RT Journal Article SR Electronic T1 18F-DCFPyL PET/CT in Patients with Subclinical Recurrence of Prostate Cancer: Effect of Lesion Size, Smoothing Filter, and Partial-Volume Correction on PROMISE Criteria JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1615 OP 1620 DO 10.2967/jnumed.120.241737 VO 61 IS 11 A1 Claudia Ortega A1 Josh Schaefferkoetter A1 Patrick Veit-Haibach A1 Reut Anconina A1 Alejandro Berlin A1 Nathan Perlis A1 Ur Metser YR 2020 UL http://jnm.snmjournals.org/content/61/11/1615.abstract AB Our purpose was to determine the effect of a smoothing filter and partial-volume correction (PVC) on measured prostate-specific membrane antigen (PSMA) activity in small metastatic lesions and to determine the impact of these changes on molecular imaging PSMA (miPSMA) scoring. Methods: Men who had biochemical recurrence of prostate cancer with negative findings on CT and bone scintigraphy were referred for 18F-DCFPyL (2‐(3‐(1‐carboxy‐5‐[(6‐18F‐fluoro‐pyridine‐3‐carbonyl)‐amino]‐pentyl) PET/CT. Examinations were performed on 1 of 2 different brands of PET/CT scanner. All suspected tumor sites were manually contoured on coregistered CT and PET images, and each was assigned an miPSMA score as per the PROMISE criteria. The PVC factors were calculated for every lesion using the anatomic CT and then applied to the unsmoothed PET images. The miPSMA scores, with and without the corrections, were compared, and a simplified rule-of-thumb (RoT) correction factor (CF) was derived for lesions at various sizes (<4 mm, 4–7 mm, 7–9 mm, and 9–12 mm). This CF was then applied to the original dataset and the miPSMA scores that were obtained using the RoT CF were compared with those obtained using the actual corrections. Results: There were 75 men (median age, 69 y; median serum PSA, 3.69 μg/L) with 232 metastatic nodes less than 12 mm in diameter (mean lesion volume, 313.5 ± 309.6 mm3). The mean SUVmax before and after correction was 11.0 ± 9.3 and 28.5 ± 22.8, respectively (P < 0.00001). The mean CF for lesions smaller than 4 mm (n = 22), 4–7 mm (n = 140), 7–9 mm (n = 50), and 9–12 mm (n = 20) was 4 (range, 2.5–6.4), 2.8 (range, 1.6–4.9), 2.3 (range, 1.6–3.3), and 1.8 (range, 1.4–2.4), respectively. Overall, the miPSMA scores were concordant between the corrected dataset and the RoT dataset for 205 of 232 lesions (88.4%). Conclusion: A smoothing filter and PVC had a significant effect on measured PSMA activity in small nodal metastases, impacting the miPSMA score.