Performance Characteristics of PET Scanners

A major goal of the PET studies is to obtain a good quality and detailed image of an object by the PET scanner, and so it depends on how well the scanner performs in image formation. Several parameters associated with the scanner are critical to good quality image formation, which include spatial resolution, sensitivity, noise, scattered radiations, and contrast. These parameters are interdependent, and if one parameter is improved, one or more of the others are compromised. A description of these parameters is given below. 

The spatial resolution of a PET scanner is a measure of the ability of the device to faithfully reproduce the image of an object, thus clearly depicting the variations in the distribution of radioactivity in the object. It is empirically defined as the minimum distance between two points in an image that can be detected by a scanner. A number of factors discussed below contribute to the spatial resolution of a PET scanner. 

Detector size One factor that greatly affects the spatial resolution is the intrinsic resolution of the scintillation detectors used in the PET scanner. For multidetector PET scanners, the intrinsic resolution (Rf) is related to the detector size d. R, is normally given by d/2 on the scanner axis at midposition between the two detectors and by d at the face of either detector. Thus it is best at the center of the FOV and deteriorates toward the edge of the FOV. For a 6-mm detector, the Ri value is mm at the center of the FOV and 6mm toward the edge of the FOV. For continuous single detectors, however, the intrinsic resolution depends on the number of photons detected, not on the size of the detector, and is determined by the full width at half maximum of the photopeak. 

Positron range A positron with energy travels a distance in tissue, losing most of its energy by interaction with atomic electrons and then is annihilated after capturing an electron (Fig. 6.1). Thus, the site of (3+ emission differs from the site of annihilation as shown in Fig. 6.1. The distance (range) traveled 

Basics of PET Imaging Physics, Chemistry, and Regulations, 

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