METHOD, SYSTEM AND COMPUTER PROGRAM PRODUCT FOR DETERMINING ISCHEMIA REGION OF THE ORGAN

Abstract

The invention relates to a method for identifying an ischaemic region (O.sub.n) of an organ based on anatomical data, wherein the ischaemic region (O.sub.n) is 0.2 to 1 part of the stenosed region at risk (O.sub.z) downstream of the threshold point (P.sub.prog). The size of the ischaemic region (O.sub.n) is proportional to the difference between the indicative value at the threshold point (P.sub.prog) and at the measuring point (P.sub.pom) in the artery. The invention also relates to a system for identifying organ ischaemia, a computer program for identifying organ ischaemia and a computer program product.

Claims

1-37. (canceled)

38. A method for identifying an ischaemic region (O.sub.n) of a heart based on anatomical data, comprising: acquiring data on the arterial tree of the heart and the shape of the heart; identifying a threshold point (P.sub.prog) in an artery at which a threshold indicative value is reached that corresponds to the ischaemia of the heart; acquiring data on the arterial tree of the heart and the shape of the heart; extracting the arterial vessels of a heart and identifying the volume of the heart; identifying a threshold point (P.sub.prog) in the artery at which a threshold indicative value is reached that corresponds to the ischaemia of the heart, and identifying the indicative value in a particular artery at the measuring point (P.sub.pom) situated downstream of the threshold point (P.sub.prog); qualifying an artery downstream of the threshold point (P.sub.prog) of the stenosed region at risk (O.sub.z) being supplied; identifying the stenosed region at risk (O.sub.z); calculating the volume of the ischaemic region (O.sub.n) as a part of the stenosed region at risk (O.sub.z), wherein the ischaemic region (O.sub.n), located at the most distal point relative to the threshold point (P.sub.prog) in the artery, represents 0.5 part of the stenosed region at risk (O.sub.z) downstream of the threshold point (P.sub.prog) plus the ratio score of 0.1 to 0.05 of the difference between the indicative value at the threshold point (P.sub.prog) and the indicative value at the measuring point (P.sub.pom); and superimposing onto the image of the heart, acquired in the step of acquiring data, the ischaemic region (O.sub.n) of the heart identified in the step of calculating.

39. The method according to claim 38, wherein the step of identifying the arterial vessels of the heart and the volume of the heart is followed by the step of identifying the pressure distribution in the tested arteries relative to the pressure at a reference point (P.sub.0).

40. The method according to claim 38, wherein the measuring point (P.sub.pom) is located approximately 20 mm downstream of the threshold point (P.sub.prog).

41. The method according to claim 38 wherein image data is acquired at the step of acquiring data, and wherein the step of acquiring data on the arterial tree and the shape of the target organ is performed by one of computed tomography angiography or invasive angiography and when the step of acquiring data is based on invasive angiography, the shape of the target organ is reconstructed based on said data.

42. The method according to claim 39, wherein the step of identifying the pressure distribution in the tested arteries is performed using an actual measurement or digital computer simulation methods.

43. The method according to claim 39, wherein the reference point (P.sub.0) is the artery outlet from the aorta or the aortic sac.

44. The method according to claim 38, wherein the indicative value is one of the fractional flow reserve (FFR) value, the ratio of the pressure at the threshold point (P.sub.prog) to the pressure at the arterial outlet, or the ratio of the pressure at the measuring point (P.sub.pom) to the pressure at the arterial outlet.

45. The method according to claim 44, wherein the threshold value indicative of the fractional flow reserve (FFR) is equal to or less than 0.8.

46. The method according to claim 44, wherein the fractional flow reserve (FFR) value is obtained based on a computed tomography scan or a computer simulation.

47. The method according to claim 38, wherein the step of qualifying (40) an artery downstream of a threshold point (P.sub.prog) of a stenosed region at risk is performed using at least one method from: a Voronoi diagram, a stem-and-crown model, an American Heart Association diagram.

48. The method according to claim 38, wherein the step of identifying a stenosed region at risk (O.sub.z) is performed by a quantitative analysis of the volume of the stenosed region at risk (O.sub.z) or by a percentage analysis relative to the total organ volume of the stenosed region at risk (O.sub.z).

49. The method according to claim 38, wherein the superimposing step is performed using a Voronoi diagram to visualise the ischaemic region (O.sub.n).

50. A system for identifying an ischaemic region (O.sub.n) of a heart based on anatomical data, comprising: a module for acquiring data on the arterial tree of the heart and the shape of the heart; a module for identifying the threshold point (P.sub.prog) in an artery at which the threshold indicative value corresponding to heart ischaemia is reached: a module for extracting arterial vessels of a heart and identifying the volume of a heart; a module for identifying a threshold point (P.sub.prog) in the artery at which a threshold indicative value is reached that corresponds to the ischaemia of the heart and a module (30.2) for identifying the indicative value in a particular artery at the measuring point (P.sub.pom) situated downstream of the threshold point (P.sub.prog); a module for qualifying an artery downstream of the threshold point (P.sub.prog) of the stenosed region at risk (O.sub.z) being supplied; a module for identifying a stenosed region at risk (O.sub.z); a module for calculating the volume of the ischaemic region (O.sub.n) as a part of the stenosed region at risk (O.sub.z), wherein the ischaemic region (O.sub.n), located at the most distal point relative to the threshold point (P.sub.prog) in the artery, represents 0.5 part of the stenosed region at risk (O.sub.z) downstream of the threshold point (P.sub.prog) plus the ratio score of 0.1 to 0.05 of the difference between the indicative value at the threshold point (P.sub.prog) and the indicative value at the measuring point (P.sub.pom); and a module for superimposing the ischaemic region (O.sub.n) of a heart onto the image of a heart acquired by the module for acquiring data.

51. The system according to claim 50, wherein the system further comprises a module for identifying the pressure distribution in the tested arteries relative to the pressure at a reference point (P.sub.0), located downstream of the module for identifying the arterial vessels of the heart and the volume of the heart.

52. The system according to claim 50, wherein the module for acquiring data acquires image data and wherein the module for acquiring data on the arterial tree and the shape of the target organ uses computed tomography angiography or the module for acquiring data on the arterial tree uses invasive angiography, and the shape of the target organ is reconstructed based on said data.

53. The system according to claim 50, wherein the module for identifying the pressure distribution in the tested arteries uses actual measurements or digital computer simulation methods.

54. The system according to claim 50, wherein the module for qualifying an artery downstream of a threshold point (P.sub.prog) of a stenosed region at risk uses at least one method from: a Voronoi diagram, a stem-and-crown model, an American Heart Association diagram.

55. The system according to claim 50, wherein the module for identifying a stenosed region at risk (O.sub.z) uses quantitative analysis of the volume of the stenosed region at risk (O.sub.z) or percentage analysis in relation to the entire organ volume of the stenosed region at risk (O.sub.z).

56. The system according to claim 50, wherein the module for superimposing uses the Voronoi diagram to visualise the ischaemic region (O.sub.n).

57. A computer program embodied on a non-transitory computer readable medium for identifying heart ischaemia, comprising instructions for performing the method according to claim 38.

58. A product of execution by a computer processor of a computer program for identifying heart ischaemia, comprising a computer readable code embodied on a non-transitory computer readable medium performing the steps of the method according to claim 38.

Description

[0084] The object of the invention is illustrated in the drawing, where:

[0085] FIG. 1 is a flow chart of the method for identifying an ischaemic region of an organ;

[0086] FIG. 2 is a spatial image of the heart with the vascular tree indicating the threshold point in the artery where the threshold value corresponding to organ ischaemia is reached;

[0087] FIG. 3 is a spatial image of the heart indicating the measuring point located downstream of the threshold point;

[0088] FIG. 4 is a spatial image of the heart indicating the stenosed region at risk, supplied by the artery downstream of the point where the FFR reaches≤0.80;

[0089] FIG. 5 is a spatial image of the heart showing the ischaemic region against the stenosed region at risk, wherein the ischaemic region makes part of the stenosed region at risk and extends in the distal direction of the artery from a point which is no more upstream than where the FFR reaches≤0.80;

[0090] FIG. 6 is a block diagram of the system for identifying organ ischaemia.

[0091] In the embodiment illustrated in FIGS. 1-5, the method for identifying an ischaemic region O.sub.n of an organ based on anatomical data includes a step of acquiring 10 data on the arterial tree of the organ and the shape of the organ. In an embodiment, the acquired data may be imaging data acquired for example by computed tomography, while in a further embodiment arterial tree data is acquired by way of invasive angiography, and the shape of the target organ is reconstructed based on such pre-acquired data.

[0092] The method then comprises extracting 20 the arterial vessels of the organ and identifying the volume of the organ. In another embodiment, the method also includes determining 21 the pressure distribution in the tested arteries, relative to the pressure at a reference point P.sub.0, wherein the reference point P.sub.0 is the point where the artery outlets from aorta, and in a further embodiment it is the aortic sac. The step of identifying 21 the distribution of pressures in the tested arteries is performed by means of actual measurement, and in another embodiment by digital methods such as computer simulation.

[0093] Then, following the step of extracting 20 the arterial vessels and optionally following the optional step of identifying 21 the pressure distribution, the method for identifying an ischaemic region O.sub.n comprises identifying 30 the threshold point P.sub.prog in the artery at which the threshold indicative value corresponding to organ ischaemia is reached, and the method comprises identifying the indicative value in the respective artery at the measuring point P.sub.pom, such as approx. 20 mm downstream of the threshold point P.sub.prog. In an embodiment, the indicative value corresponding to organ ischaemia is the fractional flow reserve, FFR, which has a threshold value equal to 0.8 or less. The FFR value is obtained based on the actual measurement and, in another embodiment, the FFR value is obtained from a computer simulation based on a computer tomography scan or invasive angiography scan. In another embodiment, the indicative value corresponding to organ ischaemia is the ratio of the pressure (or simulated pressure) at the threshold point P.sub.prog to the pressure (or simulated pressure) at the arterial outlet, and in the following example, the indicative value is the ratio of the pressure (or simulated pressure) at the measuring point P.sub.pom to the pressure (or simulated pressure) at the arterial outlet.

[0094] The subsequent step in the method is the step of qualifying 40 an artery downstream of the threshold point P.sub.prog of the stenosed region at risk O.sub.z being supplied, for example using the Voronoi diagram/method.

[0095] The method then comprises identifying 50 the stenosed region at risk O.sub.z, for example using a quantitative analysis of the volume of the stenosed region at risk O.sub.z, and in another embodiment by means of a percentage analysis relative to the total organ volume of the stenosed region at risk O.sub.z.

[0096] Moreover, the present method involves calculating 60 the volume of the ischaemic region O.sub.n as a part of the stenosed region at risk O.sub.z. The ischaemic region On is located most distal to the threshold point P.sub.prog in the artery and represents 0.2-1 part of the stenosed region at risk O.sub.z downstream of the threshold point P.sub.prog. The size of the ischaemic region O.sub.n is proportional to the difference between the indicative value at the threshold point P.sub.prog and at the measuring point P.sub.pom. In an embodiment, the ischaemic region O.sub.n represents 0.5 part of the stenosed region at risk O.sub.z downstream of the threshold point P.sub.prog plus a ratio score of 0.1 to 0.05 of the difference between the indicative value at the threshold point P.sub.prog and the indicative value at the measuring point P.sub.pom.

[0097] The final step of the present method is the step of superimposing 70 onto the image of the organ, acquired in the step of acquiring 10 data, the ischaemic region O.sub.n of the muscle identified in the step of calculating 60. In one embodiment, the step of superimposing 70 is performed using a Voronoi diagram to visualise the ischaemic region O.sub.n.

[0098] In another embodiment, the method can be used in practice as an additional imaging module overlay, such as CT-FFR, FFR-CT, FFR-QCA, invasive FFR, iFR.

[0099] For methods based on computed tomography (CT), the image of the heart acquired during the scan allows for accurate determination of its dimensions and the supply area of the individual arteries. Here, the method can further involve marking and identifying the ischaemic muscle including a calculation of its mass relative to that of the total organ. For FFR-QCA, or an invasive measurement such as FFR or iFR, in order to simulate an ischaemic region O.sub.n, it is first required to create a virtual image of the left ventricle (based on ventriculography or the distribution of the coronary arteries alone) and then only to mark and identify the ischaemic muscle in the manner described above.

[0100] In another embodiment, the data of a CT coronary artery angiography scan in the form of DICOM files encoding spatial information on the shape and volume of the heart, including the myocardium and coronary arteries and their mutual spatial arrangement were transferred via external medium or network transfer to a station of a computational unit which: [0101] 1. Extracts, for example using the software programme “cFFR version 1.4, Siemens Healthcare GmbH”, a three-dimensional image, i.e., it performs an image segmentation process which yields an image of the coronary arteries and myocardium which allows e.g., for visualising the course of the coronary arteries and identifying the location of coronary artery stenosis; [0102] 2. In the next step, for example using the programme “cFFR version 1.4, Siemens Healthcare GmbH”, the computational unit determines the pressure distributions in the coronary vessel tree based on the assumptions for the calculation of the simulated fractional flow reserve, FFR. This calculates the ratio of the pressure at a given point along the artery to the pressure where the artery outlets from the aorta, which calculation is shown as colour maps within the arteries, wherein lower distal pressure is tantamount to lower FFR; [0103] 3. The computational unit then analyses the individual FFR values along the artery, allowing to identify the threshold point P.sub.prog on the stenosed coronary artery, wherein the FFR value is equal to the threshold value (0.80), and to determine the FFR value at the point P.sub.pom, which is located 20 mm downstream of the threshold point P.sub.prog at 0.76; [0104] 4. The imaging data from the same test were read using another software, such as CT Coronary Territories from Ziosoft, which, after marking the course of the coronary arteries and marking the contour of the left ventricle using the Voronoi method, allows for ascribing the cardiac blood supply region expressed in mm.sup.3, or as % of the total, to each indicated point on each artery; [0105] 5. A threshold point P.sub.prog was identified on the stenosed artery, and the computational unit, using the Voronoi method, determined and then superimposed, onto the left ventricular image, the area of cardiac blood supply downstream of this point. It then determined its volume in mm.sup.3, or % of the total organ, i.e., identified the stenosed region at risk of O.sub.z. The result is 35% of myocardial volume; [0106] 6. Based on the magnitude of the difference in FFR values between the threshold point P.sub.prog and the measuring point P.sub.pom of 0.04, the resulting volume was converted using the following formula:

volume of ischaemic region=(0.5+0.08)*O.sub.Z%,

where a factor of 0.58 was obtained as follows: the primary factor of 0.50 increases proportionally by 0.1 part for each 0.05 increase in the FFR value at the measuring point P.sub.pom. Since the difference in FFR values at the threshold point P.sub.prog and at the measuring point P.sub.pom is 0.04, this means an increase of 0.08 in the primary factor to give a score of 20%. Then, in order to visualise the ischaemic region O.sub.n, a point was sought on the stenosed artery for which the supply area corresponds to the calculated volume of the ischaemic region O.sub.n. After marking this point using the Voronoi method, the software, such as CT Coronary Territories from Ziosoft identifies and displays the ischaemic region O.sub.n.

[0107] In the embodiment wherein the step of identifying 20 the arterial vessels of an organ and the volume of an organ is followed by the step of identifying 21 the pressure distribution in the tested arteries, relative to the pressure at the reference point P.sub.0, the reference point P.sub.0 is identified at the arterial outlet from the aorta. The pressure distribution can be determined for example using computer simulation of the pressures, such as in the software “cFFR version 1.4, Siemens Healthcare GmbH”, or in conditions of actual measurement with a coronary artery pressure probe, such as Verrata® Pressure Guide Wire, placed at a given point in the artery, and the pressure at a reference point P.sub.0 identified at a guiding catheter, whose end is located at the arterial outlet.

[0108] In an embodiment wherein the step of identifying 50 a stenosed region at risk O.sub.z is performed by quantifying the volume of the stenosed region at risk O.sub.z, the myocardial volume is determined by visually identifying and extracting the myocardium based on three-dimensional images of the heart acquired using computer tomography, or by extraction using software such as CT Coronary Territories from Ziosoft.

[0109] The Applicant conducted an experiment in which 34 patients underwent coronary CT scanning, CT-FFR scanning/simulation, and CT (computed tomography) cardiac perfusion scanning using a vasodilator (adenosine or regadenoson). Based on the results, a reference ischaemic region O.sub.n of the heart expressed as % of total myocardial mass was identified. In the patients studied, a number of points were marked on the stenosed coronary artery starting from the point of maximum stenosis (minimal lumen), in the distal direction of the artery, for which the corresponding “regions at risk” and the corresponding CT-FFR values were recorded. The results obtained were subjected to a proper analysis, which showed the following: [0110] there was no significant correlation between the percentage (%) area of actual ischaemia in the reference study and the “region at risk” expressed as % of myocardial mass marked on the stenosed coronary artery at the point of maximum stenosis. This result indicates that the region of actual ischaemia O.sub.n differs significantly (is not the same as) from the “region at risk downstream of the point of maximum stenosis”; [0111] a significant correlation between the ischaemic region O.sub.n in the reference study and the correlation derived from the % value of the stenosed muscle region identified downstream of the point where the (CT)FFR value reaches the diagnostic value of ischaemia (0.80 for the heart), the so-called stenosed region at risk O.sub.z. Correlations are both quantitative (% of the muscle in the reference method correlated with calculated % of the muscle) and qualitative (large/substantial ischaemic region On of the heart (>=10%)).

[0112] As an example, the results obtained show that the % (percentage) of the ischaemic muscle is equal to the % (percentage) of the stenosed area at risk O.sub.z of the muscle (defined at the point where CT FFR assumes the value of 0.75) multiplied by a factor of 0.62 and to which a constant of 2.9 is added. In yet another embodiment, the % (percentage) of the ischaemic muscle is equal to the % (percentage) of the stenosed region at risk O.sub.z of the muscle (defined at the point where CT FFR assumes the value 0.80) multiplied by a factor of 0.51 and to which a constant of 2.1 is added. In yet another embodiment, the % (percentage) of ischaemic muscle is equal to the averaged % (percentage) of the stenosed region at risk O.sub.z of the muscle for a number of points, divided by the averaged FFR (CT FFR or iFR) value for said points (for values below the ischaemia threshold) multiplied by a factor of 0.49 to which a constant of 1.4 is added.

[0113] It generally follows from the embodiments above that the percentage of the ischaemic region O.sub.n is on average a constant 0.50 (range 0.2-1) multiplied by the percentage (volume) of the stenosed muscle region, i.e., the stenosed region at risk O.sub.z, identified for the point at which the FFR (or CT FFR or iFR) value varying along the vessel first takes at least the threshold value for the value diagnostic of organ ischaemia (for the heart≤0.80 or iFR≤0.89). Also, the volume of ischaemic muscle increases as the dynamics of the decrease in FFR (or CT FFR or iFR) value, i.e., the lower the FFR/CTFFR/iFR at the measuring point P.sub.pom, the greater the percentage of ischaemic region O.sub.n represents relative to the stenosed region at risk O.sub.z identified downstream of the threshold point P.sub.prog. The location of the ischaemic muscle represents the region having the volume (%) as calculated above and located most distally in the stenosed region at risk O.sub.z.

[0114] In the embodiments, the Applicant has assumed that significant ischaemia is a region with at least 10% ischaemia, such as a stenosed region at risk O.sub.z of muscle>11% downstream of the point for which the FFR (or CT FFR) is 0.75, or a stenosed region at risky O.sub.z of muscle>17% downstream of the point for which the FFR (or CT FFR) is 0.80 (FIG. 4).

[0115] In another embodiment, all of the steps of the method for identifying an ischaemic region O.sub.n of an organ as described above may be performed by a computer programme for identifying ischaemia of an organ comprising instructions for performing said steps. In a further embodiment, all of the steps of the above-described method for identifying an ischaemic region O.sub.n of an organ can be performed using a computer programme product comprising a computer readable code.

[0116] As shown in FIG. 6, the system 100 for identifying an ischaemic region O.sub.n of an organ based on anatomical data, comprises a module 10.1 for acquiring data on the arterial tree of the organ and the shape of the organ, and a module 30.1 for identifying the threshold point P.sub.prog in the artery at which the threshold indicative value corresponding to organ ischaemia is reached. The system 100 also comprises: [0117] module 20.1 for extracting arterial vessels of an organ and identifying the volume of an organ; [0118] module 30.1 for identifying a threshold point P.sub.prog in an artery at which a threshold indicating value is reached that corresponds to the ischaemia of the organ and a module 30.2 for identifying the indicative value in a particular artery at the measuring point P.sub.pom situated downstream of the threshold point P.sub.prog; [0119] module 40.1 for qualifying an artery downstream of the threshold point P.sub.prog of the stenosed region at risk O.sub.z being supplied; [0120] module 50.1 for identifying a stenosed region at risk O.sub.z; [0121] module 60.1 for calculating the volume of the ischaemic region O.sub.n as a part of the stenosed region at risk O.sub.z, wherein the ischaemic region O.sub.n is 0.2-1 part of the stenosed region at risk O.sub.z downstream of the threshold point P.sub.prog, wherein the size of the ischaemic region O.sub.n is proportional to the difference between the indicative value at the threshold point P.sub.prog and at the measuring point P.sub.pom; and [0122] a module 70.1 for superimposing the ischaemic region O.sub.n of an organ onto the image of an organ acquired by the module 10.1 for acquiring data.

[0123] In another embodiment, the system 100 further comprises module 21.1 for identifying the pressure distribution in the tested arteries relative to the pressure at a reference point P.sub.0, located downstream of the module 20.1 for identifying the arterial vessels of the organ and the volume of the organ.

[0124] In further embodiments of the system 100, module 10.1 for acquiring data on the arterial tree and target organ shape data acquires image data.

[0125] In other embodiments, module 10.1 for acquiring data on the arterial tree and target organ shape data uses computed tomography angiography or uses invasive angiography, wherein the target organ shape is reconstructed based on said data.

[0126] In another embodiment of the system 100, module 21.1 for identifying the pressure distribution in the tested arteries uses actual measurements.

[0127] In another embodiment of the system 100, module 21.1 for identifying the pressure distribution in the tested arteries uses digital methods, such as computer simulation.

[0128] In further embodiments of the system 100, module 40.1 for qualifying an artery downstream of a threshold point P.sub.prog of a stenosed area at risk uses at least one method from: a Voronoi diagram, a stem-and-crown model, an American Heart Association diagram.

[0129] In another embodiment of the system 100, module 50.1 for identifying a stenosed region at risk O.sub.z uses a quantitative analysis of the volume of the stenosed region at risk O.sub.z, and in a further embodiment, module 50.1 for identifying the stenosed region at risk O.sub.z uses a percentage analysis to the total organ volume of the stenosed region at risk O.sub.z.

[0130] In another embodiment of the system 100, the superimposing module 70.1 uses the Voronoi diagram to visualise the ischaemic region On.

[0131] In one embodiment, the system 100 according to the invention is implemented on a processor in any server or PC type computing system.

[0132] In another embodiment, the system 100 comprises a processor and a memory for storing instructions that is coupled to the processor, wherein the execution of the instructions by the processor causes the processor to perform the steps of the above-described method for identifying an ischaemic region. The processor may be suitably configured to cause the software modules to perform the steps of the method for identifying an ischaemic region.

[0133] All embodiments of the method for identifying an ischaemic region of an organ O.sub.n also refer to a system for identifying an ischaemic region of an organ, a computer program for identifying an ischaemic region of an organ, and a computer program product.

[0134] Each of the blocks of the diagram illustrating the method for identifying an ischaemic region and each of the blocks of the diagram of the system for identifying an ischaemic region can be implemented by computer program instructions. Such instructions may be provided to a processor of a general-purpose computer, a special purpose computer or another programmable data processing device, such that the instructions that are executed by the processor of the computer or another programmable data processing device allow for implementing the functions as defined in the method and system diagrams.

[0135] Aspects of the present invention may be implemented by a computer or devices such as a CPU (central processing unit) or MPU (memory protection unit) which read and execute a computer program product stored in a storage device for performing the functions of the embodiments described above. Aspects of the present invention may also be implemented by a method whose steps are performed by a computer of the system or device, such as by reading and executing a program stored on a storage device for performing the functions of the above-described embodiments. Accordingly, the computer program product is delivered to a computer, for example, via a network or another storage medium used as a storage device. The computer program product according to the invention further comprises a non-volatile machine-readable medium.

[0136] Embodiments herein are provided only as non-limiting guidelines for the invention and by no means do they limit the scope of protection as defined by the claims. It should be noted that any technical solution used in the invention can be implemented using equivalent technologies without departing from the scope of protection.