Vasculature-based interactive bolus ROI placement and scan planning using 3D CT plain

Abstract

A system (FS) and related method for facilitating contrast agent-based tomography imaging. A graphical display generator (GDG) generates a graphical display (GD) of a graphical user interface (GUI) for display on a display device (DD). The graphical display (GD) may include a visualization of a segmentation in the 3D plain image and a visualization of a slider element (SL) indicating a reference position (m-ROI) along the segmentation. The reference position may be used to monitor the presence of contrast agent associated with a target anatomical feature (TAF) in a contrast agent assisted imaging phase. The event processor (EH) may instruct the graphical display generator (GDG) to update the graphical display (GD) upon receiving a user input in order to slide the slider element (SL) along the partition, the slider thereby indicating one or more different such reference positions.

Description

Technical Field

[0001] The present invention relates to a system for facilitating contrast agent-based tomographic imaging, a related method, an imaging arrangement, a computer program element and a computer-readable medium. Background Art

[0002] The 2D (two-dimensional) surview image(s) acquired prior to diagnostic CT (computed tomography) imaging plays an important role in assisting the clinical technician ("user"), for example in correct patient positioning or in achieving optimal image quality.

[0003] In addition to conventional 2D plain films (e.g., frontal and sagittal), 3D (reconstructed) plain film images (image volumes) can now be acquired at clinically acceptable doses. They offer several advantages over conventional 2D plain films and open up new possibilities for CT workflow optimization that were not possible earlier.

[0004] It is common practice in CT imaging to perform a 2D plain film scan covering the entire region of interest, including the intended "bolus" tracking location. A bolus is a volume of administered contrast material (e.g., iodine). Contrast agents can be used to enhance image contrast in anatomical structures of interest that have a low radiation absorption rate (e.g., cardiac vessels in cardiac imaging). The user then manually selects a z position on such a 2D plain film (one or more) and acquires and reconstructs corresponding axial images (also called "localizers") to define ("place") a region of interest ("ROI") for tracking the bolus or monitoring its arrival. The bolus travels with the blood flow and accumulates for a period of time at the anatomical structure of interest. The goal is to trigger imaging at the right moment to capture an image with high contrast before the bolus washes out.

[0005] Multiple localizer scans may be required to find the appropriate location for the tracking ROI. The ROI to be captured for the tracking bolus is placed within the localizer slice, and the ROI is monitored by repeatedly acquiring the single axial slice to monitor the arrival of the contrast bolus. When a threshold value of contrast-induced density is reached within the ROI, a subsequent diagnostic CTA (CT angiography) acquisition is triggered.

[0006] The main disadvantage of bolus tracking using conventional 2D plain film images or general bolus tracking is that the planning of bolus tracking during the scanning process is complex and heavily dependent on the skill and experience of the clinical user. The process is prone to errors. For example, the user requires several manual interventions, such as manual selection of z slices, placement of the ROI on the acquired localizer slices, etc. If there are human errors in the positioning of anatomical structures and the placement of the ROI in the localizer images, the diagnostic CT scan may be started at a suboptimal time. This may subsequently lead to poor image quality and incorrect diagnosis, and may lead to unnecessary re-administration of contrast agent and re-shooting of images, which has potential side effects for the patient and / or medical staff. Moreover, the manual positioning process is subject to intra- and inter-individual variability. Another disadvantage is the need to acquire (one or more) special localizer scans, which requires additional time and dose. Summary of the Invention

[0007] Therefore, there may be a need to improve the efficient operation of imaging devices. In particular, there may be a need to reliably establish the correct timing for triggering imaging operations on such imaging devices.

[0008] The objects of the invention are achieved by the subject-matter of the independent claims, wherein further embodiments are incorporated into the dependent claims. It should be noted that the aspects of the invention described below also apply to the associated method, image arrangement device, computer program element and computer-readable medium.

[0009] According to a first aspect of the present invention, there is provided a system for facilitating contrast agent-based tomographic imaging, the system comprising, in use:

[0010] an input interface for receiving a 3D plain film image volume of at least a portion of the patient acquired by a tomographic imaging device in a preparation phase prior to a contrast agent assisted imaging phase, the 3D plain film image volume including segmentation(s) of blood vessels through which a contrast agent is to pass in a later contrast agent assisted imaging phase;

[0011] a graphical display generator configured to generate a graphical display of a graphical user interface for display on a display device, the graphical display including a visualization of the segmentation and a visualization of a slider element indicating a reference position along the segmentation, the reference position suitable for monitoring the presence of contrast agent associated with at least one target anatomical feature in the later contrast agent-assisted imaging phase; and

[0012] An event handler is configured to, upon receipt of user input, instruct the graphical display generator to update the graphical display so as to cause the slider element to slide along the partition, the slider thereby indicating one or more different such reference positions.

[0013] The segmentation is preferably calculated / derived from the 3D planar images.For example, machine learning (deep learning models) can be used.

[0014] In an embodiment of the system, the graphical display generator is operable to adjust the spatial extent (e.g., shape, orientation, size) of the slider element to correspond to and vary with geometric aspects (e.g., cross-section) of the segmentation at the different reference positions.

[0015] In an embodiment, the graphical display generator is operable to lock the slider element into the orientation defined by the segmentation. This allows for assisting the user in defining clinically meaningful monitoring positions. This is less "cumbersome" as correct bolus monitoring definition may otherwise be difficult, particularly under stress.

[0016] In an embodiment, the direction is based on a centerline of the segmentation.

[0017] In an embodiment, the visualization of the segmentation is configured to clearly represent the wall portions of the vessel. For example, the wall portions can be highlighted by color or grayscale value modulation, can be drawn with dashed lines, thick lines, different colors for the background and / or the interior of the segmentation, etc. Different visualizations of the wall portions can be modulated to distinguish between calcified and non-calcified portions, or to distinguish between various levels of calcification. This helps the user avoid placing the monitoring ROI over calcified or severely calcified portions of the vessel, as such portions have been found to be less useful for bolus monitoring purposes. For better calcification definition, spectral imaging can be used when recording the plain radiographs.

[0018] In an embodiment, the graphical display generator is operable to cause the graphical display to include information regarding: i) a distance of the at least one target anatomical feature to a) a reference position of the blood vessel corresponding to a current slider position and / or b) a distance of the at least one target anatomical feature to one or more anatomical landmarks, and / or ii) an estimated contrast agent arrival time at the reference position.

[0019] In an embodiment, the system may include an output interface for communicating a user-selected one of the one or more reference positions to the imaging device for defining one end of a subset (referred to as a "scanning frame") in the image field about which projection data is to be collected by the imaging device during the imaging phase.

[0020] In an embodiment, the graphical display generator is operable to generate said graphical display to further comprise a visualization of said subset, wherein said slider element is located at said one end of said visualization of said subset.

[0021] In an embodiment, the system may include an output interface for transmitting a user-selected one of the one or more reference positions to instruct the imaging device to acquire a first set of projection data as the contrast agent propagates in the patient, and the system includes a reconstructor for reconstructing a cross-sectional tracker image in a plane passing through the selected reference position at a first image quality based on the projection data.

[0022] In an embodiment, the arrival time is based on hemodynamic modeling.

[0023] In embodiments, the blood vessel comprises at least a portion of the aorta.

[0024] Therefore, the facilitator system provides a user interface function. Users of the facilitator system can use it in conjunction with and in collaboration with a fully automated segmenter system (a machine learning ("ML")-based system or other system). While such a segmenter system may in some cases be able to find fully satisfactory suggestions for adequate bolus monitoring region definition, in many cases it is still beneficial if a human clinical user can still fine-tune the solution proposed by such an automated segmentation system. Therefore, the proposed user interface function provides an intuitive user input solution that allows the user to quickly and safely perform this fine-tuning task with good results to ultimately locate the appropriate bolus monitoring region. In particular, and by way of example, the proposed interface function allows visualization of results from, in particular (but not exclusively) ML-based solutions, and execution of such fine-tuning modifications as the user deems necessary.

[0025] As a result of the above, the proposed interface functionality facilitates a more accurate and reliable way of establishing the correct timing for diagnostic projection data acquisition. The likelihood of image retakes can be reduced, which results in lower dose exposure to staff and patients, higher imaging throughput, and lower machine wear, the latter being a particular problem in X-ray imaging, where certain machine parts (such as the anode disk) are exposed to significant temperature gradients during data acquisition.

[0026] The proposed user functionality strikes a useful balance between providing the user with the freedom to fine-tune the initial location of the monitoring region and a set of useful, clinically driven limit settings that provide meaningful guidance to users (even novice or under-stressed clinical users) to obtain appropriate results for m-ROI definition faster and more safely.

[0027] While the proposed user functionality can be used in conjunction with an automated segmenter as described above, such an automated system is not required herein. Thus, the proposed user functionality can be used without such an automated segmenter system and can instead be used, for example, to scrutinize manually segmented m-ROIs by the same user or a different user as needed. Use with fully automated, semi-automated, or manual segmenters is contemplated, but the proposed user interface functionality may be particularly beneficial with fully automated or semi-automated segmenters.

[0028] Compared to fully automated systems, the proposed system allows for a higher degree of interactivity when planning bolus tracking ROIs. Therefore, in embodiments herein, methods for interactive vessel-based bolus ROI placement and 3D CT plain film-based scan planning are proposed. The proposed user functionality targets the placement of bolus monitoring ROIs within 3D plain film scans. Working with 3D plain film imagery, as opposed to solely 2D plain film data, offers advantages that overcome the following disadvantages found when processing 2D plain film image data:

[0029] 2D plain films are associated with the inherent disadvantage that the exact 3D distance between the bolus ROI and the target anatomical structure cannot be calculated, thus not allowing the estimation of the time required for the contrast agent to reach the target anatomical region. This often results in the administration of larger amounts of contrast agent and images with suboptimal image quality.

[0030] Placement of the bolus ROI during scan planning is a complex task and heavily relies on the clinician's expertise;

[0031] Requires acquisition of special localizer scans (single z slices), which require additional time and dose to the patient. These slices are automatically acquired when the 3D plain film already covers the field of view with axial slices;

[0032] Errors by human users in locating anatomical structures and placing ROIs in the localizer image can result in starting the CT scan at a suboptimal time. This can subsequently lead to poor image quality and may result in incorrect diagnoses, image reacquisitions, patient recalls, and unnecessary administration of contrast agents with potential side effects.

[0033] With the proposed system, a user-interactive way of placing the m-ROI is provided, which enhances user convenience and allows the user to place the m-ROI according to his or her preference.

[0034] In the proposed system, segmentation of the vessel through which the bolus is expected to travel is provided. The vessel can be, for example, all or part of the aorta, or can be a partial or complete segmentation of any other vascular system of interest. Segmentation of the vascular pathway of the bolus, compared to a placed or moved bolus ROI symbol (such as a circle, ellipse, etc.), helps the user visualize the relative position of the aortic wall. In a preferred embodiment, in addition to the placed bolus m-ROI, the vessel (e.g., aorta) wall is also explicitly presented to the user. Such a system also allows, for example, the user to visualize calcifications in the aorta and place the bolus m-ROI accordingly, particularly by avoiding areas of calcification in the selected m-ROI. Material-selective imaging (such as spectral imaging) can be particularly beneficial in this regard.

[0035] The proposed interactive bolus m-ROI placement system and the proposed visualization techniques assist the user in better placing the bolus m-ROI relative to other important anatomical landmarks. For example, the landmarks may include one or more various subsections of a vessel, such as the aorta. The subsections may include the aortic arch, the ascending aorta, and the descending aorta, among others. The vessel section landmarks may be differently labeled or highlighted, thereby giving the user more control when placing the bolus m-ROI relative to the highlighted anatomical landmarks and enabling the user to make more informed decisions. Additionally or alternatively, the visualization may also assist the user by providing information regarding distance and transit time estimates relative to one or more landmarks.

[0036] The proposed system and related methods (see below) allow the user to better adjust / modify a given m-ROI placement definition along the centerline of a vessel (such as the aorta) while using distance to anatomical landmarks and visualization of the aortic wall / radius.

[0037] In yet another aspect, an imaging arrangement is provided, comprising the system of any one of the above embodiments, and one or more of the following: an imaging device, a display device, a contrast agent administration device for administering a contrast agent, and a segmenter configured to provide segmentation of a plain film image.

[0038] In another embodiment, the imaging arrangement may further include a bolus monitoring system. The bolus monitoring system may be configured for intra-image monitoring to perform monitoring based on tracker images in a predefined image neighborhood in the tracker images around a reference position. In an embodiment, the bolus monitoring system may be configured via a controller to instruct the imaging arrangement to acquire a second set of projection data at a second image quality higher than the first image quality when the intra-image monitoring unit issues a trigger signal based on one or more monitored image values ​​in the image neighborhood.

[0039] In another aspect, a method for facilitating contrast agent-based tomographic imaging is provided, comprising:

[0040] receiving a 3D plain film image volume of at least a portion of the patient acquired by a tomographic imaging device in a preparation phase prior to a contrast agent assisted imaging phase, the 3D plain film image volume including segmentation(s) of blood vessels through which a contrast agent is to pass in a later contrast agent assisted imaging phase;

[0041] generating a graphical display of a graphical user interface for display on a display device, the graphical display including a visualization of the segmentation and a slider element indicating a reference position along the segmentation, the reference position suitable for monitoring the presence of contrast agent associated with at least one target anatomical feature in the later contrast agent-assisted imaging phase; and

[0042] Upon receipt of user input the graphical display generator is instructed to update the graphical display so as to slide the slider element along the partition, the slider thereby indicating one or more different such reference positions.

[0043] In a further aspect, a computer program element is provided which, when run by at least one processing unit, is adapted to cause the processing unit to perform the method.

[0044] In a further aspect, at least one computer-readable medium is provided, having a program element stored thereon.

[0045] The system and related methods (see below) are primarily contemplated for use in the medical field. However, the principles described herein may also be applied to endeavors outside the medical field, such as contrast agent (e.g., dye)-assisted inspection of inaccessible hydraulic or piping systems, or in hydrographic inspections to understand groundwater movement, etc. As in the case of medical imaging, the system and method allow for reduced wear and tear on imaging equipment because the system and method can be used with better timing to trigger acquisition at the moment of optimal image acquisition, thereby avoiding repeated imaging.

[0046] A "user" refers to a person who operates the imaging device or oversees the imaging procedure, such as a medical professional or other person. In other words, a user is typically not a patient.

[0047] "Object" is used herein in a general sense to include animate "objects," such as human or animal patients or anatomical parts thereof, but also inanimate objects, such as items of luggage undergoing security screening or products undergoing non-destructive testing. However, this article will primarily discuss the proposed system with reference to the medical field, and thus we will refer to the "object" as a "patient" or a part of a patient, such as an anatomical structure or organ, or a group of anatomical structures or organs, of a patient.

[0048] As used herein, a "plain film image" is a 3D image volume obtained at a lower radiation dose cost than that of a subsequent diagnostic image volume and with a larger field of view (FOV) than that of the subsequent diagnostic image volume. A diagnostic image volume is required to complete or support a medical task, such as diagnosis, treatment, or other task. Plain film images are not typically used for such tasks, but may be used, for example, for planning. The FOV of a plain film image volume includes not only the anatomical structure of interest (which is the object of the medical task), but also typically captures other landmark anatomical structures that have only an auxiliary function for imaging but are not typically used for the medical task. The FOV can be a full body scan, but this is not necessarily the case in all cases. Typically, the FOV of a plain film image captures a larger portion of the anatomy (e.g., abdomen, chest, etc.).

[0049] As used herein, "z-position" or similar terms refer to one example of a reference position in the image domain used to define tracker images, as contemplated herein. "Z-position" generally refers to a position on one of the three spatial coordinate axes (the "Z-axis") spanning the image domain. Typically, this Z-axis corresponds to the axis of rotation of a rotational tomographic imager, or to an imaginary axis of rotation in an imager of a 5th generation scanner. However, the Z-axis can be different from the axis of rotation used for the reformatted slab volume, as also contemplated herein.

[0050] "Image processing" in this regard, it is observed that any processing of imagery (such as plain film images or segmentations of vessels, landmarks, m-ROIs, etc.) contemplated and described herein, in any embodiment and configuration or arrangement, includes not only processing in the image domain of image values ​​(e.g., HU values, etc.), but such reference specifically includes processing in a transform domain (e.g., frequency domain, or any other domain in which the plain film images are first transformed), with at least part of the processing occurring there, optionally re-transformed into the image domain as needed. Transforms contemplated herein include any Fourier-based transform (Laplace transform, discrete cosine transform, etc.), wavelet transform, Hilbert transform, Haar transform, distance transform, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Exemplary embodiments of the present invention will now be described with reference to the following drawings, which are not drawn to scale unless otherwise specified, and in which:

[0052] Figure 1 A schematic block diagram of a medical imaging arrangement is shown;

[0053] Figure 2 The contrast agent-based imaging protocol is illustrated;

[0054] Figure 3 The steps of a facilitator system for facilitating contrast-assisted tomographic imaging are shown;

[0055] Figure 4 shows a block diagram of a facilitator system using a graphic display generator as contemplated herein in embodiments;

[0056] Figure 5 Shown Figure 4 a schematic block diagram of a graphic display generator of a facilitator system;

[0057] Figure 6 Shows that the Figure 4 、 5 Illustration of a graphical display generated by the system;

[0058] Figure 7 shows another diagram of a graphical display according to an optional embodiment; and

[0059] Figure 8 A flow chart of a computer-implemented method for graphical user interface assisted contrast agent-based imaging is shown. DETAILED DESCRIPTION

[0060] First reference Figure 1 , Figure 1 A schematic block diagram of a medical imaging arrangement MAR as envisaged herein in an embodiment is shown. The arrangement IAR may comprise a medical imaging device IA (referred to as "imager" for short), preferably an imager of the tomographic X-ray type, whereby the imager may be a computed tomography (CT) scanner, but interventional systems of the C-arm / U-arm type are not excluded herein, for example. In some other embodiments, other tomographic modalities, such as MRI, PET or other modalities, are still not excluded herein. The medical imaging arrangement is preferably envisaged for use with contrast agent-based imaging protocols, such as angiography.

[0061] The arrangement apparatus 1AR also includes a computing system CS that is generally operable to process data (including image data) provided by the imager. The computing system may also allow for control of the operation of the imager. The computing system may be located remotely from the imaging apparatus 1A, or may be located close to the imaging apparatus 1A, for example, integrated into an operator console CS from which a user can operate the imaging apparatus, in particular, to control imaging operations to obtain medical images for diagnosis, treatment, planning (e.g., in radiotherapy or other procedures), etc.

[0062] Broadly, and as will be explained more fully below, the computing system CS includes a facilitator system FS that can be used to establish the correct timing for triggering imaging operations, thereby ensuring that good quality (contrast) images are obtained. Additionally or alternatively, the facilitator system FS supports a user input UI function that allows a clinical user to adjust, fine-tune, or define a contrast agent bolus monitoring region ("m-ROI") from the outset, where contrast agent accumulation is to be monitored, in order to accurately establish the timing for triggering imaging operations with respect to the target anatomical feature TAF. The computing system CS (and particularly its facilitator system FS) can be implemented as a cloud solution running on one or more servers. The imaging device IA can be installed in a clinical facility (e.g., in a hospital). The computing system can be installed or used in a control room next to the imaging room where the imager IA is located. In some embodiments, the computing system can be integrated into the imager IA. The imager IA can be communicatively coupled to the computing system CS via a wired or wireless (or partially both) communication channel CC. The computing system CS may be arranged as a fixed computing system (e.g., a desktop computer), or as the server, or as a mobile device (e.g., a laptop, a smartphone, a tablet, etc.). For example, the computing system CS may be arranged on a workstation WS associated with the imager IA.

[0063] Before explaining the operation of the facilitator system FS in more detail, reference is first made to the components of the imager IA, which will be explained below with respect to the facilitator system FS.

[0064] The imaging device IA is operable to generate (particularly acquire) projection data, which are forwarded via a communication channel to a computing system CS for reconstruction into tomographic (cross-sectional) images. The computing system CS runs one or more reconstructor units RECON, which implement one or more reconstruction algorithms. Typically, the reconstruction algorithms implement a mapping of the projection data, which is located in a projection domain, into an image domain. The image domain is part of a 3D space and is located in the examination region ER of the imaging device, while the projection domain is in 2D and is located at the (X-ray) detector XD of the imaging device IA.

[0065] As described above, the imaging device IA is preferably of the tomographic type and is preferably configured for multi-directional projection image acquisition. Thus, the imaging device IA is capable of acquiring projection images along different projection directions relative to the examination region ER and, therefore, the patient's anatomical region of interest (ROI). In an embodiment, acquisition is performed using a rotation system, wherein at least the X-ray source XS is arranged in a movable gantry MG.

[0066] The movable gantry (and, in one embodiment, the X-ray source XS therewith) is rotatable within the fixed gantry SG around an examination region ER, where the patient / ROI resides during imaging. Opposite the X-ray source in the movable gantry is an X-ray detector XD, which can rotate along with the gantry and X-ray source around the examination region ER to achieve different projection directions.

[0067] As in Figure 1 As schematically indicated in , the longitudinal axis or imaging axis Z of the patient can extend into the examination region ER during imaging. The patient PAT can be positioned on a patient support PS (e.g., a bed) that is at least partially positioned in the examination region ER during imaging. In some, but not all, embodiments, helical imaging protocols are contemplated herein in which there is relative lateral motion along the longitudinal axis Z between the X-ray source XS and the patient PAT. For example, the patient support PS can be advanced through the examination region ER during multi-directional projection image acquisition (e.g., during rotation of the X-ray source XS about the patient).

[0068] like Figure 1 The illustrated CT scanner arrangement is only according to one embodiment, and other tomographic imaging equipment, such as a C-arm or U-arm scanner, a cone beam CT arrangement device, a mammography imager, etc., are not excluded herein. In some embodiments, a C-arm cone beam imager is preferred herein. In addition, the multi-directional acquisition capability may not necessarily be provided by, for example, Figure 1 The rotating system shown is generated. Non-rotating imaging systems are also contemplated, for example, in 4th or 5th generation CT scanners, in which multiple X-ray sources are arranged around an examination region, for example, in a source ring. Additionally or alternatively, the detectors XD can be arranged as a detector ring around the examination region. Thus, in such systems, the X-ray source XS, the detectors XD, or both do not rotate.

[0069] There may be an operator console OC through which a user (e.g., medical personnel) controls imaging operations. For example, the user may request to initiate image acquisition, or may request a reconstruction or other operation, or may initiate data transfer to the computing system CS, or may stop such transfer as needed.

[0070] During imaging, an X-ray beam XB is emitted from the focal spot of one or more X-ray sources XS along various projection directions. Beam XB traverses an examination region, including a patient. The X-rays interact with patient tissue. As a result of these interactions, the X-ray beam XB is modified. Typically, these modifications to the X-ray beam XB include attenuation and scattering of the original incident X-ray beam. The modified X-rays are then detected as spatial distributions of varying intensities at the X-ray-sensitive pixels of detector XD.

[0071] It is not necessary in this context to acquire projection images over the entire 360° angular range around the examination region ER. Acquisition over a partial angular range, such as 270°, 180°, or even a smaller range, may be sufficient. The X-ray detector is preferably configured to acquire 2D projection images of rows and columns of intensity values ​​registered by detector pixels. That is, the detector pixels themselves can be arranged in a matrix layout. Such a 2D layout can be used for diverging imaging geometries (e.g., conical or fan-shaped beams or beams of other shapes). However, a one-dimensional detector pixel layout (e.g., along a single line) is not excluded in this context, and neither is a parallel beam geometry.

[0072] The reconstructor RECON implements one or more reconstruction algorithms to process the projection images. Specifically, the reconstructor RECON can calculate cross-sectional images V of the examination region (wherein a patient is located) for diagnostic, therapeutic, or other purposes. The reconstructor RECON is capable of generating cross-sectional volumetric image data ("image volume(s)") V. However, this does not preclude the generation of individual image slices in the examination region as needed. Therefore, the reconstructed image may be denoted herein as V and may include the entire volume, a partial volume, or a specific portion thereof. Volume reconstruction may be facilitated by helical movement and / or 2D layout of the X-ray detector XD. The scan frame SB may be user-defined, in particular by using user input UI functionality such as that supported by the facilitator system FS. The scan frame CB is a portion of space in the image domain. It is therefore a 3D object, but can be visualized as a rectangle in a 2D view, hence the name scan frame. The scan frame defines the volume to be scanned in order to acquire projection data from which the volume of the space demarcated by the scan frame is to be reconstructed. The scan frame typically includes a monitoring region m-ROI, a target anatomical feature TAF, and optionally one or more anatomical landmarks LM.

[0073] The reconstructed volume image V can be stored in a memory MEM or can be processed in other ways as needed. The reconstructed volume image V can be visualized by a visualizer VIZ. The visualizer VIZ can generate a graphical display of the volume or a given slice. The graphical display can be displayed on a display device DD. The visualizer VIZ can map part of the image volume V or the entire image volume V to grayscale values ​​or a color palette. The visualizer VIZ can control the video circuit via a suitable interface to achieve the display of the graphical display on the display device DD. In addition to or in lieu of such display, the reconstructed image V can be stored in a memory for later review or for other types of processing. Such a memory may include an image repository, for example, a database (e.g., a PACS) or other (preferably) non-volatile data storage arrangement.

[0074] The reconstructed volume image V can be manipulated, for example, by reformatting it to define a cross-sectional plane different from the cross-sectional plane defined by the imaging geometry. Such reformatting can allow a medical user to better discern tissue types or anatomical details within the patient, depending on the medical purpose at hand, such as for diagnosis or preparation for some type of treatment.

[0075] The volume V so reconstructed may be referred to herein as a target image acquired during the target or operational phase of a contrast-assisted imaging procedure. The reconstructed image V is envisioned as a diagnostic image that represents the target anatomical feature TAF (e.g., a target anatomical structure, organ, part or group of organs, different tissue types, etc.) and has sufficient contrast to safely inform a therapeutic or diagnostic decision or other medical decision, such that further imaging sessions may be performed using other imaging modalities or other tasks (tests, etc.) that may be necessary based on the imaging.

[0076] By appropriately controlling the dose to be used via the operator console OC, a (target) projection image · from which the target volume V is reconstructed is acquired with a sufficient dose. This can be done by controlling the voltage and / or amperage settings of the tube of the X-ray source XS to ensure a certain diagnostic image quality. As mentioned above, the imaging protocol envisaged herein is preferably an imaging protocol based on a contrast agent to ensure that the target anatomical features TAF (which themselves may have low radiopacity) can still be imaged with sufficient contrast. Such a target projection image acquired at a sufficiently high dose may also be referred to herein as a diagnostic projection image · in order to follow established terminology. However, this naming convention does not exclude that the projection data · and its reconstruction V will be used for tasks other than diagnosis (e.g. for treatment (in a catheterization laboratory, etc.), planning, or any other task).

[0077] The target anatomical feature TAF relates to the medical purpose of the imaging. Thus, if the patient's liver requires examination, the target anatomical feature TAF is the liver: the liver is the purpose and object of the abdominal scan to be performed.

[0078] Each target anatomical feature TAF is typically associated with an imaging protocol, a set of specifications preferably dictated by patient biological characteristics (age, weight, sex, height, BMI, medical history, etc.), certain preferred imaging settings, image contrast to be achieved, the radiation dose to be used for the target anatomical feature TAF for a given purpose, the voltage / amperage settings of the source X to be used, collimation, etc. In short, the imaging protocol encapsulates the medical knowledge for any given imaging task, purpose, target anatomical feature TAF, etc.

[0079] Prior to acquiring such a diagnostic projection image ·, and for such a low-radiopacity anatomical feature TAF, a volume of contrast agent CA (e.g., iodine or other suitable material) is administered to the patient PAT via an administration device ADA (e.g., a pump). This volume (sometimes referred to as a "bolus") of contrast agent CA then propagates through the patient with the bloodstream and accumulates at the target anatomical feature TAF. Ideally, once sufficient contrast agent CA has accumulated at the target anatomical feature TAF, only then can a diagnostic-quality diagnostic projection image be acquired. Therefore, the timing of acquisition of the diagnostic projection image · of the target image V by the imager IA is an important consideration, as it must be ensured that the concentration of contrast agent at the target anatomical feature of interest is sufficient. Only then can the reconstructed image domain target volume V be expected to have the required IQ (image quality) for image contrast, as specified by the protocol or otherwise. If this is not the case, a retake may be necessary (which should be avoided due to cost, time effort, increased dose exposure, machine wear (particularly the anode disk of the tube XS), etc.). Therefore, in this context, diagnostic acquisition timing is considered to be "get it" "once and for all."

[0080] The facilitator system FS contemplated herein facilitates such acquisition at the correct timing in contrast-assisted imaging protocols. The facilitator FS ensures that diagnostic projection image acquisition is reproducibly and reliably triggered at the correct moment when enough contrast agent has actually accumulated at the target anatomical feature TAF.

[0081] The facilitator system operates across two phases: an exploratory or preparation phase (PP) and a monitoring phase, both of which precede the target phase, in which a target volume (V) is acquired. All of these phases are preceded by an initial phase, in which an initial plain film image (V0) is acquired. This initial image (V0) is preferably a 3D (image domain) plain film volume, itself reconstructed from a first set of projection images. However, this first / initial set of projection images (V0) is acquired at a lower image quality than the projection images (TAF) that will be acquired later in the target phase and used to reconstruct the target image (V). In particular, a lower radiation dose is incurred when acquiring TAF, compared to the later dose that would be reduced due to the diagnostic scan to acquire the diagnostic projection images (TAF). This is to save dose on the patient (PAT), and also because the 3D plain film volume (V0) is used for a completely different purpose than the target volume (V): the purpose of the plain film volume / image (V0) is essentially navigation, as will be expanded upon herein: the plain film image (V0) is used to find the appropriate location to monitor bolus arrival, ensuring that imaging of the target anatomical feature (TAF) begins at the correct moment, so that the target volume (V) has the desired diagnostic-grade contrast.

[0082] exist Figure 2 The contrast agent assisted imaging protocol is schematically illustrated in FIG, and reference is now made to FIG before explaining the operation of the facilitator system FS in more detail. Figure 2 .

[0083] As previously observed, the contrast agent CA will enhance the image contrast of target structures TAF that have poor natural radiopacity. At this point, and now with more specific reference to Figure 2 , which is a schematic illustration of a portion of a blood vessel at the point of entry (shown at an "X") where a bolus CA is administered by the contrast agent administration device ADA or other device.

[0084] Blood vessels (e.g., cardiac arteries or veins of interest in cardiac imaging) are soft tissue and therefore have poor radiopacity. Therefore, if non-contrast scanning is used, the vessels are represented with low contrast. The volume of contrast agent CA travels with the blood flow and propagates through the vessel until the concentration of contrast agent accumulates at the target feature TAF, at which point the target phase can begin, where projection images of the target volume V are acquired at higher image quality.

[0085] Preferably, the target anatomical feature TAF is located upstream (the direction of blood flow is in the Figure 2 In the example of FIG. 1 , the monitoring region m-ROI is defined by a neighborhood U within the image, as will be explained in more detail later. This neighborhood U is based on the 3D segmentation m0 found in the initial plain film image V0. The neighborhood U and the segmentation m0 may relate to anatomical landmarks (such as portions of the aorta, such as the aortic arch, the descending portion of the aorta, etc.) at which the contrast agent concentration is monitored. That is, the monitoring region m-ROI may initially be defined based on anatomical landmarks according to medical knowledge, but the exact specific location within a given volume is provided by the facilitator FS.

[0086] Therefore, it is preferred to monitor the concentration of the contrast agent CA upstream of the actual target anatomical feature TAF, for example, to account for image acquisition delays. Once the concentration monitored at the monitoring region m-ROI has reached a certain minimum concentration (which can be measured by thresholding the time (t) series of the tracker images r(t) (to be explored more fully below), the acquisition of current diagnostic projection data · of the target volume V can be started, at which point the concentration at the target anatomical feature TAF can be expected to have reached an acceptable minimum concentration due to blood flow.

[0087] The spatial distance between the monitoring region m-ROI and the actual target anatomical feature TAF is primarily determined based on clinical knowledge and / or by patient characteristics, knowledge of blood flow velocity, etc. Such medical background information, including the m-ROI-TAF distance, which landmarks are used for the monitoring region m-ROI, etc., can all be encoded in the imaging protocol / specification for the imaging task / purpose at hand.

[0088] Broadly, the facilitator system FS may include a monitoring region finder MRF configured to quickly and, as described, reliably and reproducibly, but also accurately, find the correct monitoring region m0=m-ROI in the plain film volume V0 for a given patient and target anatomical feature TAF. Preferably, the operation of the facilitator system FS is such that it is well integrated into existing CT workflows.

[0089] The monitoring region finder MRF can be implemented as a segmenter SEG, for example based on a machine learning ("ML") model M. Examples of such a model M may include artificial neural networks, in particular of the convolutional type. A CNN capable of multi-scale processing (such as a U-net architecture) may be used. Any other machine learning model may be used. Instead of ML, more classical segmentation techniques such as region growing, segmentation based on shape models, etc. may be used.

[0090] While the monitoring region finder MRF of the facilitator system FS may thus be capable of fully automatic operation and providing a monitoring region m-ROI without further / any user input (other than specifying an imaging protocol or a target anatomical feature TAF), it is specifically envisaged herein that the facilitator FS comprises a user interface functionality UI allowing a user to interact with the estimated m-ROI position m0. In particular, the facilitator FS requests user interaction. It is specifically provided herein that certain components of the monitoring region finding process may be specifically adjusted by the clinical user at his pleasure via a user interface UI (such as a graphical user interface (GUI)) specifically configured for such user interaction. The user request for such adjustment of m0 may be communicated to the bolus monitoring system MS via a touch screen TS, a pointer tool (computer mouse CM, stylus STY) or the like (see below Figure 3 ). Such user interaction is preferably envisioned herein as a dynamic real-time experience: upon such user-requested adjustments regarding the found monitoring region m-ROI, a recalculation of the relevant components is triggered, and their display may be updated as many times as the user requests such changes or adjustments.

[0091] Thus, the facilitator system FS (in particular due to its user interface functionality UI) allows finding the correct monitoring area, which in turn facilitates finding the correct moment t=t0 for the start of the target phase and controlling the imaging device IA, so as to reliably acquire higher quality projection images from which the target volume V can be reconstructed.

[0092] Before turning to the operation of the user function UI in more detail, first refer to the schematic diagram. Figure 3, which illustrates some basic operational aspects of the proposed facilitator system FS in relation to an (optional) monitoring region finder MRF cooperating with a bolus monitoring system MS as part of a computing system CS. Specifically, and as illustrated at A), an initial 3D plain film volume V0 is segmented with respect to one or more suitable anatomical landmarks to be used as bolus monitoring regions m-ROIs.

[0093] Based on the estimated m-ROI segmentation m0, a reference position z0 in the volume is identified, which can be, for example, a set position along the rotation / imaging axis Z of the imager IA. Preferably, a reference point P, such as a centroid or other point, is defined in the 3D segmented subvolume m0. Point P can be projected onto the Z axis to define the reference position z0.

[0094] The tracker image r is then reconstructed from the corresponding set of low-dose projection images acquired at appropriate sampling intervals around the reference position z0. t time series.

[0095] In some or each such tracker image r(t), a monitoring neighborhood U (shown as a small circle) at B) is automatically defined based on a reference point P. The neighborhood U around P can be an ellipsoid, a sphere, or the like (or, in a 2D view, an ellipse, etc.), and due to the proposed user interaction features, an event handler EH can be used to allow the user to change any one or more of P, z0, or U as needed. It will therefore be understood that the monitoring region m-ROI can be defined by two elements: its position in 3D, as given by the reference position z0; and its spatial extent for monitoring purposes, as represented in the tracker image rt, as defined by the neighborhood U. A change in at least one of the elements P, z0, or U will result in an automatic and consistent change in the other element or elements.

[0096] In a series of tracker images r(t), the concentration of contrast agent reached is monitored after a bolus injection at a neighborhood, which defines the set monitoring location m-ROI. An example is shown as a contrast curve c at C) given a tracker image and an image neighborhood U. U (t). In such a curve, the contrast value HU (Hounsfield units) in the neighborhood U is recorded over time t. The CA concentration, and therefore the contrast, is expected to increase over time during the ramp-up phase, then level off and reach saturation during the plateau phase, and then decrease during the decline phase as the contrast agent is washed out. Figure 3 Only the ramp-up phase is shown.

[0097] A thresholding strategy based on image values ​​can be used in monitoring the neighborhood U to trigger an acquisition signal for acquiring a diagnostic projection image from which the target volume V can be reconstructed. This acquisition should be triggered after the contrast agent concentration (or HU value in the contrast curve c) has reached a certain minimum value, which can be lower than the expected maximum value at the target anatomical feature TFA, as this is expected to be slightly downstream of the monitoring region m-ROI / U. Instead of basing the above thresholding on monitoring absolute HU values, the gradient of HU values ​​can be monitored alternatively or additionally as needed.

[0098] However, in some embodiments where latency is not an issue, the monitoring region and the target anatomical feature may coincide, in which case thresholding can be performed such that the diagnostic projection image acquisition is triggered at the maximum concentration value during the plateau phase. For example, the maximum value can be found using a gradient-based approach.

[0099] The set of projection images acquired at the set sampling rate from which the tracker image is reconstructed may have a lower quality (lower dose) than the projection images acquired at a later diagnostic acquisition phase. For example, the image quality may be similar to the image quality of the projection images acquired from which the plain film image V0 is reconstructed.

[0100] The size (field of view ["FOV") of the plain film (also called "scout") image volume V0 is preferably selected so that the plain film image volume V0 includes not only the target feature TAF, but also at least one of the anatomical landmarks at which the bolus should be monitored. If in doubt, the plain film scan can be a whole-body scan, but this is not always necessary, as in some cases a scan over the applicable body region (e.g., an abdominal scan, a head scan, a chest scan, a leg scan, etc.) may be sufficient.

[0101] Although the contrast in such a plain film image V0 is usually very poor due to the low dose, it may be sufficient to broadly locate the landmarks of the m-ROI and optionally the target anatomical features TAF. The latter can also be marked manually by the user (see below).

[0102] Once the system FS has found the reference position z0 based on the segmentation m0, it may be necessary to adjust the imaging geometry, for example by moving the patient table relative to the gantry, so that a tracker image around the reference position can be obtained by reconstruction from a series of projection images acquired at the aforementioned sampling intervals. However, in a preferred embodiment, such repositioning of the patient table or gantry is not necessary, as the distance between the target anatomical feature and the monitoring position is approximately known, and the plain film volume V0 is preferably acquired from the outset to cover a sufficiently large volume. For example, the FOV of the plain film positioning volume V0 can be linked to automatic planning, so that a very large FOV plain film image is generally not required to collect anatomical background information (e.g., for detecting landmarks, etc.). Such automatic planning is a facility that allows the detection of the target anatomical feature TAF in the plain film image V0 or allows the definition of the FOV to be used. If desired, the automatic planning facility can be implemented by suitable image processing (e.g., again by segmentation). However, the detection and knowledge of the location of the TAF can also be provided manually by the user, or by means based on or not based on machine learning. Generally, it is assumed herein that the location of the target anatomical feature TAF is known, and the main focus in this disclosure is the reliable positioning of the monitoring region m-ROI.

[0103] The m-ROI segmentation m0 is a 3D segmentation, i.e., it is defined by a 3D subvolume in the plain image m0·V0. This subvolume, which has a spatial extension in all three spatial directions (X, Y, Z), is preferably anatomically aware, in that it corresponds to (and in particular conforms to) the spatial structure of the anatomical structure at that location in terms of shape, size, and orientation. For example, the segmentation m0 can conform to the spatial structure of an anatomical landmark associated with the target anatomical structure. Thus, the segmentation can at least partially follow the anatomical / tissue boundaries of the landmark. This allows the user to quickly visually verify at a glance whether the segmentation m0 proposed by the monitoring region finder MRF is medically meaningful.

[0104] Typically, a relatively small segmented anatomical structure m0 can be used for the definition of the reference position z0 and, separately therefrom, for the neighborhood U in the tracker slice image passing through the reference position z0. As described above, the reference position z0 can be located on the imaging axis Z. However, this is not required in this context, as the initial planar volume V0 can also be provided for reformatting, and the reference position z0 can be a point on any geometric line used for the reformatting and, therefore, different from the rotation / imaging axis Z.

[0105] Notably, dose savings can be achieved because the initial localizer tracker image r0 does not require separate projection data acquisition, as it can be synthesized purely computationally from the plain film volume V0. Specifically, the neighborhood U used in the "live" tracker image for live monitoring of bolus arrival can already be defined on this prototype tracker image synthesized from the already available plain film 3D image V0. No dose needs to be introduced to determine the neighborhood U, which represents the spatial extension of the monitored region of interest (m-ROI), as represented in the tracker image. Furthermore, both the reference position and neighborhood U determination can be performed in a single step based solely on the plain film image V0 and the thus synthesized localizer tracker image r0. This is more convenient and faster for the clinical user, and this "one-step" operation can still be easily integrated into existing CT workflows as practiced in medical facilities worldwide. It should be understood that the use of the localizer tracker image r0 is not dependent on its display, and such a display is not actually required in all embodiments herein for the purpose of neighborhood U definition, as described in the single-step setup.

[0106] It should be understood that the monitoring region finder MRF described above is merely an optional component of the facilitator system FS as contemplated herein. In practice, the initial indication of the monitoring region m0 can also be provided purely manually as a segmentation of the plain film volume V0. It need not come from the monitoring region finder MRF or any other such automated computer system. In practice, the user may have provided it manually through annotations and may later change their mind, or another clinical user may have already provided an indication of the location of the monitoring region, etc.

[0107] However, as in Figure 4 As schematically shown in the block diagram of , it is contemplated herein that the facilitator system FS is to comprise a graphic display generator GDG. The graphic display generator GDG is operable to generate a graphic display GD on a display device DD. The graphic display GD comprises a visualization of at least part of the segmentation of the vessel in question (such as the aorta) and a graphical indication SL of the current position of the monitoring region, regardless of how it may have been provided by any user or by a computerized automated system (such as a monitoring region finder MRF).

[0108] The graphical display generator GDG assists the (clinical) user in interactively finding the correct monitoring region by repositioning the graphical indicator SL. The graphical display generator GDG allows the user to change the current position of the graphical indicator SL for the monitoring region via a supported user interface UI. The graphical indicator SL is "anatomy-aware" and dynamically adapts to fit the current anatomical environment based on the segmented vessels. Optionally, additional useful contextual information (such as landmarks, relative distances, expected bolus arrival time, etc.) is displayed corresponding to the current position of the graphical indicator SL, as will be described in more detail below.

[0109] The graphic display generator, the display device DD including the visualization of the graphic display GD thereon and the user input device UI interact to form an interactive graphical user interface GUI, as preferred herein. Figure 4 As shown, the graphic display generator GDG receives as input a 3D slice volume having a segmentation s(VS) of a vessel of interest VS and a definition D of a current marker position for the monitoring region. Regardless of how it is obtained, this initial definition D=m0 may comprise a single 3D coordinate in the 3D segmented slice volume V0 or a set of such coordinates, such as any one or more of a reference point P, a neighborhood U around P, and an associated z0 position, such as Figure 3 As shown, a view of the volume V0 and at least a portion of the vessel segmentation s=s(VS) are rendered for display, including a graphical indicator SL that is displayed to mark the current position of the monitoring region m-ROI based on the received definition m0=D. The graphical indicator SL can be drawn as a circle, ellipse, or other marking symbol or region delimiter. Preferably, the shape and orientation are such that the graphical indicator SL is within the segmented region.

[0110] With further reference to vessel segmentation, in some embodiments of the proposed method, segmentation of the vessel(s) is performed based on the anatomy being scanned (the aorta for the heart, the pulmonary artery for the liver or abdominal examinations, etc.). This can be specified in the imaging protocol as previously described. The segmentation is based on the low-dose plain film image(s), rather than the (higher) dose images used later in the diagnostic scan. Displaying the vessel segmentation in addition to the bolus ROI (such as represented by a circle in other geometric figures) can help (particularly guide) the user to place the m-ROI in a clinically appropriate manner with greater confidence. For example, and in some embodiments, this guidance function is facilitated by the displayed vessel segmentation also including segmentation of the calcification(s) within the vessel, which are typically areas that one may want to avoid when placing the bolus m-ROI. Thus, the plain film images can be recorded using an imager configured for spectral imaging (such as dual energy or any other), and the images can be spectrally processed using a material decomposition algorithm to better define the calcified wall portions. Calcified wall portions w of a blood vessel may be graphically drawn differently than non-calcified wall portions.

[0111] Now go to Figure 5 A block diagram illustrating the operation of the graphic display generator as part of the Facilitator FS is shown in greater detail. Proceeding from left to right, the imaging device is operable to acquire a low-dose plain film 3D volume V0 as described. In some less preferred embodiments, 2D plain films are also contemplated; however, the clinical benefits of the proposed Facilitator FS technology are best brought to the fore in the context of 3D plain film imaging.

[0112] The flat-panel 3D volume V0 may be supplied by the imager IA, preferably in an online setting, although this does not exclude later retrieval from an image database.

[0113] The Monitoring Region Finder MRF can provide an initial segmentation m0 for the m-ROI. The Monitoring Region Finder MRF may or may not be integrated into the Facilitator FS, but is optional in either case. One possible detection / output from the Monitoring Region Finder MRF can also be one or more landmarks LM around which the m-ROI circle can be placed.

[0114] In fact, in some cases the monitoring region finder MRF is an external system with no such functional connection to the facilitator FS. But of course, the facilitator FS can very well be connected to the monitoring region finder MRF via a wireless or wired network connection interface (such as in a hospital information system) to form a more extensive imaging support arrangement. The monitoring region finder MRF can be implemented, for example, in a cloud system to process the images produced by (one or more) imagers IA and then segment these images as needed or automatically. The segmented volume V0 can then be stored and can be loaded by the facilitator system FS if and when viewing and monitoring region adjustment is required. In any embodiment, the monitoring region finder MRF can be a segmenter component powered by a machine learning model M to segment the low quality (high noise) 3D volume for the initial spatial definition D of the monitoring region therein.

[0115] Optionally, an initial definition D=m0(s)=m0 of the locations of the monitoring regions in the segmentation s may be provided manually by the user by any means, such as by leaving annotations as applied by a suitable user interface UI'. Of course, the monitoring region finder MRF may be omitted entirely.

[0116] The segmentation of the structure of the vessel of interest VS in the plain film volume VO can be provided by a separate (vessel) segmenter SEG, or the segmenter SEG can be part of the monitoring region finder MR. Even if the monitoring region finder MRF is used, the vessel segmenter SEG can still be a separate component and does not need to be associated with the optional monitoring region finder MRF. In some embodiments, the vessel segmenter SEG is part of the facilitator system.

[0117] The segmenter SEG that provides the vessel segmentation s(VS) can be ML-driven (e.g., deep learning), or based on a shape model (MBS), or based on any other segmentation algorithm, such as region growing, etc. In either case, it is configured to cope with the low SNR in low-dose plain film images to achieve good segmentation. As in the case of the initial segmentation m0 of the initial m-ROI, the vessel segmentation s=s(VS) is a 3D segmentation, thus forming a sub-volume in the plain film volume V0. In an embodiment, the vessel segmentation SEG can be configured to transfer the contrast segmentation from the spectral CT image to the virtual non-contrast image. An ML-based approach can be used. The segmenter SEG can use an ML model M', such as an artificial neural network (NN), in particular a convolutional type (CNN). NN or other models configured for multi-scale processing can be used, such as NN models with a U-net architecture, or other bottleneck-type models using a convolution operator followed by a deconvolution operator. Such models include, for example, the U-net architecture or its homologues, as described in "U-Net: Convolutional Networks for Biomedical Image Segmentation" by O. Ronneberger et al. (available online on the arXiv repository under the reference code arXiv:1505.04597 (2015)). The segmenter SEG can also be configured to extract the centerline CL and / or radius of the vessel (such as the aorta) segmentation s. This can be done using existing skeletonization or distance transform methods. The centerline CL can be visualized, as will be explained in more detail below.

[0118] Alternatively, instead of using such a segmenter SEG, the user may provide vessel segmentation based on 3D annotations, although this may be cumbersome and time consuming.

[0119] Regardless of how it is segmented, the vessel VS may represent all or part of the aorta, for example, or it may be part or all of any other vessel that is of interest for the medical task at hand and through which a bolus is expected to travel.

[0120] The vessel segmentation s(VS) in the plain film volume V0 and the initial definition m0 of the monitoring region position therein are then processed by a graphic display generator GDG to generate a graphic display GD for viewing on a display device DD. The graphic display generator GDG controls the display device DD via a suitable video circuit interface to display the graphic display GD on the display device DD. The graphic display GD is schematically represented in Figure 5 The graphical display GD comprises a visualization of the segmentation s=s(VS) or a portion thereof and a visualization of the monitoring area indicator SL within the area of ​​the segmentation s based on the initial position definition m0.

[0121] While the graphical display GD is displayed on the display device DD, the user can request a modification of the currently indicated monitoring area according to the graphical indicator widget SL using a user input device UI (such as a keyboard KB, a stylus STY, or a computer mouse CM) or any other pointer tool. Alternatively, the graphical display generator GDG can interact with the display device DD to support a touchscreen TS facility as another embodiment of a user interface UI facility through which the user can input a modification request for the currently indicated monitoring area. In some of the mentioned UI embodiments (such as the pointer tool STY, CM, or the touchscreen TS functionality), the user can interact with the indicator widget SL to request a repositioning and / or resizing of the currently indicated monitoring area. To this end, and preferably in this context, the indicator is configured as a sliding element SL that can be slid along the partition s to allow the user to reposition the currently suggested monitoring area to a more appropriate location based on their medical knowledge. This type of sliding element has been found to provide immediate visual feedback and can support users in quickly achieving a satisfactory monitoring position definition even in time-critical and stressful situations (such as in a trauma room or a busy clinical environment with an overwhelming workload, staff shortages, etc.). Furthermore, the sliding element allows for quick and intuitive input of such repositioning requests. Therefore, throughout most of this disclosure, the indicator SL will be referred to herein as a slider element or simply as a "slider" SL. For example, if desired, the slider SL may also support requests for reorientation and / or resizing via click and drag actions. However, preferably, the slider SL is automatically and dynamically resized / reoriented by the graphic display generator GDG, for example, when the slider SL is slid along a partition s (such as along the centerline of the partition s), or when a user requests a change in the view drawing / reformatting of the volume, etc., as will be described in more detail below.

[0122] Once the graphic display generator receives such a user request for a position adjustment via the user input UI, the event handler EH operates to capture the adjustment request event and pass it to the graphic display generator GDG. The event may include a specification of the nature of the request, such as the next expected position of the slider SL, its size, etc. Alternatively, the event may be mapped to a specification such as. The graphic display generator GDG processes the event specification to update the graphic display accordingly. The updated graphic display GDG now indicates the new position of the monitoring area by modifying the position of the SL elements along the segmentation. When drawn to be displayed at the new position, the geometry of the slider element SL may be modified accordingly, as will be described in more detail below.

[0123] The user-requested adjustment of the position of the slider SL can be performed multiple times. Once the user is satisfied that a suitable position has been found, the position of the m-ROI indicated by the slider SL can be assigned via the output interface OUT as the final monitoring position m(s). This final position m(s) can then be communicated to the imaging device via a suitable control interface, for example, to its operator console OC, to initiate a monitoring phase that can be coordinated by the (bolus) monitoring system MS. During this monitoring phase, based on the now-indicated position (and extent) of the monitoring region m-ROI, the monitoring system MS instructs the imaging device IA to acquire a tracker projection data stream around the region m-ROI. As coordinated by the monitoring system MS, the tomographic reconstructor RECON reconstructs a tracker image stream therefrom, which is monitored by the intra-image monitoring unit of the monitoring system MS for voxel value changes at the monitoring region. For example, image values, such as those based on the HU values ​​of the tracker image stream, are thresholded. Any other monitoring strategy can be used instead of or in combination with thresholding. Image value changes are indicative of bolus arrival. Once the monitoring unit of the monitoring system MS concludes that the bolus has indeed reached the indicated position m(s) based on thresholding or any other applicable such monitoring strategy, the monitoring system MS sends a new signal to the imager IA to acquire a new set of projection data, but this time at a diagnostic dose that is higher than the dose used for the plain film scan V0 or the tracker image r(t). A fully contrasted target volume V can then be reconstructed by the reconstructor RECON from the diagnostic projection data. The target volume V can then be displayed on the display device DD or any other display device to support the user in the clinical goal / purpose of the imaging. Depending on the clinical context, the purpose can be any one or more of treatment, diagnosis, planning, medical analysis, etc., or any other purpose. The target volume V can be processed (e.g., analyzed, etc.), stored, and distributed as needed.

[0124] Figure 6 is an illustration of a graphical display GD that may be generated by a graphical display generator GDG according to an example embodiment.

[0125] Graphics display GD includes 3D rendering (e.g., isosurface, etc.), or as Figure 6 The user can select a view of the volume V of the 2D cross-sectional view in the cross-sectional plane and a visualization S of the segmentation s=s(SV) of the vessel of interest VS. Figure 6 In the example shown, the vessel of interest is a portion of the aorta shown in a sagittal view. As a third visualization component, there is a graphical widget of a slider SL drawn as an ellipse, but it can have any shape or size as long as it remains within the region / volume marked by the segmentation s of the vessel of interest VS.

[0126] The view can be in any plane and does not have to be Figure 6 sagittal as so illustrated in the figure. Views in the frontal plane, the transverse plane are also envisaged herein as standard views and are therefore non-standard reformattings in planes different from the standard planes as defined in the image domain. If such a change of view is requested (whether it is a reformatted or standard), the visual elements of the graphical display are adjusted accordingly. For example, the segmented aorta and the slider symbol SL are redrawn in a correct and consistent geometric perspective. The user can request a change of view at any time at his or her leisure by issuing a request event via the UI. The event handler EH intercepts this and mediates the view change. To this end, the graphical display generator may include a geometry view generator that is aware of the geometry of the imaging domain and is configured to apply geometric operations of the projected geometry to redraw the graphical display into any view as required, wherein the redrawing of the visual components includes the segmentation s and the slider SL as described above.

[0127] The segmentation boundary of the aorta VS is indicated by a dashed line, and such a rendering is actually envisioned. Therefore, the segmentation preferably includes different visual modulations to represent the wall W of a vessel VS (such as the aorta). It has been found that such different visual renderings of the vessel wall portions W better assist the user in placing / visualizing the slider element SL for the defined monitoring region. Thus, even for novice users or users in stressful situations, a realistic and clinically meaningful spatial specification of the monitoring region m-ROI can be quickly achieved. The visual modulation of the wall portions can differentiate between calcified and non-calcified vessel wall portions, as described above.

[0128] The graphic display generator GDG may also include a failsafe measure that assists the user in better positioning the slider FL for m-ROI specification. This may be achieved by the graphic display generator GDG constraining the apparent movement of the slider SL during adjustment to a single dimension (primarily sliding along the direction of the vessel, which may also include curved portions).

[0129] More specifically, and in an embodiment, the slider is locked to the course of the vessel, as may be defined by a tangent to its centerline / curve. Thus, the slider SL may only be slidable / movable in motion along a tangent to the centerline CL of the vessel segment s. The centerline CL may also be visualized in the graphical display GD, for example as Figure 6 . Any line type may be used herein for the centerline and for the wall W indication of the vessel segmentation s, and the dashed and dotted line modulations selected are merely illustrative examples herein. In addition to or in lieu of line type modulation, a separate and distinct visual modulation encoded by color, hue, or grayscale value may be used to separate the wall W and / or centerline from the remaining bulk of the vessel segmentation.

[0130] An adjustment request may result in the sliding element SL being dragged from one position (indicated as (1)) to the next position (2), and then (3), as Figure 6 As illustrated by the bracket numbers and related arrows.

[0131] The slider element SL itself can have any suitable form or shape. Preferably, the shape depends on the view being drawn and remains consistent with view changes. For example, the slider can be drawn as an ellipse, a circle or can have any other shape. The shape can change as the user requests a new view, such as from sagittal to transverse, etc. For example, the shape can be an ellipse in a sagittal plane view, but can change to a circle when the user requests a view in the transverse plane instead. View changes can also be requested by the user interface UI. For example, when the pointer tool is operated in a predefined way (such as a right mouse click or other), a pop-up drop-down menu widget can appear, and the user can then select a new view, which is then drawn on the display device DD by the graphic display generator GDG.

[0132] The user can also request resizing or reorienting of the slider SL using the user interface UI. Resizing may be limited by the region d marked by the vessel segmentation. In a preferred embodiment, when the user requests to slide the slider element along the centerline SL and within the segmentation region, the slider SL is automatically resized to conform to the diameter or width of the segmentation s. In other words, the slider element SL of a given geometry (e.g., an ellipse) is resized to a maximum size while remaining within the segmentation walls W. For example, a circle inscribed within a specific diameter around the segmentation centerline is preferably completely within the segmented vessel region s. Thus, when the slider SL is slid along the centerline SL, the slider SL appears to be constantly contacting the wall portion W of the segmentation s, as the sliding is initiated by the user requesting a corresponding position adjustment via the user input interface UI. To the user, this automatic conformity of the slider SL to the geometry of the vessel segmentation can appear as a dynamic expansion or contraction of the slider SL as it is dragged through the vessel segmentation, whose width (cross-section) varies. Automatic conformity of the slider to the vessel segmentation geometry is also provided, regardless of whether the slider SL is slid along a curved or straight portion of the segmentation s (VS).

[0133] As one possible embodiment of the user interface UI contemplated herein, the sliding of the sliding element along a tangent to the center line SL can be achieved simply by keyboard tapping. Thus, in such or similar embodiments, the user is invited to press either of two designated keyboard keys to issue a slide SL repositioning event. For example, each of the keys can indicate one of two movement directions of the slider SL, depending on Figure 6Up or down in one view, which can correspond to left or right in other views, etc. Additionally or alternatively, the user interface can allow the user to increase / decrease the diameter of the bolus ROI circle. For example, in a touchscreen embodiment, this can be accomplished by the user performing certain predefined gestures. Alternatively, in a keyboard-based embodiment, the user can click a set of predefined keys to request such a change in the size of the displayed m-ROI. For example, the set of "plus / minus" keys can be appropriately assigned to allow the user to request changes, such as m-ROI size.

[0134] In some embodiments, adjustment of the slider SL's position is restricted to occurring only tangentially to the segmentation's center CL. Thus, the slider's movement is locked to the segmentation process. Therefore, in a preferred embodiment, the graphic display generator GDG is configured to support retracting the monitoring region m-ROI only along the segmentation, thereby resetting the slider SL. Other repositioning requests can be ignored or converted to keep the slider SL within the segmentation's boundaries. If the initial definition m0 of the current monitoring region m-ROI violates this policy, the initial definition can be automatically corrected so that the slider SL in its initial position is within the segmentation. The user can be notified of this automatic correction.

[0135] Some forms of user interaction supported by the graphical display generator GDG can include instructions via mechanical input. For example, in touchscreen interaction TS, the user places their finger on the current position and performs a drag movement on the screen to cause the slider element to slide. Other examples include computer mouse CM or stylus STY events that can indicate operations such as dragging. In mechanical user interface arrangements where the user describes motion, such as through touchscreen actions, a stylus, or a mouse, the registered motion is analyzed by the event handler EH and parsed into a component of motion parallel to the current centerline CL, which is tangent to the current position of the slider SL. The event handler of the graphical display generator GDG projects this parallel component of the requested motion onto the tangent to the centerline. Only this projected parallel component is then used to slide the slider SL to the next position. Thus, the graphical display generator GDG implements the movement of the slider SL along the tangent only in proportion to this projected motion component. In this way, by projecting the motion component onto the instantaneous tangent to the centerline SL, the apparent motion of the slider can be constrained to occur only along the centerline and thus locked to the segmentation.

[0136] As will be appreciated from the above, the Graphic Display Generator (GDG) supports several constraints, such as automatic conformal resizing of the slider (SL) to conform the geometry of its graphical representation to the width of the segmentation, and a lock feature whereby the requested reposition is locked to the segmentation's alignment (e.g., centerline). These constraint functions form a useful fail-safe measure, as shown in the current view, which can be disabled if desired. The sizing of the slider (SL) as a function of the instantaneous segmentation width and the lock feature for forced linear repositioning help even novice or undertrained users quickly find the true bolus monitoring position, thereby reducing the likelihood of retakes, increasing patient throughput, and the like.

[0137] However, it should be understood that locking the sliding motion to the tangent line of the vessel segmentation may not be necessary in all embodiments. In addition, the graphic display generator GDG may include features that can allow the user to disable any one or more constraints in order to place the sliding element SL more freely, as may be required in some circumstances.

[0138] As an additional optional feature, in addition to displaying the segmentation s and the sliders SL in or around the segmentation s, the graphic display generator GDG also supports the display of useful medical background information. The mentioned medical background information can be provided by a medical background information provider MCP. The medical background information provider MCP can be part of the facilitator system FS, or the facilitator system FS is configured to be appropriately interfaced with such a medical background information provider MCP. The medical background information provider MCP can include a landmark segmenter LMS module and / or a physiological modeling machine PMM configured to provide distance d and / or transit time information.

[0139] Therefore, in some embodiments, and as Figure 6 As illustrated, the graphic display generator GDG can be operated to cause the display of medical background information, such as the transit time T of the bolus and / or the distance d to certain anatomical landmarks LM, ANAj (as shown, j=1-5) as a function of the current slider SL position. Such medical background information can be usefully and contextually appropriately displayed in information pop-up widgets CL1-CL3. Such widgets (called type pop-up in Figure 6) can be generated by a graphic display generator GDG in association with the changing position (1), (2), (3) of the sliding element SL, wherein the information in the pop-up windows CL1-CL3 is dynamically updated. The pop-up windows CL1, Cl2, CL3 may include information about the distance d to various landmarks LM as measured from the corresponding ((1), (2) or (3))) current position of the slider SL and the expected arrival time T of the bolus. In addition to or instead of indicating such time T and distance d information to the landmark LM, the time T and / or distance d may refer to the target anatomical feature TAF to be imaged. The pop-up windows are called upon user request or automatically when the slider SL slides along the segmentation. The pop-up windows Cl1-Cl3 may be persistent or timed. If persistent, the user may force it to exit by, for example, clicking on the pop-up window upon a close request. If displayed persistently or automatically upon user request, the time and / or distance information is automatically and dynamically updated.

[0140] In particular, useful landmarks LM for cardiac applications may include any one or more of the aortic valve, the coronary ostia, the bifurcation points of the renal and hepatic arteries, and such landmarks LM may be included to facilitate better planning. Knowing the 3D locations of such landmarks enables a useful differentiator in 3D radiograph-based planning, namely the ability to include in planning the true 3D distance between the bolus tracking ROI and the relevant landmarks.

[0141] Regarding transit time, the physiological modeling machine (PMM) can optionally be configured to implement a hemodynamic model to calculate a transit time T estimate from a landmark to a distance d. For example, the distance for the plain film volume V0 can be determined based on landmark segmentation, as provided by the landmark segmenter (LMS) module. The hemodynamic model can incorporate textbook knowledge about flow rates, or patient-specific information such as current heart rate or blood pressure, as well as a model of the patient's vasculature derived from a 3D plain film. Using transit time, bolus tracking position can be normalized relative to time delay, and information can be displayed to the technician when modifying the position of the bolus m-ROI. Thus, distance and transit time information can be obtained from a medical background information provider who implements such hemodynamic modeling, or can be queried through a suitable interface database to locate such a distance and transit time model.

[0142] In an embodiment, the graphical display GD may include visualization of certain aspects of the hemodynamic modeling, such as color-coded streamlines, velocity fields, or pressure fields.

[0143] Pop-up windows CL1-3 can be used with particular advantage in conjunction with a locking feature, wherein the slider's movement is locked to the path of the centerline CL. Locking the slider SL to the centerline in this manner provides a guidance function that avoids time-consuming user interaction to freely place the bolus tracking ROI (typically circular) and allows the user to "slide" the ROI along the centerline instead. For example, for each or some possible positions, the distance d to the relevant landmark ANAj is displayed in pop-up windows CL1-3. This can facilitate standardization of bolus tracking, such as "always place the ROI 10 cm downstream of the left coronary artery ostium for coronary scans." Additionally, the radius of the bolus tracking ROI can be dynamically adjusted based on the local radius of the aorta VS.

[0144] In addition to displaying such a pop-up window, the location of the relevant landmark can be indicated by an indicator widget (box, circle, ellipse, etc.). The information in the location of the landmark LM may have been segmented for use already in the received plain film volume v0, or the facilitator system FS may include one or more landmark segmenter modules LMS, whether they are ML-based, MBS-based, or based on any technology, as long as the segmenter module LMS is appropriately configured to cope with the expected low signal-to-noise ratio (SNR) due to low-dose acquisition. Again, as with the segmentation s of the vessels, the segmentation of the landmark LM is 3D, as is the 3D subset of the plain film volume V0. Segmentation of such anatomical landmarks LM can be achieved by employing ML-based landmark detection techniques, by segmenting spots around the landmarks, or by using more traditional image processing methods that take into account the geometric and anatomical properties of the landmark relative to the aorta or other vessels of interest, such as in the MBS shape segmentation technique.

[0145] Once a suitable placement has been found according to the current position of the slider SL, the user can indicate this by issuing a specific event via the user interface UI, for example by tapping a specific key, or by performing a specific gesture, click event, etc. in a touch screen embodiment. In either case, the extent and current position of the slider SL are considered to indicate the monitoring region m-ROI, and the specification of said current position / extent (size) is dispatched to the imaging device and monitoring system MS via the output port OUT to initiate the acquisition of the tracker image as described above, so as to facilitate the acquisition of the final full contrast image V.

[0146] Figure 7 A second embodiment of the graphic display GD is shown. In addition to the slider element SL, a scan frame SB area is indicated, for example, by a rectangular area of ​​dashed, dotted, solid or any line type. This scan frame visualization SB is adjusted together with the position of the slider element, such as Figure 2At one moment in time, the scanning frame shown in solid lines is associated with one position of the slider element SL, while the same is true for the scanning frame shown in dotted lines at the next position once the slider SL is moved.

[0147] Preferably, one end of the scan frame (e.g., one of its edges / planes) passes through the currently indicated slider element SL. The end portion of the scan frame defines a 3D subset of the image domain along the rotation / imaging axis Z, for which tracker projection images r(t) are acquired once a suitable position of the monitoring region is found (as indicated by the slider SL). The monitoring region is included in the scan frame, preferably at its edge / end portion. By default, and depending on the applicable scanning protocol, the scan frame is volumetrically selected to include the TAF and preferably one or more landmarks ANAj. Graphically indicating the scan frame SB in this manner, i.e., simultaneously with the underlying segmentation and the position of the slider SL, allows the user to better assess or understand the imaging operation to be performed.

[0148] Therefore, in embodiments herein, it is contemplated that planning of the bolus tracking m-ROI can be combined with simultaneous planning of the reconstruction box SB. Since it is generally preferred to start scanning at the bolus tracking position, manipulation of the ROI position can be combined with definition of upper or lower reconstruction box limits in order to avoid having to reposition the examination table before scanning can begin.

[0149] Depending on the selected protocol and target anatomy, the user can use the UI to place the slider SL for the bolus m-ROI at the uppermost or lowermost end of the planning box SB around the centerline CL of the aortic wall W. Such placement ideally starts the scan at the corresponding start / end position of the target organ TAF and avoids the stage movement that would otherwise be required to cover the entire target organ.

[0150] The scan box size, its lower and upper ends can be estimated by the ML model M, as can be used on the monitoring region finder MRF, which estimates not only the m-ROIm0, but also the applicable scan box size. Alternatively, the scan box size is specified in the imaging protocol and retrieved from the graphic display generator GDG and used to draw the scan box, as Figure 7 As shown. Alternatively, the scan frame SB is still manually marked by the user using the user interface UI in a graphical manner. As a further alternative, the vessel segmenter SEG estimates the scan frame and the vessel segmentation s(VS). The imaging protocol information can be used as background information for this estimation.

[0151] In some embodiments, the act of placing the slider SL in the final position may automatically initiate (by interacting with the monitoring system MS) a scan at the corresponding start / end positions of the target organ according to the scan frame SB and thereby avoid movement of the table PS that might otherwise be required to cover the entire target organ TAF.

[0152] Thus, in an embodiment, the reconstruction box SB planning may be coupled to the adjustment of the bolus tracking position m according to the user interface UI.

[0153] It can be understood from the disclosure of this article that Figure 6 、 7 The diagrams are highly schematic and merely illustrative of embodiments. Therefore, the specific configuration and drawing of the slider SL, vessel / organ segmentation s, centerline CL, wall W, pop-up windows CL1-3, etc. are exemplary, and any modifications of any of these elements are contemplated herein as long as they support the aforementioned advantages and enable guidance functionality for rapid, consistent, reproducible, and accurate placement of the monitoring region of interest (m-ROI) in (preferably 3D) plain film scans.

[0154] Now refer to Figure 8 , which shows a flow chart of a method for facilitating a contrast agent-assisted image protocol, particularly in finding and adjusting the location and extent of a monitoring region based on a graphic display generator and its graphic display as described above. However, it should be understood that the steps described below are not necessarily related to the system as described above.

[0155] At step S810 , a segmentation s of a target vessel VS in a plain film low-dose reconstructed volume V0 and an initial indication of a monitoring position for the segmentation are received. The plain film low-dose reconstructed volume V0 may also be received in this manner.

[0156] In step S820, the segmentation with an indication of the current monitoring position is visualized against the background of the view of the plate body V in a graphical display. This can be done, for example, as an overlay graphic on the plate image. The current position of the bolus monitoring area can be indicated by a slider graphical element LS having a shape (such as an ellipse, a circle, etc.) that is sized to correspond to the width of the segmentation at the current position. The slider S GUI widget is preferably inside the segmentation.

[0157] At step S830 , the event handler monitors a request from a user to change the location of the current monitoring area.

[0158] If such a request is received, the monitoring position is changed accordingly by repositioning the slider in step S840.

[0159] Preferably, the user request received at step S840 to change the slider position is modified so that the apparent movement of the graphical slider from the current position on the segmentation to the newly requested position is constrained to move only along the segmentation. Thus, the repositioning movement is locked to a corresponding tangential direction to the segmentation centerline. Thus, the slider is moved to the new position on and along the centerline. Any other directional components in the request are transformed (e.g., by projection) to act only along the centerline of the elongated segmentation / volume of the vessel.

[0160] Optionally, and in addition, in step S840, the size (e.g., width) of the shape of the graphical indicator of the monitoring area is automatically adjusted to follow and vary with the width of the segmentation, so that the graphical slider SL always remains within the perimeter of the segmentation. Preferably, the size is enlarged or reduced according to the possibly varying width of the segmentation, so that the slider SL slides along and contacts the boundary portion of the segmentation drawn in the visualization.

[0161] At step S850, the graphical display is drawn to include additional visualization(s), as desired, such as any one or more of the following: a scan box for later tracker imaging / information regarding bolus arrival / transit and / or distance to landmarks / a separate graphical indication of the vessel wall (outline, highlighting, etc.).

[0162] Landmark distances and crossing / arrival times are relative to the current position of the monitoring area as set by the slider.

[0163] The scan frame can be indicated as a graphical indicator, such as a rectangle or a square. The scan frame marks the area where projection data is to be collected for trajectory imaging and / or final angiographic image acquisition. The scan frame volume includes the monitoring area and the target anatomical feature TAF, as well as optionally one or more landmarks. The scan frame visualization is preferably drawn to change in conjunction with changes in the position request of the monitoring area. Preferably, one of the ends of the scan frame (e.g., one of the edges of the edge of the rectangular representation) is drawn and positioned so as to pass through the currently indicated position of the slider element.

[0164] The step S850 of drawing a graphical display may also include a dedicated visualization of the vessel boundaries (separate from the visualization of the main segmentation body).

[0165] After one or more requests to change the position of the monitoring location, a satisfactory position / size / orientation for the monitoring region m-ROI is established, a corresponding approval signal is issued at step S860, and the coordinates of the currently indicated position of the slider SL are transmitted to the imaging device to request the acquisition of a low-dose tracker projection image at said location and its reconstruction to generate a series of tracker images at step S870, allowing monitoring of image value changes caused by the arrival of the bolus at said location.

[0166] At step S880 , the tracker image at the indicated location is monitored for changes in image values ​​indicative of an impending bolus.

[0167] Once it is concluded at step S870 that a sufficient amount of contrast agent has accumulated to the downstream target anatomical feature, the TAF contrast agent concentration has entered the plateau phase PP, and a second signal for projection data acquisition is issued at step S890 to acquire a fully contrasted diagnostic projection image at a higher dose, based on which the contrast target image volume V can be reconstructed at step S900.

[0168] The segmenter SEG that can be used to calculate the (vessel VS) segmentation s of the plain film image V0 can be ML-based. In the ML approach, an ML model (such as a convolutional neural network (CNN) or other) is trained based on training data. The training data can include a plain film input image x. The plain film input image x (indeed, any plain film image) has very poor contrast and may not always be reliably or even impossible to annotate with respect to the ground truth m-ROI, even for human experts. In this case, a training data generator system can be operable to generate training data pairs (x, y) based on noise simulation as follows. A set of existing historical 3D diagnostic images (spectral or non-spectral images) of the general body part of interest for which the model is to be trained is located in a database query in a medical database, such as in a PACS or other. In such diagnostic images, clinical experts can easily implement annotations to define the location and extent of the m-ROI. The high IQ (image quality) of the diagnostic images used for annotation is then artificially reduced by simulating noise and adding this noise to the diagnostic images, thereby simulating the low-dose effect in plain film imaging and thus obtaining artificially generated samples that represent instances of the plain film volume with a good approximation. Thus, the noise-corrupted 3D image samples can be used as training inputs x, while the annotations on the high-quality images serve as the associated ground truth y. Therefore, the training data generator system can include a noise simulator and a noise adder to generate as many training data pairs as needed according to the above principles. However, as observed above, the facilitator system FS can be used with any segmenter system, whether they are ML-based or not.

[0169] The components of the facilitator system FS may be implemented as one or more software modules running on one or more general purpose processing units PU (e.g., a workstation associated with an imager IA), or on a server computer associated with a group of imagers.

[0170] Alternatively, some or all components of the facilitator system FS may be implemented in hardware (e.g., a suitably programmed microcontroller or microprocessor, such as an FPGA (field programmable gate array)), or as a hard-wired IC chip, application-specific integrated circuit (ASIC) integrated into the imaging system IA. In another embodiment, the facilitator system FS may be implemented in part software and part hardware.

[0171] The different components of the facilitator system FS may be implemented on a single data processing unit PU. Alternatively, some or more components are implemented on different processing units PU, possibly arranged remotely in a distributed architecture and connected in a suitable communication network (e.g., in a cloud setup or a client-server setup, etc.).

[0172] One or more features described herein can be configured or implemented as / with circuits encoded in a computer-readable medium and / or a combination thereof. The circuits may include discrete and / or integrated circuits, systems on a chip (SOCs) and combinations thereof, machines, computer systems, processors and memories, computer programs.

[0173] In a further exemplary embodiment of the present invention, a computer program or a computer program element is provided, which is characterized in that it is adapted to execute the method steps of the method according to one of the preceding embodiments on a suitable system.

[0174] Therefore, the computer program element can be stored on a computer unit, which can also be part of an embodiment of the present invention. The computer unit can be adapted to perform the steps of the method described above or to induce the performance of the steps of the method described above. In addition, it can be adapted to operate components of the apparatus described above. The computer unit can be adapted to automatically operate and / or execute user commands. The computer program can be loaded into a working memory of a data processor. The data processor can thus be equipped to perform the method of the present invention.

[0175] This exemplary embodiment of the invention covers both a computer program that right from the beginning uses the invention and a computer program that by means of an up-date turns an existing program into a program that uses the invention.

[0176] Furthermore, the computer program element can provide all necessary steps for implementing the procedure of an exemplary embodiment of the method as described above.

[0177] According to a further exemplary embodiment of the present invention, a computer-readable medium, for example a CD-ROM, is proposed, wherein the computer-readable medium has a computer program element stored on the computer-readable medium, the computer program element being described in the preceding section.

[0178] The computer program may be stored and / or distributed on a suitable medium, in particular but not necessarily a non-transitory medium, such as an optical storage medium or a solid-state medium provided together with or as part of other hardware, but the computer program may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0179] However, the computer program may also be present on a network such as the World Wide Web and can be downloaded from such a network into the working memory of a data processor. According to a further exemplary embodiment of the present invention, a medium for making a computer program element available for downloading is provided, which computer program element is arranged to perform a method according to one of the previously described embodiments of the present invention.

[0180] It should be noted that embodiments of the present invention have been described with reference to different subject matters. Specifically, some embodiments are described with reference to method-type claims, while other embodiments are described with reference to apparatus-type claims. However, those skilled in the art will appreciate from the above and following descriptions that, unless otherwise indicated, any combination of features relating to different subject matters, in addition to any combination of features belonging to one type of subject matter, is also considered disclosed by this application. However, all features can be combined to provide synergistic effects that exceed the simple sum of the features.

[0181] Although the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary rather than restrictive. The present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention from a study of the drawings, the disclosure, and the appended claims.

[0182] In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may perform the functions of several items recited in the claims. The fact that specific measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope. Such reference signs may consist of numbers, letters, or any alphanumeric combination.

Claims

1. A system (FS) for facilitating contrast agent-based tomographic imaging, the system comprising: an input interface (IN) for receiving a 3D plain film image volume (V0) of at least part of a patient (PAT) acquired by a tomographic imaging device (IA) in a preparation phase prior to a contrast agent-assisted imaging phase, said 3D plain film image volume including segmentation(s) of blood vessels (VS) through which a contrast agent is to pass in a later contrast agent-assisted imaging phase; a graphic display generator (GDG) configured to generate a graphic display (GD) of a graphical user interface (GUI) for display on a display device (DD), said graphic display (GD) comprising a visualization of said segmentation and a visualization of a slider element (SL) indicating a reference position (m-ROI) along said segmentation, said reference position being suitable for monitoring the presence of contrast agent associated with at least one target anatomical feature (TAF) in said later contrast agent-assisted imaging phase; as well as an event handler (EH) configured to, upon receipt of user input, instruct said graphical display generator (GDG) to update said graphical display (GD) so as to cause said slider element (SL) to slide along said segmentation, said slider thereby indicating one or more different such reference positions.

2. The system according to claim 1, wherein: The graphic display generator (GDG) is operable to adjust the spatial extent of the slider element to correspond to and vary with geometric aspects of the segmentation at the different reference positions.

3. A system according to any one of the preceding claims, wherein The graphic display generator (GDG) is operable to lock the slider element into an orientation defined by the segmentation.

4. The system according to claim 3, wherein: The direction is based on the centerline of the segmentation.

5. A system according to any one of the preceding claims, wherein The visualization of the segmentation is configured to clearly represent a wall portion (W) of the blood vessel (VS).

6. A system according to any one of the preceding claims, wherein The graphic display generator (GDG) is operable to cause the graphic display to include information regarding: i) the distance of the at least one target anatomical feature (TAF) to a) the reference position of the blood vessel corresponding to the current slider position and / or b) the distance of the at least one target anatomical feature (TAF) to one or more anatomical landmarks, and / or ii) an estimated contrast agent arrival time at the reference position.

7. The system according to any one of the preceding claims, comprises an output interface (OUT) for transmitting a user-selected reference position of the one or more reference positions to the imaging device for defining one end of a subset in the image domain, and the imaging device is to collect projection data about the subset during the imaging phase.

8. A system according to any one of the preceding claims, wherein A graphical display generator (GFDG) is operable to generate said graphical display (GD) to further comprise a visualization of said subset, wherein said slider element is located at said one end of said visualization (SB) of said subset.

9. The system according to any one of the preceding claims 1-8 comprises an output interface (OUT) for transmitting a user-selected reference position among the one or more reference positions to instruct the imaging device (IA) to acquire a first set of projection data when the contrast agent propagates in the patient, and the system comprises a reconstructor (RECON) for reconstructing a cross-sectional tracker image in a plane passing through the selected reference position with a first image quality based on the projection data.

10. The system according to any one of the preceding claims 6 to 8, wherein: The arrival times are based on hemodynamic modeling.

11. A system according to any one of the preceding claims, wherein The blood vessel includes at least a portion of the aorta.

12. A method for facilitating contrast agent-based tomographic imaging, comprising: receiving (S810) a 3D plain film image volume (V0) of at least part of a patient (PAT) acquired by a tomographic imaging apparatus (IA) in a preparation phase prior to a contrast agent assisted imaging phase, the 3D plain film image volume including segmentation(s) of blood vessels (VS) through which a contrast agent is to pass in a later contrast agent assisted imaging phase; generating (S820) a graphical display (GD) of a graphical user interface (GUI) for display on a display device (DD), said graphical display (GD) comprising a visualization of said segmentation and a visualization of a slider element (SL) indicating a reference position (m-ROI) along said segmentation, said reference position being suitable for monitoring the presence of contrast agent associated with at least one target anatomical feature (TAF) in said later contrast agent assisted imaging phase; as well as Upon receiving a user input a graphical display generator (GDG) is instructed (S840) to update said graphical display (GD) so as to slide said slider element (SL) along said partition, said slider thereby indicating one or more different such reference positions.

13. An imaging arrangement (IAR) comprising a system (SYS) according to any one of the preceding claims, and one or more of the following: the imaging apparatus (IA), the display device (DD), a contrast agent administration apparatus (ADA) for administering a contrast agent, a segmenter (SEG) configured to provide the segmentation(s), a bolus monitoring system (MS).

14. A computer program element adapted, when run by at least one processing unit, to cause the processing unit to perform the method according to claim 12.

15. At least one computer-readable medium, on which a program element according to claim 14 is stored.

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