Motion compensation in emission tomography

With the ever-improving spatial resolution available in single photon emission computed tomography (SPECT) and, especially, in positron emission tomography (PET), the unavoidable organ and subject motion is becoming one of the dominant factors limiting the practically achievable spatial resolution in the tomographic images. Moreover, uncorrected subject motion can lead to potentially severe image artifacts and compromise the quantitative integrity of the data.The latter is of special importance in PETwhere quantitative assessment of tracer concentrations is commonplace both in static investigations via so-called standardized uptake values (SUVs) and in dynamic studies aiming at tracer kinetic modeling and quantification of the corresponding transport constants. Correction of the heart cycle – related motion in cardiac applications has a long tradition and is covered extensively in the literature. Correction of breathing-related organmotion in emission tomography, however, has drawn considerable interest only in recent years in the context of oncological PET.This ismainly due to the demands of therapy responsemonitoring and radiation treatment planning. The third important area is high-precision motion correction of random head motion in brain investigations. In this chapter, we give an overview of the methods employed to minimize – and possibly eliminate – the motion influence in emission tomography.