Method of obtaining a value of an occlusion pressure of a compartment

Abstract

In a method of obtaining a value of an occlusion pressure of a compartment, in particular a blood vessel, a time series of ultrasound image frames of a region of tissue including the compartment is obtained during a time interval. An occlusion state of the compartment is observed during the time interval. A varying external pressure is exerted on the region of tissue during the time interval, wherein the external pressure is chosen in such a way that the compartment changes between a non-occluded state to an occluded state at least twice during the time interval. A progression of external pressure is measured during the time interval and external pressure values (41) assigned to the ultrasound image frames are stored. In the time series of ultrasound image frames image frames are identified that correspond to a change between the non-occluded state and the occluded state of the compartment. The value of the occlusion pressure (44) is determined from the external pressure values (41) assigned to the identified image frames.

Description

[0001] Method of obtaining a value of an occlusion pressure of a compartment

[0002] Technical Field

[0003] The invention relates to a method of obtaining a value of an occlusion pressure of a compartment, in particular a blood vessel. It further relates to a device for obtaining a value of an occlusion pressure of a compartment, in particular a blood vessel.

[0004] Background Art

[0005] There are various applications in which an occlusion pressure of a compartment of the human or animal body, in particular a blood vessel such as a vein or artery, is determined. They serve to determine blood pressure or the pressure prevailing in a vessel that is connected to the blood vessel or in direct mechanical contact with the blood vessel that is examined.

[0006] Corresponding methods may include the compression of the respective compartment by an external force until it is occluded. They require the steps of locating the correct compartment and measurement site, the identification of an occlusion of the vessel and the determination of the occlusion pressure.

[0007] Known methods are either complicated to operate, requiring the operation of at least two devices that are positioned at different locations on the patient's body, or prone to errors with respect to locating the correct compartment, reliably identifying the occlusion and / or determining the correct occlusion pressure.

[0008] 28947-WO - PR / qub Keller Schneider Patent-

[0009] 5. September 2025 und Markenanwalte AG Summary of the invention

[0010] It is the object of the invention to create a method pertaining to the technical field initially mentioned, that mitigates the aforementioned problems.

[0011] The solution of the invention is specified by the features of claim 1. According to the invention, the method comprises the steps of: a) during a time interval, obtaining a time series of ultrasound image frames of a region of tissue including the compartment; b) observing an occlusion state of the compartment during the time interval; c) exerting a varying external pressure on the region of tissue during the time interval, wherein the external pressure is chosen in such a way that the compartment changes between a non-occluded state to an occluded state at least twice during the time interval; d) measuring a progression of external pressure during the time interval and storing external pressure values assigned to the ultrasound image frames; e) in the time series of ultrasound image frames identifying image frames corresponding to a change between the non-occluded state and the occluded state of the compartment; and f) determining the value of the occlusion pressure from the external pressure values assigned to the identified image frames.

[0012] The time interval covers at least two independent occlusion events, i. e. two transitions between the non-occluded state and the occluded state of the compartment separated by a non-occluded phase. Preferably, the transition from the non-occluded to the occluded state is monitored. Therefore, preferably the minimum protocol is as follows:

[0013] 28947-WO - PR / qub Keller Schneider Patent-

[0014] 5. September 2025 und Markenanwalte AG i) placing the probe onto the patient's skin, looking for the compartment to be examined and adjusting the location of the probe until the compartment is centered in the ultrasound image; ii) make sure that the initial external pressure exerted onto the skin by the probe is small and that the compartment is non-occluded; iii) increasing the external pressure until the compartment is occluded (preferably the external pressure is increased even more to make sure that the occluded state has actually been achieved); iv) releasing the external pressure until the compartment is non-occluded again; v) increasing the external pressure again until the compartment is occluded again.

[0015] Steps iv) and v) may be repeated once or several times. In order to obtain reliable results with small statistical errors it is preferable to monitor at least 3-5 occlusion events. Preferably, each identified occlusion event will correspond to a unique identification of one of the ultrasound image frames. This correspondence may be direct (e. g. by storing a unique identification of the frame) or indirect (e. g. by storing a time stamp of the occlusion that may later be correlated with time stamps of the frames).

[0016] The occlusion state may be observed in real time, already during the measurement phase. This allows for adjusting the external pressure to further compress the compartment or release the compression. The observation may happen manually, on the basis of realtime ultrasound images that are displayed e. g. on a screen in the field of vision of the user. Alternatively or in addition, the occlusion state may be observed automatically, by tracking the deformation of the compartment. This allows for controlling a device for automatically applying more or less external pressure and / or for providing a feedback to the user requesting more or less external pressure.

[0017] 28947-WO - PR / qub Keller Schneider Patent-

[0018] 5. September 2025 und Markenanwalte AG Alternatively, the occlusion state of the compartment is only observed after the measurement phase, when replaying the time series of ultrasound image frames as discussed in more detail below. In this case, set values of the external pressure may be used, and the user is instructed to increase the external pressure until a set maximum value is reached and then to decrease the external pressure until a lower value is reached, which ensures that the compartment transitions to its non-occluded state.

[0019] During the measurement phase, after the compartment to be examined has been identified and the probe has been correspondingly placed, the probe will be held at the same position on the surface of the patient's skin for the entire series of measurements. It is only the external pressure that will be varied. That the probe is properly positioned during the measurement phase is preferably monitored based on real-time ultrasound images shown on a display in the field of view of the user. The monitoring may be done automatically, and the user may be alerted if there is a relevant positional change during the time interval.

[0020] Preferably, an external pressure value is assigned to any frame of the time series of ultrasound image frames, wherein the assigned value is a pressure value measured by a sensor essentially at the time of taking the ultrasound image frame, i. e. the stored sample rate of the external pressure values corresponds to that of the image frames. However, in principle, it is possible to have a stored sample rate of pressure values that is lower or higher than the image rate. In the first case, external pressure values may be obtained for image frames by interpolation if needed. In the second case, only some of the external pressure values or suitable averages of several external pressure values will be used. Usually, the actual sample rate of the sensor for the external pressure will be (considerably) higher than the frame rate, i. e. there will be a downsampling step to obtain the external pressure values to be assigned to the image frames and stored. This step may include suitable averaging procedures.

[0021] 28947-WO - PR / qub Keller Schneider Patent-

[0022] 5. September 2025 und Markenanwalte AG The occlusion of the compartment, in particular of the blood vessel, is identified based on the compartment's geometry under the influence of external pressure. In particular, the compartment or blood vessel is considered to be occluded when it is completely compressed, i. e. the walls of the compartment that run essentially perpendicular to the direction of the external force touch each other and the remaining distance between them is zero. This corresponds to blocking the medium flow through the vessel. This means that occlusion of a media-conducting vessel may be identified without the need for Doppler ultrasound, i. e. non-Doppler probes may be used. This reduces the complexity and costs of ultrasonic probes and processing hardware that may be used in the context of the invention. Nevertheless, the invention may be embodied with Doppler devices and images, respectively.

[0023] The invention is particularly suitable for the measurement of pressures in blood vessels, where it is assumed that the external pressure that is needed to occlude the vessel essentially corresponds to the internal pressure of the vessel. It may as well be used for the examination of other compressible compartments. In certain cases, it will be necessary to convert the external pressure to a value of the occlusion pressure. This may be done e. g. by a supervised machine learning model or by using conversion tables.

[0024] The inventive method may be implemented using a device comprising the following: a) an ultrasound probe comprising an ultrasound array for acquiring ultrasound images and a force sensor for measuring an external pressure exerted by the ultrasound probe to the skin of a patient; b) a processor adapted to receiving ultrasound image data and external pressure values from the ultrasound probe; storing a time series of ultrasound image frames corresponding to the received image data and external pressure values assigned to the ultrasound image frames;

[0025] 28947-WO - PR / qub Keller Schneider Patent-

[0026] 5. September 2025 und Markenanwalte AG simultaneously displaying the time series of ultrasound image frames and the assigned external values in a replay mode; receiving user input for identifying image frames corresponding between a nonoccluded and an occluded state of a compartment shown in the time series of ultrasound image frames; and determining the value of the occlusion pressure from the external pressure values assigned to the identified image frames.

[0027] The inventive method and device allow for an easy and reliable determination of the occlusion pressure of compartments, in particular blood vessels. Obtaining a number of measurements in a short time period reduces the statistical errors and ensures that errors affecting single measurements of the series may be identified. In addition, the procedure is intuitive for the user.

[0028] Preferably, at least some of the image frames are identified in the time series when replaying the time series of ultrasound image frames after the time interval. This means that the inventive method is divided into at least two phases: the measurement phase and the annotation phase. In the measurement phase, the actual measurements are taken, yielding the time series of ultrasound image frames and the assigned external pressure values. In the annotation phase, the ultrasound image frames are replayed, in particular in a video-like manner, and those frames are identified which correspond to occlusion events. This allows for reducing the workload on the user relating to the measurement as well as to the annotation and thus yields more reliable results.

[0029] Preferably, there are several replay options, in particular two or more of the following: a) replay in real time (replay speed 100%); b) replay in slow motion (replay speed < 100%); c) accelerated replay (replay speed > 100%);

[0030] 28947-WO - PR / qub Keller Schneider Patent-

[0031] 5. September 2025 und Markenanwalte AG d) replay frame-by-frame.

[0032] These options may be controlled in known ways, using e. g. scrollbars, forward / backward buttons, etc.

[0033] Preferably, when replaying the time series of ultrasound image frames, the external pressure values assigned to the frames are displayed simultaneously. This makes sure that all relevant information is shown and allows in particular for identifying potential inconsistencies or flaws.

[0034] Preferably, the external pressure values for at least a subsection of the time interval are shown simultaneously, in particular as a curve, and a value assigned to a currently displayed image frame is highlighted. This allows for easily navigating through the time series of image frames and for easily identifying those subsections of the time series relating to occlusion events. Highlighting may be effected e. g. by superposing a pointing object (e. g. a line) indicating the position on the curve which corresponds to the currently displayed ultrasound image.

[0035] In a preferred embodiment of the inventive method, a user is given the possibility of manually selecting ultrasound image frames to be identified as corresponding to the change between the non-occluded state and the occluded state. Selection is preferably done in the annotation (replay) phase and may consist in confirming that a presently displayed image frame is to be considered to correspond to an occlusion event, e. g. being the first frame showing the compartment completely occluded.

[0036] Preferably, the system prohibits an identification of several frames relating to the same occlusion event, e. g. by prohibiting the selection of several image frames having a distance in time falling below a certain threshold.

[0037] In some advantageous embodiments of the inventive method, a proposal for an image frame to be identified is automatically generated and the user is given the possibilities

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[0039] 5. September 2025 und Markenanwalte AG of confirming, discarding and adjusting the proposal. This makes the process simpler and faster. Adjusting the proposal may be enabled by providing forward / back buttons allowing for proceeding through the time series frame-by-frame.

[0040] For the automatic generation of the proposal, the compartment may be tracked in the ultrasound image frames and characteristic quantities relating to the compartment may be analyzed to identify the onset of occlusion. As an example, an area of the region of the ultrasound image representing the compartment may be tracked, and occlusion is deemed to happen when the area reaches a value of zero (i. e. the compartment vanishes). Alternatively, or in addition, linear quantities such as an extension in the direction of impact of the external pressure, or quantities characterizing the shape of the region representing the compartment may be used.

[0041] Preferably, the process includes a third phase after the measurement and annotation phase, namely the review phase. In this phase, the external pressure values assigned to the identified ultrasound image frames of the time interval are simultaneously displayed and any one of the values is selectable by the user in order to review the ultrasound image frame the selected value is assigned to as well as ultrasound image frames preceding and following this ultrasound image frame. This allows for obtaining a complete picture of the series of measurements.

[0042] Preferably, in the review phase, identified occlusions may be removed and adjusted. Also, it may be advantageous, if values or groups of values may be selectively excluded from analysis (in particular from calculating the occlusion pressure). Furthermore, it is preferred that additional occlusions may be added, if necessary.

[0043] Preferably, the external pressure is manually applied by pressing an ultrasound probe against the skin of the patient. This is the most simple and intuitive case. As mentioned above, the users may be assisted by specific proposals instructing them to increase or decrease the pressure.

[0044] 28947-WO - PR / qub Keller Schneider Patent-

[0045] 5. September 2025 und Markenanwalte AG Alternatively, a mechanism is provided that allows for automatically controlling the exerted external pressure based on a protocol and / or on a feedback loop based on measured external pressure values and / or the observed state of occlusion.

[0046] Preferably, the external pressure is measured using a force sensor on the ultrasound probe. Corresponding probes are available, see e. g. WO 23 / 104390 A1 of the applicant.

[0047] Force sensors may measure a force, e. g. based on the deformation or displacement of components due to the impact of the force or based on piezoelectric energy generated due to the impact. In the present context, pressure sensors are encompassed by the term "force sensor": they are based on the same measurement principles and basically output an equivalent value.

[0048] Preferably, the duration of the time interval is at least 3 s, in particular at least 6 s, most preferably at least 12 s.

[0049] On the one hand, this ensures that the temporal resolution of the image frames and the pressure values is sufficient to ensure that the moment of occlusion and the related value of external pressure is indeed captured. With higher temporal resolution (in particular image frame rate) shorter time intervals may be feasible. Preferably, the number of frames captured within the time interval is at least 50, preferably at least 80.

[0050] On the other hand, in particular when examining compartments that are affected by the pulsation of the blood flow and / or breathing movements, such as blood vessels, this ensures that the time interval covers several phases of the blood pulsation and breathing cycles. Experiments have shown that in the case of blood vessels a measurement cycle (occlusion-release) takes about 3-5 s, i. e. a duration of the time interval of 12-15s allows for about 3-5 measurements. In practice, it will be advantageous to foresee even longer time periods of about 1-2 min. The experiments have shown that those durations are

[0051] 28947-WO - PR / qub Keller Schneider Patent-

[0052] 5. September 2025 und Markenanwalte AG feasible, and this allows for taking at least about 10-20 measurements, thus reducing statistical error and allowing for the exclusion of questionable events.

[0053] Preferably, the value of the occlusion pressure is determined from the external pressure values assigned to the identified image frames by taking an average or median of the external pressure values. For taking the average or median, certain values (e. g. "outliers" or the lowest and highest values) may be disregarded. The selection of the values to be taken into account or to be disregarded, respectively, may be manual or automatic. A weighted average may be taken, wherein the weighting factors may depend e. g. on the position of a measurement in the time interval or external values (such as values relating to the pulse or breathing cycle, etc.).

[0054] Preferably, at least one further statistical quantity is obtained from the assigned external pressure values, the further statistical quantity being chosen from a maximum, a minimum, and a standard deviation. This allows for assessing the quality of the measurements and thus the determined value of the occlusion pressure.

[0055] The statistical quantities obtained from the sequences of measurements of the occlusion pressure allow for a reliable comparison of the results obtained at different points in time.

[0056] Preferably, a contour of the compartment is identified in image data representing the time series of ultrasound image frames and displayed superimposed on the image frames. This facilitates in particular the identification of an occlusion event. The identification and highlighting of the contour may be implemented in the measurement phase and / or the annotation (replay) phase.

[0057] The contour may be represented by an object of a predetermined shape, e. g. an ellipse, where parameters of the object (e. g. lengths, eccentricities, areas) as well as the object's position and potentially the object's angular orientation may be fitted to the

[0058] 28947-WO - PR / qub Keller Schneider Patent-

[0059] 5. September 2025 und Markenanwalte AG compartment identified in the image data. Alternatively, the contour follows the shape of the contour of the compartment as identified in the image data as closely as possible.

[0060] Preferably, at least some of the image frames corresponding to a change between the non-occluded state and the occluded state of the compartment are automatically identified in the time series by processing image data representing the time series of ultrasound image frames. The results of the automatic identification may be presented to the user for confirmation as described above or directly used for further processing.

[0061] In a preferred embodiment of the inventive method, the compartment is tracked along a plurality of image frames of the time series of ultrasound image frames, at least one geometric property of the tracked compartment is determined for each of the plurality of image frames, and the automatic identification of at least some of the image frames corresponding to a change between the non-occluded state and the occluded state of the compartment is based on the at least one geometric property.

[0062] Preferably, the image data is processed using a supervised machine learning method. Such methods may be used for the identification of the compartment contour as well as for the identification of occlusion events. They may be trained by manually highlighting the contour of the vessel or identifying frames relating to occlusion events by a user. If the results of the identification of occlusion events are presented to the user for confirmation, dismissal or adjustment, the feedback of the user may be directly used for retraining the underlying model, thus rapidly improving the suggestions.

[0063] As an alternative or in addition to machine learning, the image data may be processed by standard image processing algorithms using the known first or second order approaches.

[0064] Other advantageous embodiments and combinations of features come out from the detailed description below and the entirety of the claims.

[0065] 28947-WO - PR / qub Keller Schneider Patent-

[0066] 5. September 2025 und Markenanwalte AG Brief description of the drawings

[0067] The drawings used to explain the embodiments show:

[0068] Fig. 1 A representation of a scan screen of a graphical user interface (GUI) of an embodiment of a system according to the invention;

[0069] Fig. 2 a representation of the GUI during the measurement process with an open lumen;

[0070] Fig. 3 a representation of the GUI during the measurement process with an occluded lumen;

[0071] Fig. 4-6 representations of the GUI during the processing of a sequence of measurement frames;

[0072] Fig. 7-8 representations of the results screen of the GUI;

[0073] Fig. 9 a representation of the history screen of the GUI;

[0074] Fig. 10 a flowchart of the inventive method for obtaining a value of an occlusion pressure of a compartment; and

[0075] Fig. 11 a schematic diagram of a system according to the invention.

[0076] In the figures, the same components are given the same reference symbols.

[0077] Preferred embodiments

[0078] The Figures 1 -9 illustrate the operation of an embodiment of a measuring system according to the invention. Fig. 10 shows a flowchart of the inventive method for obtaining a value of an occlusion pressure of a compartment.

[0079] After startup of the system, the user is presented with a welcome screen. This screen allows for starting a measurement process by pressing a "Start" button as well as for

[0080] 28947-WO - PR / qub Keller Schneider Patent-

[0081] 5. September 2025 und Markenanwalte AG consulting the results of previous measurements by pressing a "Measurement History" button.

[0082] By pressing the start button, the user will be presented with the scan screen as shown in Fig. 1. The ultrasound image 1 is displayed in real time, together with the pressure indicator 2 in mmHg close to the right top corner of the screen. In this right top corner an indication 3 including the date and time of the measurement as well as an identification number is also displayed. Further, the ultrasound frequency 4 is indicated (here 15 MHz).

[0083] Along the left edge of the display, the following parameters are displayed, and buttons allow for adjusting the respective parameters: i) the displayed depth 5 of the image in mm together with a first button 5.1 for reducing the displayed depth and a second button 5.2 ("+") for increasing the displayed depth; ii) the gain 6 in dB together with a first button 6.1 for reducing the gain and a second button 6.2 ("+") for increasing the gain; iii) the focus value 7 together with a first button 7.1 for reducing the focus value and a second button 7.2 ("+") for increasing the focus value; iv) the frequency 8 together with a first button 8.1 ("10 MHz") for choosing a frequency of 10 MHz and a second button 8.2 ("15 MHz") for choosing a frequency of 15 MHz; the button representing the presently active value is highlighted (here the second button 8.2).

[0084] Below these elements, in the bottom left corner, a "Start Recording" button 9 is arranged.

[0085] In a first step 101, a pressure sensor of the probe is calibrated. Prior to calibration, the pressure indicator 2 of the GUI is missing and the user is instructed to holding the CP

[0086] 28947-WO - PR / qub Keller Schneider Patent-

[0087] 5. September 2025 und Markenanwalte AG Probe in his / her hand in a certain orientation, without exerting any pressure on the membrane. The probe then calibrates automatically. During the calibration, the front membrane of the CP Probe must only be in contact with the surrounding air, so that there is no contact pressure. The correspondingly measured pressure value is considered to relate to a pressure of 0 mmHg (reference).

[0088] The pressure indicator 2 must indicate 0 mmHg before the measurement begins. This signalizes that the calibration is complete. Then, in a further step 102, the user places the head of the probe on the skin of the patient, at the location where the vessel to be examined is assumed to be. In the scan screen, the user can search for and visualize the target area and correspondingly relocate the probe. As soon as the correct location is found, the user presses the "Start Recording" button 9 (step 103). This starts the recording of a sequence of ultrasound image frames. The user holds the CP Probe perpendicular to the skin surface, keeps its position and progressively increases the contact pressure (step 104).

[0089] During this process, the display is switched to the view shown in Figure 2. Again, the ultrasound image 1 is displayed in real time, together with the pressure indicator 2 in mmHg close to the right top corner of the screen. In this right top corner an indication 3 including the date and time of the measurement as well as an identification number is also displayed. Further, the ultrasound frequency 4 is still indicated.

[0090] However, the buttons along the left edge of the display are replaced by an indication 11 of the recording time in minutes and seconds ("mm:ss") as well as a "Cancel" button 12 and a "Finish Recording" button 13.

[0091] Lumina representing vessels are identified using an algorithm described in more detail below and the edges of the identified lumina are highlighted, cf. edge indication 14. If more than one lumen are identified in the image, in a first configuration a single lumen is highlighted, namely the one closest to the central axis of the ultrasound device

[0092] 28947-WO - PR / qub Keller Schneider Patent-

[0093] 5. September 2025 und Markenanwalte AG (corresponding to the central vertical axis of the displayed ultrasound image). In a second configuration, all lumen are highlighted simultaneously. Choice between the configurations may be done prior to the measuring process in a configuration menu and / or using additional buttons (not present in the shown embodiment) in the live view shown in Fig. 2.

[0094] Characteristic quantities relating to the lumen may be used for further processing the captured data, e. g. for automatically generating a proposal for the frame corresponding to the occlusion of the vessel. In certain embodiments, each lumen may be represented by an ellipse, wherein the area and / or the lengths of its major and minor axis and / or the ratio between these lengths and / or the ellipse's eccentricity are used as characteristic quantities. Occlusion may be considered e. g. to correspond to one of the following events: the area reaches zero; the length of the minor axis reaches zero; the ratio between the minor and the major axis reaches zero; the eccentricity reaches 1.

[0095] In the processing, two or more of the quantities and / or events may be combined. The quantities may be processed directly or as components of input vectors into a machine learning model.

[0096] The user checks whether the vessel has collapsed due to the external pressure (decision 105). If not, the pressure is further increased (step 104). A collapse is identified (see Fig. 3) when the edge indication disappears (in variants of the system, the edge indication will not disappear but change shape, e. g. to a point or small cross). As can be seen from Fig. 3, the lumen disappears 11 seconds into the recording (see indication 11), at a pressure of 10 mmHg (as shown by the pressure indicator 2).

[0097] 28947-WO - PR / qub Keller Schneider Patent-

[0098] 5. September 2025 und Markenanwalte AG After identification of a collapse, the vessel is decompressed by reducing the externally applied pressure (step 106) at least until the lumen reappears in the ultrasound image (decision 107). The user repeats the compression-decompression cycle as many times as necessary, passing several occlusion events. After a sufficient number of cycles (decision 108), the user removes the probe from the patient and presses the "Finish Recording" button 13 (step 109). The video representing the sequence of frames will be stored.

[0099] The user can cancel the recording at any time with the "Cancel" button 12 and will go back to the scan screen. The video representing the sequence of frames will be discarded.

[0100] A warning message with a countdown will alert the userwhen approaching the maximum possible video duration of 2 minutes. The video recording will automatically stop at 2 minutes (decision 108). Again, the video representing the sequence of frames is stored.

[0101] After the actual measurement phase with recording of the ultrasound image frames, the user can view the video recording (step 110) and mark occlusion frames (step 111). The corresponding user interface is shown in Figure 4. An ultrasound frame 21 is displayed in real time, together with the respective pressure value 22 in mmHg close to the right top corner of the screen. In this right top corner, the indication 23 including the date and time of the measurement represented by the frame as well as the identification number is also displayed. Further, the ultrasound frequency 24 with which the frame was generated is indicated.

[0102] Along the bottom edge of the display, a curve 25 representing the progression of external pressure with time is displayed. Using a button 26, the user may play or halt the video, wherein the button 26 shows "Play" when the video is paused and "Pause" when the video is playing.

[0103] When the video is playing, the external pressure curve 25 moves in such a way that the central vertical line indicates the point on the curve 25 relating to the presently displayed

[0104] 28947-WO - PR / qub Keller Schneider Patent-

[0105] 5. September 2025 und Markenanwalte AG frame. When the video is halted, the user may add a point in time relating to an occlusion by pressing an "Add" button 27. Furthermore, the user may move frame by frame using arrow buttons 28.1, 28.2 in order to identify the exact frame relating to the onset of occlusion. Fast browsing through the video is possible using a scroll bar 29 below the external pressure curve 25.

[0106] When an occlusion is added, a marker is placed on the pressure timeline and a counter of the number of marked occlusions is updated (see Figure 5). This is shown by a further indicator 30 below the pressure value 22. The occlusion markings are shown in the external pressure curve 25 and consecutively numbered. As soon as at least one occlusion is marked, the user may press an "Edit" button 31 above the "Add" button 27. This allows for editing the position of an occlusion along the timeline or removing occlusion markings (by pressing button 27, which will be changed to "Remove" in this phase of operation). Displayed frames that correspond to an occlusion are highlighted with a light blue contour.

[0107] When the user has correctly marked all occlusions (cf. Figure 6) (decision 112), he or she may press the "Done" button 32 above the "Play / Pause" button 26 (step 113). The frame numbers relating to the identified occlusions will then be stored together with the other data relating to the respective series of measurements and the user will be directed to the results screen shown in Figure 7 (step 114).

[0108] This screen is divided into three sections arranged one above the other. In the central section, the marked occlusions 41 are represented. Each marked occlusion is referred to by a point in a coordinate system, having time on the horizontal axis and external pressure on the vertical axis. In the top section, the following information is displayed: i) the number 42 of marked occlusions; ii) the minimum external pressure 43 assigned to one of the occlusions; iii) the maximum external pressure 44 assigned to one of the occlusions;

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[0110] 5. September 2025 und Markenanwalte AG iv) the average external pressure 45 assigned to the occlusions; v) the standard deviation 46.

[0111] In the bottom section, four buttons are arranged one next to the other, from left to right: i) a first button 51 "Discard Result", which allows for discarding the entire measurement series; ii) a second button 52 "Save" for saving the results and leaving the results screen; iii) a third button 53 "Review Frames" for returning to the user interface as described above, in connection with Figures 4-6 showing the marked frame relating to the selected marker in the central section (decision 115), if any; and iv) a fourth button 54 "Measurement History" to proceed to the history screen, this button is only available after the measurement has been previously saved or discarded.

[0112] The user can click on any marker in the central section to see more details about the occlusion (occlusion pressure, occlusion timestamp in the recording), cf. Fig. 8. A corresponding window 55 is displayed adjacent to the marker and the number of occlusion, the corresponding pressure value and the time into the measurement process are shown for the respective marked occlusion. The window 50 features a "back" arrow 56 and a "forward" arrow 57. They allow for easily switching to the previous or next marked occlusion, respectively.

[0113] After click on the "Measurement history" button 54 (step 116), the history screen as shown in Fig. 9 is displayed (step 117). The history screen is always available to the user to review previously saved recordings. The history screen reports the following data, line by line for the respective measurement series, from left to right: an ID number of the measurement series; date and time of the measurement series;

[0114] 28947-WO - PR / qub Keller Schneider Patent-

[0115] 5. September 2025 und Markenanwalte AG the number of marked occlusions;

[0116] - the average occlusion pressure;

[0117] - the duration of the measurement series; and

[0118] - the serial number of the system that has been used for taking the measurements.

[0119] By clicking on a row, the corresponding result page (cf. Fig. 7, 8) is shown to the user.

[0120] The Figure 11 schematically represents an ultrasound imaging device providing B-mode ultrasound images of a compartment 82. The probe 60 includes an ultrasound array 61 for transmitting and receiving ultrasound waves 66 in a manner known as such. On its contact surface with the skin surface 81 of a subject, the probe 60 is provided with a flexible membrane 62, delimiting a fluid chamber 63. A pressure sensor 64 is provided for measuring the pressure within the fluid chamber 63. The ultrasound array 61 and the pressure sensor 64 are connected to a probe processor 65 for preprocessing the received data, controlling the probe's components and connecting the probe to external devices. A corresponding device is described in WO 23 / 104390 A1 of the same applicant.

[0121] The probe 60 is connected to unit 70 including a processor 71 receiving in particular the ultrasound image data and the pressure values obtained from the pressure sensor 64. The processor accesses a store 72, in particular for storing the data received from the probe 60. The processor 71 is also connected to a touchscreen 73, which allows for displaying the graphical user interface as described above and for receiving user input.

[0122] The invention is not restricted to the described embodiment. In particular, the design of the GUI as well as the display and interaction elements may be arranged differently. Some of the elements may be missing or further elements may be added.

[0123] 28947-WO - PR / qub Keller Schneider Patent-

[0124] 5. September 2025 und Markenanwalte AG

Claims

Claims1. A method of obtaining a value of an occlusion pressure of a compartment, in particular a blood vessel, comprising the steps of: a) during a time interval, obtaining a time series of ultrasound image frames of a region of tissue including the compartment; b) observing an occlusion state of the compartment during the time interval; c) exerting a varying external pressure on the region of tissue during the time interval, wherein the external pressure is chosen in such a way that the compartment changes between a non-occluded state to an occluded state at least twice during the time interval; d) measuring a progression of external pressure during the time interval and storing external pressure values assigned to the ultrasound image frames; e) in the time series of ultrasound image frames identifying image frames corresponding to a change between the non-occluded state and the occluded state of the compartment; f) determining the value of the occlusion pressure from the external pressure values assigned to the identified image frames.

2. The method as recited in claim 1, wherein at least some of the image frames are identified in the time series when replaying the time series of ultrasound image frames after the time interval.

3. The method as recited in claim 2, wherein when replaying the time series of ultrasound image frames the external pressure values assigned to the frames are displayed simultaneously.28947-WO - PR / qub Keller Schneider Patent-5. September 2025 und Markenanwalte AG4. The method as recited in claim 3, wherein the external pressure values for at least a subsection of the time interval are shown simultaneously, in particular as a curve, and wherein a value assigned to a currently displayed image frame is highlighted.

5. The method as recited in one of claims 2 to 4, wherein a user is given the possibility of manually selecting ultrasound image frames to be identified as corresponding to the change between the non-occluded state and the occluded state.

6. The method as recited in claim 5, wherein a proposal for an image frame to be identified is automatically generated and wherein the user is given the possibilities of confirming, discarding and adjusting the proposal.

7. The method as recited in any of claims 1 to 6, wherein the external pressure values assigned to the identified ultrasound image frames of the time interval are simultaneously displayed and wherein any one of the values is selectable by the user in order to review the ultrasound image frame the selected value is assigned to as well as ultrasound image frames preceding and following this ultrasound image frame.

8. The method as recited in any of claims 1 to 7, wherein the external pressure is manually applied by pressing an ultrasound probe against the skin of the patient.

9. The method as recited in claim 8, wherein the external pressure is measured using a force sensor on the ultrasound probe.

10. The method as recited in any of claims 1 to 9, wherein the duration of the time interval is at least 3 s, in particular at least 6 s, most preferably at least 12 s.

11. The method as recited in any of claims 1 to 10, wherein the value of the occlusion pressure is determined from the external pressure values assigned to the identified image frames by taking an average or median of the external pressure values.28947-WO - PR / qub Keller Schneider Patent-5. September 2025 und Markenanwalte AG12. The method as recited in claim 1 1, wherein at least one further statistical quantity is obtained from the assigned external pressure values, the further statistical quantity being chosen from a maximum, a minimum, and a standard deviation.

13. The method as recited in any of claims 1 to 12, wherein a contour of the compartment is identified in image data representing the time series of ultrasound image frames and displayed superimposed on the image frames.

14. The method as recited in any of claims 1 to 13, wherein at least some of the image frames corresponding to a change between the non-occluded state and the occluded state of the compartment are automatically identified in the time series by processing image data representing the time series of ultrasound image frames.

15. The method as recited in claim 14, wherein the compartment is tracked along a plurality of image frames of the time series of ultrasound image frames, wherein at least one geometric property of the tracked compartment is determined for each of the plurality of image frames and wherein the automatic identification of the at least some of the image frames corresponding to a change between the non-occluded state and the occluded state of the compartment is based on the at least one geometric property.

16. The method as recited in one of claims 13 to 15, wherein the image data is processed using a supervised machine learning method.

17. Device for obtaining a value of an occlusion pressure of a compartment, in particular a blood vessel, comprising: a) an ultrasound probe comprising an ultrasound array for acquiring ultrasound images and a force sensor for measuring an external pressure exerted by the ultrasound probe to the skin of a patient; b) a processor adapted to28947-WO - PR / qub Keller Schneider Patent-5. September 2025 und Markenanwalte AGreceiving ultrasound image data and external pressure values from the ultrasound probe; storing a time series of ultrasound image frames corresponding to the received image data and external pressure values assigned to the ultrasound image frames; simultaneously displaying the time series of ultrasound image frames and the assigned external values in a replay mode; receiving user input for identifying image frames corresponding between a non-occluded and an occluded state of a compartment shown in the time series of ultrasound image frames; determining the value of the occlusion pressure from the external pressure values assigned to the identified image frames.28947-WO - PR / qub Keller Schneider Patent-5. September 2025 und Markenanwalte AG

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