JP2009145112A - Body surface monitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a body surface monitor capable of accurately measuring the existence and quantity of radioactive contamination on the body surface of a subject according to the body surface shape of the subject. <P>SOLUTION: This monitor comprises: a body shape measuring device 4 measuring the body shape of a subject 1; a monitor main body 3 equipped with a plurality of radiation detectors 2 which detect the radiation irradiated from the body surface of the subject; and a data processor 10 computing the body surface radioactive contamination density of the subject from the body shape measurement data of the subject and the detected values of the radiation detectors. While the radiation detection efficiency is corrected according to the distance, obtained by measuring the surface body shape of the subject, between the radiation detector and the body surface of the subject, an alarm is output in the case of inconsistency that the radiation detection limit value does not attain a predetermined value or the distance is largely separated from a predetermined distance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a body surface monitor that measures radiation emitted from the surface of a human body.

  When a worker who has worked in a radiation control area in a facility that handles radioactive materials leaves the radiation control area, the radiation emitted from the body surface is measured by a body surface monitor to check for radioactive contamination. Yes.

  In general, a conventional body surface monitor is a radioactive contamination on the body surface of a subject by a radiation detector fixed to the monitor body to measure the front, back, side, head, and temporal region of the subject. Measure. Here, as for the radiation detector for head measurement, the distance to the subject can be kept constant by moving up and down according to the height of the subject. Since the radiation detector is fixedly installed, the distance between the radiation detector and the body surface changes depending on the body shape of the subject. In general, a plastic scintillation detector is used as the radiation detector, and the detection efficiency is calculated based on the case where the radiation source is at a predetermined position with respect to the radiation detector. Depending on the relative positional relationship, the detection efficiency of the radiation detector changes.

As described in Patent Document 1 below, the detection efficiency of the detector is expressed by the term “response R” of the radiation detector. In this Patent Document 1, the distance to the subject is also measured. Although this “response R” is corrected, the details of the correction calculation are not mentioned, and the distance measurement and correction are limited to only the head of the subject.
JP-A-3-92788

  The conventional body surface monitor described above is based on the assumption that the subject and the radiation detector are at a certain distance, and the contamination distribution on the subject's body surface is also relative to each radiation detector after calibration. Since radiation measurement is performed on the assumption that the relationship exists uniquely, there is a problem that radiation measurement with high accuracy cannot be performed.

  For example, when the subject is far away from the radiation detector than the distance at which calibration was performed, or when the body surface contamination of the subject is at a position where the detection efficiency is lower than the position at which calibration was performed Will be evaluated as a value lower than the actual contamination. In addition, when the distance from the radiation detector is large, there may be a portion that does not reach the detection limit defined by law.

  The present invention has been made to solve the above-described problems, and can accurately measure the presence and amount of radioactive contamination on the body surface of a subject according to the body surface shape of the subject. An object is to provide a surface monitor.

  In order to solve the above problems, a body surface monitor according to the present invention includes a body shape measuring device for measuring a body shape of a subject, and a plurality of radiation detectors for detecting radiation emitted from the body surface of the subject. And a data processing device for calculating the body surface radioactive contamination density of the subject from the body shape measurement data of the subject and the detection value of the radiation detector, and the subject's body The radiation detection efficiency is corrected according to the distance between the radiation detector and the subject's body surface obtained by measuring the shape, and the distance is set when the radiation detection limit value does not reach a specified value. In the case of inconsistency that is farther than a certain distance, an alarm is output.

  According to the present invention, it is possible to provide a body surface monitor that can accurately measure the presence and amount of radioactive contamination on the body surface of a subject according to the body surface shape of the subject.

Embodiments of a body surface monitor according to the present invention will be described below with reference to FIGS.
FIG. 1 is a diagram showing a configuration of a body surface monitor according to the present embodiment, and (a) is a diagram showing an arrangement of a monitor main body and a body shape measuring apparatus.

  The monitor main body 3 has a small chamber shape, and includes a plurality of radiation detectors 2 for detecting radiation on the body surface of the subject 1 and a drive mechanism for swinging or moving each radiation detector 2 on the upper portion 3a and the door portion 3b. ing. The body shape measuring device 4 is provided with a camera 5 for photographing the subject 1 and a lifting device 6 for lifting the camera 5 on the entrance side. FIG. 1B is a view of the body shape measuring device 4 as viewed from vertically above. The camera 5 is provided in two directions at right angles to the subject 1 and measured. The image of the camera 5 is transmitted to the image measuring device 7 described later. As shown in FIG. 1C, the body shape of the subject 1 may be measured using a plurality of photoelectric sensors 8 and ultrasonic sensors 9 that can perform distance measurement instead of the camera 5. Good. Before entering the monitor body 3, the subject 1 stands by at the body shape measuring device 4, and the camera 5 measures the total length of the subject 1.

FIG. 2 is a configuration diagram of a measurement data processing system provided in the body surface monitor of the present embodiment. The measured value obtained by processing the image data from the camera 5 by the image measuring device 7 is transmitted to the data processing device 10 and is combined with the vertical height data of the camera 5 calculated from the encoder of the camera lifting device 6. The body shape of the examiner 1 is measured. In the data processing apparatus 10, the distance characteristic and distribution characteristic data of each radiation detector 2 measured using a calibration source, that is, the detection efficiency η _{X that} varies depending on the relative position of the radiation detector 2 with respect to the detection surface. _{, Y} (α) and detection limit surface contamination density A _{X, Y} (α) are registered in advance.

  Here, instead of the image measuring device 7, the photoelectric sensor 8, and the ultrasonic sensor 9, the body shape data of the subject registered in advance for each ID may be read out and used using the ID card reader 11. Is possible.

  In the body surface monitor of the present embodiment configured as described above, the body shape calculated from the image measuring device 7, the photoelectric sensor 8, and the ultrasonic sensor 9 or the body shape recorded on the ID card is preliminarily stored as data. It collates with the characteristic data which the radiation detector 2 registered in the processing apparatus 10 has.

The operation will be described with reference to the flowchart of FIG.
After measuring the body shape of the subject (step S2), the detection surface of each radiation detector 2 is represented by XY coordinates, and at a certain point (i, j) on the surface of the subject body perpendicular to the detection surface. The distance to a is compared with the characteristic data η _{X, Y} (α) of the radiation detector 2 registered in the data processing device 10 to detect the detection efficiency η of each point on the body surface of the subject. _{i, j} (a _{i, j} ) is calculated. Similarly, the detection efficiencies at all points on the detection surface are calculated (step S3).

Similarly, by collating with the characteristic data A _{X, Y} (α) registered in the data processing apparatus 10, the detection limit surface contamination density A _{i, j} ( a _{i, j} ) is calculated, and detection limits at all points on the body surface of the subject are calculated. At this time, the detection limit surface contamination density A is calculated by the following equation (1).

Although all points have been described above, the detection limit surface contamination density A _{i, is} obtained by averaging the detection efficiencies η _{X, Y} (α) at several surrounding points so as to have a predetermined area as appropriate _{. j} (a _{i, j} ) may be calculated.

Next, it is determined whether or not there is a part exceeding the allowable detection limit (step S4), and the detection limit A _{i, j} (a) at each point on the body surface of the subject is a predetermined value as shown in FIG. If there is a point larger than that, that is, if there is a part that is far away from the radiation detector 2, the voice guidance of the guidance device 12 or the guidance on the screen is used to represent the subject. An appropriate site name is instructed to prompt the user to approach the radiation detector 2 (step S5).

Furthermore, a measure for changing the measurement time to be longer is performed so that the specified detection limit can be satisfied (step S6). At this time, the measurement time Ts ′ to be changed is calculated using the following equation (2).

The detection efficiency η _{i, j} (a _{i, j} ) on the body surface of the subject is used even when the surface contamination density of the subject is calculated from the measured value of radiation from the body surface of the subject. . That is, the surface contamination density M is calculated using the following formula (3) (step S8).

Here, the detection efficiency may be averaged according to the body shape of the subject as in the following equation (4).

In consideration of evaluation on the safe side in the carry-out inspection, the minimum value of the detection efficiency η _{i, j} (a _{i, j} ) may be adopted as the detection efficiency as shown in the following equation (5).

  According to the body surface monitor of the present embodiment, the measurement value can be corrected by using the characteristic data of the radiation detector that changes depending on the body shape of the subject and the distance and distribution of the radiation source, and the detection limit can be set. By changing the measurement time so that it is satisfactory, and by giving guidance instructions, the subject himself / herself can approach a specific part of the radiation detector, so accurate radiation can be obtained according to the body shape of the subject. Inspection and access control can be performed.

The structure of the body surface monitor of embodiment of this invention is shown, (a) is an elevation which shows the structure and arrangement | positioning of a monitor main body and a body shape measuring apparatus, (b) is a top view of a body shape measuring apparatus, (c ) Is a plan view showing another example of a body shape measuring apparatus. The block diagram which shows the structure of the measurement data processing system with which the body surface monitor of embodiment of this invention is equipped. The flowchart which shows operation | movement of the body surface monitor of embodiment of this invention. The graph explaining operation | movement of the body surface monitor of embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Examinee, 2 ... Radiation detector, 3 ... Monitor main body, 3a ... Monitor main body upper part, 3b ... Monitor main body door part, 4 ... Body shape measuring device, 5 ... Camera, 6 ... Camera raising / lowering device, 7 ... Image Measuring device, 8 ... photoelectric sensor, 9 ... ultrasonic sensor, 10 ... data processing device, 11 ... ID card reader, 12 ... guidance device.

Claims (10)

  A body shape measuring device for measuring the body shape of the subject, a monitor body including a plurality of radiation detectors for detecting radiation emitted from the body surface of the subject, and body shape measurement data of the subject; A data processing device for calculating a body surface radioactive contamination density of a subject from detection values of the radiation detector, and the radiation detector and the subject obtained by measuring the body shape of the subject The radiation detection efficiency is corrected according to the distance to the body surface, and an alarm is issued if the radiation detection limit value does not reach the specified value or if the distance is larger than the set distance. Body surface monitor characterized by output.   The body surface monitor according to claim 1, wherein in the case of the mismatch, the measurement time is changed to be longer.   The body surface monitor according to claim 1, wherein in the case of the mismatch, guidance is given to the subject so that the body part approaches the radiation detector.   The body surface monitor according to claim 1, wherein the body shape measuring device includes a camera and an image measuring device.   The body surface monitor according to any one of claims 1 to 3, wherein the body shape measuring device includes a plurality of photoelectric sensors.   The body surface monitor according to claim 1, wherein the body shape measuring device includes a plurality of ultrasonic sensors.   The body surface monitor according to any one of claims 1 to 3, wherein a distance between the body surface of the subject and the radiation detector is measured at a plurality of points, and an average value thereof is used.   The distance between the body surface of the subject and the radiation detector is measured at a plurality of points, and the point with the lowest detection efficiency is used on each radiation detector surface. Body surface monitor.   The distance between the body surface of the subject and the radiation detector is measured at a plurality of points, and the distribution characteristics and distance characteristics of the radiation detector at the points are collated. Body surface monitor as described.   10. The body surface monitor according to claim 1, wherein body shape data recorded in advance on an ID card or the like is used instead of the body shape measurement data.

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