JPH04208138A - Method and device for measuring blood vessel - Google Patents

Abstract

PURPOSE:To enable blood vessel edges to be extracted at any time by using subtraction image data, producing blood vessel profiles, using prescribed values set according to photographing conditions and extracting blood vessel edges from the profiles. CONSTITUTION:An X-ray processing device 2 takes in image data from an image supplying device 1 and processes the data, and supplies the processed data to a TV monitor 3 for display on it. Namely, plotographing conditions are set to photograph objects of inspection, under which conditions a difference is gained between mask image data before injecting an angiography agent and live image data after injecting an angiography agent by a subtracter 30 for subtraction image data. By using this subtraction image data, blood vessel profiles are produced with a profile circuit 32, from which profiles blood vessel edges are extracted by using prescribed values set sccording to photographing conditions. This can always extract the blood vessel edges with accuracy.

Description

Detailed Description of the Invention [Objective of the Invention] (Use of p?-[-1 1 Ono) The present invention creates a profile of a blood vessel from retraction image data, and uses this profile to identify one part of the blood vessel. The present invention relates to a method for measuring blood vessel t1 and an apparatus for the same.

(Prior Art) Conventionally, in radiographic diagnostic equipment and typical X-ray diagnostic equipment (-2), when determining a blood vessel diameter from a DSA (digital subtraction angiography) image, a blood vessel profile is created17, A method is used in which a certain feature point of this blood vessel profile is extracted (2) and the feature point is defined as the edge of the blood vessel (hereinafter referred to as an edge).

FIG. 7 is a diagram showing 11'-soji extraction of this type of blood vessel. If the X-ray imaging system such as the X-ray tube and X-ray controller is ideal, and there are no scattered rays and no image blur, the data for the blood vessel profile will be zero as shown in Figure 7. Points other than the above become blood vessels, so from point a to point a4
It is possible to determine the diameter of the blood vessel.

However, in actual X-ray photography, scattered rays are present and the image is blurred, so image data is not zero in an area wider than the actual blood vessel diameter.

Therefore, in order to extract the edges of the blood vessels that are too narrow, for example, a certain threshold value (a certain positive value) is used, and the feature points where the image data of the blood vessel profile intersects with this threshold value are used. This characteristic point is used as the edge of the blood vessel.

Further, as a method for extracting the edge of the blood vessel, for example, there is a method of finding an inflection point of the profile of the blood vessel and using this inflection point as the edge of the blood vessel.

However, the shape of the profile differs depending on the imaging conditions, such as the tube current and voltage of the X-ray tube, the thickness of the subject, and the grid used to remove scattered radiation. For this reason, if an attempt is made to determine the edge of a blood vessel using the same threshold value or inflection point, the correct blood vessel edge cannot be determined and the actual blood vessel diameter cannot be accurately measured.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a blood vessel measurement method and an apparatus thereof that can improve the accuracy of blood vessel edge extraction.

[Configuration of the Invention (Means for Solving the Problems) The present invention has taken the following measures in order to solve the above problems and achieve the objects. That is, the present invention provides a radiography system that sets imaging conditions for imaging a subject, and detects the difference between mask image data before vascular contrast agent injection and live image data after vascular contrast agent injection under the imaging conditions. subtraction means for obtaining subtraction image data; means for creating a blood vessel profile using the subtraction image data; and means for extracting blood vessel edges from the profile using predetermined values set according to the imaging conditions. It is characterized by having the following.

In addition, the radiography system sets the imaging conditions for subject imaging, and the difference between the mask image data before the angiographic contrast agent injection and the live image data after the angiographic contrast agent injection is calculated under the imaging conditions, and the subtraction image data is obtained. a step of creating a blood vessel profile using the subtraction image data and setting a predetermined value according to the imaging conditions; and a step of extracting blood vessel edges from the profile using the predetermined value. It is characterized by becoming.

(Effects) By taking such measures, the following effects are achieved. A blood vessel profile is created using subtraction image data obtained from mask image data and live image data, and blood vessel edges are extracted from the profile using predetermined values set according to the imaging conditions. Even if the scattered radiation dose changes due to changes in the imaging conditions of the imaging system, the edges of blood vessels can always be accurately extracted.

(Embodiment) FIG. 1 is a diagram showing a schematic configuration of an embodiment of a blood vessel measuring device according to the present invention, and FIG. 2 is a diagram for explaining a blood vessel measuring method. In FIG. 1, the blood vessel measuring device is applied to an X-ray diagnostic device and is configured as follows.

The X-ray image processing device 2 takes in image data from the image data supply device 1, processes the image data,
The processed image data is supplied to the TV monitor 3 for displaying it.

The image data supply device 1 is configured as follows. X
The ray tube 10 irradiates X-rays to the subject 12, and is also an X-ray imaging system that sets imaging conditions for imaging the subject, such as tube voltage, tube current, subject thickness, and removal of scattered rays. is an X-ray tube 10. Subject 12. The X-ray controller 401 is composed of a grid (not shown).

Image intensifier 14 (hereinafter referred to as 1.1.
That's what it means. ) detects the X-rays transmitted through the subject 1-2 and converts the detected X-rays into an optical image. The TV left camera 8 has a lens 16a.

] -6b etc., the optical system 16 incident from 1.1.14 is converted into TV video data, and this T
It supplies V video data to the X-ray image processing device 2.

The x1i1 image processing device 2 is configured as follows. Analog/digital converter (hereinafter referred to as ADC)
Reference numeral 20 converts analog TV video data captured from the TV left camera 8 into digital TV video data (hereinafter referred to as image data).

The output terminal of the ADC 20 is the live memory 22. It is connected to the mask memory 24.

The mask memory 24 is a memory having a pixel matrix size, and stores mask image data M before angiographic contrast agent injection.

The live memory 22 is a memory having a size equal to the pixel matrix size, and stores the live image data L taken in from the ADC 20 after the angiographic contrast agent has been injected.

The logarithmic converter 26 logarithmically transforms the live image data L and supplies the logarithmically transformed live image data L1 to the subtracter 30, and the logarithm converter 28 logarithmically transforms the mask image data M and supplies the logarithmically transformed mask image. Subtractor 3 for data M
0.

The subtractor 30 calculates the difference between the logarithmically transformed live image data L1 and the logarithmically transformed mask image data M, obtains subtraction image data S for a blood vessel image as shown in FIG. sub)・Rakuction image data S
is supplied to the profile circuit 32.

The profile circuit 32 takes in the subtraction image data S from the subtractor 30 and selects an arbitrary blood vessel image among the blood vessel images shown in FIG. 3, for example, in a direction orthogonal to the running direction of the blood vessel. (From start point b1 to end point b
2), a blood vessel profile PL as shown in FIG. 4 is created, and this blood vessel profile PL is supplied to the blood vessel diameter control circuit 34. The profile PL of this blood vessel is tll
- It has a peak characteristic, and the pixel value of each pixel point corresponding to a blood vessel is large.

On the other hand, the X-ray:1 controller 40 issues control commands for the tube voltage (KV) and tube current (mA) to the X-ray tube 10, and also supplies the imaging conditions to the threshold value calculation circuit 42. .

The threshold calculation circuit 42 calculates the amount of scattered X-rays according to the imaging conditions taken in from the X-ray controller 40.
,, A threshold value S HL (also referred to as a threshold level) as a predetermined value for obtaining the edge of the blood vessel is changed in accordance with the amount of scattered X-rays.

The blood vessel edge measurement circuit 34 is connected to the profile circuit 32.
Two characteristic points, namely, the edge of the blood vessel (l l +
a2 is extracted, and this blood vessel's = 9- gill 7al, a7. is supplied to the TV monitor 3.

On the other hand, as shown in FIG. 2, the method for extracting the edges of blood vessels involves setting the imaging conditions for imaging the subject using the radiography system (step S1), and under the imaging conditions, the X-ray tube 10 step S2), obtain mask image data before angiographic contrast agent injection (step S), obtain live image data after angiographic contrast agent injection (step S4), and calculate the difference between these image data and perform subtraction. Obtain image data (Step S)
, a blood vessel profile is created along a direction perpendicular to the running direction of the blood vessel using this subtraction image data (step S6), and a step S7 of setting a predetermined value according to the imaging conditions; Step S8 of extracting blood vessel edges from the profile using the values.

Next, the X-ray diagnostic apparatus shown in FIG. 1 and the blood vessel edge extraction method shown in FIG. 2 will be explained with reference to the drawings.

First, set the imaging conditions using the X-ray imaging system.
-- (Step S1). Then, when relatively smaller tube current and tube voltage are applied to the X-ray tube 0 than the X-ray controller 40, X-rays are emitted from the X-ray tube 10 under the above-mentioned imaging conditions (step S2
), the transmitted X-rays that have passed through the subject 12 are converted into an optical image by 1.1.14.

The optical image is sent to the TV left camera 8 via lenses 16a and 16b.
The TV video data is converted to TV video data by
The data is converted into digital image data by the DC 20. The mask image data M of only the bones before the contrast agent injection is stored in the mask memory 24 (step S3), and the live image data L after the contrast agent injection is stored in the live memory 22 (step S4).

Then, the live image data L,
The mask image data M is logarithmically transformed using the following equation.

M,=1ogM L,=1ogL If a T conversion table is prepared and the live image data L and mask image data M are logarithmically converted using this conversion table, high-speed processing can be performed. These image data are then supplied to a subtracter 30.

Next, subtraction image creation by the subtractor 30 will be explained. Mask image data M1 after log conversion. The live image data L1 is subtracted by the subtractor 30 using the following equation, thereby creating subtraction image data S (step S5).

S=M, -L.

Next, the profile circuit 32 selects a blood vessel of interest in the →nobtraction image data,
The running direction of the blood vessel and the profile PL of the blood vessel in the direction orthogonal thereto are created as shown in FIG. 5 (step S6).
. As shown in the figure, the blood vessel profile PL has a relatively steep single peak characteristic due to the relatively small amount of scattered X-rays.

At the same time, when the imaging conditions are taken into the threshold calculation circuit 42 from the X-ray controller 40, the threshold calculation circuit 42
Accordingly, a threshold value SHL which is relatively close to zero and which has changed in accordance with the relatively small scattered dose corresponding to the imaging condition is supplied to the blood vessel edge measurement circuit 34 (step S7). Then, the profile circuit 3 uses the relatively close to zero threshold SHL changed by the threshold calculation circuit 42
By intersecting the blood vessel profile PL, which has relatively steep unimodal characteristics taken in from
, a2 are extracted (step Ss).

Therefore, the edges of blood vessels can be extracted correctly.

Next, when a relatively high tube voltage or tube current is applied to the X-ray tube 10 from the X-ray controller 40, the profile circuit 32
The profile PL2 obtained from the above has a relatively gentle single peak characteristic as shown in FIG. At the same time, when the imaging conditions from the X-ray controller 40 are taken into the threshold value calculation circuit 42, the threshold calculation circuit 42 calculates that the imaging conditions, that is, the high tube voltage and tube current, cause a relatively large amount of scattered radiation. A large threshold value S HL 2 is supplied to the blood vessel edge measuring circuit 34 .

That is, among the imaging conditions, by increasing the threshold value as the imaging tube voltage (KV) is higher or as the subject 12 is thicker, it is possible to always accurately extract the edge al+''2 of the blood vessel.

As described above, according to this embodiment, the blood vessel profile PL is created using the subtraction image data S obtained from the mask image data M and the live image data L, and the threshold value SHL is changed according to the imaging conditions. Since the edge aI+a2 of the blood vessel is extracted from the profile using this changed predetermined value, the edge of the blood vessel can always be accurately extracted even if the scattered radiation dose changes due to changes in the imaging conditions of the X-ray imaging system. be able to. As a result, the accuracy of blood vessel edge extraction can be improved.

Note that the present invention is not limited to the embodiments described above. In the two embodiments, an X-ray diagnostic apparatus has been described, but the present invention can also be applied to, for example, a radiological diagnostic apparatus using gamma rays. It goes without saying that various other modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, a blood vessel profile is created using subtraction image data obtained from mask image data and live image data, and the blood vessel profile is created using predetermined values set according to imaging conditions. Since blood vessel edges are extracted from the profile, blood vessel edges can always be accurately extracted even if the scattered radiation dose changes due to changes in the imaging conditions of the radiographic system. As a result, it is possible to provide a blood vessel measurement method and device that can improve the accuracy of blood vessel edge extraction.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a blood vessel measuring device according to the present invention, and FIG. 2 is a diagram showing a blood vessel, i.
Figure 3 is a diagram for explaining the measurement method, Figure 3 is a diagram showing a subtraction image, Figure 4 is a diagram showing a blood vessel profile, and Figures 5 and 6 are for changing the threshold value depending on the imaging conditions. Diagram for explaining the method for finding the edges of blood vessels, No. 7
The figure is a diagram for explaining blood vessel edge extraction using an ideal X-ray imaging system. DESCRIPTION OF SYMBOLS 1... Image data supply device, 2... X-ray image processing device, 3... TV monitor, 1o... X-ray tube, 12...
・Subject, 14... Image intensifier, 1
6 a. 16b...Lens, 18...TV left camera 2o...
ΔDC, 22... Live memory, 24... Mask memory, 26.28... Logarithmic converter, 3o... Subtractor, 32... Profile circuit, 34 River vessel diameter measurement circuit, 40. ... X-ray controller, 42... Threshold calculation circuit, PL... Blood vessel profile, SHL...
threshold. Applicant's agent Patent attorney Takehiko Suzue] 6 - Figure 3 al a2 Higgsef 1, ÷ Pibbutton L also al a2 50 pt
>,i.

Claims (2)

[Claims] (1) A radiography system that sets imaging conditions for object imaging, and subtraction that calculates the difference between mask image data before vascular contrast agent injection and live image data after vascular contrast agent injection under the imaging conditions. subtraction means for obtaining image data;
A blood vessel characterized by comprising means for creating a profile of the blood vessel using the subtraction image data, and means for extracting edges of the blood vessel from the profile using predetermined values set according to the imaging conditions. Measuring device. (2) Set the imaging conditions for subject imaging using the radiography system, and under the imaging conditions, calculate the difference between the mask image data before vascular contrast agent injection and the live image data after angiographic contrast agent injection, and subtract A procedure for obtaining image data, creating a profile of a blood vessel using this subtraction image data, and setting a predetermined value according to the imaging conditions; and a procedure for extracting edges of the blood vessel from the profile using the predetermined value. A blood vessel measurement method characterized by comprising: