JPH01129840A - Bone salt concentration measuring apparatus - Google Patents

Abstract

PURPOSE:To employ an inexpensive X-ray tube easy to control and operate and to secure sufficient safety and measuring accuracy, by providing a comparing detection part for detecting X-rays by a pulse count system and using the pulse count system as the main detection part in a measuring object transmitting radiation detecting unit. CONSTITUTION:In a comparing detection part E, the number of the generated pulses of an X-ray detector 7 generating pulses proportional to the quantity of the transmitted X-rays of the X-ray beam emitted from a radiation beam emitting unit B are counted by the first pulse counter 8 and the counting result is inputted to an analyzer U. The X-ray beam passed through the comparing detection part E is incident to a measuring object support unit A to perform the absorption of X-rays corresponding to the bone salt concentration of the bones B, B of an object 3 to be measured and the residual transmitted X-rays are incident to a measuring object transmitting radiation detecting unit C. A main detection part D generates a pulse proportional to the quantity of incident X-rays in a main detection part 10 and the number of the generated pulses are counted by the second pulse counter 11 and the counting result is inputted to the analyzer U.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bone mineral density measuring device for measuring the content of bone minerals (e.g. hydroxyapatite), and more specifically, to a bone mineral density measuring device for measuring the content of bone minerals (e.g. hydroxyapatite). The present invention relates to a bone mineral density measuring device in which a radiation beam emitting unit and an incident radiation detecting unit, which are arranged to face each other, are configured to be able to two-dimensionally scan the measurement object support unit.

[Conventional technology]

Such a bone mineral density measuring device is suitable for use in patients with age-related or postmenopausal osteoporosis 9 and renal osteogenesis imperfecta in artificial dialysis patients.

It is used to diagnose diseases with abnormal bone metabolism, such as bone diseases caused by abnormalities of vitamin D metabolism and hormone metabolism, and to measure the effects of administered drugs, and the need for this has increased as the elderly population has increased in recent years. In the current situation,
Therefore, it can be configured and obtained at a lower cost, and
There is a need for the development of a bone mineral density measuring device that has excellent operability and safety, and can provide sufficient measurement accuracy.

As a typical conventional bone mineral density measuring device, there is one known from, for example, Japanese Patent Publication No. 53-9119, which is constructed as shown in FIG.

That is, in FIG. 2, A is a measurement object support unit formed by placing and fixing a water bag 2 containing water W on a fixed stage l, and a non-measuring person (patient) The arm, which is the part to be measured, is inserted into the body in a predetermined position.

Note that the most appropriate location for this measurement is around the lower middle 1'/3 of the forearm on the side opposite to the dominant arm. This is because it has been proven that there is a very high correlation (approximately 99%) in mineral content between the radius bone and other bones of the body in that area. It goes without saying that the arm that is the measurement site (hereinafter referred to as the measurement target S) is composed of the bones B, which are the direct measurement object, and the surrounding tissue M (muscles, etc.), and the surrounding tissues. In order to eliminate measurement errors due to individual differences in M (differences between fat and thin), the water bag 2 contains water W equivalent to its surrounding set 1iM.

Further, b is a radiation beam emitting unit disposed below the measurement object support unit, for example, +2J
(Iodine 125), ``'Am (Americium 241)
It consists of a sealed wire fiq and an emission collimator p configured to emit a radiation beam of a constant intensity using a radioisotope having a relatively long half-'01 period (60 days in '1) such as .

And C is a measurement target transmitted radiation detection unit,
It is arranged above the measurement object support unit (A) so as to face the radiation beam output unit (b) with the measurement object support unit (A) in between, and detects the radiation that has passed through the measurement object S through the incident collimator (r). It consists of a radiation detector S and an amplifier t. In this case, the radiation detector S uses a current (analog signal)
Although an example using an output type detector is shown, a scintillation detector may also be used.

Incidentally, the radiation beam emitting unit b and the measuring object transmitted radiation detecting unit C are integrally connected to each other, although not particularly shown here, and are two-dimensional with respect to the measuring object supporting unit l-A. It is configured to be able to scan (in the left-right direction and in the direction perpendicular to the plane of the paper in FIG. 2).

Further, U is an analyzer for measuring the bone mineral density of the measurement target S based on the detection signal inputted from the amplifier t in the measurement target transmitted radiation detection unit C, and ■ displays the measurement result. / Indicates an output device for recording.

(Problems to be Solved by the Invention) As described above, in the conventional bone mineral density measuring device, as a radiation source in the radiation beam emitting unit b,
Because a sealed radioactive isotope source q was used,
By using a radioactive isotope with a long half-life, it is possible to obtain a radiation beam of very low output and stable constant intensity. Therefore, while reducing the exposure dose and increasing safety, , has the advantage of ensuring excellent measurement accuracy (in other words, that is why
However, on the other hand, (a) although it is possible to obtain a radiation beam of constant intensity for a very short period of time, strictly speaking, The intensity of the emitted radiation from radioisotopes changes over time (at +GSR, it is halved in 60 days), so in order to maintain sufficient measurement accuracy, correction calculations that correspond to changes in the emitted radiation intensity over time are required. (b) Radiation control is difficult and there are restrictions on installation locations, etc. (1) Complex and troublesome work such as lead shielding is required when starting and stopping the device, and operability is poor. There were drawbacks.

Therefore, the present inventors developed a radiation beam emitting unit l-b.
The radioactive isotope sealed wire 1E (p
Instead of X, which is inexpensive and very easy to manage and operate
I thought that it would be possible to use a radiation tube, and after various studies, I found that it would be possible to use a radiation tube with a low output (for example, a few hundred μA) that could sufficiently reduce the exposure dose to ensure safety, and also reduce power consumption. When using an X-ray tube (based on a power supply of output (e.g. 500m
It has been found that there is a fatal trade-off problem in that an X-ray tube (with a power supply of A level) must be used, but the intended purpose cannot be achieved in terms of safety and running costs.

The present invention was made as a result of continued research to overcome the above-mentioned difficulties, and its purpose is to provide a radiation source that is extremely inexpensive and extremely easy to manage and operate as a radiation source in a radiation beam emitting unit. Although it uses an X-ray tube,
The purpose of this invention is to develop and provide a highly versatile bone mineral density measuring device that can ensure sufficient safety and measurement accuracy.

Means for Solving Problem C] In order to achieve the above object, the bone mineral density measuring device according to the present invention has the basic configuration as described at the beginning, and uses a radiation source as a radiation source in the radiation beam emitting unit. In addition to using an X-ray tube, a comparison detection section for detecting X-rays emitted from the radiation beam emitting unit by a pulse counting method is provided, and the measurement target i3
A pulse counting system is used as the main detection section in the over-radiation detection unit, and the bone mineral density of the measurement target is measured based on a comparison result of both detection results by the comparison detection section and the main detection section. It has the characteristic of being.

[Effect]

The effects achieved due to this characteristic configuration are as follows.

That is, according to the bone mineral density measuring device according to the present invention, as will become clearer from the description of specific embodiments described later, (i) X as a radiation source in the radiation beam emitting unit;
Because it uses a wire tube, it has a longer lifespan than conventional sealed radioisotope sources, so replacement frequency is extremely low, and running costs are extremely low. (ii) 0N10FF of the switch for the X-ray tube
Because you can easily start and stop the device just by operating it,
Radiation management and operation are extremely easy, and bone mineral density measuring devices that use this X-ray tube do not have the restrictions on installation location as they do when using conventional sealed radioisotope sources. (iii) In addition to the measuring target transmitted radiation detection unit as the original detection unit, a comparative detection unit for monitoring is provided to detect radiation emitted from the radiation beam output unit. The device is configured to detect X-rays, and is configured to measure the bone mineral density of the measurement target based on the comparison result of both detection results by the comparison detection unit and the main detection unit of the measurement target transmitted radiation detection unit. Therefore, even if the intensity of the emitted X-rays from the X-ray tube in the radiation beam emitting unit is unstable, the fluctuation in the intensity of the emitted X-rays itself is always confirmed by the comparison detection section. Since the structure is configured so that the above-mentioned
As a vA tube, it is possible to sufficiently reduce the exposure dose and ensure sufficient safety, while also reducing power consumption (running costs).
(iv) The comparison detection section and the main detection section of the measuring target transmitted radiation detection unit are both constructed of a pulse counting type. Therefore, from this point as well, the current (
Compared to the case of using an analog signal output type, it has various advantages such as guaranteeing extremely high measurement accuracy.

〔Example〕

Hereinafter, a specific embodiment of the bone mineral density measuring device according to the present invention will be described with reference to FIG.

That is, as shown in FIG. 1, they are opposed to each other with a fixedly provided measurement object support unit A (the structure of which is the same as that of the conventional structure explained in FIG. 2). As shown in FIG. They are connected to each other and are configured to be movable within a predetermined range in the left-right direction in FIG. There is.

In this example, the radiation beam emitting unit B is arranged above the measurement object support unit, and the measurement object transmitted radiation detection unit C is arranged below the measurement object support unit A. As in the case of the conventional example explained in FIG. 2, the units 7 B and C may be arranged upside down from this example.

The radiation beam emitting unit B includes a low-power XvA tube 3 as a radiation source, a stabilized power supply 4 for supplying a constant current (approximately 500 μA in this example) to the low-power XvA tube 3, and an output from the X-ray tube 3. X-rays (which are also a type of radiation, but their energy range is quite broad as they are) are made monochromatic (narrow down their energy range).
It consists of a ray filter 5 and an output collimator 6 for converging the monochromatic X-rays that have passed through the X-ray filter 5 into a beam and outputting the same. Further, in the figure, SW is a switch for the X-ray tube 3, and its 0N10
Starting and stopping of the X-ray tube 3 can be easily controlled by operating the FF.

A comparison detection section E is provided between the radiation beam emission unit B and the measurement object support unit A for detecting the intensity of the X-ray beam emitted from the radiation beam emission unit B by a pulse counting method. It is being That is, the comparison detection section E detects a part (certain percentage) of the X4m beam emitted from the radiation beam emission unit B.
For example, it consists of a proportional counter tube that generates a pulse proportional to the amount of XwA that passes through it.
It consists of a ray detector 7 and a first pulse counter 8 for counting the number of pulses generated by the X-ray detector 7, and the pulse counting results by the first pulse counter 8 will be described in detail later. It is input to analyzer U.

The emitted X-ray beam that has passed through the comparison detection section E is incident on the measurement object support unit) A, and is directed to the bones B and B of the measurement object S.
After X-ray absorption is performed according to the bone mineral density (content) of
The remaining transmitted X-rays are incident on the measurement target transmitted radiation detection unit C.

The measurement target transmitted radiation detection unit C includes an incident collimator 9 for collimating the transmitted radiation XwA that has passed through the measurement target support unit A and is incident in a scattered state.
A, 9B, and a main detection section for detecting the intensity of X-rays passing through the incident collimators 9A, 9B by a pulse counting method. That is, the main detection part is incident XI! 91 (for example, a scintillation detector consisting of a combination of Na1 (Tn) and PMT (photomultiplier tube)), and the number of pulses generated by the main detector 10 is counted. The pulse counting result by the second pulse counter 11 is input to the analyzer U in the same way as the pulse counting result by the first pulse counter 8 in the comparison detection section. ing.

In the analyzer U, the amount of X-rays detected by the comparison detection section E and the amount of X-rays detected by the main detection section in the measurement target transmitted radiation detection unit C (
In other words, the bone mineral density of the measurement target is calculated and measured based on the comparison result with the original measurement X-ray glue that passed through the measurement target unit A, and the measurement result is sent to the output device V (display, recorder, etc.). It is output.

In this way, the actual x incident on the measurement target unit A
! Since the amount of IA is constantly monitored by the comparative detection unit E and reflected in the calculation measurement of bone mineral density, even if the amount of X-rays emitted from the radiation beam emitting unit B fluctuates, the fluctuation The measurement accuracy does not deteriorate due to this, and therefore, there is no need to provide any special correction means that takes into account the variation in the amount of X-rays.

By the way, in the present invention, with the intention of improving measurement accuracy as much as possible, both the main detection section and the comparison detection section E in the measuring object transmitted radiation detection unit C are configured to be of a pulse count type. However, if some deterioration in measurement accuracy is acceptable, the detectors and E may be constructed using a method other than the pulsed force mount method (for example, a current conversion method).

Moreover, the comparison detection section E may be incorporated into the radiation beam emitting unit B.

(Effects of the Invention) As is clear from the detailed description above, according to the bone mineral density measuring device according to the present invention, an X-ray tube is used as a radiation source in the radiation beam emission unit, and A comparison detection section for detecting the amount of emitted X-rays by a pulse count method is provided, and a pulse count method is used as the main detection section in the measurement target transmitted radiation detection unit, and the comparison detection section and the main detection section are provided. Since it is configured to measure the bone mineral density of the measurement target based on the comparison result of both detection results by the detection unit, compared to the conventional configuration using a sealed radioisotope source, In addition to significantly reducing running costs, radiation management and operation are extremely easy.
In addition, there are no restrictions on the installation location, and the product as a whole is extremely versatile.Moreover, as the X-ray tube, the exposure dose is sufficiently small to ensure sufficient safety, and the consumption Various excellent effects are exhibited, such as being able to ensure sufficiently high measurement accuracy while using a low-output device that can keep power consumption to a minimum.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram showing a specific embodiment of the bone mineral density measuring device according to the present invention. Further, FIG. 2 is for explaining the technical background of the present invention and the problems of the prior art, and shows an overall schematic configuration diagram of a conventional bone mineral density measuring device. 3...X-ray tube (ray source), A...Measurement object support unit 7), B...
Radiation beam emission unit, C...Measurement object transmitted radiation detection unit, D...Main detection section, E...Comparison detection section. Applicant Horiba Manufacturing Co., Ltd. Representative Patent Attorney Hideo Fujimoto

Claims (1)

[Scope of Claims] A radiation beam emitting unit and a measurement object transmitted radiation detection unit, which are arranged to face each other with a measurement object support unit in between, are configured to be capable of two-dimensional scanning with respect to the measurement object support unit. A certain bone mineral density measuring device uses an X-ray tube as a radiation source in the radiation beam emission unit, and includes a comparison detection section for detecting the X-rays emitted from the radiation beam emission unit by a pulse counting method. and using a pulse counting system as the main detection section in the measurement object transmitted radiation detection unit, and detecting the bone mineral density of the measurement object based on the comparison result of both detection results by the comparison detection section and the main detection section. A bone mineral density measuring device configured to perform measurement.