JPH06178768A - Bond-salt quantity measuring device - Google Patents

Abstract

PURPOSE:To simplify the constitution of an X-ray detecting part, in a bone salt quantity measuring device in which X-rays of two kinds of energies are emitted on a subject to be measured, and the transmitted X-ray quantities thereof are measured by using scintillators and a photoelectric signal conversion element, and on the basis of the measured result the bone salt quantity is calculated. CONSTITUTION:A scintillator 11 whose effective atomic number is relatively small and whose fluorescence output is large, and a scintillator 12 whose effective atomic number is large and whose fluorescence output is small and also whose transparency is high are laminated so as to constitute one scintillator, and the device is made up by connecting a photoelectric signal conversion element 7 to the output side of the scintillator 12 having high transparency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bone mineral content measuring device having a simplified X-ray detector.

[0002]

2. Description of the Related Art A bone mineral content measuring device is a device for measuring the bone density of a living body, and in recent years, a device based on the dual energy X-ray absorption method has become mainstream. In this method, X-rays of two types of energy are applied to the object to be measured, and the X-ray transmission amount thereof is measured using a scintillator and an optical / electrical signal conversion element that converts the optical output of the scintillator into an electric signal. The bone density (bone mineral content) is calculated from the measurement results.

FIG. 3 shows a conventional bone mineral content measuring device of this type. In FIG. 3, the X-ray beam emitted from the X-ray tube 1 is applied to the DUT 3 through the filter 2. Here, the filter 2 is for converting an X-ray beam emitted from the X-ray tube 1 having a continuous energy distribution into an X-ray beam having an energy distribution having two peaks.

The X-ray beam transmitted through the object 3 to be measured is
It is incident on scintillators 4 and 5 having different thicknesses. The thin scintillator 4 mainly detects low energy X-rays, and the thick scintillator 5 detects the remaining high energy X-rays.

The light output (scintillation light) of each of the scintillators 4 and 5 enters a photomultiplier tube 7 through a light guide 6. Some parts of the photomultiplier tube 7 are made of metal and cannot be placed behind the scintillator 4, so the light guide 6 is used.

The electric pulse output of each photomultiplier tube 7 is appropriately multiplied by an amplifier 8 and then counted by a counting circuit 9. The counting result of each counting circuit 9 is fetched by a computer 10. , Where bone density is calculated.

[0007]

As described above, in the prior art, the circuits at the subsequent stages of the scintillators 4 and 5 are required for each of the scintillators 4 and 5, and the photomultiplier tube 7 is placed behind the scintillator 4. Since it is not possible to do so, the light guide 6 is required, and the structure of the X-ray detection unit becomes complicated.

It is an object of the present invention to provide a bone mineral content measuring device in which the construction of the X-ray detecting section is simplified.

[0009]

SUMMARY OF THE INVENTION The above-mentioned object is to irradiate an object to be measured with X-rays of two types of energy, and convert the X-ray transmission amount of the scintillator and the light output of the scintillator into an electric signal. Measurement using an electric signal conversion element, in the bone mineral content measuring device for calculating the bone mineral content from the measurement result, the scintillator, at least one is transparent, and the effective atomic number and the magnitude of the optical output to each other. The optical / electrical signal conversion element is composed of a stack of two different scintillators, and the optical / electrical signal conversion element is achieved by coupling the output side of the transparent scintillator of the two scintillators.

[0010]

One of the two scintillators absorbs low-energy X-rays well, the other absorbs high-energy X-rays, and the scintillation lights have different magnitudes.

According to this, the difference between the two scintillators can be detected by the difference in the optical output, and the circuit after the scintillator can be shared. Further, since the scintillator portion has a single structure, it is possible to dispose an optical / electrical signal conversion element such as a photomultiplier tube behind the scintillator, and a light guide is not required.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the bone mineral content measuring device according to the present invention. In FIG. 1, the X-ray beam emitted from the X-ray tube 1 passes through the filter 2 and then irradiates the DUT 3. The filter 2 emits an X-ray beam emitted from the X-ray tube 1 having a continuous energy distribution,
This is for changing to an X-ray beam having an energy distribution having two peaks.

The X-ray beam transmitted through the object 3 to be measured is
It is incident on the scintillators 11 and 12. Here, the scintillator 11 is composed of a substance having a relatively small atomic number and large scintillation light, such as thallium-activated sodium iodide. The scintillator 12 has a larger atomic number than the scintillator 11, emits less scintillation light, and is made of a highly transparent material, such as germanium bismuth oxide.

In such scintillators 11 and 12, low energy X-rays are mainly absorbed by the scintillator 11, and high energy X-rays are mainly absorbed by the scintillator 12. Then, the scintillation light output of the scintillator 11 passes through the scintillator 12 and
The scintillation light output of is directly incident on the photomultiplier tube 7.

The electric pulse output of the photomultiplier tube 7 is
After being multiplied appropriately by the amplifier 8, it is input to the counting circuits 13 and 14. Of the counting circuits 13 and 14, the counting circuit 13 discriminates and counts pulses having a large wave height among the input pulses, and the counting circuit 14 discriminates and counts pulses having a small wave height among the input pulses. Then, the outputs of the respective counting circuits 13 and 14 are taken into the computer 10, where the bone density is calculated.

According to the above-mentioned embodiment, compared with the conventional device,
The photomultiplier tube 7 and the amplifier 8 can be shared by the high energy X-ray detection system and the low energy X-ray detection system, and the photomultiplier tube 7 can be arranged behind the scintillators 11 and 12, so that the light guides 6, 6 are provided. (See FIG. 3) becomes unnecessary.

In the above embodiment, the photomultiplier tube 7 is used as the optical / electrical signal conversion element for converting the scintillation light into the electric pulse signal, but the photodiode 15 may be used as shown in FIG. . In FIG. 2, other parts are the same as in FIG.

[0018]

As described above, according to the present invention, an element such as a photomultiplier tube for converting scintillation light into an electric pulse signal and an amplifier are provided as a high energy X-ray detection system, as compared with a conventional apparatus. It can also be used as a low energy X-ray detection system, and since an optical / electrical signal conversion element such as a photomultiplier tube can be arranged behind the scintillator, a light guide is not required and the configuration of the X-ray detection unit can be improved. The effect is that it can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a device of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram of a conventional device.

[Explanation of symbols]

 1 X-ray tube 2 Filter 3 Object to be measured 4 Scintillator 5 Scintillator 6 Light guide 7 Photomultiplier tube (optical / electrical signal conversion element) 8 Amplifier 9 Counting circuit 10 Computer 11 Scintillator (scintillator laminate) 12 Scintillator (scintillator laminate) ) 13 counting circuit 14 counting circuit 15 photodiode

Claims (1)

[Claims] 1. An X-ray having two kinds of energy is applied to an object to be measured, and the X-ray transmission amount thereof is measured using a scintillator and an optical / electrical signal conversion element for converting an optical output of the scintillator into an electric signal. In the bone mineral content measuring device for calculating the bone mineral content from the measurement result, the scintillator is a laminated body of two scintillators, at least one of which is transparent and which has different effective atomic numbers and different light output magnitudes. The optical / electrical signal conversion element is connected to the output side of a transparent scintillator of the two scintillators, and the bone mineral content measuring device is constituted.