PET/CT Anatomy: Variations and Artifacts

Abstract

The individual component of integrated positron emission tomography (PET)/computed tomography (CT) systems can introduce artifacts when images are combined and fused. Because the two systems are integrated and heavily dependent on each other, specific problems arise in addition to the normal variants of the individual system. Artifacts and variants are related to the technology, patient, operator, and algorithm.¹ The technology of detectors and electronics determines spatial and temporal resolution of the modalities. The hardware electronics determine temporal resolution of the PET acquisition. Bed motion and pitch have an effect on the longitudinal axis sampling and determine the z-axis resolution in CT. This combination together with the final reconstruction software determines the three-dimensional spatial resolution of the system.² Motion and movement artifacts are difficult to resolve and are attributable to involuntary and uncontrollable movement of internal organs, as well as preventable shift and sliding because of patient discomfort during scanning. Artifacts induced by respiration are inevitable and cannot be circumvented when patients are imaged over an extended period of time.3 Several interesting physiologic variants have been identified with PET/CT. Foremost among these is the identification of brown fat as fluorodeoxyglucose-avid tissue in the supraclavicular area and paramediastinum.