Tokyo Shibaura Denki Kabushiki Kaisha

The Director of the National Institute of Radiological Sciences, Science

Mineki Nishikawa

Tomohiko Kihara

Eiichi Tanaka

Takehiro Tomitani

Norimasa Nohara

Makoto Kakegawa

Tsutomu Yamakawa

A scintillation camera including an arrangement for correcting for a non-linear response of scintillation. Reference correcting amounts determined during calibration mode operation are stored at lattice points in a matrix corresponding to position signals applied from a radiation position calculation circuit, position signal applied from the radiation position calculation circuit is A/D-converted every scintillation event. During a measuring mode operation, a correcting amount relating to a point on coordinates is calculated on the basis of reference correcting amount at each lattice point in a unit lattice region, the lattice points enclosing the point on coordinates which corresponds to the digitalized position signal. The correcting amount is added to position signal applied from the radiation position calculation circuit. First and second random generators are arranged to apply first and second independent random data for every scintillation event. These first and second random data are added, as lower grade bits, to X and Y components of the position signal and the correcting amount at the point on coordinates is calculated taking these added data for a detected position signal.

Scintillation camera

A method for controlling a scintillation camera has a step of, under the control of a CPU, displacing a radiation source displacing device to which is fixed a radiation source and obtaining a center of sensitivity of a photomultiplier tube to be measured. After the center of sensitivity including the effects of the waveform shaping circuit is obtained, the radiation source is displaced in a plurality of directions relative to the center of sensitivity under the control of the CPU, so as to obtain an average photomultiplier tube response (PMT response) as a function of distance from the center of sensitivity of the photomultiplier tube. The CPU compares the obtained average PMT response with a reference PMT response which provides an image of optimal uniformity to obtain data by which the average PMT response approaches the reference PMT response. Based on this data, the CPU obtains parameters of the waveform shaping circuit to provide a response close to the reference PMT response.

Method and apparatus for controlling scintillation camera

In a scintillation camera having apparatus for shortening waveforms, a regulating circuit for preventing display of signals representing unwanted .gamma. rays having excessive intensity including a device for comparing the peak of the shortened waveform representing the total light energy received by the camera from the .gamma. ray with a preset reference range between an upper limit and the saturation level of the pre-amplifiers of the camera and for generating a signal while the total light energy exceeds the reference range, a circuit for generating an output for a predetermined time after the signal ceases and an AND gate for blocking access to the display during the period of the output.

A plurality of input signals are applied to input terminals of first and second priority encoders according to the order of priority in ascending and descending orders, respectively. The encoded output signals of the first and second priority encoders are exclusive-ORed for each corresponding pair of significant bits. A single event detection is executed only if exclusive OR is effected for all the corresponding pairs of significant bits.

Apparatus for detecting single event

A scintillation camera including a memory having a plurality of addresses corresponding to the elements of the matrix-like divided image of a scintigram and to the points in the camera head for registering radiation. The addresses in the memory are designated to correspond to incidence position signals of points of radiation determined by a position-calculating circuit. A pulse-height analyzer also receives the signals of radiation registered by the camera head and issues an unblanking signal to control apparatus if the signal is significantly stronger than background noise. The control apparatus, triggered by the unblanking signal, initiates the comparison of the content of the designated address in memory with a predetermined minimum value of radiation in a comparator and when the content is less than the minimum value the control apparatus adds one to the content and restores the increased content to the designated address. When the content is at least equal to the minimum value, the control apparatus issues the unblanking signal to display apparatus to display the radiation at the designated address. A timer stops access of the unblanking signals to the display apparatus after a preset time, thus excluding display at those elements of the display wherein the accumulated radiation is less than the minimum at the expiration of the preset time.

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Tochigi, Japan

Mineki Nishikawa