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Scatter correction in Positron Emission Tomography

University of British Columbia

Positron Emission Tomography (PET) aims to identify metabolic functioning through imaging the in situ physiological progression of a metabolic analogue tagged with a positron emitting radio-isotope. Following ejection, the positron promptly annihilates with a surrounding electron giving rise to two oppositely directed y-rays of equal energy. By coincidentally detecting the collinear y-rays, PET is able to characterize the underlying metabolite distribution and concentration. Physical scattering of one of the two coincident y-rays inside the medium supporting the metabolite will result in a mispositioning of the decayed radio-tracer. The set of all scattered events, following acquisition, will contribute background to the set of unscattered or primary events. Camera sensitivity to this activity concentration is improved by acquiring events over all possible coincident detector pairs. This kind of volumetric or 3D PET imaging also increases the likelihood that the camera will accept scatter events. The present research investigates a spatially variant convolution type method to extricate the scatter component from the total measured events in 3D imaging. In the scope of the. present work a spatially variant kernel will be derived which upon convolution with measured 3D PET image data will return a matching scatter component. Based on this, kernel a computer algorithm is developed, implemented and performance tested on known activity distribution sources. It is found that the present algorithm performs better or of equal merit in comparison to,, pre-existing scatter correction algorithms. Moreover, the position variable algorithm is optimized to perform within a clinical setting.

Thesis/Dissertation

application/pdf

2009-01-31

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http://hdl.handle.net/2429/4058

Physics

University of British Columbia

UBCV

DSpace