RT Journal Article SR Electronic T1 Patient Weight–Based Acquisition Protocols to Optimize18F-FDG PET/CT Image Quality JF Journal of Nuclear Medicine Technology JO J. Nucl. Med. Technol. FD Society of Nuclear Medicine SP 72 OP 76 DO 10.2967/jnmt.110.081661 VO 39 IS 2 A1 Akio Nagaki A1 Masahisa Onoguchi A1 Norikazu Matsutomo YR 2011 UL http://tech.snmjournals.org/content/39/2/72.abstract AB The choice of injected dose of 18F-FDG and acquisition time is important in obtaining consistently high-quality PET images. The aim of this study was to determine the optimal acquisition protocols based on patient weight for 3-dimensional lutetium oxyorthosilicate PET/CT. Methods: This study was a retrospective analysis of 76 patients ranging from 29 to 101 kg who were injected with 228–395.2 MBq of 18F-FDG for PET imaging. The study population was divided into 4 weight-based groups: less than 45 kg (group 1), 45–59 kg (group 2), 60–74 kg (group 3), and 75 kg or more (group 4). We measured the true coincidence rate, random coincidence rate, noise-equivalent counting rate (NECR), and random fraction and evaluated image quality by the coefficient of variance (COV) in the largest liver slices. Results: The true coincidence rate, random coincidence rate, and NECR significantly increased with increasing injected dose per kilogram (r = 0.91, 0.83, and 0.90; all P < 0.01). NECR maximized at 10.11 MB/kg in underweight patients. The true coincidence rate differed significantly among the 4 groups, except for group 3 versus group 4 (P < 0.01). The ratio of the true coincidence rate for group 2 to groups 3 and 4 was 1.4 and 1.6, respectively. The average random fraction for all 4 groups was approximately 35%. The COV of the 4 groups differed for all pairs (P < 0.01). The COVs in overweight patients were larger than those in underweight patients, and image quality in overweight patients was poor. Conclusion: We modified acquisition protocols for 18F-FDG PET/CT according to the characteristics of a 3-dimensional lutetium orthosilicate PET scanner and PET image quality based on patient weight. The optimal acquisition time was approximately 1.4–1.6 times longer in overweight patients than in normal-weight patients. Estimation of optimal acquisition times using the true coincidence rate is more important than other variables in improving PET image quality.