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EP-4637560-B1 - EVALUATION OF BLOOD FLOW PARAMETERS

EP4637560B1EP 4637560 B1EP4637560 B1EP 4637560B1EP-4637560-B1

Inventors

  • FLORENT, RAOUL
  • THIS, Alexandre
  • SCHMITT, HOLGER
  • LEVRIER, CLAIRE
  • VAN DER HORST, Arjen

Dates

Publication Date
20260513
Application Date
20231218

Claims (15)

  1. A system (100) for evaluating blood flow parameters, the system comprising one or more processors (110) configured to: receive (S110) angiographic image data (120) representing a motion of a front (130 1 , 130 2 ) of an injected contrast agent along a vessel (140) in each of a first haemodynamic state and a second haemodynamic state; analyse (S120) the angiographic image data (120) to determine a transit time or a transit velocity, for the vessel (140) in each state, the transit time in each state being calculated based on a time taken for the front to pass between a proximal position (150 p ) in the vessel and a distal position (150 d ) in the vessel, and the transit velocity in each state being calculated based on one or more distances traversed by the front between the proximal position (150 p ) in the vessel and the distal position (150 d ) in the vessel, and one or more corresponding time intervals; output (S130) a value of one or more blood flow parameters (160) for the vessel (140), the value of the one or more blood flow parameters being calculated based on the values of the transit times or the values of the transit velocities; and output (S140) sequences of a first angiogram (170 1 ) and a second angiogram (170 2 ), the first angiogram and the second angiogram being generated from the angiographic image data (120) and depicting the motion of the fronts (130 1 , 130 2 ) along the vessel (140) in the first haemodynamic state and the second haemodynamic state, respectively; and wherein the sequences of the first angiogram (170 1 ) and the second angiogram (170 2 ) are synchronised such that the fronts in both angiograms leave the proximal position (150 p ) in the vessel simultaneously.
  2. The system according to claim 1, wherein the sequences of the first angiogram (170 1 ) and the second angiogram (170 2 ) repetitively depict the motion of the fronts (130 1 , 130 2 ) along the vessel (140) in the first haemodynamic state and the second haemodynamic state, respectively; wherein the motion of the fronts (130 1 , 130 2 ) depicted in the first angiogram (170 1 ) and the second angiogram (170 2 ), is synchronised such that in each repetition the fronts in both angiograms simultaneously leave the proximal position (150 p ) in the vessel (140).
  3. The system according to claim 2, wherein the sequences of the first angiogram and second angiogram are synchronised such that a faster moving front depicted in the first angiogram is paused or stalled when the front has reached the distal position in the vessel.
  4. The system according to claim 2, wherein a delay occurs prior to each repetition, and wherein during the delay the fronts (130 1 , 130 2 ) in both angiograms (170 1 , 170 2 ) are depicted at the proximal position (150 p ) in the vessel (140).
  5. The system according to claim 2, wherein a delay occurs after each repetition, and wherein during the delay the fronts (130 1 , 130 2 ) in both angiograms (170 1 , 170 2 ) are depicted at the distal position (150 d ) in the vessel (140).
  6. The system according to any previous claim, wherein the received angiographic image data (120) comprises a temporal sequence of images representing the motion of the front (130 1 , 130 2 ) of the injected contrast agent along the vessel (140) in each of the first haemodynamic state and the second haemodynamic state, and wherein the one or more processors (110) are configured to: generate the first angiogram (170 1 ), and the second angiogram (170 2 ), from the temporal sequence of images representing the first haemodynamic state and the second haemodynamic state, respectively; and analyse the angiographic image data (120) to determine the transit time or the transit velocity for the vessel (140) in each of the first haemodynamic state and the second haemodynamic state, by: tracking a position of the front (130 1 , 130 2 ) in the temporal sequence of images; defining the proximal position (150 p ) and the distal position (150 d ) in the vessel (140); and calculating the transit time or the transit velocity, based on the tracked positions of the front in relation to the proximal position (150 p ) and the distal position (150 d ).
  7. The system according to claim 6, wherein the calculating the transit velocity based on the tracked positions comprises: calculating, for the tracked positions, a corresponding distance (190) traversed by the front (130 1 , 130 2 ) along the vessel (140) from a reference position in the vessel; calculating an average velocity of the front (130 1 , 130 2 ) between the proximal position (150 p ) and the distal position (150 d ), the average velocity being calculated so as to minimise, for a plurality of images in the temporal sequence in which the front is located between the proximal position and the distal position, a difference between the distance traversed by the front along the vessel (140) in the image and a distance traversed by the front along the vessel at the average velocity; and using the average velocity as the transit velocity.
  8. The system according to claim 6 or claim 7, wherein the one or more processors (110) are further configured to: overlay each of the first angiogram (170 1 ), and the second angiogram (170 2 ) with a marker depicting the front (130 1 , 130 2 ) of the injected contrast agent in the respective angiogram.
  9. The system according to any one of claims 6 - 8, wherein the one or more processors (110) are further configured to: track a path of the injected contrast agent in the temporal sequence of images; and overlay each of the first angiogram (170 1 ) and the second angiogram (170 2 ) with a trace depicting the tracked path of the injected contrast agent in the respective angiogram.
  10. The system according to claim 9, wherein the trace depicts the centerline of the tracked path of the injected contrast agent in the temporal sequence of images, and wherein a distal end of the path corresponds to the tracked position of the front (130 1 , 130 2 ) in the temporal sequence of images.
  11. The system according to any previous claim, wherein the proximal position (150 p ) corresponds to an anatomical landmark, or an interventional device landmark.
  12. The system according to any one of claims 6 - 11, wherein the one or more processors (110) are further configured identify a portion of the vessel (140) comprising the proximal position (150 p ) and the distal position (150 d ) in each of the first angiogram (170 1 ) and the second angiogram (170 2 ).
  13. The system according to claim 12, wherein the one or more processors (110) are configured to identify the portion of the vessel (140) by providing an overlay region (180 1 , 180 2 ) encompassing a length of the vessel between the proximal position (150 p ) and the distal position (150 d ) in each of the first angiogram (170 1 ) and the second angiogram (170 2 ); and wherein the one or more processors (110) are configured to determine a shape of the overlay region by: tracking a path of the injected contrast agent in the temporal sequence of images; and defining a shape of the overlay region such that the shape of the overlay region encompasses the tracked path of the injected contrast agent between the proximal position (150 p ) and the distal position (150 d ) in the temporal sequence of images.
  14. The system according to claim 13, wherein: the overlay region (180 1 , 180 2 ) in each of the first angiogram (170 1 ), and the second angiogram (170 2 ) comprises a fixed shape; or wherein the overlay region (180 1 , 180 2 ) in each of the first angiogram (170 1 ), and the second angiogram (170 2 ) comprises a temporally-varying shape, and wherein the temporally-varying shape is determined for a current image in each angiogram based on the tracked path of the injected contrast agent in the corresponding image in the temporal sequence of images and zero or more earlier or later images in the temporal sequence of images.
  15. The system according to any previous claim, wherein the one or more blood flow parameters (160) include one or more of: the coronary flow reserve, CFR, or the index of microvascular resistance, IMR, or the maximal flow ratio, MFR.

Description

Technical Field The present disclosure relates to the evaluation of blood flow parameters. A system, a computer-implemented method, and a computer program product, are disclosed. Background Various parameters have been developed for assessing blood flow in the vasculature. Some of these parameters are evaluated using measurements of the blood flow in two different haemodynamic states. For instance, the Coronary Flow Reserve "CFR" is a blood flow parameter that is used as a measure of the ability of the coronary arteries to respond to an increase in the heart's demand for oxygen. The CFR is calculated from measurements of the blood flow in both the basal state, i.e. the resting state, and also in the hyperemic state, i.e. when blood flow is increased as compared to the basal state. The Maximal Flow Ratio "MFR" is another example of a blood flow parameter that may be evaluated using measurements of the blood flow in two different haemodynamic states. The MFR is a measure of the change in maximal blood flow as a result of an intravascular procedure, such as percutaneous transluminal coronary angioplasty, "PCTA". The MFR is calculated from measurements of the blood flow in both a pre-procedural haemodynamic state, and also in a post-procedural haemodynamic state in order to compare the blood flow between the two states. Other blood flow parameters, including the Index of Microcirculatory Resistance "IMR" may be evaluated separately for each of two different haemodynamic states using measurements of the blood flow from only the corresponding state. For instance, a value for the IMR may be calculated from measurements of the blood flow in each of a pre-procedural haemodynamic state, and a post-procedural haemodynamic state, in order to compare the blood flow between the two states. The techniques that are currently available for measuring blood flow parameters include invasive techniques, and angiographic techniques. Invasive techniques involve the use of intravascular temperature-sensing devices, flow-sensing devices, and pressure-sensing devices, to measure blood flow. Angiographic techniques involve the injection of a contrast agent into the vasculature in order to provide visibility of the blood flow with imaging techniques such as X-ray, and magnetic resonance imaging "MRI". Features in the resulting images are then analysed in order to evaluate the blood flow. One group of such angiographic imaging techniques involves the measurement of blood flow by tracking a front of an injected contrast agent bolus and determining the so-called "transit time" or the "transit velocity" in a blood vessel. The transit time is defined as the time taken for the front of the injected contrast agent to pass between specified proximal and distal positions in a vessel. The transit velocity is defined as the average speed of the front of the injected contrast agent between specified proximal and distal positions in a vessel. Angiographic techniques for measuring blood flow parameters are often preferred over invasive techniques due to their reduced procedural complexity. However, physicians that are more familiar with invasive techniques can be suspicious of the reliability of blood flow parameters that have been measured angiographically. This hampers the adoption of angiographic techniques for measuring blood flow parameters, and presents a barrier to the exploitation of their benefits. Document US2016089097A1 may be considered to disclose a system for evaluating blood flow parameters, the system comprising one or more processors configured to: receive angiographic image data representing amotion of a front of an injected contrast agent along a vessel in each of a first haemodynamic state and a second haemodynamic state; analyse the angiographic image data to determine a transit time, for the vessel in each state, the transit time in each state being calculated based on a time taken for the front to pass between a proximal position in the vessel and a distal position in the vessel; output a value of one or more blood flow parameters for the vessel, the value of the one or more blood flow parameters being calculated based on the values of the transit times; and output sequences of a first angiogram and a second angiogram, the first angiogram and the second angiogram being generated from the angiographic image data and depicting the motion of the fronts along the vessel in the first haemodynamic state and the second haemodynamic state, respectively; and wherein the motion sequences of the first angiogram and the second angiogram are synchronised such that the fronts in both angiograms leave the proximal position in the vessel. Summary According to one aspect of the present disclosure, a system for evaluating blood flow parameters, is provided. The system includes one or more processors configured to: receive angiographic image data representing a motion of a front of an injected contrast agent along a vessel in each of a first ha