PURPOSE: To investigate whether PET characterization according to NEMA NU 2-2001 guidelines may be used to optimize acquisition protocols for cardiac PET studies or whether a dedicated heart+torso phantom is needed.
METHOD AND MATERIALS: A PET/CT unit (Discovery-LS, GEMS) was first fully characterized according to NEMA NU 2-2001 guidelines using the complete set OF standard NEMA test objects (PTW, Freiburg, Germany) and F-18 in a wide range OF activities (0 to 3300MBq) in 2-D and 3-D acquisition modes. The characterization parameters obtained (NEC, correction for count losses and random events) were compared to corresponding parameters measured in the dedicated heart+torso phantom with F-18 filled heart walls (PTW, Freiburg, Germany) that better render clinical conditions.
RESULTS: The accuracy OF correction for count losses and random events assessed with the set OF NEMA test objects is within 7% for activities well above the NEC1R peak in both 2-D and 3-D mode (error <6.5% for activity <3134MBq in 2-D and <4.4% for activity <637 MBq in 3-D). Significant differences in NEC results were obtained between data measured using NEMA test objects and the heart+torso phantom (2-D: NEC1R maximal activity is 2358MBq and 636MBq for the NEMA and heart+torso phantom, respectively; 3-D: NEC1R maximal activity is 224MBq and 163MBq for the NEMA and heart+torso phantom, respectively).
CONCLUSION: Although the NEMA guidelines apply to PET systems used for oncological studies, they cannot readily be used to optimize activity and acquisition parameters for cardiac PET, especially when working with very high activities as needed to quantify myocardial blood flow with short-lived radioisotopes.
CLINICAL RELEVANCE/APPLICATION: Cardiac PET is gaining clinical acceptance and OPTIMIZATION OF activity with acquisition parameters is required to minimize patient dose and obtain accurate quantitation OF myocardial blood flow.