RT Journal Article SR Electronic T1 NEMA NU 2 Performance Tests for Scanners with Intrinsic Radioactivity JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 822 OP 826 VO 45 IS 5 A1 Watson, Charles C. A1 Casey, Michael E. A1 Eriksson, Lars A1 Mulnix, Tim A1 Adams, Doug A1 Bendriem, Bernard YR 2004 UL http://jnm.snmjournals.org/content/45/5/822.abstract AB Performance tests on lutetium oxyorthosilicate (LSO)–based PET scanners cannot be conducted strictly according to the National Electrical Manufacturers Association (NEMA) NU 2 standards because of the presence of intrinsic radioactivity within the LSO crystal scintillator material. This background radiation gives rise mainly to random coincidence events but also to a small number of true coincidences, which cannot be eliminated from measurements on such scanners and must therefore be corrected for in the data analysis. The current NU 2 standards do not take account of these backgrounds and hence can lead to erroneous results on LSO-based machines. Nevertheless, the intent of the standards can be met with appropriate modifications to the acquisition and processing procedures. In this paper, we propose certain changes to the NEMA specifications to accommodate this class of scanners. These changes affect mainly the estimation of sensitivity, scatter, randoms, and count losses. Using these modified procedures, the NU 2 performance of LSO-based systems can accurately be measured.