Calculation Method and System for Fractional Flow Reserve Based on Real-Time Vascular Images

Abstract

The present invention discloses a method and system for calculating fractional flow reserve based on real-time vascular images. The method includes: acquiring a first image and a second image of a target blood vessel, where the first image is a preoperative vascular image and the second image is a real-time angiography image of the blood vessel during the operation; respectively identifying the blood vessel contour according to the first image or the second image, calculating the initial lumen area, and registering the first image and the second image; calculating the predicted virtual fractional flow reserve before stent expansion and the real fractional flow reserve after expansion according to the lumen area of the registered first image, the input ideal expansion area, and the selected implantation point; this application form can assist in judging whether the current stent landing point and model selection can effectively relieve ischemia caused by the lesion, helps the operator select the stent model and the stent landing point during coronary intervention surgery, and improves the surgical efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of medical image processing, and particularly relates to a method and system for calculating fractional flow reserve based on real-time vascular images. Background Art

[0002] Fractional Flow Reserve (FFR for short) can accurately evaluate the severity of myocardial ischemia in patients and is used as a functional evaluation index in clinical practice to guide whether coronary intervention is needed and for postoperative evaluation. However, due to certain limitations in using a guide wire to measure FFR in clinical practice, relevant researchers have developed methods for calculating FFR based on images. However, existing FFR calculation systems cannot determine the real-time changing FFR, resulting in a certain lag and being unable to predict the safety of the implantation process in advance. Summary of the Invention

[0003] Therefore, the purpose of the present invention is to provide a method and system for calculating fractional flow reserve based on real-time vascular images, which calculates the fractional flow reserve during the coronary stent implantation process according to real-time visual images.

[0004] To achieve the above purpose, a method for calculating fractional flow reserve based on real-time vascular images of the present invention includes the following steps:

[0005] S1. Obtain a first image and a second image of a target blood vessel; the first image is a preoperative blood vessel image; the second image is a real-time angiography image of the target blood vessel during the operation, and the real-time angiography image includes stent information;

[0006] S2. Register the first image and the second image; display the stent contour in the first image according to the registration relationship;

[0007] S3. Calculate the lumen area corresponding to the stent contour of the first image to calculate the predicted virtual fractional flow reserve before the stent is actually expanded and the real fractional flow reserve after expansion;

[0008] Among them, the lumen area corresponding to the stent contour of the first image is calculated according to the input ideal expansion area of the stent to calculate the predicted virtual fractional flow reserve before the stent is actually expanded; the lumen area corresponding to the stent contour of the first image is calculated according to the expanded stent contour to calculate the real fractional flow reserve after expansion.

[0009] Further preferably, when the first image is an angiography image, the registration relationship between the first image and the second image is the corresponding relationship of the coordinates of a specific position of the target blood vessel in the first image and the second image.

[0010] Further preferably, when the first image is an intravascular imaging sequence, the registration relationship between the first image and the second image is: the corresponding relationship between the target blood vessel position captured in a specific frame of the intravascular imaging sequence and the coordinates of the corresponding target blood vessel position in the second image.

[0011] Further preferably, it further includes generating a longitudinal section diagram according to the intravascular imaging sequence; using the longitudinal section diagram to determine whether the implantation position of the stent can cover the lesion area.

[0012] Further preferably, in S3, when calculating the predicted virtual fractional flow reserve before the actual expansion of the stent and the real fractional flow reserve after the expansion, the following formula is used for calculation:

[0013] =

[0014] Wherein, represents the blood flow, represents the lumen area of the blood vessel segment of interest, including the lumen area corresponding to the stent contour, represents the blood density, is the friction term, represents the proximal pressure.

[0015] Further preferably, in S3, when calculating the predicted virtual fractional flow reserve, it further includes:

[0016] When there is no plaque, the ideal expansion area of the stent is used as the lumen area corresponding to the stent contour;

[0017] When there is a plaque, according to the composition, size, pressure of the balloon and the ideal expansion area of the stent, the lumen area corresponding to the stent contour after the stent expansion is predicted.

[0018] Further preferably, when there is a plaque, the lumen area corresponding to the stent contour is calculated according to the following formula:

[0019]

[0020] Wherein, is the ideal expansion area of the stent, is the arc occupied by the plaque, is the average thickness of the plaque, is the inflation pressure of the stent balloon, is the elastic modulus of the plaque.

[0021] The present invention also provides a calculation system for the fractional flow reserve based on real-time vascular images, used to implement the steps of the above-mentioned calculation method for the fractional flow reserve based on real-time vascular images, including an image acquisition module, an image processing module and an image display module;

[0022] The image acquisition module is configured to acquire a first image and a second image of a target blood vessel; the first image is a pre-operative blood vessel image; the second image is a real-time angiography image of the target blood vessel during the operation, and the real-time angiography image includes stent information;

[0023] The image processing module registers the first image and the second image; and displays a stent contour in the first image according to the registration relationship;

[0024] Calculate the lumen area corresponding to the stent contour of the first image to calculate the predicted virtual fractional flow reserve (FFR) before the stent is actually expanded and the real FFR after expansion;

[0025] The image display module includes at least four graphical user interface components, wherein the first graphical user interface component is used to obtain the user's option for the virtual FFR or the real FFR; the second graphical user interface component is used to display the first image; the third graphical user interface component is used to display the second image; the fourth graphical user interface component displays an FFR change curve in response to the option selected in the first graphical user interface component, the blood vessel radius calculated from the corresponding blood vessel image, and the virtual FFR or the real FFR;

[0026] Further preferably, the first image displayed by the second graphical user interface component is an angiography image or an imaging sequence.

[0027] Further preferably, when the second graphical user interface component displays an intravascular imaging sequence, it further includes generating a longitudinal section according to the intravascular imaging sequence; and using the longitudinal section to determine whether the implantation position of the stent can cover the lesion area.

[0028] The method and system for calculating the fractional flow reserve based on real-time blood vessel images disclosed in this application, compared with the prior art, has at least the following advantages:

[0029] This technical solution can calculate the virtual FFR of the current target blood vessel after implanting a specific type of stent, assist in judging whether the current stent landing point and selection can effectively relieve the ischemia caused by the lesion, help the operator select the stent type and the stent landing point during coronary intervention surgery, and improve the surgical efficiency.

[0030] When selecting the true fractional flow reserve (FFR), during the process of the doctor dilating the balloon, the software automatically and real-time detects the balloon dilation size, displays the expanded stent contour at the position corresponding to the stent balloon coverage in the first image, and automatically measures the balloon dilation size at different positions to update the lumen area at the corresponding positions. The true FFR is calculated based on the updated lumen area. This technical solution can display the current target vessel FFR in real time, evaluate the effect of the interventional surgery in a timely manner, facilitate the operator to respond to adverse phenomena, effectively shorten the operation time, and improve the operation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic flowchart of the method for calculating the fractional flow reserve based on real-time vascular images according to the present invention.

[0032] Figure 2 It is a schematic diagram of the interface layout of the system for calculating the fractional flow reserve based on real-time vascular images according to the present invention.

[0033] Figure 3 It is a schematic diagram of the interface layout when the first image is an angiogram image.

[0034] Figure 4 It is a schematic diagram of the interface layout when the first image is an intravascular imaging sequence.

[0035] Figure 5 It is a schematic diagram of the system interface when selecting the virtual fractional flow reserve.

[0036] Figure 6 It is a schematic diagram of the system interface when selecting the true fractional flow reserve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] As Figure 1 shown, the method for calculating the fractional flow reserve based on real-time vascular images provided by an embodiment of the present invention on the one hand includes the following steps:

[0039] S1. Obtain a first image and a second image of the target vessel; the first image is a preoperative vascular image; the second image is a real-time angiogram image of the target vessel during the operation, and the real-time angiogram image includes stent information;

[0040] S2. Register the first image and the second image; display the stent contour in the first image according to the registration relationship;

[0041] Preferably, when the first image is an angiogram image, the registration relationship between the first image and the second image is the corresponding relationship of the coordinates of specific positions of the target vessel in the first image and the second image.

[0042] Further preferably, when the first image is an intravascular imaging sequence, the registration relationship between the first image and the second image is: the corresponding relationship between the position of the target blood vessel captured in a specific frame of the imaging sequence and the coordinates of the corresponding target blood vessel position in the second image.

[0043] Further preferably, it further includes generating a longitudinal section diagram according to the intravascular imaging sequence; and using the longitudinal section diagram to determine whether the stent can cover the lesion area.

[0044] It should be noted that the stent contour in this application refers to the contour of the stent in the blood vessel, and does not limit whether the stent has been expanded or fully expanded.

[0045] During the operation process, the operator can observe the position of the stent in the second image in real time. The system displays the stent contour in the first image according to the registration relationship between the first image and the second image, and estimates the virtual lumen area before the stent expansion or calculates the real lumen area after the stent expansion (when not distinguished, it is collectively referred to as the lumen area in the text), which is convenient for subsequent calculations.

[0046] S3. Calculate the lumen area corresponding to the stent contour in the first image to calculate the predicted virtual fractional flow reserve before the actual expansion of the stent and the real fractional flow reserve after the expansion;

[0047] Among them, the lumen area corresponding to the stent contour in the first image is calculated according to the ideal expansion area of the input stent to calculate the predicted virtual fractional flow reserve before the actual expansion of the stent; the lumen area corresponding to the stent contour in the first image is calculated according to the stent contour after the expansion to calculate the real fractional flow reserve after the expansion.

[0048] It should be noted that the virtual fractional flow reserve refers to the predicted fractional flow reserve when the stent has entered the blood vessel and is in the unexpanded state; the real fractional flow reserve refers to the fractional flow reserve when the stent has entered the blood vessel and is in the fully expanded state.

[0049] Specifically , where represents the proximal pressure, which can be approximated by the patient's aortic pressure, can be calculated by Formula 1:

[0050]

[0051] Among them, represents the change with the blood vessel position, represents the blood flow, represents the lumen area of the blood vessel segment of interest, including the lumen area corresponding to the stent contour; represents the blood density, is the friction term.

[0052] In clinical practice, the length dimension of the vascular segment of interest selected by the operator is greater than the length dimension of the stent.

[0053] Therefore, it is calculated using the following formula:

[0054] =

[0055] As can be seen from the above formula, for the same first image of the same lesion site, the difference in the calculation of the virtual fractional flow reserve and the true fractional flow reserve lies in the calculation of the lumen area corresponding to the stent contour.

[0056] The following separately describes the calculation of the virtual fractional flow reserve and the true fractional flow reserve:

[0057] S301, the operator inputs the virtual fractional flow reserve requirement, and the doctor inputs the ideal expansion area of the stent through the interactive interface. The ideal expansion area is information that the doctor can obtain when selecting the stent type. By moving the stent balloon in the blood vessel to adjust the landing point of the stent, the second image acquires real-time data, and based on the registration relationship, the predicted expanded stent contour is updated and displayed in real time at the position corresponding to the stent balloon coverage in the first image. And calculate the lumen area corresponding to the stent contour according to the ideal expansion area of the stent, and calculate the virtual fractional flow reserve using the lumen area corresponding to the stent contour. Further, the lumen area at this position can be determined according to the wall tissue at different positions. If there is no plaque, the lumen area corresponding to the stent contour is equal to the ideal expansion area of the stent; if there is a plaque, the lumen area after stent expansion is predicted according to the composition, size, pressure of the balloon, and the ideal expansion area of the stent 。

[0058] The lumen area is calculated according to the following formula:

[0059]

[0060] Where is the ideal expansion area of the stent, is the arc occupied by the plaque, is the average thickness of the plaque, is the inflation pressure of the stent balloon, is the elastic modulus of the plaque.

[0061] S302, the operator inputs the true fractional flow reserve requirement. During the process of expanding the balloon, the software automatically and real-time detects the expansion size of the stent in the second image, and based on the aforementioned registration relationship, the expanded stent contour is correspondingly displayed in the first image, and the expansion size of the stent at different positions is automatically measured as the lumen area corresponding to the stent contour. Calculate the true fractional flow reserve according to the lumen area corresponding to the stent contour.

[0062] This technical solution can display the true FFR of the current target blood vessel in real time, promptly evaluate the effect of interventional surgery, facilitate the operator to respond to adverse phenomena, effectively shorten the operation time and improve surgical efficiency.

[0063] like Figure 2 As shown, the present invention also provides a calculation system for blood flow reserve fraction based on real-time vascular images, which is used to implement the steps of the above-mentioned calculation method for blood flow reserve fraction based on real-time vascular images, including an image acquisition module, an image processing module and an image display module, wherein the real-time angiography image includes stent information;

[0064] An image processing module registers the first image and the second image; and displays the stent outline in the first image according to the registration relationship;

[0065] The lumen area corresponding to the stent outline of the first image is calculated to calculate the predicted virtual blood flow reserve fraction before the stent is actually expanded and the real blood flow reserve fraction after the expansion.

[0066] The image display module includes at least four graphical user interface components, wherein the first graphical user interface component is used to obtain the user's option for the virtual blood flow reserve fraction or the real blood flow reserve fraction; the second graphical user interface component is used to display the first image; the third graphical user interface component is used to display the second image; the fourth graphical user interface component displays the FFR change curve in response to the option selected in the first graphical user interface component and the vessel radius calculated from the corresponding vessel image and the virtual FFR or the real FFR. The first image displayed by the second graphical user interface component is a vascular angiography image or an intravascular imaging sequence.

[0067] When the second graphical user interface component displays an intravascular imaging sequence, it also includes generating a longitudinal section view according to the intravascular imaging sequence; and using the longitudinal section view to determine whether the stent can cover the lesion area.

[0068] During the implantation of the stent balloon, the surgeon tracks the position of the stent balloon in real time in the second image displayed by the third graphical user interface component, and displays the area covered by the stent balloon in real time in the first image according to the registration relationship between the first image and the second image. Figure 3 As shown, the second graphical user interface component displays the first image acquired before the operation, which is exemplarily an angiography image. The solid line segment AB shown in the figure is the area covered by the stent balloon displayed based on the registration relationship; when the first image is an intravascular imaging sequence, as shown in FIG. Figure 4As shown, the second graphical user interface component displays the first image obtained before the operation, which is exemplarily an intravascular image and its generated longitudinal section. The solid line segment AB shown in the figure is the area covered by the stent balloon displayed based on the registration relationship. This helps the surgeon observe whether the current stent landing site can cover the lesion area.

[0069] At this time, the virtual fractional flow reserve option or the real fractional flow reserve option can be selected through the first graphical user interface component.

[0070] Figure 5 An example of the system interface schematic diagram is given when the first image is an angiogram. This technical solution can calculate the virtual FFR of the current target vessel after implanting a specific model of stent, assist in judging whether the current stent landing site and stent selection can effectively relieve the ischemia caused by the lesion, helps the surgeon select the stent type and the stent landing site during coronary intervention surgery, and improves the surgical efficiency.

[0071] Figure 6 When the real fractional flow reserve is selected, during the process of dilating the balloon, the software automatically and real-time detects the stent dilation size, displays the expanded stent contour at the position corresponding to the stent balloon coverage in the first image, and automatically measures the balloon dilation size at different positions as the lumen area corresponding to the stent contour. The real fractional flow reserve is calculated according to the lumen area corresponding to the stent contour. This technical solution can display the FFR of the current target vessel in real time, evaluate the effect of the interventional surgery in a timely manner, facilitate the surgeon to respond to adverse phenomena, effectively shorten the operation time, and improve the surgical efficiency.

[0072] Obviously, the above embodiments are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for calculating blood flow reserve fraction based on real-time vascular images, characterized in that: The following steps are involved: S1, acquiring a first image and a second image of a target blood vessel; the first image is a preoperative blood vessel image; the second image is a real-time angiography image of the target blood vessel during surgery, the real-time angiography image including stent information; S2, registering the first image and the second image; and displaying the stent outline in the first image according to the registration relationship; S3, calculating the lumen area corresponding to the stent outline of the first image to calculate the predicted virtual blood flow reserve fraction before the stent is actually expanded and the real blood flow reserve fraction after the expansion; when calculating the predicted virtual blood flow reserve fraction before the stent is actually expanded and the real blood flow reserve fraction after the expansion, the following formula is used: = in, Indicates blood flow, represents the lumen area of ​​the vessel segment of interest, including the lumen area corresponding to the stent outline, represents the blood density, is the friction term, Indicates proximal pressure; Among them, the lumen area corresponding to the stent outline of the first image is calculated according to the input ideal expansion area of ​​the stent, so as to calculate the predicted virtual blood flow reserve fraction before the actual expansion of the stent; the lumen area corresponding to the stent outline of the first image is calculated according to the stent outline after expansion, so as to calculate the real blood flow reserve fraction after expansion.

2. The method for calculating blood flow reserve fraction based on real-time vascular images according to claim 1, characterized in that: The first image is a blood vessel angiography image, and the registration relationship between the first image and the second image is the corresponding relationship between the coordinates of a specific position of the target blood vessel in the first image and the second image.

3. The method for calculating blood flow reserve fraction based on real-time vascular images according to claim 1, characterized in that: The first image is an intravascular imaging sequence, and the registration relationship between the first image and the second image is: the correspondence between the target blood vessel position captured in a specific frame in the intravascular imaging sequence and the corresponding target blood vessel position coordinates in the second image.

4. The method for calculating blood flow reserve fraction based on real-time vascular images according to claim 3, characterized in that: The method also includes generating a longitudinal section image according to an intravascular imaging sequence; and using the longitudinal section image to determine whether the implantation position of the stent can cover the diseased area.

5. The method for calculating blood flow reserve fraction based on real-time vascular images according to claim 1, characterized in that: In S3, the predicted virtual blood flow reserve fraction is calculated, which also includes: When there is no plaque, the ideal expansion area of ​​the stent is the lumen area corresponding to the stent profile; When plaque is present, the lumen area corresponding to the stent profile after stent expansion is predicted based on the composition and size of the plaque, the pressure of the balloon and the ideal expansion area of ​​the stent.

6. The method for calculating blood flow reserve fraction based on real-time vascular images according to claim 5, characterized in that: When plaque exists, the lumen area corresponding to the stent outline is calculated according to the following formula: in, is the ideal expansion area of ​​the stent, is the arc occupied by the plaque, is the average plaque thickness, Inflation pressure of the stent balloon, is the plaque elastic modulus.

7. A system for calculating blood flow reserve fraction based on real-time vascular images, characterized in that: The steps for implementing the method for calculating the blood flow reserve fraction based on real-time vascular images as described in any one of claims 1 to 6 include an image acquisition module, an image processing module and an image display module; The image acquisition module is used to acquire a first image and a second image of the target blood vessel; the first image is a preoperative blood vessel image; the second image is a real-time angiography image of the target blood vessel during the operation, and the real-time angiography image includes stent information; An image processing module registers the first image and the second image; and displays the stent outline in the first image according to the registration relationship; Calculating the lumen area corresponding to the stent outline of the first image to calculate the predicted virtual blood flow reserve fraction before the stent is actually expanded and the real blood flow reserve fraction after the stent is expanded; The image display module includes at least 4 graphical user interface components, wherein the first graphical user interface component is used to obtain the user's option for the virtual blood flow reserve fraction or the real blood flow reserve fraction; the second graphical user interface component is used to display the first image; the third graphical user interface component is used to display the second image; and the fourth graphical user interface component displays the FFR change curve in response to the option selected in the first graphical user interface component and the vascular radius calculated from the corresponding vascular image and the virtual FFR or the real FFR.

8. The blood flow reserve fraction calculation system based on real-time vascular images according to claim 7, characterized in that: The first image displayed by the second graphical user interface component is an angiography image or an imaging sequence.

9. The blood flow reserve fraction calculation system based on real-time vascular images according to claim 8, characterized in that: When the second graphical user interface component displays an intravascular imaging sequence, it also includes generating a longitudinal section view according to the intravascular imaging sequence; and using the longitudinal section view to determine whether the implantation position of the stent can cover the lesion area.

Images