Optimization of basic adjustable data-acquisition parameters for continuous three-dimensional whole-body FDG-PET

The SET-3000 G/X (Shimadzu Corp., Kyoto, Japan) has a large aperture and functions as a three-dimensional (3D) dedicated PET scanner. However, the large number of line of responses in the SET-3000 G/X scanner creates a large volume of sinogram data and prolongs reconstruction time in iterative reconstruction. The purpose of this study was to optimize basic acquisition parameters (maximum ring difference and span) for sensitivity and spatial resolution for 3D whole-body (18)F-FDG PET. METHODS: Detector rings and image planes numbered 50 and 99, respectively. In sensitivity measurement, the maximum ring difference (MRD) was changed from 1 to 49. In the measurement of spatial resolution, the span was changed from 3 to 21. For sensitivity and spatial resolution measurements, the standard protocols defined by the Japan Radioisotope Association (JRIA) 1994 and the National Electrical Manufacturers Association (NEMA) NU 2-2001 were used. We also evaluated the corresponding image noise by placing identical ROI on the reconstructed images. RESULTS: The total sensitivity of MRD=49 was 85.7 cps/Bq/ml in a uniform phantom (15 cm diameter, 30 cm tall cylinder) filled with (18)F. This was approximately two times higher than MRD=13. The image noise in the center of the axial FOV decreased with increasing MRD. Spatial resolution was slightly decreased as MRD increased, but axial resolution deteriorated with a span of more than 11. CONCLUSION: Optimum basic data-acquisition parameters for whole-body (18)F-FDG PET were MRD 49 to obtain maximum sensitivity and span 9 to avoid decreasing spatial resolution. Additionally, it was concluded that the basic data-acquisition parameters should be carefully selected for 3D whole-body (18)F-FDG PET in order to maximize the efficiency of PET measurement.