| 摘要 |
PURPOSE:To make it possible to discriminate whether the position of a radioactive substance is present in the body surface or in the deep part of the body, by the energy spectrum of gamma rays measured from the outside of the body from such a fact that the scattering ratio of gamma rays is increased along with the previous distance in the human body. CONSTITUTION:A detector 2 measures radioactive rays emitted from a person 1 to be inspected by a drive mechanism 3 along the surface of the body while a control operation part 10 detects the approximate position of contamination from each signals of a drive control part 8 and a radioactive ray measuring part 9 and it is further determined whether the position of a radioactive substance is present in the body surface or in the deep part of the body by operation. In the constitutional elements of the energy spectrum of gamma rays measured at a contaminated part, there are a peak due to photoelectric effect, a Compton scattering component issued to the energy side thereof and a peak due to rearward scattering and the counting value of the photoelectric effect component is represented by the area Ap corresponding to a part above a straight line connecting the skirt point (b) of the high energy side of peak and the skirt point (d) of the lower energy side thereof while the counting value of the rearward scattering component is represented by an area AB encircled by points (e), (f), (g), (h) and AB/AP is calculated from the areas AP, AB. A spectrum index is continuously reduced along the depth of a contaminated position and the contamination on the body surface and that in the body can be easily discriminated. |
