Performance evaluation of PET scanners: testing of geometric arc correction by off-centre uniformity measurement

The aim of this study was to demonstrate the necessity of an off-centre uni formity measurement during performance evaluation and acceptance testing of a positron emission tomography (PET) system. To this end, the effect of di fferent methods of geometric are correction on image uniformity was conside red. The are correction routine of the system software of a particular PET scanner family was tested in computer simulations, phantom measurements and a patient study. Various methods of geometric are correction - nearest nei ghbour interpolation, linear interpolation and cubic smoothing spline inter polation - were applied to the same data. Uniformity was evaluated both vis ually and quantitatively using intensity profiles and regions of interest. The are correction routine of the PET scanner family produced significant r ing artefacts and led to overestimation of tracer uptake by up to 15%. Sinc e uniformity measurements are usually performed using a cylindrical phantom at the cc centre of the transverse field of view, these artefacts are not detected. In conclusion, the standards for performance evaluation of a PET scanner should be extended by inclusion of an off-centre uniformity measure ment at the edge of the transverse field of view. On the basis of our compa rison of different methods for geometric are correction, we suppose that cu bic smoothing spline interpolation might improve the relation between stati stical noise reduction and spatial resolution as compared with conventional linear interpolation.