PT - JOURNAL ARTICLE AU - Nivedita Rana AU - Manpreet Kaur AU - Harmandeep Singh AU - Bhagwant Rai Mittal TI - Dose Optimization in <sup>18</sup>F-FDG PET Based on Noise-Equivalent Count Rate Measurement and Image Quality Assessment AID - 10.2967/jnmt.120.250282 DP - 2021 Mar 01 TA - Journal of Nuclear Medicine Technology PG - 49--53 VI - 49 IP - 1 4099 - http://tech.snmjournals.org/content/49/1/49.short 4100 - http://tech.snmjournals.org/content/49/1/49.full SO - J. Nucl. Med. Technol.2021 Mar 01; 49 AB - The present study aimed to optimize the injected dose of 18F-FDG in whole-body PET/CT scans and assess its effect on noise-equivalent count rate (NECR) and visual image quality (IQ). Methods: Patients scheduled to undergo 18F-FDG PET/CT were prospectively recruited in the study from January to December 2019, regardless of the indication or underlying disease. Patients were divided into 4 groups and injected with different amounts of 18F-FDG radioactivity per kilogram of body weight (1.85, 3.7, 5.5, and 7.4 MBq/kg). All patients underwent 18F-FDG PET/CT studies, and NECRlocal was calculated by noting the trues rate, total prompts, and randoms rate for each bed position. Whole-body NECRglobal was calculated as the average NECR for all bed positions. IQ was qualitatively assessed for each bed position (IQlocal) and for whole-body PET (IQglobal) by 2 readers using 5-point scores based on prevalence of noise, contrast, and lesion detectability. NECR and IQ were compared among all 4 activity groups. Patients were also subdivided into 4 body-mass-index groups (group I, 15–20 kg/m2; group II, 20.1–25 kg/m2; group III, 25.1–30 kg/m2; and group IV, 30.1–35 kg/m2) for comparison. A P value of less than 0.05 was considered significant. Results: In total, 109 patients underwent 18F-FDG PET/CT studies after injection of different amounts of 18F-FDG radioactivity and a mean uptake time of 62.32 min. The mean NECRglobal and IQglobal for each group were significantly different from other groups (P &lt; 0.05), with NECR and IQ being higher in high-activity groups than in low-activity groups. The overall IQ was acceptable in all patients, even in the lowest-activity group (1.84 MBq/kg). The mean NECRglobal and IQglobal were significantly different in all 4 body-mass-index groups (P &lt; 0.05), except between groups II and III (P &gt; 0.05). NECRlocal and IQlocal correlated moderately (r = 0.64). Conclusion: Optimization of injected 18F-FDG radioactivity from 7.4 MBq/kg (200 μCi/kg) to 1.85 MBq/kg (50 μCi/kg) resulted in acceptable IQ, despite a reduction in NECR.