Perelman School of Medicine at the University of Pennsylvania

Physics and Instrumentation Group

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Performance Standards (NEMA)

NEMA NU 4-2008 comparison of preclinical PET imaging systems.

Goertzen AL, Bao Q, Bergeron M, Blankemeyer E, Blinder S, Canadas M, Chatziioannou AF, Cinelle K, Elhami E, Jans H-S, Lage E, Lecomte R, Sossi V, Surti S, Tai Y-C, Vaquero JJ, Vicente E, Williams DA, Laforest R.

J Nucl Med, vol. 53, pp. 1300-1309, 2012.

The National Electrical Manufacturers Association (NEMA) standard NU 4-2008 for performance measurements of small-animal tomographs was recently published. Before this standard, there were no standard testing procedures for preclinical PET systems, and manufacturers could not provide clear specifications similar to those available for clinical systems under NEMA NU 2-1994 and 2-2001. Consequently, performance evaluation papers used methods that were modified ad hoc from the clinical PET NEMA standard, thus making comparisons between systems difficult. Methods: We acquired NEMA NU 4-2008 performance data for a collection of commercial animal PET systems manufactured since 2000: microPET P4, microPET R4, microPET Focus 120, microPET Focus 220, Inveon, ClearPET, Mosaic HP, Argus (formerly eXplore Vista), VrPET, LabPET 8, and LabPET 12. The data included spatial resolution, counting-rate performance, scatter fraction, sensitivity, and image quality and were acquired using settings for routine PET. Results: The data showed a steady improvement in system performance for newer systems as compared with first-generation systems, with notable improvements in spatial resolution and sensitivity. Conclusion: Variation in system design makes direct comparisons between systems from different vendors difficult. When considering the results from NEMA testing, one must also consider the suitability of the PET system for the specific imaging task at hand.


PET performance measurements using the NEMA NU 2-2001 standard.

Daube-Witherspoon ME, Karp JS, Casey ME, DiFilippo FP, Hines H, Muehllehner G, Simcic V, Stearns CW, Adam L-E, Kohlmyer S, Sossi V.

J Nucl Med, vol. 43, pp. 1398-1409, 2002.

The NU 2-1994 standard document for PET performance measurements has recently been updated. The updated document, NU 2-2001, includes revised measurements for spatial resolution, intrinsic scatter fraction, sensitivity, counting rate performance, and accuracy of count loss and randoms corrections. The revised measurements are designed to allow testing of dedicated PET systems in both 2-dimensional and 3-dimensional modes as well as coincidence gamma cameras, conditions not considered in the original NU 2-1994 standard. In addition, the updated measurements strive toward being more representative of clinical studies, in particular, whole-body imaging. Methods: Performance measurements following the NU 2-1994 and NU 2-2001 standards were performed on several different PET scanners. Differences between the procedures and resulting performance characteristics, as well as the rationale for these changes, were noted. Results: Spatial resolution is measured with a point source in all 3 directions, rather than a line source, as specified previously. For the measurements of intrinsic scatter fraction, sensitivity, and counting rate performance, a 70-cm line source is now specified, instead of a 19-cm-long cylindric phantom. The longer configuration permits measurement of these performance characteristics over the entire axial field of view of all current PET scanners and incorporates the effects of activity outside the scanner. A measurement of image quality has been added in an effort to measure overall image quality under clinically realistic conditions. This measurement replaces the individual measurements of uniformity and of the accuracy of corrections for attenuation and scatter. Conclusion: The changes from the NU 2-1994 standard to the NU 2-2001 standard strive toward establishing relevance with clinical studies. The tests in the updated standard also are, in general, simpler and less time-consuming to perform than those in the NU 2-1994 standard.


Performance standards in positron emission tomography.

Karp JS, Daube-Witherspoon ME, Hoffman EJ, Leewellen TK, Links JM, Wong W-H, Hichwa RD, Casey ME, Colsher JG, Hitchens RE, Muehllehner G, Stoub EW.

J Nucl Med, vol. 32, pp. 2342-2350, 1991.

A standard set of performance measurements is proposed for use with positron emission tomographs. This set of measurements has been developed jointly by the Computer and Instrumentation Council of the Society of Nuclear Medicine and the National Electrical Manufacturers Association. The measurements include tests of spatial resolution, scatter fraction, sensitivity, count rate losses and randoms, uniformity, scatter correction, attenuation correction, and count rate linearity correction.