of Google, Inc.). An augmented reality device or a virtual reality device can be used both to input information into the computer by user interaction and to display information outputted by the computer. Another example of a display device would be a standard computer monitor comprising for example a liquid crystal display operatively coupled to the computer for receiving display control data from the computer for generating signals used to display image information content on the display device. A specific embodiment of such a computer monitor is a digital lightbox. An example of such a digital lightbox is Buzz®, a product of Brainlab AG. The monitor may also be the monitor of a portable, for example handheld, device such as a smart phone or personal digital assistant or digital media player.

The invention also relates to a computer program comprising instructions which, when on the program is executed by a computer, cause the computer to carry out the method or methods, for example, the steps of the method or methods, described herein and/or to a computer-readable storage medium (for example, a non-transitory computer- readable storage medium) on which the program is stored and/or to a computer comprising said program storage medium and/or to a (physical, for example electrical, for example technically generated) signal wave, for example a digital signal wave, such as an electromagnetic carrier wave carrying information which represents the program, for example the aforementioned program, which for example comprises code means which are adapted to perform any or all of the method steps described herein. The signal wave is in one example a data carrier signal carrying the aforementioned computer program. The invention also relates to a computer comprising at least one processor and/or the aforementioned computer-readable storage medium and for example a memory, wherein the program is executed by the processor.

Within the framework of the invention, computer program elements can be embodied by hardware and/or software (this includes firmware, resident software, micro-code, etc.). Within the framework of the invention, computer program elements can take the form of a computer program product which can be embodied by a computer-usable, for example computer-readable data storage medium comprising computer-usable, for example computer-readable program instructions, "code" or a "computer program" embodied in said data storage medium for use on or in connection with the instruction- executing system. Such a system can be a computer; a computer can be a data processing device comprising means for executing the computer program elements and/or the program in accordance with the invention, for example a data processing device comprising a digital processor (central processing unit or CPU) which executes the computer program elements, and optionally a volatile memory (for example a random access memory or RAM) for storing data used for and/or produced by executing the computer program elements. Within the framework of the present invention, a computer-usable, for example computer-readable data storage medium can be any data storage medium which can include, store, communicate, propagate or transport the program for use on or in connection with the instruction-executing system, apparatus or device. The computer-usable, for example computer-readable data storage medium can for example be, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus or device or a medium of propagation such as for example the Internet. The computer-usable or computer-readable data storage medium could even for example be paper or another suitable medium onto which the program is printed, since the program could be electronically captured, for example by optically scanning the paper or other suitable medium, and then compiled, interpreted or otherwise processed in a suitable manner. The data storage medium is preferably a non-volatile data storage medium. The computer program product and any software and/or hardware described here form the various means for performing the functions of the invention in the example embodiments. The computer and/or data processing device can for example include a guidance information device which includes means for outputting guidance information. The guidance information can be outputted, for example to a user, visually by a visual indicating means (for example, a monitor and/or a lamp) and/or acoustically by an acoustic indicating means (for example, a loudspeaker and/or a digital speech output device) and/or tactilely by a tactile indicating means (for example, a vibrating element or a vibration element incorporated into an instrument). For the purpose of this document, a computer is a technical computer which for example comprises technical, for example tangible components, for example mechanical and/or electronic components. Any device mentioned as such in this document is a technical and for example tangible device. The expression "acquiring data" for example encompasses (within the framework of a computer implemented method) the scenario in which the data are determined by the computer implemented method or program. Determining data for example encompasses measuring physical quantities and transforming the measured values into data, for example digital data, and/or computing (and e.g. outputting) the data by means of a computer and for example within the framework of the method in accordance with the invention. A step of “determining” as described herein for example comprises or consists of issuing a command to perform the determination described herein. For example, the step comprises or consists of issuing a command to cause a computer, for example a remote computer, for example a remote server, for example in the cloud, to perform the determination. Alternatively or additionally, a step of “determination” as described herein for example comprises or consists of receiving the data resulting from the determination described herein, for example receiving the resulting data from the remote computer, for example from that remote computer which has been caused to perform the determination. The meaning of "acquiring data" also for example encompasses the scenario in which the data are received or retrieved by (e.g. input to) the computer implemented method or program, for example from another program, a previous method step or a data storage medium, for example for further processing by the computer implemented method or program. Generation of the data to be acquired may but need not be part of the method in accordance with the invention. The expression "acquiring data" can therefore also for example mean waiting to receive data and/or receiving the data. The received data can for example be inputted via an interface. The expression "acquiring data" can also mean that the computer implemented method or program performs steps in order to (actively) receive or retrieve the data from a data source, for instance a data storage medium (such as for example a ROM, RAM, database, hard drive, etc.), or via the interface (for instance, from another computer or a network). The data acquired by the disclosed method or device, respectively, may be acquired from a database located in a data storage device which is operably to a computer for data transfer between the database and the computer, for example from the database to the computer. The computer acquires the data for use as an input for steps of determining data. The determined data can be output again to the same or another database to be stored for later use. The database or database used for implementing the disclosed method can be located on network data storage device or a network server (for example, a cloud data storage device or a cloud server) or a local data storage device (such as a mass storage device operably connected to at least one computer executing the disclosed method). The data can be made "ready for use" by performing an additional step before the acquiring step. In accordance with this additional step, the data are generated in order to be acquired. The data are for example detected or captured (for example by an analytical device). Alternatively or additionally, the data are inputted in accordance with the additional step, for instance via interfaces. The data generated can for example be inputted (for instance into the computer). In accordance with the additional step (which precedes the acquiring step), the data can also be provided by performing the additional step of storing the data in a data storage medium (such as for example a ROM, RAM, CD and/or hard drive), such that they are ready for use within the framework of the method or program in accordance with the invention. The step of "acquiring data" can therefore also involve commanding a device to obtain and/or provide the data to be acquired. In particular, the acquiring step does not involve an invasive step which would represent a substantial physical interference with the body, requiring professional medical expertise to be carried out and entailing a substantial health risk even when carried out with the required professional care and expertise. In particular, the step of acquiring data, for example determining data, does not involve a surgical step and in particular does not involve a step of treating a human or animal body using surgery or therapy. In order to distinguish the different data used by the present method, the data are denoted (i.e. referred to) as "XY data" and the like and are defined in terms of the information which they describe, which is then preferably referred to as "XY information" and the like.

In the field of medicine, imaging methods (also called imaging modalities and/or medical imaging modalities) are used to generate image data (for example, two- dimensional or three-dimensional image data) of anatomical structures (such as soft tissues, bones, organs, etc.) of the human body. The term "medical imaging methods" is understood to mean (advantageously apparatus-based) imaging methods (for example so-called medical imaging modalities and/or radiological imaging methods) such as for instance computed tomography (CT) and cone beam computed tomography (CBCT, such as volumetric CBCT), x-ray tomography, magnetic resonance tomography (MRT or MRI), conventional x-ray, sonography and/or ultrasound examinations, and positron emission tomography. For example, the medical imaging methods are performed by the analytical devices. Examples for medical imaging modalities applied by medical imaging methods are: x-ray radiography, magnetic resonance imaging, medical ultrasonography or ultrasound, endoscopy, elastography, tactile imaging, thermography, medical photography and nuclear medicine functional imaging techniques as positron emission tomography (PET) and Single-photon emission computed tomography (SPECT), as mentioned by Wikipedia.

The image data thus generated is also termed “medical imaging data”. Analytical devices for example are used to generate the image data in apparatus-based imaging methods. The imaging methods are for example used for medical diagnostics, to analyse the anatomical body in order to generate images which are described by the image data. The imaging methods are also for example used to detect pathological changes in the human body. However, some of the changes in the anatomical structure, such as the pathological changes in the structures (tissue), may not be detectable and for example may not be visible in the images generated by the imaging methods. A tumour represents an example of a change in an anatomical structure. If the tumour grows, it may then be said to represent an expanded anatomical structure. This expanded anatomical structure may not be detectable; for example, only a part of the expanded anatomical structure may be detectable. Primary/high-grade brain tumours are for example usually visible on MRI scans when contrast agents are used to infiltrate the tumour. MRI scans represent an example of an imaging method. In the case of MRI scans of such brain tumours, the signal enhancement in the MRI images (due to the contrast agents infiltrating the tumour) is considered to represent the solid tumour mass. Thus, the tumour is detectable and for example discernible in the image generated by the imaging method. In addition to these tumours, referred to as "enhancing" tumours, it is thought that approximately 10% of brain tumours are not discernible on a scan and are for example not visible to a user looking at the images generated by the imaging method.

Mapping describes a transformation (for example, linear transformation) of an element (for example, a pixel or voxel), for example the position of an element, of a first data set in a first coordinate system to an element (for example, a pixel or voxel), for example the position of an element, of a second data set in a second coordinate system (which may have a basis which is different from the basis of the first coordinate system). In one embodiment, the mapping is determined by comparing (for example, matching) the color values (for example grey values) of the respective elements by means of an elastic or rigid fusion algorithm. The mapping is embodied for example by a transformation matrix (such as a matrix defining an affine transformation).

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention is described with reference to the appended figures which give background explanations and represent specific embodiments of the invention. The scope of the invention is however not limited to the specific features disclosed in the context of the figures, wherein

Fig. 1 illustrates the basic steps of the method according to the first aspect;

Fig. 2 shows an embodiment of the present invention, specifically the method according to the first aspect;

Fig. 3 is a flow diagram showing an embodiment of the method according to the first aspect; and

Fig. 4 is a schematic illustration of the system according to the fifth aspect.

DESCRIPTION OF EMBODIMENTS

Fig. 1 illustrates the basic steps of the method according to the first aspect, in which step S11 encompasses acquisition of the first medical image data, step S12 encompasses acquisition of the second medical image data and subsequent step S13 encompasses acquisition of the transformation data. On the basis of these datasets, step S14 determines the region position data.

Fig. 2 illustrates an embodiment of the present invention that includes all essential features of the invention. In this embodiment, the entire data processing which is part of the method according to the first aspect is performed by a computer 2. Reference sign 1 denotes the input of data acquired by the method according to the first aspect into the computer 2 and reference sign 3 denotes the output of data determined by the method according to the first aspect.

Fig. 3 shows an embodiment of the method according to the first aspect. In step S31 , at least one of a conventional (absorption contrast) CT scan, a dark-field CT, and a phase contrast CT is acquired. Step S32 continues with delineating the target in the acquired CT scan, generating a target contour. In subsequent step S33, treatment planning is performed on at least one of the acquired scans. Step S34 then acquires an x-ray image, consisting of at least one of an absorption contrast image, a phase contrast image or a dark-field contrast image. In optional step S35, the absorption contrast DRR and the absorption contrast x-ray image are used to acquire first transformation data based on matching image representations of bony tissue. Optional step S36 uses the first transformation data as an initial alignment for starting soft tissue localization. Step S37 is directed to soft tissue localization for which at least one of the following items a) to d) is used: a) Alignment of phase contrast DRR and phase contrast x-ray image, in which DRR can be created out of phase contrast CT or conventional CT (e.g. by machine learning) b) Alignment of dark-field contrast DRR and dark-field x-ray image, in which DRR can be created out of dark-field CT or conventional CT (e.g. by machine learning) c) Alignment of target contour to at least one of phase contrast and dark-field x- ray image d) Alignment of target contour to artificially created hybrid image (e.g. out of phase contrast and dark-field image)

In optional step S38, soft tissue localization is performed based on a 4D absorption contrast, 4D phase-contras, or 4D dark-field CT, for example by generating dynamic DRRs.

Fig. 4 is a schematic illustration of the medical system 4 according to the fifth aspect. The system is in its entirety identified by reference sign 4 and comprises a computer 5, an electronic data storage device (such as a hard disc) 6 for storing at least the patient data and a medical device 7 (such as a radiation treatment apparatus). The components of the medical system 4 have the functionalities and properties explained above with regard to the fifth aspect of this disclosure.

Physical background:

Using grating-based phase-contrast imaging, one is able to not use only the particle properties but also the wave properties of x-rays and the complementary contrast modalities of x-ray phase contrast and dark-field image are obtained in addition to the conventional x-ray absorption. Thereby, the Talbot effect is essential for grating-based phase-contrast imaging. When a sufficient coherent wavefront illuminates a periodic object, a self image of the object is produced at multiple distances.

Technical background:

A grating interferometer (consisting of three gratings) is placed and aligned in the beam path. Thereby, the individual gratings can fulfill the following tasks:

- Source grating: First grating positioned in the beam path, close to the x-ray source. The source grating is mandatory to fulfill the coherence reguirements which cannot be achieved with conventional, low-brilliance (incoherent) x-ray tubes. It divides the initial beam into an array of small (individually coherent), sources, increasing the effective spatial coherence of the x-ray wavefront.

- Phase grating: Second grating within the beam path. The phase grating modulates the beam and is used to create an interference pattern. When passing through the phase grating the wavefront is diffracted into distinct orders at different directions, leading to an interference pattern. After propagating the Talbot distance, which depends on the grating period, the distorted wavefront repeats itself and the self-image is created.

- Analzyer grating: Last grating positioned in the beam path, typically close to the detector. The analyzer grating makes the refracting, scattering and attenuating effects of the sample resolvable.

As typically the pixel size of the detector is at least one order of magnitude larger than the grating period, the phase-shift cannot be resolved directly, but needs to be extracted from a so-called “stepping curve”. Thereby, the intensity is measured (as the sum over several grating periods covering the detector) for different grating positions, and the respective signals are extracted via the amplitude, mean intensity and phase shift of the fitted sinusoidal. In addition, to calculate the effect of the sample to the individual signals, it is required to acquire a reference measurement, i.e. a stepping curve detected without the presence of any object in the beam.

Claims

Brainlab AG Attorney’s File: P101261 WO XV CLAIMS

1. A computer-implemented medical method of determining the position of an image rendering of a region of interest in medical image data, the method comprising the following steps: a) first medical image data is acquired (S11 ) which describes a two- dimensional digital first image including image information of a region of interest in a patient’s body, wherein positions in the first image are defined in a first spatial reference system, wherein the position of the region of interest in the first image is predetermined; b) second medical image data is acquired (S12) which describes a second two- dimensional digital second image including image information describing the region of interest, wherein the second image has been generated using grating-based phase contrast imaging and positions in the second image are defined in a second spatial reference system; c) transformation data is acquired (S13) which describes a spatial transformation between the first spatial reference system and the second spatial reference system; d) region position data is determined (S14) based on the first medical image data and the second medical image data and the transformation data, wherein the region position data describes positional information associated with the image information describing the region of interest in the second image.

2. The method according to the preceding claim, wherein the region of interest comprises or consists of soft tissue.

3. The method according to any one of the preceding claims, wherein the region of interest comprises or consists of a target of a medical procedure to be carried out on the patient.

4. The method according to any one of the preceding claims, wherein the first medical image data has been or is generated by generating tomographic image data describing a digital tomographic image of the region of interest by applying a computed x-ray tomography imaging modality and generating, as the first image, a digitally reconstructed radiograph from the tomographic image data, wherein the tomographic image describes at least one of an absorption contrast computed x-ray tomography and an x-ray dark-field contrast computed tomography.

5. The method according to any one of the preceding claims, wherein the second image comprises at least one of an absorption contrast x-ray image and an x- ray dark-field image.

6. The method according to any one of the preceding claims, wherein the spatial transformation is predetermined or has been or is determined based on the first medical image data and the second medical image data, for example by matching an image rendering in the first image describing bony tissue to an image rendering in the second image describing bony tissue.

7. The method according to any one of the preceding claims, wherein the first medical image data has been generated from or constitutes planning image data describing a digital planning image including an image rendering of the region of interest usable for planning a medical procedure on the region of interest, wherein the medical procedure comprises or consists of for example radiation therapy.

8. The method according to any one of the preceding claim, wherein the position of the region of interest in the first image corresponds to a planned position, the method comprising determining, based on the first medical image data and the region position data and the transformation data, position correspondence data describing whether the position of the region of interest in the second image corresponds to the planned position and, if the position correspondence data describes that the position of the region of interest in the second image does not correspond to the planned position, determining medical device control data based on the first medical image data and the second medical image data and the transformation data, wherein the medical device control data describes a control command to be issued to a medical device for conducting a medical procedure in the region of interest.

9. The method according to the preceding claim, wherein the medical device comprises or consists of a radiation therapy device.

10. The method according to any one of the two immediately preceding claims, wherein the control command describes at least one of an adjustment of a trajectory of a radiation treatment beam and a position of the patient relative to the radiation therapy device, for example to account for a deviation between a planned trajectory and the position of the region of interest in the second image.

11 . The method according to any one of the preceding claims, wherein the position of the region of interest in the first image has been determined by delineating, for example manually delineating, a contour of the region of interest in the first image.

12. The method according to any one of the preceding claims, wherein the first medical image data has been or is generated by generating tomographic image data describing a digital phase contrast computed x-ray tomographic image of the region of interest by applying a computed x-ray tomography imaging modality and generating, as the first image, a digitally reconstructed differential phase contrast radiograph from the tomographic image data, and the second image is a differential phase contrast x-ray image, wherein the region position data is determined by aligning the digitally reconstructed differential phase contrast radiograph with the differential phase contrast x-ray image.

13. The method according to the preceding claim, wherein the position of the region of interest in the first image has been determined by delineating, for example manually delineating, a contour of the region of interest in the first image, and wherein the region position data is determined by aligning the contour to a corresponding image rendering in the differential phase contrast x-ray image.

14. The method according to any one of the preceding claims, wherein the first medical image data has been or is generated by generating tomographic image data describing a digital dark-field contrast computed x-ray tomographic image of the region of interest by applying a computed x-ray tomography imaging modality and generating, as the first image, a digitally reconstructed dark-field contrast radiograph from the tomographic image data, and the second image is a dark-field contrast x-ray image, wherein the region position data is determined by aligning the digitally reconstructed dark-field contrast radiograph with the dark-field contrast x-ray image.

15. The method according to the preceding claim, wherein the position of the region of interest in the first image has been determined by delineating, for example manually delineating, a contour of the region of interest in the first image, and wherein the region position data is determined by aligning the contour to a corresponding image rendering in the dark-field contrast x-ray image.

16. The method according to any one of the preceding claims, wherein the first medical image data has been or is generated by generating tomographic image data describing a computed x-ray tomographic image of the region of interest by applying a computed x-ray tomography imaging modality and generating, as the first image, a digitally reconstructed radiograph from the tomographic image data, and the second image is a hybrid image generated from a differential phase contrast x-ray image and a dark-field contrast image, wherein the position of the region of interest in the first image has been determined by delineating, for example manually delineating, a contour of the region of interest in the first image, and wherein the region position data is determined by aligning the contour to a corresponding image rendering in the second image.

17. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of the preceding claims; and/or a computer-readable storage medium on which the program is stored; and/or a computer comprising at least one processor and/or the program storage medium, wherein the program is executed by the processor; and/or a data carrier signal carrying the program; and/or a data stream comprising the program.

18. A medical system (4), comprising: a) the at least one computer (5) according to the preceding claim; b) at least one electronic data storage device (6) storing at least the patient data; c) an x-ray imaging device for generating the second medical image data; and d) a radiation treatment apparatus (7) comprising a treatment beam source and a patient support unit for carrying out radiation therapy on the patient, wherein the at least one computer is operably coupled to the at least one electronic data storage device for acquiring, from the at least one data storage device, the first medical image data, and to the radiation treatment apparatus for issuing a control signal to the radiation treatment apparatus for controlling, on the basis of the region position data, at least one of the operation of the treatment beam source or the position of the patient support unit.

19. The system according to the preceding claim, wherein the x-ray imaging device is configured to generate grating-based phase contrast x-ray images.