Impact of patient weight and emission scan duration on PET/CT image quality and lesion detectability

Abstract

This study was performed to prospectively evaluate fast PET/CT imaging protocols using lutetium oxyorthosilicate (LSO) detector technology and 3-dimensional (3D) image-acquisition protocols.

Methods: Fifty-seven consecutive patients (30 male, 27 female; mean age, 58.6 +/- 15.7 y) were enrolled in the study. After intravenous injection of 7.77 MBq (0.21 mCi) of (18)F-FDG per kilogram, a standard whole-body CT study (80-110 s) and PET emission scan were acquired for 4 min/bed position in 49 patients and 3 min/bed position in 8 patients. One-minute-per-bed-position data were then extracted from the 3- or 4-min/bed position scans to reconstruct single-minute/bed position scans for each patient. Patients were subgrouped according to weight as follows: <59 kg (<130 lb; n = 15), 59-81 kg (130-179 lb; n = 33), and >or=82 kg (>or=180 lb; n = 9). Three experienced observers recorded numbers and locations of lesion by consensus and independently rated image quality as good, moderate, poor, or nondiagnostic.

Results: The observers analyzed 220 reconstructed whole-body PET images from 57 patients. They identified 114 lesions ranging in size from 0.7 to 7.0 cm on the 3- (n = 8) and 4-min/bed position images (n = 49). Of these, only 4 were missed on the 1-min/bed position scans, and all lesions were identified on the corresponding 2-min/bed position images. One- and 2-min/bed position image quality differed significantly from the 4-min/bed position image reference (P < 0.05).

Conclusion: LSO PET detector technology permits fast 3D imaging protocols whereby weight-based emission scan durations ranging from 1 to 3 min/bed position provide similar lesion detectability when compared with 4-min/bed position images.