Societe De Commercialisation Des Produits De La Recherche Appliquee Socpra Sciences Sante Et Humaines S.e.c.

Socpra Sciences Sante Et Humaines S.e.c.

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Université De Sherbrooke

Roger Lecomte

David Lapointe

Jean-Daniel Leroux

Jules Cadorette

Rejean Fontaine

Marc Dumoulin

Réjean Fontaine

Laurence Convert

Rèjean Fontaine

Vitali Selivanov

Jean-Baptiste Michaud

Hicham Semmaoui

Nicolas Viscogliosi

Phillipe Berard

Abdelhamid Saoudi

An image reconstruction system and method based on image projection data collected by an imaging system having N tubes of response (TORs) having Naxial translation symmetries and Nin-plane rotation symmetries between the TORs. A system matrix mapping image projection data to pixels of an image is used, where the pixels are positioned according to a polar or cylindrical coordinate grid. During image reconstruction, matrix-vector computations are performed between the system matrix and vectors containing image estimates or image projection estimates. The matrix-vector computations are accelerated by structuring the system matrix coefficients, image vectors, and projection measurement vectors in such a way that symmetric data is stored in contiguous memory locations. Further, instead of storing the coefficients for all TOR and voxel combinations, matrix coefficients for only the subset of non-symmetric TOR and voxel combinations are stored, and the same coefficients are reused for the other symmetric TOR/voxel combinations.

Image reconstruction based on accelerated method using polar symmetries

A blood counting device comprises a capillary conduit for drawing from a subject in which a radiotracer has previously been injected a quantity of blood in the micro-liter range to produce in the capillary conduit a flow of blood from which beta radiation is emitted. At least one direct beta radiation detector is placed closely adjacent to the capillary conduit. The direct beta radiation detector consists of a semiconductor photodiode which detects the beta radiation from the flow of blood when directly hit by this beta radiation.

Micro-volumetric blood radioactivity counter

An iterative image reconstruction method used with an imaging system that generates projection data, the method comprises: collecting the projection data; choosing a polar or cylindrical image definition comprising a polar or cylindrical grid representation and a number of basis functions positioned according to the polar or cylindrical grid so that the number of basis functions at different radius positions of the polar or cylindrical image grid is a factor of a number of in-plane symmetries between lines of response along which the projection data are measured by the imaging system; obtaining a system probability matrix that relates each of the projection data to each basis function of the polar or cylindrical image definition; restructuring the system probability matrix into a block circulant matrix and converting the system probability matrix in the Fourier domain; storing the projection data into a measurement data vector; providing an initial polar or cylindrical image estimate; for each iteration; recalculating the polar or cylindrical image estimate according to an iterative solver based on forward and back projection operations with the system probability matrix in the Fourier domain; and converting the polar or cylindrical image estimate into a Cartesian image representation to thereby obtain a reconstructed image.

Image reconstruction methods based on block circulant system matrices

A digital method and system allowing crystal identification in radiation detector machines is described. The crystal identification is based on recognition of radiation detector signal shape through discrimination of detector signal's dynamic characteristics. The digital method is based on recursive and non-recursive algorithms, such as adaptive filtering combined or not with quantization methods. These digital algorithms, commonly used in other engineering applications, were modified and tailored for radiation detection. Although the method was specially designed for crystal identification measurement, which is exemplified here, it can effectively recognize the detector signal shape in any radiation detection context.

Digital identification and vector quantization methods and systems for detector crystal recognition in radiation detection machines

A method for single photon counting transmission computed tomography (CT) is described. The method is based on an apparatus consisting of a radiation source and detectors on an opposite side of the subject from the source. The radiation source is for example an X-ray tube. The detectors are independently connected to parallel, fast, low-noise processing electronics capable of recording and counting individual X-ray photons at very high rate. In one embodiment of the invention, said detector is made of a scintillator coupled to a photodetector. The photodetector can be an avalanche photodiode (APD). The method comprises the steps of: directing the low energy radiation source toward the subject; detecting the radiation transmitted through the subject towards the detectors and recording the position and energy of each individual X-ray photon; rotating the radiation source and detectors around the subject; recording data for each position of the radiation source and detectors around the subject to form projections; and creating a CT image from the recorded projection data. The proposed method allows enhancing CT image contrast and reducing radiation dose to the patient by counting individual X-ray photons.

Method and system for low radiation computed tomography

A detector assembly for multi-modality PET/SPEC/CT scanners comprises a first layer for detecting low energy gamma radiation and X-rays and a second layer for detecting high energy gamma radiation. The first layer is generally transparent to high energy gamma radiation. The second layer may advantageously provide measurement of depth of interaction of the high energy radiation. The first layer is preferably in the form of a thin CsI(TI) scintillator, while the second layer includes a pair of LSO/GSO scintillators. The detector assembly includes a photodetector, preferably in the form avalanche photodiode to transform the light signals from the scintillators into electric signals. The detector assembly is advantageously incorporated in a multi-modality PET/SPECT/CT scanner allowing simultaneous transmission and emission imaging with the same detection geometry.

Detector assembly for multi-modality scanners

The present invention relates to a scintillation detector for a tomograph comprising at least two scintillators having different scintillation characteristics and being optically coupled to a photodetector.

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Sherbrooke, Canada

Roger Lecomte