WO2017097074A1

WO2017097074A1 - Method for calculating blood flow volume of blood vessel per unit time and blood flow velocity

Info

Publication number: WO2017097074A1
Application number: PCT/CN2016/104655
Authority: WO
Inventors: 涂圣贤; 楚淼; 杨璐璐; 刘冰; 陈亚珠
Original assignee: 博动医学影像科技（上海）有限公司
Priority date: 2015-12-10
Filing date: 2016-11-04
Publication date: 2017-06-15
Also published as: CN105559810A; CN105559810B

Abstract

A method for calculating a blood flow volume of a blood vessel per unit time and a blood flow velocity comprises: selecting an interest region and calculating and fitting out a fitting curve at which the gray scale of the interest region varies with time, in an image sequence, calculating a time point at which the gray scale fitting curve has the highest descending (or ascending) speed, and integrating the gray scale varying fitting curve within a preset time interval by taking the time point as a center, so as to obtain an area value; and obtaining a blood flow volume per unit time corresponding to the area value, and in combination with the lumen area of the blood vessel, further acquiring a blood flow velocity. A blood flow volume within an entire cardiac cycle time is calculated by taking the position at which the gray scale fitting curve has the highest descending (or ascending) speed as a center, so that the blood flow volume per unit time and the blood flow velocity can be calculated more accurately, thereby effectively avoiding errors caused by calculation in improper time intervals.

Description

Calculation method of blood flow and blood flow velocity in vascular unit time

Technical field

The invention relates to the application in the medical field, in particular to an accurate, rapid and non-invasive calculation of blood flow and blood flow velocity per unit time based on image.

Background technique

Vascular stenosis caused by plaque affects myocardial blood supply and poses a threat to human health. Coronary angiography can show the severity of coronary stenosis, but it does not reflect the functional significance of stenosis. The blood flow reserve fraction (FFR) was evaluated as the gold standard for the diagnosis of coronary function, which is defined as the ratio of the maximum blood flow that the coronary artery can provide to the myocardium and the maximum blood supply flow when the coronary artery is completely normal. In the maximum hyperemia state, the ratio of the pressure at the distal end of the stenotic lesion to the proximal pressure of the stenosis is calculated.

Invasive invasive pressure measurements of blood vessels by pressure sensors are not only labor intensive, but also risk of damaging blood vessels. The geometric model of the coronary system can be obtained by three-dimensional or two-dimensional quantitative coronary angiography for computer hydrodynamic analysis. However, the current speed acquisition method is obtained by semi-automatic (artificial + computer) method, and the reconstruction process needs to accurately outline the blood vessel boundary. Longer and the operator has a lot of experience, and needs to manually determine the starting position of the contrast agent into the coronary artery (starting frame) and the end position (end frame) filling the target distal end. In addition, the contrast agent is fully in the microcirculation. The filling process during expansion is relatively short, and the vessel segment of interest typically only occupies a certain period of a heartbeat cycle, which results in a very large difference in blood flow velocity determined during different periods of the heartbeat cycle. In addition, under normal circumstances, only a narrow blood vessel is reconstructed, ignoring the influence of the side branch on the blood flow velocity, resulting in a large error between the blood flow velocity and the actual value finally calculated by the method, which affects The accuracy of the subsequent blood flow reserve score (FFR) solution results.

In the prior art, the typical methods for calculating blood flow velocity are as follows:

First-distribution analysis method: see Comparative Document 1 (Wong JT, Ducote JL, Tong X, Hassanein MT, Sabee M. Automated Technique for Angiographic Determination of Coronary Blood Flow and Lumen Volume 1 [J]. "Academic Radiology", 2006, 13 ( 2): 186-194), Wong et al. proposed a method of first-distribution analysis to calculate blood flow velocity. The method firstly uses an iodine contrast agent calibration platform to fill a tube with a known radius and length with an iodine contrast agent of known full density, and then performs X-ray angiography to fit the integrated gradation value with the iodine from the angiographic result of the tube. Linearity of mass change curve. Using coronary angiography, the integrated gray value of the coronary region of interest is extracted with time. According to the fitted gray value-iodine mass linear curve, the curve of iodine contrast agent quality over time in the region of interest is obtained. Under the condition of knowing the density of iodine contrast agent, the curve of intravascular fluid volume over time in the region of interest can be obtained, and the blood flow and blood flow velocity can be obtained from the volume time curve. A disadvantage of this technique is that the region of interest does not shift correspondingly as the target vessel position of the contrast sequence moves; and there is no provision for the period of time for calculating the mean blood flow velocity, possibly a non-integer number of cardiac cycles. The accuracy of the blood flow and blood flow velocity obtained by the technical solution is low, and the stability of the data is poor.

TIMI frame method: see comparison file 2 (Tu S, Barbato E, Koszegi Z et al. Fractional flow reserve calculation from 3-dimensional quantitative coronary angiography and TIMI frame count: a fast computer model to quantify the functional significance of moderately obstructed coronary Arteries [J]. JACC Cardiovascular interventions, 2014, (7): 768-777), this document 2 discloses the following scheme: playing a coronary angiography image, observing the contrast agent entering the proximal anatomical landmark of the target vessel to the distal anatomical landmark The number of frames experienced by the point, according to the frame rate of the contrast image, obtains the transmission time of the contrast agent from the proximal marker point to the distal marker point. The three-dimensional reconstruction of coronary angiography is used to obtain the distance between the marker points, and the transmission time of the contrast agent is obtained. The distance divided by the transmission time is approximated as the blood flow velocity.

Digital tracking method: see Comparative Document 3 (Chen Xingxin, Luo Bingzhen, Yang Ruihua, Chen Lili. Clinical study of coronary angiography digital tracking technology for measuring coronary blood flow velocity[J]. Journal of Biomedical Engineering, 2007, 24(2): 294- 298), the document 3 discloses the following technical solution: a film ring coronary angiography sequence image, selecting a target blood vessel, and using digital tracking technology to measure the distance between two frames or N frames (marker points) image movement (diameter or curve) and The elapsed time automatically calculates the blood flow velocity.

Doppler guide wire method: See Comparative Document 1, which also discloses that a Doppler guide wire is inserted into a coronary vessel, and the blood flow velocity is measured by the Doppler effect generated between the ultrasonic vibration source and the relatively moving blood.

Temperature dilution method: The pressure guide wire is inserted into the coronary blood vessel, and the room temperature physiological saline is injected into the coronary artery, which is diluted with the flow of blood, and absorbs heat of the blood to raise the temperature. This temperature dilution process is detected by the thermistor in the front section of the catheter, and the temperature time dilution curve can be obtained by the detector recording. According to the thermal dilution theory, the blood flow velocity is inversely proportional to the average transit time of the indicator, and the blood flow velocity can be calculated from the temperature time dilution curve.

Although the above patent documents give a method of calculating blood flow or blood flow velocity per unit time from different angles and different calculation methods, they still have at least one or more of the following technical defects:

(1) The measurement accuracy of blood flow velocity is limited by the estimation of the length of the blood vessel and the short overlap of the coronary angiography.

(2) It is necessary to manually determine the starting position (starting frame) of the contrast agent into the coronary artery and the end position (end frame) of filling to the distal end of the target, and the calculation accuracy is affected by human factors.

(3) The calculation of the blood flow velocity is measured before the contrast agent leaves the segment of the blood vessel of interest, and the filling speed of the contrast agent is fast, and the time passing through the segment of the blood vessel of interest only takes up a certain period of a heartbeat cycle (usually less than A cardiac cycle), which causes the blood flow velocity determined during different periods of the heartbeat cycle to be the mean of the blood flow velocity of the non-integer cardiac cycle, which is significantly different from the actual mean blood flow velocity.

(4) Selecting a large region of interest, such as the entire coronary arteries and the microvessels of the myocardium perfused downstream, to calculate, can not ensure that the contrast of the image in the process of filling the region of interest is reduced or rising. For an integer number of cardiac cycles, this will result in a large deviation between the calculated unit time blood flow or blood flow velocity mean and actual unit time blood flow or mean blood flow velocity.

(5) Direct measurement of blood flow velocity is invasive, and the Doppler blood flow guide instrument is expensive and difficult for patients to support, which limits the clinical application of the method.

(6) The contrast region of interest does not shift correspondingly as the target vessel position moves in the contrast sequence, resulting in a change in the gray value in the region of interest not only due to the transmission of the contrast agent in the target vessel, but also due to the target vessel Removal and migration of the side branch vessels result in inaccurate blood flow or blood flow velocity per unit of time calculated.

Summary of the invention

The technical problem to be solved by the present invention is to provide a new method for calculating blood flow and blood flow velocity per vascular unit time, and the specific solutions include:

A method for calculating blood flow per unit time of a blood vessel, the method comprising: determining a region of interest of a blood vessel; calculating and fitting a grayscale fitting curve in the region of interest; determining a maximum grayscale within a predetermined time interval a value curve or a minimum gray value curve; calculating an area value of the area surrounded by the maximum gray value curve or the minimum gray value curve and the gray fitting curve in the predetermined time interval; and obtaining the area value based on the area value of the area The unit time blood flow.

A method for calculating a blood flow velocity of a blood vessel, the method comprising: determining a region of interest of a blood vessel; calculating and fitting a grayscale fitting curve in the region of interest; determining a maximum gray value within a predetermined time interval a curve or a minimum gray value curve; calculating an area value of a region surrounded by a maximum gray value curve or a minimum gray value curve and a gray fitting curve in a predetermined time interval; and obtaining an area value corresponding to the area value based on the area value of the area Blood flow per unit time; based on the blood flow per unit time and the lumen area of the blood vessel, the blood flow velocity of the blood vessel is obtained.

Preferably, the region of interest comprises a main branch vessel into which a contrast agent is injected and a branch thereof.

Preferably, the change of the position of the region of interest at different heartbeat times is detected by the target image tracking, thereby obtaining an optimal region of interest.

Preferably, the method further comprises: receiving an X-ray contrast image sequence of the blood vessel, selecting a region of interest; and selecting a gray-scale histogram in the region of interest in each frame of contrast before the start time is filled with the contrast agent, The gray histogram calculates the gray value in the region of interest under each frame, and fits the gray level fitting curve of the gray level with time according to the gray value.

Preferably, the method further comprises: determining a first time point, and a maximum value and a minimum value of the gray level fitting curve in a predetermined time interval centered on the first time point;

Preferably, the maximum gray value curve is a curve obtained by using a maximum value of the gray level fitting curve in the predetermined time interval as an ordinate; the minimum gray value curve is a gray level fitting curve in a predetermined time interval. The minimum value is the curve made by the ordinate.

Preferably, when the trend of the gradation fitting curve is decreasing, the first time point is a time point at which the gradation value of the gradation fitting curve decreases the fastest; when the gradation fitting curve changes trend When rising, the first time point is the time point at which the gray value rises fastest in the gray fitting curve.

Preferably, when the trend of the gradation fitting curve is decreasing, the slope of each point on the gradation fitting curve is calculated, and a point at which the slope is negative and the absolute value of the slope is the largest is obtained, and the point is a decrease in the gradation value. The fastest time point; when the trend of the gray fitting curve is rising, the slope of each point on the gray fitting curve is calculated, and the slope is obtained as a positive value, and the point where the value of the slope is the largest is the gray value rising. The fastest time.

Preferably, the calculating process of the area area value further includes: when the gradation fitting curve change trend is decreasing, acquiring a first time point in the gradation fitting curve, where the first time point is Integrating the gray fitting curve in the predetermined time interval of the center, calculating the area value of the maximum gray value curve and the gray level fitting curve in the predetermined time interval; when the gray fitting curve changes When the potential is rising, acquiring a first time point in the gray level fitting curve, integrating the gray level fitting curve in the predetermined time interval centered on the first time point, and calculating the predetermined time interval The area value of the area surrounded by the minimum gray value curve and the gray level fitting curve.

Preferably, the predetermined time interval is an integer number of cardiac cycles, and the integer is greater than or equal to 1.

Preferably, the predetermined time interval is a cardiac cycle, including each half of the cardiac cycle before and after the first time point; wherein the first and second half of the cardiac cycle time interval is that the contrast agent begins to fill After the region of interest of the vessel, this period of time before the region of interest is not fully filled.

Preferably, by checking the correspondence table, the blood flow per unit time corresponding to the area value of the area can be obtained, and the pair

It should be tabled as a correspondence table between blood flow rates of different area values and unit time.

Preferably, the lumen area of the blood vessel can be obtained by a three-dimensional quantitative measurement method.

Preferably, the fitting formula of the gradation fitting curve is:

g(t)=a ₀ +a ₁ t+a ₂ t ² +...+a _n t ⁿ ; where a ₀ , a ₁ , a ₂ , ... a _n are fitting coefficients, and t is time.

Preferably, the cardiac cycle is determined according to the electrocardiogram, or the number m of frames between the peak-to-peak value of the gray value calculated according to the original gray-scale curve before the fitting is calculated, and the cardiac cycle T=m/f is calculated, where f represents the frame of the contrast frequency.

Preferably, the original gray scale change curve is a raw data curve made by the gray value calculated by the gray histogram in the region of interest in each frame of the contrast image.

Preferably, after receiving the coronary angiography of the heart and obtaining the region of interest of the blood vessel, the obtained blood flow velocity can be used to evaluate the effect of blood vessel stenosis on blood flow velocity, or to calculate the FFR value of the stenotic blood flow reserve fraction.

Preferably, after obtaining a region of vascular interest by receiving a renal artery angiography image, the obtained unit time blood flow or blood flow velocity is used to evaluate changes in renal artery sympathetic nerve ablation before and after renal artery sympathetic nerve ablation, or for real-time use. Changes in blood flow and blood flow velocity per unit time during ablation were assessed.

Preferably, after obtaining the region of interest of the blood vessel based on the angiography of the tumor-bearing region, the obtained unit time blood flow or blood flow velocity can be used to evaluate the change in blood supply before and after the treatment of the tumor to prompt the therapeutic effect.

Preferably, after obtaining an area of interest of the blood vessel by receiving an arterial angiogram, the obtained blood flow velocity can be used to calculate a pressure drop or a blood flow reserve fraction (FFR) value of the stenotic blood vessel in the peripheral blood vessel.

The invention has the beneficial effects that the technical solution provides a new calculation method of blood flow and blood flow velocity per unit time, which ensures that the calculated blood flow per unit time and the blood flow velocity are the average values of blood flow velocity in an integer number of cardiac cycles. Thereby effectively avoiding the selection of inappropriate time periods, the calculated average unit time blood flow and blood flow velocity are calculation errors caused by the mean within the non-integer cardiac cycle. Using the change of the gray value of the image of the region of interest to find the blood flow velocity with time can not only achieve non-invasive diagnosis, but also selectively increase or eliminate the side branch blood flow to adapt to different applications.

DRAWINGS

Figure 1 is a gray histogram of a coronary angiography image;

2A is a schematic diagram showing changes in gray scale of a blood vessel before filling of a contrast agent;

2B is a schematic view showing changes in blood gray scale after filling of a contrast agent;

Figure 3 is a schematic diagram showing changes in blood flow velocity in different cardiac cycles measured by the Doppler guidewire method;

4 is a schematic diagram of an original gray scale variation curve and a gray scale fitting curve in different cardiac cycles of a region of interest;

Figure 5 is a schematic diagram of the calculation principle of blood flow and blood flow velocity per unit time.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described in the following with reference to the accompanying drawings 1-5 in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. example. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention are within the scope of the present invention.

Example 1

The present invention provides a method for calculating blood flow and blood flow velocity per vascular unit time, and specifically includes the following steps: First, determining a region of interest of a blood vessel (a preferred method is to select an angiogram by receiving X-ray angiography of the blood vessel a region of interest); secondly, calculating and fitting a grayscale fitting curve in the region of interest; secondly, obtaining a maximum grayscale value curve within a predetermined time interval; and secondly, calculating a maximum grayscale value within the predetermined time interval The area value S surrounded by the curve and the gray fitting curve; again, based on the area value S of the area, the blood flow Q per unit time corresponding to the area value is obtained; finally, the blood vessel is combined The lumen area, the blood flow velocity V of the blood vessel is obtained.

Preferably, the method may further comprise: determining a first time point, and a maximum value and a minimum value of the gray level fitting curve in a predetermined time interval centered on the first time point. Preferably, the first time point is a time point at which the gray value in the gray fitting curve decreases the fastest. The maximum gray value curve is a curve obtained by taking the maximum value of the gray fitting curve in the predetermined time interval as the ordinate.

Preferably, the change of the position of the region of interest at different heartbeat moments can be detected by the target image tracking registration, thereby obtaining the best region of interest. It should be emphasized that the region of interest in the prior art does not shift correspondingly as the target vessel position of the contrast sequence moves, resulting in a change in the gray value in the region of interest not only due to the transmission of the contrast agent in the target vessel, It is also possible that the calculated blood flow velocity is inaccurate due to the removal of the target blood vessel and the movement of the side branch vessels. The movement of the target vessel position of the contrast sequence is very common and can be caused by the beating of the heart, the breathing and movement of the patient.

Since the filling speed of the contrast agent is faster, the filling of the entire region of interest usually takes a short time. Therefore, it is preferable to select the entire cardiac period (T) within the predetermined time interval, that is, two-thirds before and after the first time point. The gradation fitting curve is integrated in the interval of one cardiac cycle to obtain the area value S. Wherein, the interval of one-half of the cardiac cycle time before and after the first time point is further preferably after the contrast agent begins to fill the region of interest of the blood vessel,

This period of time before the area of interest is not fully filled. In a preferred embodiment, the period of time comprises myocardial and microcirculation perfusion, and therefore, preferably, the selected region of interest is a myocardium that is perfused with the vessel segment of interest.

By checking the correspondence table, the unit time blood flow Q corresponding to the area value S can be obtained, and the correspondence table is a correspondence table between different area values and blood flow rates of different unit time, and the table can pass multiple times and repeatability. A large number of routine experiments were obtained and the table was updated based on later experimental data.

Among them, in calculating the cardiac cycle, a preferred calculation method is to obtain a cardiac cycle based on the electrocardiogram data. Or calculate the cardiac cycle T=m/f by calculating the number m of frames between the peak-to-peak value of the original gray-scale curve obtained from the histogram. Where f represents the frame frequency of the contrast. The original gray scale change curve is a curve obtained by directly calculating the gray value obtained from the contrast histogram of each frame, and is a raw data curve; the gray scale fitting curve is a curve obtained by fitting means according to the original data.

Preferably, the first time point is a time point at which the gray value in the gray fitting curve decreases the fastest. The point at which the slope is negative and the absolute value is the largest can be obtained by calculating the slope of each point on the gradation fitting curve. The point is the time point at which the gray value drops the fastest.

Preferably, the vascular lumen area A is obtained by a three-dimensional quantitative measurement method, and the average blood flow velocity is V=Q/A.

When it is to be noted, the present embodiment analyzes the case where the gray value change in the case of general angiography is a downward trend, that is, in the case where the obtained gradation fitting curve is a descending curve, by selecting the curve The point at which the gray value decreases the fastest is the first time point, and the predetermined time interval is determined centering on the first time point, and the maximum gray value curve is obtained based on the maximum value of the gray fitting curve of the predetermined time interval. Thereby, the curve area enclosed by the maximum gradation value curve and the gradation fitting curve in the predetermined time interval centered on the first time point is calculated.

However, in some contrast images, the gray value of the contrast agent is larger than the gray value before filling, and the gray value changes to an upward trend, that is, the obtained gray fitting curve is a rising curve, and at this time, It is necessary to detect the fastest rising time point in the gray fitting curve as the first time point; and obtain the minimum value of the gray fitting curve in the front and rear half of the cardiac cycle centered on the first time point; A minimum gray value curve is made for the ordinate; a curve area surrounded by the minimum gray value curve and the gray fitting curve in a predetermined time interval centered on the first time point is calculated. In this case, the slope of each point on the gradation fitting curve is calculated, and the slope is obtained as a positive value, and the point at which the value of the slope is the largest is the time point at which the gradation value rises the fastest.

Example 2

Referring to Figure 1, coronary angiography uses human soft tissue and contrast agents to absorb different degrees of radiation in the contrast image.

The image has a different high contrast between the blood vessels and the surrounding tissue. The color depth of each pixel in the contrast image is represented by a gray value, and the larger the gray value, the brighter the pixel. The gray histogram is the simplest and most useful tool in digital images. It represents the number of pixels with a certain gray level in the image. The horizontal coordinate is the gray value. The value range is preferably 0-255, and the ordinate. Indicates the number of occurrences of the gray value in the image. The value range is preferably 0-N, where N is the number of image pixels.

As shown in Figure 2, we chose to include a narrow vessel as the region of interest, including the main branch of the contrast agent injected and its branches. The blood vessels have higher gray values before they enter the contrast agent (Figure A) and cannot be distinguished from the surrounding soft tissue. After entering the contrast agent (Figure B) contrast agent with blood Flow diffusion, because the contrast agent absorbs the radiation more strongly, the gray value of the region of interest decreases, and the blood vessel color becomes darker. After several cardiac cycles, the contrast agent is diluted and the gray value of the region of interest is increased. Therefore, the rate of change of the gray value of the region of interest reflects the blood flow velocity within the lumen.

The average blood flow velocity is similar in each cardiac cycle, but the selection of different time periods has a great influence on the calculation of the average blood flow velocity. As shown in Figure 3, the blood flow velocity curves were measured directly in different cardiac cycles using the Doppler guidewire method. The average blood flow velocities obtained by different time periods T1 and T2 with the same time interval are greatly different. Therefore, in order to ensure accurate calculation values, it is preferable to select an integer number of cardiac cycles for blood flow velocity mean calculation, such as a whole cardiac cycle.

As shown in FIG. 4, the gray value of each frame of the contrast region of interest is extracted, and the gray scale fitting curve g(t) is fitted. For example, three or more (ie, N>=3) cardiac cycles are preferentially selected, and before the start time is the contrast agent filling, a gray histogram in the region of interest in each frame of contrast is extracted, and each gray histogram is calculated by the gray histogram. The gray value in the region of interest under the frame, and fitting the gray fitting curve g(t) according to the gray value, the fitting formula is a polynomial fitting:

g(t)=a ₀ +a ₁ t+a ₂ t ² +...+a _n t ⁿ ; where a ₀ , a ₁ , a ₂ , ... a _n are fitting coefficients, and t is the time at which the contrast agent fills the blood vessel The time is the time calculated from the first frame of image acquisition.

In general, the cardiac cycle can be obtained from the ECG data. In the absence of electrocardiogram data, the number of frames m between the peak-to-peak values of the original gray-scale curve obtained from the histogram can be calculated, and the cardiac cycle is obtained by the formula T=m/f, where f represents the frame frequency of the contrast.

As shown in Fig. 5, a point (t0, g(t0)) at which the absolute value of the slope is maximum during the gradation of the gradation value is obtained, and the point is determined as the first time point. The area value S of the area (shaded area in the figure) surrounded by the curve g(t) in the one-half cardiac cycle [t1, t2] and the maximum gray value curve g(t1) before and after the first time point is calculated. Wherein, the maximum gray value curve g(t1) is a curve made by the maximum value of the curve g(t) in the [t1, t2] time period; the shadow area value S and a cardiac cycle blood flow Q is proportional to, that is, S∝Q.

Example 3

It should be noted that the X-ray angiography used in the embodiments of the present invention may be cardiac coronary angiography, peripheral angiography such as renal angiography, carotid angiography, or the like, or angiography before and after tumor treatment. The unit time blood flow or blood flow velocity obtained based on the above different contrast modes can be used for key parameter indicators in different disease condition analysis, and obtains better accuracy than the prior art parameter indicators. Sex and precision. For example, calculation of blood flow velocity based on coronary angiography can be used to assess the effect of vascular stenosis on blood flow velocity, as well as subsequent calculation of pressure differences or flow reserve fraction (FFR) values for stenotic vessels; renal angiography can be used in renal arteries Sympathetic ablation is used to assess changes in blood flow per unit time of renal arteries before and after sympathetic nerve ablation, or to assess changes in blood flow and blood flow velocity per unit time during ablation in order to demonstrate the effect of ablation; Contrast calculation of blood flow or blood flow velocity per unit time can be used to assess changes in blood supply before and after treatment to suggest a therapeutic effect.

In a specific embodiment, the present invention provides a method for calculating a blood flow reserve fraction FFR of a certain segment of blood vessels, based on the average blood flow velocity or maximum mean blood flow velocity obtained by the method for calculating blood flow velocity in the present invention. And combined with other geometric parameters of the segment of the blood vessel, the pressure drop or FFR value of the blood vessel is obtained by a corresponding calculation formula. The method includes receiving geometric parameters of the segment of blood vessels, the blood vessel including a proximal end point and a distal end point, the geometric parameters including a first geometric parameter representing an area (or diameter) of a proximal cross section of the blood vessel segment; a second geometric parameter representing the area (or diameter) of the distal cross section of the vessel segment; a third geometric parameter representing a cross-sectional area (or diameter) of the vessel member at a first location between the proximal end and the distal end Taking the proximal end point as a reference point, based on the geometric parameters and the distance from the point on the vessel segment to the reference point, the reference lumen diameter function and the geometric parameter difference function are calculated; the geometric parameter difference function is obtained at multiple scales a difference derivative function corresponding to a plurality of scales is obtained; the scale refers to a resolution, that is, a distance between two adjacent points when the derivative is numerically calculated; and the method for calculating the blood flow velocity is obtained by using the method of the present invention. The vessel segment calculates its corresponding maximum mean blood flow velocity at the mean blood flow velocity of conventional coronary angiography; the blood is obtained based on the multi-scale difference derivative function and the maximum mean blood flow velocity Ratio at the first position of the second flow between the first pressure and blood pressure at the proximal end, i.e., fractional flow reserve.

One of the innovations of the present invention is that the blood flow rate in the whole cardiac cycle is calculated centering on the fastest position of the grayscale fitting curve, thereby more accurately calculating the blood flow and blood flow velocity per unit time, which is effective. The error caused by the calculation of the inappropriate time interval is avoided. The invention has the beneficial effects that the technical solution provides a new calculation method of blood flow and blood flow velocity per unit time, which ensures that the calculated blood flow per unit time and the blood flow velocity are the average values of blood flow velocity in an integer number of cardiac cycles. Thereby effectively avoiding the misalignment

When the time period is selected, the calculated unit time blood flow and the mean blood flow velocity are calculation errors caused by the mean within the non-integer cardiac cycle. Using the change of the gray value of the image of the region of interest with time The blood flow rate not only achieves a non-invasive diagnosis, but also selectively increases or eliminates the side branch blood flow to suit different applications.

While the present invention has been described in its preferred embodiments, the present invention is not intended to be limited thereto, and the present invention may be modified and improved without departing from the spirit and scope of the invention. The scope of protection is defined by the terms of the claims.

Claims

A method for calculating blood flow per unit time of a blood vessel, the method comprising:

Determining the region of interest of the vessel;

Calculating and fitting a gray level fitting curve in the region of interest;

Determining a maximum gray value curve or a minimum gray value curve within a predetermined time interval;

Calculating a region value of a region surrounded by a maximum gray value curve or a minimum gray value curve and a gray fitting curve in a predetermined time interval;

Based on the area value of the area, the blood flow per unit time corresponding to the area value is obtained.
A method for calculating a blood flow velocity of a blood vessel, the method comprising:

Determining the region of interest of the vessel;

Calculating and fitting a gray level fitting curve in the region of interest;

Determining a maximum gray value curve or a minimum gray value curve within a predetermined time interval;

Calculating a region value of a region surrounded by a maximum gray value curve or a minimum gray value curve and a gray fitting curve in a predetermined time interval;

Obtaining a blood flow per unit time corresponding to the area value based on the area value of the area;

The blood flow velocity of the blood vessel is obtained based on the blood flow per unit time and the lumen area of the blood vessel.
The method according to claim 1 or 2, wherein the region of interest comprises a main branch vessel into which a contrast agent is injected and a branch thereof.
The method according to claim 1 or 2, characterized in that the change of the position of the region of interest at different heartbeat times is detected by the target image tracking, thereby obtaining an optimal region of interest.
The method according to claim 1 or 2, wherein the method further comprises:

Accepting the X-ray contrast image sequence of the blood vessel, selecting the region of interest; selecting the starting time for the filling of the contrast agent, calculating the total gray value in the region of interest in each frame of contrast, and fitting the gray scale with time according to the gray value A varying grayscale fit curve.
The method according to claim 1 or 2, wherein the method further comprises:

Determining a first time point, and a maximum value and a minimum value of the gradation fitting curve in a predetermined time interval centered on the first time point;

Preferably, the maximum gray value curve is a curve obtained by using a maximum value of the gray level fitting curve in the predetermined time interval as an ordinate; the minimum gray value curve is a gray level fitting curve in a predetermined time interval. The minimum value is the curve made by the ordinate.
The method according to claim 6, wherein when the change trend of the gradation fitting curve is decreasing, the first time point is a time point at which the gradation value of the gradation fitting curve decreases the fastest; When the change trend of the gradation fitting curve is rising, the first time point is a time point at which the gradation value of the gradation fitting curve rises fastest.
The method according to claim 7, wherein when the trend of the gradation fitting curve is decreased, the slope of each point on the gradation fitting curve is calculated, and a point at which the slope is negative and the absolute value of the slope is the largest is obtained. The point is the time point at which the gray value decreases the fastest; when the change trend of the gray fitting curve is rising, the slope of each point on the gray fitting curve is calculated, and the slope is obtained as a positive value, and the slope is The point with the largest value is the time point at which the gray value rises the fastest.
The method according to claim 7 or 8, wherein the calculation process of the area area value further comprises:

When the gradation fitting curve change trend is decreasing, acquiring a first time point in the gradation fitting curve, and integrating the gradation fitting curve in the predetermined time interval centered on the first time point Calculating a maximum gray value curve in the predetermined time interval and an area value of the area surrounded by the gray level fitting curve;

When the gradation fitting curve change trend is rising, acquiring the first time point in the gradation fitting curve, and integrating the gradation fitting curve in the predetermined time interval centered on the first time point And calculating a region value of the area surrounded by the minimum gray value curve and the gray level fitting curve in the predetermined time interval.
The method according to any one of claims 1-9, wherein the predetermined time interval is an integer number of cardiac cycles, and the integer is greater than or equal to one.
The method according to claim 10, wherein the predetermined time interval is a cardiac cycle, including each one-half cardiac cycle before and after the first time point; wherein the first time point is two-thirds before and after A cardiac cycle time interval is the period of time before the contrast agent begins to fill the region of interest of the vessel, before the region of interest is fully filled.
The method according to any one of claims 1-11, wherein the unit time blood flow corresponding to the area value of the area is obtained by checking the correspondence table, wherein the correspondence table is different blood values of different area values and unit time. Correspondence table between flows.
A method according to any one of claims 1-12, wherein the vascular lumen area is obtainable by a three-dimensional quantitative measurement method.
The method according to any one of claims 1 to 13, wherein the fitting formula of the gradation fitting curve is:

g(t)=a 0 +a 1 t+a 2 t 2 +...+a n t n ; where a 0 , a 1 , a 2 , ... a n are fitting coefficients, and t is time.
The method according to any one of claims 1 to 14, wherein the cardiac cycle is determined according to the electrocardiogram, or the number m of frames between the peak-to-peak value of the gray value obtained from the original gray-scale curve before the fitting is determined, The cardiac cycle T = m / f is calculated, where f represents the frame frequency of the contrast.
The method of claim 15 wherein said raw grayscale profile is a raw data curve of grayscale values computed from a grayscale histogram of the region of interest in each frame of the contrast image.
The method according to any one of claims 2 to 16, wherein the obtained blood flow velocity is used to evaluate the effect of blood vessel stenosis on blood flow velocity after receiving a coronary artery angiography to obtain a region of interest of the blood vessel. Or follow-up calculation of the stenotic blood flow reserve fraction FFR value.
The method according to any one of claims 1 to 16, wherein after obtaining a region of interest of the blood vessel by receiving a renal artery angiography image, the obtained unit time blood flow or blood flow velocity is used for renal artery sympathetic nerve ablation. To assess changes in renal artery sympathetic nerve before and after ablation, or to assess changes in blood flow and blood flow velocity per unit time during ablation to suggest ablation therapy.
The method according to any one of claims 1 to 16, wherein the obtained unit time blood flow or blood flow velocity is available for evaluating the tumor after receiving the vascular angiography based on the tumor region. Changes in blood supply before and after treatment to suggest a therapeutic effect.
A method for calculating a pressure drop or a blood flow reserve fraction (FFR) of a segment of blood vessels, wherein the average blood flow velocity of the segment of blood vessels is calculated based on the method for calculating blood flow velocity according to any one of claims 2-16, Combined with other geometric parameters of the segment of the blood vessel, the pressure drop or FFR value of the segment of the blood vessel is obtained by a corresponding calculation formula.