Method and apparatus for controlling scintillation camera

Claim 1

A scintillation camera control apparatus comprising: means for forming visible light from radiation emitted from radioisotopes in a body; means for converting the visible light from the radiation to electrical impulses including a two dimensional array of photomultiplier tubes which receive the visible light from common radiation and give electrical impulses as a result thereof, said photomultiplier tubes having their own response curve as a function of a distance from the center of sensitivity; means for determining said own response curve relative to predetermined apparent radiations so as to obtain a measured response curve for calibrating; means for calibrating said measured response curve by correcting the electrical impulses from said converting means, said calibrating means including a threshold circuit for removing from the electrical impulses those signals having a level lower than a predetermined threshold level, said predetermined threshold level being controlled in response to energy levels of the electric impulses; a nonlinear circuit having a parameter for nonlinearity correction, said parameter being controlled in response to the measured response curve; and a separating circuit connected between the threshold circuit and the nonlinear circuit, said separating circuit electrically separating the threshold circuit from the nonlinear circuit in such a manner that the control of both said predetermined threshold level of the threshold circuit and said parameter of the nonlinear circuit can be independently performed.

Claim 4

A method for calibrating the nonlinearity of a scintillation camera, comprising the steps of: forming visible light from a radiation source fixed to a radiation source displacing device, said displacing device being movable in a two dimensional plane; exposing a photomultiplier tube to said visible light for generating electrical impulses; determining the center of sensitivity of said photomultiplier tube by supplying a control signal to said displacing device, thereby displacing the radiation source along said two dimensional plane of said displacing device; using a multichannel analyzer to measure the response of said photomultiplier tube as a function of distance from the center of sensitivity to provide a measured response curve of said photomultiplier tube; comparing the measured response curve of said photomultiplier tube with a reference response curve for the multiplier tube so as to provide an image of optimum uniformity which is stored in advance; generating a value for making the measured response curve of said photomultiplier tube close to the reference response curve; selecting first a threshold level of a threshold circuit in response to the energy level of electrical impulses; and selecting secondly a parameter of a nonlinear circuit in response to said generated value, whereby the nonlinear circuit provides an output close to the reference response curve.

Claim 5

A method for calibrating the nonlinearity of a scintillation camera, comprising the steps of: forming visible light from a radiation source fixed to a radiation source displacing device, said displacing device being movable in a two dimensional plane; exposing a photomultiplier tube to said visible light for generating electrical impulses; determining the center of sensitivity of said photomultiplier tube by supplying a control signal to said displacing device, thereby displacing the radiation source along said two dimensional plane of said displacing device; using a multichannel analyzer to measure the response of said photomultiplier tube as a function of distance from the center of sensitivity to provide a measured response curve of said photomultiplier tube; comparing the measured response curve of said photomultiplier tube with a reference response curve for the multiplier tube so as to provide an image of optimum uniformity which is stored in advance; generating a value for making the measured response curve of said photomultiplier tube close to the reference response curve; selecting first a threshold level of a threshold circuit in response to the energy level of electrical impulses; and selecting secondly a parameter of a nonlinear circuit in response to said generated value, whereby the nonlinear circuit provides an output close to the reference response curve.