Positioning Error Induced by Axial Sampling in Positron Emission Tomography

摘要

A multi-slice positron camera organizes data as a set of parallel slices whose thickness is defined by the axial response function (ARF) of the tomograph. This ARF is usually not uniform and the sensitivity is maximum for a point source located at the center of the slice. As a consequence, the partial volume effect (quantitation loss for structures that are smaller than two to three times the FWHM resolution) will be dependent not only on the size of the structure but also on its relative position with regard to the ARF. We have developed a computer simulation to analyze this effect. Objects of different size and shape are examined and it is shown that on a system with a 6 mm axial resolution (FWHM), a shift of 3 mm can introduce more than 10% variation on the final measurement. The simulation is confirmed by experimental results on a high resolution PET. We conclude that positioning and repositioning must be handled with great care in order to make reproducible measurements and allow accurate partial volume corrections. 7 refs., 3 figs., 5 tabs.