JPS6351842A - X-ray ct apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an X-ray CT apparatus.

(Prior Art) Generally, in an X-ray CT apparatus, a detector (
This detector is referred to as a main detector), and images are reconstructed based on X-ray information from this main detector.

(Problem to be solved by the invention) However, in addition to the X-rays that are originally intended to be measured, the X-rays entering the main detector include scattered rays generated from the object, for example, so conventional devices cannot always There was a problem of obtaining accurate X-ray information.

An object of the present invention is to solve the above problems and provide more accurate X-ray information.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a scattered radiation detector provided at a position outside the scanning plane and corresponding to at least one of the main detector groups. The structure is as follows.

(for production) Since the present invention has the above configuration, it operates as follows.

That is, a scattered radiation detector placed outside the Su-V-Yen plane at a position corresponding to the main detector detects approximately the same amount of scattered radiation as the scattered radiation entering the main detector. Therefore, more accurate X-ray information can be obtained by detecting the scattered radiation component based on the data from the scattered radiation detector and removing it from the scan data from the main detector.

(Example) The illustrated embodiment will be described below.

First Embodiment FIG. 1 is a perspective view showing the main parts of an embodiment in which the present invention is applied to a so-called third generation X-ray CT apparatus, and FIG. 2 is a side view thereof.

1 is an X-ray source, which irradiates the subject P with X-rays.

Reference numeral 2 denotes a main detector group in which a large number of main detectors are arranged in an arc shape, and detects the X-rays within the scan plane A that are emitted from the X-ray source 1 and transmitted through the subject 1).

Reference numeral 3 denotes a scattered radiation detector, which is placed outside the scan plane A at a position corresponding to at least one of the main detector group 2. The illustrated device has eight C-type detectors, and by making the number of scattered radiation detectors 3 smaller than the number of main detectors 2, cost reduction is achieved. In addition, the scattered radiation detector 3
The same type of detector as the main detector 2 is used so that the energy characteristics for X-rays are the same.

In this embodiment, the X-ray source 1, main detector BY2, and scattered ray detector 3 rotate integrally around the scan center O-O, and the scattered ray detector 3 rotates around the scan center. It is placed to face.

Therefore, when scanning is performed in this embodiment, the X-ray source 1, main detector group 2, and scattered radiation detector 3 rotate integrally around the scan center O-O, and the X-rays are emitted from the X-ray source 1. X containing scattered rays within the scan plane Δ that was irradiated and transmitted through the subject P
When the ray enters the single detector 2, only the scattered rays enter the scattered ray detector 3 since this is outside the skin plane A. Therefore, more accurate X-ray information can be obtained by detecting the scattered radiation component based on the data from the scattered radiation detector 3 and removing it from the scan data from the main detector.

In the case of this embodiment, the number of scattered radiation detectors 3 is greater than the main detector 2.
, it is not possible to obtain scattered radiation data for each data of all the main detectors 2. Therefore, the data obtained from the scattered radiation detectors 3 is interpolated to calculate the scattering received by the main detector 2. It is necessary to overestimate the dose, but this point will be discussed later.

<Embodiment 2> FIG. 3 is a perspective view showing a main part of an embodiment in which the present invention is applied to a so-called fourth generation X-ray CT apparatus.

This embodiment differs from the first embodiment in that the main detector 2 is arranged in an annular shape and is fixed.

Therefore, in this embodiment, only the X-ray source 1 and the scattered radiation detector 3 rotate, and the main detector 2 and the scattered radiation detector 3 rotate.
The positional relationship between the main detector 2 and the scattered radiation detector 3 will change sequentially, but at each moment, the correspondence between the main detector 2 and the scattered radiation detector 3 is the same as in the first embodiment, and the scattered radiation detector 3 There is no difference in the fact that more accurate X-ray information can be obtained by detecting scattered radiation components based on data from the main detector and removing them from the scan data from the main detector.

Furthermore, although not shown, if the scattered radiation detectors 3 are also arranged in an annular shape, only the X-ray source 1 needs to be rotated.

<Third Embodiment> FIG. 4 shows a block diagram of the entire X-ray C apparatus using the above-described embodiment.

As mentioned above, if the number of scattered ray detectors 3 is smaller than the number of main detectors 2, it is not possible to obtain scattered ray data for each data of all the main detectors 2. It is necessary to interpolate the data obtained from 17 to determine the scattered radiation dose received by the main detector 2, Jft. Furthermore, in order to obtain more accurate X-ray source information, it is necessary to correct the difference in sensitivity to X-rays between the scattered ray detector 3 and the main detector 2, and to
It is desirable to correct the difference in scattered radiation dose due to the difference in the position of the main detector and the main detector 20, but the present embodiment is configured to perform these corrections as well.

In FIG. 4, 10 is a scanner F-111 which collects data from the main detector group of the scanner 10.
This is the Evening Collection Department (DAS).

12 is a calculation unit, which calculates the
The ratio of the scattered radiation dose due to the sensitivity to the radiation and the proximity of the position is calculated, and the calculation result is output.

The R1 method or the lead pin method is employed as a means for determining the above ratio. When employing the RI method, a RadioOISOtope is placed at the center of the scan or at an arbitrary position in the scan area, data from the main detector 2 and the scattered radiation detector 3 are collected simultaneously, and the ratio of each is determined. When using the spear pin method,
A subject that emits scattered radiation is placed in the scan area, and a lead pin is hung between the subject and the main detector 2. In this case, since the main line does not hit the main detector located on the line connecting the focal point and the lead pin, it is possible to measure scattered radiation from areas other than the line of sight of the lead pin. At the same time, the scattered radiation was measured using a scattered radiation detector.
Find the ratio to the output of the main detector. Here, the spear pin is under the condition that it covers the out-of-focus X-rays by ''-minutes.
Make the width sufficiently narrow.

Reference numeral 13 denotes a memory that stores calculation results from the calculation unit 12.

Reference numeral 14 denotes a correction unit, which adjusts the amount of scattered radiation of the scattered radiation detector 3 based on the ratio of the scattered radiation amount due to the difference in sensitivity and position of the scattered radiation detector 3 and the main detector 2 relative to X-rays, which is stored in the memory 13. By correcting the data, interpolating the corrected data, detecting the scattered radiation component estimated to have entered the main detector, and subtracting and removing it from the scan data from the main detector, more accurate X-rays can be obtained. It is designed to generate information.

1, linear interpolation or spline interpolation is employed as the interpolation means. Further, reference correction is applied to data from the scattered radiation detector.

15 is a reconstruction unit that reconstructs an image based on the data from the correction unit 14; 16 is a display unit that displays the image reconstructed by the reconstruction unit 15; and 17 is a control unit for controlling the scanner 10 and the calculation unit 12. The controller is the system that controls the system.

In the above-mentioned apparatus, before scanning an actual subject, a scan is performed in advance using the RI method or button pin removal, and the above-mentioned ratio is calculated by the calculation unit 12 and stored in the memory 13.
Remember it. After that, when the object is scanned in the same way, accurate X-ray information corrected by the ratio and interpolation in the memory is obtained by the correction unit 14, and this is reconstructed by the reconstruction unit 15. An image with high resolution will be displayed on the display unit 16. Note that the task of obtaining the above ratio needs to be performed every time the subject is scanned.
It is sufficient to do it every predetermined number of times.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above embodiments, and can be modified as appropriate within the scope of the gist of the present invention.

For example, the number of scattered radiation detectors may be the same as the number of main detectors. In this case, interpolation as described above becomes unnecessary.

Furthermore, if a Gd202S scintillator photodiode, as disclosed in Japanese Patent Application No. 57-86269Q, is used as the scattered radiation detector, the temperature coefficient will be small and there will be no need for complicated calibration.

[Effects of the Invention] As detailed above, according to the present invention, the scattered ray detector located at the center of the scan and at the position corresponding to the main detector receives approximately the same amount of scattered rays as the scattered rays entering the main detector. Since scattered radiation is detected, more accurate X-ray information can be obtained by detecting the scattered radiation component based on the data from this scattered radiation detector and removing it from the skin X-ray data from the main detector. Monkey 3゜

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main parts of the first embodiment of the X-ray CT apparatus according to the present invention, FIG. 2 is a top side view of the same, and FIG.
FIG. 4, which is a perspective view of the embodiment, is a block diagram of the entire X-ray CT equipment using the present invention. 1... X-ray source, 2... Main detector, 3... Scattered radiation detector, A... Scanning surface.

Claims (4)

[Claims] (1) X-ray CT equipped with an X-ray source that irradiates the subject with X-rays and a main detector group that detects the X-rays within the scan plane that are emitted from the X-ray source and transmitted through the subject. The apparatus is characterized in that a scattered radiation detector is provided at a position outside the scanning plane and corresponding to at least one of the main detector groups.
Ray CT device. (2) The X-ray CT apparatus according to claim 1, wherein the number of the scattered ray detectors is smaller than the number of main detectors. (3) The X-ray CT apparatus according to claim 1 or 2, wherein the scattered ray detector rotates integrally with the X-ray source around the scan center. (4) The X-ray detector according to claim 1 or 2, wherein the scattered ray detector is fixed without rotating integrally with the X-ray source.
Ray CT device.