JPS63222210A - Image distortion measuring phantom - Google Patents

Abstract

PURPOSE:To measure image distortion with high accuracy, by arranging spherical distortion measuring members having high radiation absorptivity and a small diameter to the surface or interior of a plate-shaped support member, which has low radiation absorptivity and high rigidity, in a lattice pattern. CONSTITUTION:A rectangular support member 7 is formed of a material having low radiation absorptivity and high rigidity, for example, a synthetic resin or an acrylic resin. A large number of distortion measuring members 8 are arranged to the surface of interior of the support member 7 in a lattice pattern so that an adjacent interval (d) is provided by required quantity to form an image distortion measuring phantom 6. Each of the distortion measuring members 8 is formed of a material having high radiation absorptivity, for example, a small steel sphere. The diameter of the small sphere is set to about 0.1-5mm and the interval (d) is set to about 5-50mm. Points A'-D' where an image is formed in a distorted state are detected by an image intensifier using the phantom 6 as an object to irradiate the same with radioactive rays from a radiation source and converting said rays to visible light to be compared with points A-D where an image is supposed to be originally formed and image distortions P1-P4 are measured. By this method, image distortion is measured with high accuracy.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an image distortion measurement phantom for measuring image distortion generated by the detection surface of a radiation detector in a radiographic imaging apparatus, and in particular, to The present invention relates to an image distortion measurement phantom that can accurately detect the position of an image and measure image distortion with high precision.

[Conventional technology]

As a radiation detector in a radiographic imaging device, an image intensifier (hereinafter abbreviated as r1.1.J), etc., which converts a radiation image transmitted through a subject into visible light, is used. .

This 1.1. Since the detection surface of the radiation detector is spherical, the image that is incident on the spherical detection surface, converted into visible light, and formed on the output surface of the radiation detector is distorted. Therefore, in order to correct the image distortion, it is necessary to measure the image distortion caused by the radiation detector in advance. Conventionally, as an image distortion measurement phantom 1 for measuring the image distortion, as shown in FIG. 4, thin steel wires 2a and 2b are used.
A lattice-like structure in which the elements are arranged vertically and horizontally at appropriate intervals has been proposed. Then, radiation is irradiated from a radiation source using the image distortion measurement phantom 1 as a subject, and each intersection point 3, 3° of the wire rods 2a, 2b arranged in a grid shape is 1.1.
The position where the image is distorted and formed is detected, and each of the above intersection points 3, 3 .・
... was measuring image distortion by comparing it with the position where the image should originally be formed.

[Problem that the invention seeks to solve]

However, in such a conventional image distortion measurement phantom 1, since the wire rods 2a and 2b are continuous in the vertical and horizontal directions and their diameters are small, the intersection point 3 is not clearly imaged, and each of the above-mentioned intersection points It was difficult to extract distorted imaging points of 3, 3 degrees, etc. Therefore, it was difficult to measure the distortion of one image. In addition, each of the above intersection points 3, 3. Even if the distorted imaging points of ... can be extracted, the intersection point 3 is the two wire rods 2a,
2b intersect, the shape of the intersection 3 is different when viewed from directly above and from an angle, and as shown in Figure 5, the radiation source is 4a → 4b → 4c. 4a when the exposure angle changes due to movement.

The size of the imaged points 5a, 5b, 5c at the intersection point 3 due to radiation irradiation from each direction of 4b, 4c was different, and the center position also changed for each imaged point 5a, 5b, 5c. . Therefore, the position of the distorted image forming point at each intersection point 3, 3°, etc. was shifted depending on the radiation exposure angle, and the position of the distorted image forming point could not be detected accurately. Therefore, it was not possible to measure image distortion with high accuracy.

Therefore, one object of the present invention is to provide an image distortion measurement phantom that can solve such problems.

[Means for solving problems]

The means of the present invention for solving the above-mentioned problems is to form a spherical shape with a small diameter made of a material with a high radiation absorption coefficient on the surface or inside of a flat support member made of a material with a low radiation absorption coefficient and high rigidity. This is done by using an image distortion measurement phantom in which a large number of strain measurement members are arranged and fixed in a scattered manner over substantially the entire surface of the support member, adjacent to each other with a required distance between them.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of an image distortion measurement phantom according to the present invention. This image distortion measurement phantom 6 is connected to a radiation detector 1, for example, 1.1.
This is for measuring image distortion caused by the detection surface of the supporting member 7 and a large number of distortion measuring members 8, 8 . It consists of a combination of...

The support member 7 supports and fixes strain measurement members 8, 8°, etc., which will be described later, and is formed into a rectangular flat plate made of a material with a low radiation absorption coefficient and high rigidity, such as synthetic resin or acrylic resin. has been done.

The reason why the support member 7 is made of a material with a low radiation absorption coefficient is to allow the radiation to pass through well when irradiated from the radiation source, and to prevent shadow images from remaining due to the radiation. . Also.

The strain measuring members 8, 8 . are made of a highly rigid material while maintaining flatness. . . is held at a constant position with respect to the irradiation radiation.

On the surface or inside the support member 7, there are a number of strain measurement members 8, 8. ...is fixed. This strain measurement member 8 is for extracting a strain imaged point due to radiation irradiation from a radiation source, and is made of a material 1 having a high radiation absorption coefficient, such as steel, and is formed into a spherical shape with a small diameter. They are arranged and fixed in a matrix over substantially the entire surface of 7, with adjacent intervals d equally spaced by a required amount.

The size of the strain measuring member 8 is set to be about several pixels when formed as an image by radiation irradiation, and specifically, the diameter is about 0.1 to 5 IIll, for example. This is because a peak of the imaging point as an image is likely to appear when the size is around this level.

Further, the distance d between the adjacent strain measuring members 8, 8 is the same as the distance d between the adjacent strain measuring members 8, 8. The distance is determined by interpolating the distortion at an arbitrary position between the distortion imaging points of . The strain measurement member 8 is made of a material with a high radiation absorption coefficient so that it can absorb the radiation well when it is irradiated from the radiation source, and its imaged point can be sufficiently recognized as an image. This is to do so. Moreover, the reason why the strain measurement member 8 is made spherical is that a sphere has the same shape and the same center no matter what direction it is viewed from, and as shown in FIG. Even if the exposure angle changes by moving like 4C, 4a.

The sizes of the imaged points 9a, 9b, and 9c of the strain measurement member 8 are always the same when radiation is irradiated from each direction of 4b and 4c, and the center position is also the same as each imaged point 9a.

This is because 9b and 9c match.

Then, the image distortion measurement phantom 6 configured in this way
A large number of strain measuring members 8, 8, . ...is 1.1, as shown in Figure 3.
．． Image forming point A' r B ' + C'
Detecting the position of HD'T..., each strain measuring member 8, 8. ... is the position A where the image should originally be formed.

What is necessary is to measure the image distortion P 9 P2j P3f P4t... at each point in comparison with B, C, D, . . . . At this time, for the reason explained with reference to FIG. 2, each distorted imaging point A I , B / , C / ,
P1. P,,P,,P4.・・・
・Can be measured with high precision.

In addition, in FIG. 1, a large number of strain measurement members 8°8, .
Although the strain measurement members 8, 8, . If the positions of .

In addition, in the above explanation, the radiation detector mainly refers to 1.1. Although the above description is based on the case where a radiation detector is used, other radiation detectors that cause image distortion can be similarly applied.

〔Effect of the invention〕

Since the present invention is constructed as described above, a large number of small-diameter, spherical strain measuring members 8° 8,... having a high radiation absorption coefficient are installed on substantially the entire surface of the flat support member 7, which has a low radiation absorption coefficient. By arranging and fixing them in a dotted manner, the strain measuring members 8, 8
．． The image of ... is clearly formed, and its distorted image point A /
, B/, C/, D/, . . . can be clearly extracted. In addition, each distorted imaging point A/,
The positions of B/, C/, D/, ... will not shift even if the radiation exposure angle from the radiation source changes, and the position of the distorted image point will be accurately detected. be able to. Therefore, the image distortion measurement phantom 6 of the present invention
According to the detection surface of a radiation detector → → →
→ Image distortion P, P, P, P4 caused by can be measured with high precision.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an embodiment of the image distortion measurement phantom according to the present invention, and Fig. 2 shows a state in which the size and center position of the imaged point of the distortion measurement member do not change even if the radiation exposure angle changes. FIG. 3 is an explanatory diagram showing the state of image distortion measurement. FIG. 4 is a plan view showing a conventional image distortion measurement phantom. FIG. 5 is an explanatory diagram showing the state of image distortion measurement. FIG. 3 is an explanatory diagram showing a state in which the size and center position of the imaging point at the intersection of the two images change. 6... Image distortion measurement phantom, 7... Support member,
8... Strain measurement member, d... Interval.

Claims (1)

[Claims] A large number of strain measuring members made of a material with a high radiation absorption coefficient and formed in a spherical shape with a small diameter are placed on or inside a flat support member made of a material with a low radiation absorption coefficient and high rigidity. An image distortion measurement phantom characterized in that the image distortion measurement phantom is arranged and fixed in dots adjacent to each other at a required distance over substantially the entire surface.