JPH0712948A - Scattered ray detector, and detecting device for scattered ray and quality thereof - Google Patents

Abstract

PURPOSE:To highly accurately correct a radiographic diagnostic device, especially, X-ray CT device as a whole by simultaneously performing correction on both scattered rays and quality of the rays at every detected data (angle data). CONSTITUTION:A scattered ray detector 7 is constructed in two stages, an upper stage 7a and lower state 7b, so that the upper stage 7a can detect X rays of relatively low energy and the lower stage 7b can detect X ryas of relatively high energy and the quality of scattered rays, namely, main rays can be assumed from the ratio between the outputs of the upper and lower stages 7a and 7b simultaneously with the detection of the quantity of scattered rays from the output of the upper stage 7a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scattered radiation detector and a scattered radiation detector for correcting the output of a radiation detector due to the influence of scattered radiation or radiation quality changes in a radiation image diagnostic apparatus such as an X-ray CT apparatus. The present invention relates to a radiation quality detecting device.

[0002]

2. Description of the Related Art An image diagnostic apparatus using radiation, for example X
In the X-ray CT apparatus, eliminating the influence of scattered rays and changes in radiation quality is an important factor for improving image quality. As a method of eliminating the influence of scattered radiation, there are conventionally used a method using a collimator and a grid, a method of measuring and correcting a scattered dose by a radiation detector for detecting scattered radiation (scattered radiation detector), and the like. Further, there are various correction methods for the change in the radiation quality, such as using the data obtained by using phantoms having different sizes.

A method of eliminating the influence of scattered radiation by the scattered radiation detector is to install a detector dedicated to scattered radiation, that is, a scattered radiation detector, in a region outside the main line of X-rays, and to output the signal from this detector. Based on this, the scattered dose is estimated and corrected. Conventionally, the detector used in this method is, for example, as described in Japanese Patent Application No. 3-221826, a detector from a single stage for blocking X-rays and finally converting it into a signal current. The scattered radiation correction amount was determined by the output signal.

In FIG. 3, an object 3 is irradiated with an X-ray (main line) 4 from an X-ray focal point 1 through a collimator 2, and an X-ray detector (main detector) 6 converts the X-ray into an electric current. The scattered radiation 5 is detected by the scattered radiation detector 7 and sent to the data processor 8. The data processing device 8 determines the scattered radiation correction amount based on the signal from the scattered radiation detector 7, and corrects the signal from the X-ray detector 6.

[0005]

In the above-mentioned prior art, no information on the quality of the scattered radiation 5 can be obtained.
In the line CT apparatus, there is a problem in that it is not possible to estimate the quality change of the main line 4 for each angle data and perform comprehensive correction including the scattered dose.

An object of the present invention is to detect a scattered dose and a change in X-ray quality at the same time and for each detection data (angle data in the case of an X-ray CT apparatus), and to correct them. An object is to provide a detector and a scattered radiation / ray quality detecting device.

[0007]

The above object can be achieved by constructing a scattered radiation detector by stacking two radiation detectors for converting radiation into an electric current in two stages.

[0008]

The radiation detector on the scattered radiation incident side (upper stage) of the scattered radiation detector detects X-rays having relatively low energy, and the lower radiation detector has relatively high energy transmitted through the upper radiation detector. Detect X-rays. The quality of the incident X-ray can be estimated from the ratio of the output from the upper radiation detector and the output from the lower radiation detector. Since there is a fixed relationship between the quality of scattered radiation and the quality of the main line, it is possible to estimate the quality of the main line from the ratio of the outputs of the upper radiation detector and the lower radiation detector. It is possible to calculate the correction amount of the change in the radiation quality. The amount of correction of scattered radiation can be calculated in the same manner as in the prior art by the output of any radiation detector, usually the upper radiation detector.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a scattered radiation detector and scattered radiation according to the present invention.
It is a block diagram which shows an example of the X-ray CT apparatus to which the radiation quality detection apparatus was applied. In FIG. 1, 1 to 6 are the same as in FIG. 7 and 8 also show a scattered radiation detector and a data processing device as in FIG. 3, but the present invention is configured as follows.

That is, the scattered radiation detector 7 has an upper and lower two-stage structure, and is configured to extract signals from the upper and lower scattered radiation detectors 7a and 7b. In addition, the data processing device 8
Not only determines the scattered radiation correction amount based on the signal from the scattered radiation detector 7 such as the upper scattered radiation detector 7a and corrects the signal from the X-ray detector 6, but also determines the upper and lower scattered radiation detectors 7
The incident X depends on the ratio of the signals (magnitude) from a and 7b.
The quality of the ray (scattered ray 5) is estimated. Since there is a fixed relationship between the quality of the scattered ray 5 and the quality of the main line 4, the quality of the main line 4 is estimated by the ratio of the output signals of the upper and lower scattered ray detectors 7a and 7b. Therefore, the data processing device 8 estimates the quality of the main line 4 by this, and in addition to the conventional correction of the scattered dose, also corrects the change in the quality of the beam.

The correction processing by the data processing device 8 will be described below. That is, the scattered radiation 5 generated in the subject 3
Is a two-tiered scattered radiation detector 7 (upper and lower scattered radiation detector 7
a, 7b). Upper and lower scattered radiation detectors 7a, 7
The signal from b is sent to the data processor 8 and the amount to be corrected is determined. The amount to be corrected is represented as follows, for example.

Α = f1 (I1) (1) β = f2 (I1, I2) (2) γ = f3 (α, β) (3) XH = X + γ (4)

Here, α: scattered radiation correction amount I1: output of upper scattered radiation detector 7a f1: function of (I1) β: amount of radiation quality correction I2: output of lower scattered radiation detector 7b f2: (I1, I2) function γ: total correction amount f3: function of (α, β) XH: corrected data X: output of X-ray detector 6. Regarding the ray quality correction amount in the equation (2), in practice, the relationship between the ratio of I1 and I2 and the ray quality may be obtained in advance by irradiating the phantom with RI or the like.

In the X-ray CT apparatus of FIG. 1, if the scattered radiation detector 7 is arranged at an appropriate position near the X-ray detector 6,
It is possible to acquire the data necessary for the scattered radiation correction and the radiation quality correction at the same time.

FIG. 2 is a sectional view showing a concrete example of the scattered radiation detector 7 in FIG. The upper and lower scattered radiation detectors 7a and 7b that constitute the two-layered scattered radiation detector 7 are each mainly composed of a phosphor (scintillator) and a photoelectric conversion element (photodiode).

Such a two-layered scattered radiation detector 7
In the (upper and lower scattered radiation detectors 7a and 7b), the scattered radiation 5 enters the scintillator 11 of the upper scattered radiation detector 7a, is converted into fluorescence, and is converted into a current (I1) by the photodiode 12. This current is led to the data processing device 8 (see FIG. 1) via the wiring board 13. In this upper scattered radiation detector 7a, X having a relatively low energy is used.
The line is detected.

Scattered rays 5 transmitted through the upper scattered ray detector 7a
′ Is incident on the scintillator 16 of the lower scattered radiation detector 7b, converted into a current (I2) by the photodiode 17, and guided to the data processing device 8 via the wiring board 18. The lower scattered radiation detector 7b detects X-rays having a relatively high energy that have passed through the upper scattered radiation detector 7a.

Reference numerals 14 and 19 are containers for housing the upper and lower scattered radiation detectors 7a and 7b, respectively. Also, 21 is above,
This is an adjusting metal plate for making the ratio of the outputs I1 and I2 from the lower scattered radiation detectors 7a and 7b proper.

One or a plurality of the scattered ray detectors 7 are arranged in the vicinity of the main detector 6, and when a plurality of scattered ray detectors 7 are arranged, the main detector 6 to be corrected for each scattered ray detector 7. The elements are divided and assigned.

[0020]

As described above, according to the present invention, the scattered radiation detector can simultaneously obtain the data necessary for the correction regarding the scattered radiation and the change in the radiation quality. This allows
Compared to the conventional method that corrects the influence of scattered radiation and the influence of change in radiation quality without being separated, like the correction using the phantom, the influence of scattered radiation and change in radiation quality can be corrected individually and at each detection time. Can be grasped (for each angle data), and there is an effect that a more accurate correction can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an X-ray CT apparatus to which a scattered radiation detector and a scattered radiation / ray quality detecting device according to the present invention are applied.

FIG. 2 is a sectional view showing a specific example of a scattered radiation detector in FIG.

FIG. 3 is a block diagram showing an example of an X-ray CT apparatus to which a conventional scattered radiation detector and a conventional scattered radiation / ray quality detecting device are applied.

[Explanation of symbols]

 1 X-ray focus 2 Collimator 3 Subject 4 X-ray (main line) 5 Scattered line 6 X-ray detector (main detector) 7 Scattered line detector 7a Upper scattered line detector 7b Lower scattered line detector 8 Data processing device 11 Scintillator (phosphor) 12 Photodiode (photoelectric conversion element) 13 Wiring board 14 Container 16 Scintillator (phosphor) 17 Photodiode (photoelectric conversion element) 18 Wiring board 19 Container 21 Adjustment metal plate

Claims (3)

[Claims] 1. A scattered radiation detector comprising two radiation detectors for converting radiation into an electric current, which are stacked in two stages. 2. The scattered radiation detector according to claim 1, wherein the two radiation detectors each include a phosphor and a photoelectric conversion element. 3. A scattered radiation detector formed by stacking two radiation detectors for converting radiation into an electric current in two stages, and based on the output (I1) of one of the scattered radiation detectors. The correction amount of the scattered radiation is calculated and the output (I
A scattered radiation / ray quality detecting apparatus comprising: a processing device for calculating a radiation quality correction amount based on 1) and the output (I2) of the other radiation detector.