JPS5950346A - Device for detecting proton-ray image - Google Patents

Abstract

PURPOSE:To adjust the Bragg peak position to obtain a proton-ray image superior in contrast of an image and a resolving power, by providing an absorbing material capable of varying a thickness absorbing an energy of the proton ray at a front surface of a photosensitive surface. CONSTITUTION:The proton ray emitted from a proton-ray source 11 decreases the energy, consequently the speed at the time of passing through an object. The energy of the proton ray transmitted through the object is absorbed by the absorbing material 13, and the proton ray indicates the Bragg peak near the photosensitive surface of a photographic film or the fluorescent screen of an image tube and is damped. In this time, the position indicating the Bragg peak is controlled by varying the thickness of the material 13, and by increasing or decreasing the energy quantity of the proton ray absorbed by the material 13. The structure of the material 13 consists of a combination of one pair of wedge- shaped pieces, and the thickness can be varied continuously by sliding said material in the arrow direction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a proton beam image detection device that emits one proton beam toward a subject to see through a human body.

The proton beam image detection device utilizes the phenomenon that after the primary proton beam emitted from the proton beam source passes through the subject, the specific ionizing power locally increases behind the subject. This will be explained in more detail below with reference to FIG. In other words, as a proton with 9m energy moves through the air or matter, its energy decreases and its speed decreases, and it stops after traveling a certain distance. At this time, the curve showing the relationship between the number of ion pairs produced per unit length of the proton range (specific separation power) and the range is called the Bragg curve, as shown in Figure 5 (■]). As shown in Figure 6, the specific ionization power does not change very much when the proton speed is large, but when it becomes small, it rapidly increases and reaches its maximum value at point (P).This point (P) is the Bragg・Referred to as peak)
The speed suddenly becomes zero at point (C) where it becomes zero. The position and size of the Bragg peak when the proton beam is emitted toward the subject are determined by the energy of the transmitted proton beam, and when the energy of the primary proton beam emitted from the proton beam source is constant, , is a function of the tissue of the subject (, F. The state is shown in FIGS. 5(A) and 5(C).

In the figure, the solid line shows the Bragg curve for the primary proton beam (when there is no object), and the dashed line shows the Bragg curve for the transmitted proton beam that passes through the object. When a photosensitive plate or a fluorescent plate is placed, the difference in defective ionization potential based on the difference in subject tissue can only be obtained as a small value of △Ia, since this area is within the plateau region, and there is only a slight modulation. In position (a), edges and edges of the subject and hard tissue will be detected.On the other hand, in position (g) of Q)) "6 plate or fluorescent plate" If you put
As shown in Figure (c) K, the position and size of the Bragg peak vary depending on the tissue of the subject, so that it is detected as a large specific ionizing power difference of /Vb. Also (1
)) has a high photosensing ability considering the effective energy distribution of protons. Therefore, the most important technical problem in a proton beam image detection device is to generate a Brassoge peak near the photosensitive surface or fluorescent surface. The purpose of this work was to solve this technical problem.

Hereinafter, referring to FIGS. 1 to 4, the present invention (
II! I am explaining the formation.

As part of its configuration is shown in Figure 1, the proton beam image detection device includes a proton beam source +1 that emits proton beams toward the subject.
11, and a photosensitive surface or fluorescent surface (121) that receives the proton beam transmitted through the subject. It is characterized by a variable-thickness absorbent material (1 m) that absorbs water.

In this proton beam image detection device 6, the proton beam emitted from the proton beam source (1) reduces its energy and therefore its speed as it passes through the object.

The energy of the proton beam transmitted through the object is further absorbed by the absorbing material (131, and the figure shows the case of the fluorescent surface + 121 of the photosensitive surface of the photographic film or the fluorescent surface of the image tube (image tube U4)). Bragg
It shows a peak and is braked. In this case, the position showing the Bragg peak can be determined by - changing the thickness of the absorbent sowing, and its absorption 4
It is adjusted by increasing or decreasing the energy of the proton beam absorbed by 1 (131).The state is shown in FIG.

In the figure, the solid line indicates the Bragg curve when the thickness of the absorption layer (13) is thinner and when it is thicker than the dashed line Q.

Next, the structure of the absorbent material +131 will be explained. Absorbent material 0
3+ may be of any type as long as its thickness can be changed, and its contrivance INρ1 is shown in FIGS. 2 and 3.

In the illustrated example, the thickness can be continuously changed by sliding a pair of wedge-shaped pieces 7911 together in the direction of the arrow. In this 4-hour combination, only one wedge-shaped piece overlaps the other, which can be effectively used as an absorbing part.
is within the range of To make a pair of wedge-shaped pieces, for example, as shown in FIG. The absorbent material (13) may be shaped like a grid as shown in FIGS. 2 and 3.

Scattered radiation generated from the subject can be removed. Note that the absorbent material (13) is made of lead foil, for example.

The proton beam image detection device is configured as described above frr,
By changing the thickness of the absorbing material, the position of the Bouwa-Ig peak can be adjusted, so it is possible to obtain a proton beam image with excellent contrast and resolution of the shadow f-image.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a part of the configuration of the proton beam single-image detection device according to the present invention, Fig. 2 is a sectional view showing one embodiment of the absorbing material, and Figs. 3 and 3 are also partially enlarged perspective views. , FIG. 4 is a diagram for explaining the method of manufacturing the absorbent material. In addition, Fig. 5 is a diagram for explaining the principle of imaging in a proton beam single-parallel detector (i', j). Fig. 6 is a diagram showing the state of change L of the Bragg curve depending on the thickness of the absorbing material. 11... Proton beam source 12... Fluorescent surface 13... Absorption paulownia Fig. 1 Fig. 2 Fig. = = Knee: μ 3rd (j3 ff14>47°1 Fig. 5 (A) (B) Bowl size

Claims (1)

[Scope of Claims] 1. A proton beam image detection device comprising a proton beam source that emits one proton beam toward a subject, and a photosensitive surface or fluorescent surface that receives the proton beam that has passed through the subject. . A proton beam image detection device, characterized in that an absorber U having a variable thickness for absorbing the energy of the proton beam is disposed in front of the photosensitive surface or the fluorescent surface. 2. The proton beam image detection device according to claim 1, wherein the absorbing material is a pair of slidable wedge-shaped pieces. 3. The proton beam image detection apparatus according to claim 1 or 2, wherein the absorbing material is Grid 4J-'''.