Enhanced reconstruction for PET scanner with a narrow field of view by using backprojection method

Abstract

There are several reconstruction methods for positron emission tomography (PET), but iterative methods based on maximum likelihood estimation are primarily used. In this paper, we propose a 2D reconstruction method for PET scanners that have a narrow field of view in the tangential direction and are based on the backprojection method. If a PET scanner has a reduced field of view in the tangential direction, the reconstructed image obtained by 2D (filtered) backprojection produces significant distortions. We used the Raytest ClearPET <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM</inf> scanner to obtain measurements. The used ClearPET scanner has reduced field of view in tangential direction. By knowing the geometry of the ClearPET scanner, we determined a necessary compensation to reduce the undesirable effects caused by the narrow field of view. We also added dithering to the measured data to minimize the quantization effect. Ultimately, the image obtained by the proposed compensation was significantly improved when compared to the backprojection method. Unlike iterative reconstruction methods, the proposed algorithm is faster, but the resulting images show the object captured by the ClearPET scanner less accurately. The proposed algorithm can be implemented as an initial estimate in 2D reconstruction when using an iterative method to accelerate convergence.