Abstract: An emission CT apparatus for detecting, in positions around an examinee, radiation from radioactive nuclides introduced into the examinee and having accumulated in a site of concern, in order to acquire density distribution images (sectional images) of the nuclides in sections of the site of concern. The apparatus comprises a gamma camera for detecting the radiation, a rotary device for revolving the gamma camera stepwise round the examinee, an image memory for collecting image data from the gamma camera for respective time frames defined by dividing a period of time for which the gamma camera stands still at each angular position, a computing unit for determining a center of gravity of the image data in each time frame, an adder for adding image data, with the center of gravity brought into agreement, in each time frame, thereby to obtain image data in a direction of each angular position (view), and an image reconstruct unit for reconstructing an image based on the image data of each view corrected.

Abstract: A radiation detector has a larger plural number of scintillators arranged closely and two-dimensionally together and a smaller plural number of photomultiplier tubes optically connected to this scintillator group. Specified regions on mutually opposite surfaces of these scintillators are covered with an optically reflective material and the areas covered by this reflective material vary according to the order in which these scintillators are arranged.

Abstract: In an apparatus for automatically stabilizing the amplification degrees of photomultipliers (PMT's) in a detector having a scintillator and a plurality of PMT's, the PMT's (3) are classified into groups (A, B, C and D) and arranged such that the PMT's of the same group are not disposed adjacent to each other. Outputs taken from the PMT's (3) are classified according to the groups and summed in adders (6) allotted to the respective groups. A sum signal taken from a group which includes a PMT disposed closest to a scintillation is analyzed by a pulse height analyzer (14). The outputs from the pulse height analyzer are collected in a counter memory (15) as statistical data on a change in the amplification degrees of PMT's. Data on the high voltage to be applied to each PMT (3) is recorded beforehand in a register (17) and this data is corrected by a data processing circuit (16) in accordance with the statistical data.

Abstract: A radiation imaging apparatus provided with a pulse height analyzer for checking whether the pulse height of the energy signal produced in response to each scintillation event falls within an energy window set for the particular (x,y) coordinate position of the scintillation. The pulse height analyzer has a memory for storing a plurality of energy windows each for a particular one of the coordinate positions in the scintillator and each having a particular central level and a particular width such that the nonuniformity of the sensitivity of the detector due to the position-dependency of the energy signal and/or other causes can be corrected. A preliminary pulse height analyzer may be provided to increase the counting rate of energy signals useful for image production.