Commissariat a L'energie Atomique

Sopha Medical

Smv International

Michel Tararine

Alain Chapuis

Bernard Thevenin

Claude Janin

Corinne Mestais

Edmond Tournier

Monique Marcaud

Jean-Francois Benard

Device and method for nuclear locating by iterative computing of barycenter, and application to gamma-cameras

Method and apparatus for determining a position of an event. The system processes signals from an assembly of N photodetectors and includes a signal generator for producing a signal representing the value of the maximum, or the energy, of a pulse delivered by the photodetector and is digitized. It also includes a signal generator for producing a threshold-exceeded signal for each photodetector when the amplitude of the signal representing the value of the maximum, or the energy, of the digitized pulse is greater than the threshold. It also includes a signal generator common to the photodetectors, for delivering a signal representing a position of an event as a function of the threshold-exceed signals. This device can be used with gamma cameras.

Device and method for determining the assumed position of a phenomenon relative to a set of photodetectors, and application to gamma-cameras

A process for processing signals delivered by a gamma camera including two detectors (23, 26, 28, 24, 27 and 29) on either side of a radioactive body (25), each of the detectors (23, 26, 28, 24, 27 and 29) producing analogue electric signals (x.sup.+, x.sup.-, y.sup.+, y.sup.- and w) consisting of pulses relevant to the impacts of gamma-ray photons (.gamma.' and .gamma.') on the detectors (23 and 24), the coordinates of the impact points being calculated from compressed signals, and the detection of the impact being performed in parallel by coincidence.

Process for processing pulses delivered by a gamma camera and a gamma

A method for the correction of uniformity of a gamma camera comprising a detector giving, for each pixel i,j having coordinates x.sub.i, y.sub.i, a number n.sub.ij representing the number of scintillations recorded in said pixel. The method comprises an initial step consisting in:

Method for correcting the uniformity of a gamma camera

A gamma camera includes means for the localization of scintillations produced under the effect of a gamma radiation in a scintillator crystal, the localization means including an array of photomultiplier tubes with gain control obtained by means of calibrated light pulses, and a localization circuit wherein each photomultiplier tube is connected, firstly, through a diode called a resolution diode, to a weighting circuit comprising a network of resistors connected to output adders and, secondly, to a linearizing circuit giving a signal called a linearity signal. The linearizing circuit also gives, for a duration at least equal to the duration of the calibrated light pulses, a pulse to inhibit the resolution diode with respect to the electrical pulses delivered by the photomultiplier tube in response to the light pulses.

Gamma camera with gain compensation

The coordinates X and Y of the location of a scintillation crystal excited by nuclear radiation are determined as a function of the signals X.sup.+, X.sup.-, Y.sup.+, Y.sup.- produced conventionally by an electronic circuit associated with the scintillation crystal. The signals X.sup.+, X.sup.-, Y.sub.+ and Y.sup.- are digitized and the digital coordinate X (respectively Y) is obtained as the product of a first digital data item X.sup.+ -X.sup.- (respectively Y.sup.+ -Y.sup.-) and a second digital data item inversely proportional to the energy of the nuclear radiation received. To prevent beats in the value of the coordinates X and Y, which leads to a moire phenomenon in the radiation image, a random element is introduced into the calculation, for example by adding p random bits to the first digital data item.

Process for locating nuclear radiation with reduction of moire phenomenon

A multiple interpolation process for image correction involves the precalculation of interpolation contributions relative to all the possible locations of the points of an elementary mesh. The positions of these locations are determined as a function of an interpolation fineness to be obtained. It is shown that this precalculation can be obtained without significantly enlarging the memory of an apparatus used. In addition, the performance speed permits the 'in flight' definition of images and the display of weakly defined images in highly defined images.

Multiple interpolation process for image correction

Device for locating nuclear radiation and radiation image formation device incorporating such a locating device. The locating device comprises a detection head having a crystal for converting a nuclear radiation into photons and a plurality of transducers for converting the photons into electric signals. These signals are received in a position coder, which has in series a weighting circuit for supplying analog signals X.sup.+, X.sup.-, Y.sup.- (and optionally Z), a digitizing device for digitizing the analog signals and a digital computer for producing digital signals X.sub.N, Y.sub.N defining the position of a nuclear radiation exciting the crystal.

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Sceaux, France

Michel Tararine