JPH09330413A - Blood vessel tracking processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify inputting operation and to reduce time for blood vessel tracking processing by accurately calculating the tracking starting direction of only a desired blood vessel in a blood vessel processing method which tracks a blood vessel from a designated tracking start point to a tracking finish point to display the result and which repeats tracking by searching at angles in some range by setting the direction of a tracking line obtained by the search last time to be a tracking direction until reaching the surrounding of the tracking finish point. SOLUTION: This method is provided with a blood vessel tracking starting direction calculating means (step 13) calculating an average density on each straight line extended radially from the tracking start position concerning the inside of the circle of a radius, which is provided with the tracking start point in a center and proportional to the point, before starting the blood vessel tracking processing, selects a tracking candidate line based on the average density and gives prescribed weight setting the direction of the tracking finish point to be maximum to the average density of the tracking candidate line to calculate the tracking starting direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a blood vessel tracking processing method capable of tracking and displaying only a desired blood vessel among one or a plurality of blood vessels traveling in various shapes (routes).

[0002]

2. Description of the Related Art Conventional blood vessel tracking methods, for example, digital subtraction angiography (DSA)
As a method of blood vessel tracking, which is the first step when measuring the blood vessel stenosis rate in the device, if the blood vessel to be traced is specified in the range from the tracking start point to the tracking end point on the blood vessel image displayed on the monitor, the blood vessel is automatically There is a blood vessel tracking processing method for tracking and displaying the result. Further, in such a blood vessel tracking processing method, there is a method of repeating the processing of searching the tracking line in a certain range with respect to the previous (temporally preceding) search direction.

Such a blood vessel tracking processing method will be described below. For tracking, first, a search is started in the tracking start direction from the tracking start point input by the operator. The tracking start direction is a direction that serves as a reference when performing the first search from the tracking start, and is input by the operator or calculated from the density value around the tracking start point. A certain range centered on the tracking start direction from the tracking start point input by the operator,
For example, from the tracking start direction −90 ° to the tracking start direction + 90 °
The average concentration value on each straight line radially extending from the tracing start point at an angle in the range is calculated, and the straight line having the maximum value among the straight lines having the maximum value is set as the tracing line. The reason why the tracking line is searched in a certain range here is that the blood vessel is basically considered to always move forward without making a sudden return.
Therefore, the tracking start direction for performing the first search should be approximately the direction in which the blood vessel should advance. In the search for the next tracking line, the direction of the tracking line obtained in the previous search is set as the tracking direction, and the search is performed at an angle within a certain range. Such tracking is repeated until the area around the tracking end point is reached. Further, in order to reliably track the desired blood vessel, the tracking is similarly performed from the tracking end point toward the tracking start point, and both tracking lines are combined to complete the process.

[0004]

According to the above-mentioned prior art, the operator inputs a tracking start point, a tracking end point, a tracking start direction from the tracking start point, and a tracking start direction from the tracking end point in order to perform tracking. The input operation was complicated. Also, in the automatic calculation of the tracking direction, the direction of high density (assuming that the blood vessel is represented by high density) is selected as the blood vessel from the average density value around the tracking start point, and some of the selected blood vessels are selected. In the direction of the track until the end of the track is reached (International Jou
rnal of Cardiac Imaging) 5: 75-83, 1990.)
There was a problem that processing time was required.

An object of the present invention is to provide a blood vessel tracking processing method which can reduce the labor of input operation and can shorten the processing time.

[0006]

[Means for Solving the Problems] The above object is a blood vessel tracking processing method for tracking a blood vessel from a designated tracking start point to a tracking end point and displaying the result, which is obtained by a previous search. In the method of repeating the tracking by performing a search in a certain range of angles with the direction of the traced line as the tracking direction, until the tracking start point is reached, the tracking start point is centered before the start of the blood vessel tracking process. Calculate the average density value on each straight line extending radially from the tracking start point within a circle with a radius proportional to the density at that point, select a tracking candidate line based on that average density value, and average the tracking candidate lines. This is achieved by providing a blood vessel tracking start direction calculating means for calculating the tracking start direction by performing a predetermined weighting on the density value so that the tracking end point direction is maximized. Before starting the blood vessel tracking process, the blood vessel tracking start direction calculation means calculates an average density value on each straight line radially extending from the above tracking start point within a circle having a radius centered at the tracking start point and being proportional to the density of that point. Calculate and select a tracking candidate line based on the average density value,
The average density value of the tracking candidate line is given a predetermined weighting that maximizes the direction of the tracking end point to calculate the tracking start direction.
As a result, the tracking start direction can be correctly calculated even when there is an extremely curved blood vessel or a branch at the tracking start point, and it is possible to reduce the labor of input operation and the processing time.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing an embodiment of a blood vessel tracking processing method according to the present invention. As shown in FIG. 1, in the method of the present invention, the operator first inputs the tracking start point and the tracking end point of the blood vessel to be tracked on the blood vessel image displayed on the monitor (step 11). Next, the image data including the blood vessel image is read (step 12), the density value of the input point and its surroundings and predetermined weighting are performed to calculate the blood vessel tracking start direction (step 13). This step 13 part is the main part of the method of the present invention. Next, using the tracking start point and the tracking end point input in step 11 and the blood vessel tracking start direction calculated in step 13, a tracking line is calculated in the same manner as in the conventional method, and then the same tracking line as in the conventional method is calculated. Is repeated until reaching around the tracking end point (step 14).

FIG. 2 is a flow chart showing the details of an example of the blood vessel tracking start direction calculating means (calculating the blood vessel tracking start direction in step 13) in the method of the present invention. First, from the input tracking start point and tracking end point and the image data, the average density on each straight line extending radially from the above tracking start point within a circle having a radius centering on the tracking start point and being proportional to the density of that point. Values are calculated from the angle 0 ° to 360 ° with respect to the x-axis (reference axis) (step 21). Next, the direction (angle) having the maximum value among the calculated average density values is calculated (step 22), and the average density value in the direction having the maximum value is weighted (step 23). Then, the direction in which the maximum value direction average density value × weight in step 23 is the maximum value is calculated (step 24).

Here, the weight in step 23 becomes 1 in the direction from the tracking start point to the tracking end point, and becomes smaller as it goes away from that direction, for example, as shown in FIGS. 3 (a) to 3 (c). Such a weight (function). Among these, the weight shown in (a) is suitable for almost correctly calculating the tracking start direction in most blood vessel shapes.
The weight shown in (b) is particularly effective when there is a blood vessel branch near the tracking start point. The weight shown in (c) is suitable for correctly calculating the direction even for a blood vessel that is once separated from the tracking end point when the tracking direction is toward the high density portion.

FIG. 4 is an explanatory diagram showing an example in which the above-described blood vessel tracking start direction calculation is applied to a substantially linear blood vessel.
(A) is a figure which shows the mode of calculation of the blood-vessel tracking start direction. Here, the average density value on each straight line radially extending from the tracking start point in the circle having an appropriate radius with the tracking start point as the center and the average density value when the angle with respect to the x-axis is calculated from 0 ° to 360 ° The maximum value (Fig. 4)
FIG. 4B shows the result of calculating the weighted values shown in FIG. 3A (see FIG. 4C).

FIG. 5 is an explanatory diagram showing an example in which the above-described blood vessel tracking start direction calculation is applied to an extremely curved blood vessel, and FIG. 5A is a diagram showing a state of the blood vessel tracking start direction calculation. Here, the average density value on each straight line radially extending from the tracking start point in the circle having an appropriate radius with the tracking start point as the center and the average density value when the angle with respect to the x-axis is calculated from 0 ° to 360 ° The maximum value (see FIG. 5B) among them shows the result of calculating the value when predetermined weighting is performed (see FIG. 5C).

FIG. 6 is an explanatory diagram showing an example in which the above-described blood vessel tracking start direction calculation is applied to a blood vessel having a branch near the tracking start point, and FIG. 6A is a diagram showing a state of the blood vessel tracking start direction calculation. is there. Here, as in FIG. 5, when the average density value on each straight line radially extending from the tracking start point in a circle with an appropriate radius centered on the tracking start point is calculated from the angle 0 ° to 360 ° with respect to the x axis. The result of calculating a value when predetermined weighting is performed on the average density value and the maximum value thereof (see FIG. 6B) is shown (FIG. 6C).
reference).

If the example of FIG. 4 is further explained, in this example, the tracking start point is the center and the surroundings are from 0 ° to 360 °.
The result of calculating the average density value up to ° is the graph of FIG. Usually, the blood vessel has the highest concentration near the center, and therefore has a maximum value in the direction indicating the center of the blood vessel. At this time, as shown in the graph of FIG. 4B, even if the maximum value B is higher in concentration, the graph of FIG. A has a larger value, and the tracking direction selected is the maximum value A direction.

Similarly in the example of FIG. 5, the result of calculating the average density value from 0 ° to 360 ° around the tracking start point is the graph of FIG. 5 (b). Here, the graph of FIG. 5C is obtained by multiplying the average density values of the local maximum values A and B by weights that maximize the direction of the tracking end point, and the larger value of the local maximum values is set as the tracking start direction. In order to
The direction of the maximum value A is selected as the tracking start direction.

Similarly in the example of FIG. 6, the graph of FIG. 6B shows the result of calculating the average density value from 0 ° to 360 ° around the tracking start point. In this example, there are three maximum values (A, B, C), but the average density value is weighted to maximize the direction of the tracking end point.
The graph of (c) is obtained, and the largest value among the maximum values in this graph is set as the tracking start direction, so the direction of the maximum value B is selected as the tracking start direction.

According to the above-described embodiment, since the correct tracking start direction can be obtained for almost all blood vessels by the blood vessel tracking start direction calculation means, the operator does not need to input the tracking start direction, and the curve bends extremely. Even in the case of a blood vessel or a blood vessel having a branch, the blood vessel can be traced only by designating two points of the tracking start point and the tracking end point.

[0017]

As described above, according to the present invention, the tracking start direction of the blood vessel is calculated in consideration of both the direction of the tracking end point and the average density value of 360 ° around the tracking start point.
The tracking start direction can be calculated correctly not only for almost straight blood vessels, but also for extremely curved blood vessels and blood vessels with branches near the tracking start point. By specifying only two points, the tracking start point and the tracking end point, Tracking can be done. That is, the labor of input operation can be reduced. In addition, since the direction of the blood vessel from the tracking start point to the tracking end point can be reliably calculated, it is not necessary to perform tracking in all directions, and the tracking time can be shortened (the blood vessel tracking processing time can be shortened).

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of the method of the present invention.

FIG. 2 is a flowchart showing details of an example of blood vessel tracking start direction calculation means in the method of the present invention.

FIG. 3 is a diagram showing an example of a weighting function used in the processing step in FIG.

FIG. 4 is an explanatory diagram showing an example in which the blood vessel tracking start direction calculation in the method of the present invention is applied to a substantially linear blood vessel.

FIG. 5 is an explanatory diagram showing an example in the case of being applied to an extremely curved blood vessel.

FIG. 6 is an explanatory diagram showing an example in the case of applying the same to a blood vessel having a branch near the tracking start point.

[Explanation of symbols]

11 step of inputting tracking start point and tracking end point of blood vessel to be tracked 12 step of reading image data including blood vessel image 13 blood vessel tracking start direction calculation step 14 tracking line calculation (tracking processing) step

Claims (1)

[Claims] 1. A blood vessel tracking processing method for tracking a blood vessel from a designated tracking start point toward a tracking end point and displaying the result, wherein the direction of a tracking line obtained in a previous search is tracked. In the method of repeating the tracking by searching at an angle within a certain range as the direction until reaching the vicinity of the tracking end point, before starting the blood vessel tracking processing, the radius proportional to the concentration of the tracking start point as the center Calculate the average density value on each straight line that extends radially from the tracking start point within the circle, select the tracking candidate line based on the average density value, and set the tracking end point direction to the average density value of the tracking candidate line. A blood vessel tracking processing method comprising: a blood vessel tracking start direction calculation unit that calculates a tracking start direction by performing a predetermined weighting that maximizes the weight.