# Impact of Uptake Period on 18F-DCFPyL-PSMA PET/CT Maximum Standardised Uptake Value

## TL;DR

This study shows that waiting 120 minutes after injection gives the most accurate results for a key imaging measurement in prostate cancer diagnosis.

## Contribution

The study identifies 120 minutes as the optimal uptake period for 18F-DCFPyL-PSMA PET/CT SUVmax measurements.

## Key findings

- SUVmax values increased significantly with longer uptake periods, especially between 60 and 120 minutes.
- The largest SUVmax change was 29.98% between 60 and 120 minutes.
- Image acquisition at 120 minutes is recommended for more accurate prostate cancer diagnosis.

## Abstract

The accuracy of PSMA PET imaging can be influenced by the time between the injection of the imaging agent and when the scan is taken. This study explored how different time intervals (60, 90 and 120 min) affect the measurement of SUVmax, a key value used in diagnosing prostate cancer. The results showed that longer times consistently led to higher SUVmax values, with the most significant change seen between 60 and 120 min. These findings suggest that waiting 120 min before scanning may provide the most accurate results for this type of imaging. Additional research is needed to confirm if this timing is effective for other similar imaging methods.

Background: The maximum standardised uptake value (SUVmax) can potentially be affected by the uptake period during PSMA PET imaging. The optimal image acquisition period for 2-(3-{1-carboxy-5-[(6-18F-fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (18F-DCFPyL)PSMA PET/CT is yet to be established. This study aims to evaluate the effect of the uptake period on the SUVmax in diagnosing localised, clinically significant prostate cancer using 18F-DCFPyL-PSMA PET/CT. Methods: Sixty biopsy-naive men with one or more PI-RADS 4 or 5 lesions of at least 10 mm on multiparametric MRI (mpMRI) were enrolled to undergo 18F-DCFPyL-PSMA PET/CT. SUVmax was prospectively measured following an uptake period of 60, 90 and 120 min post injection of 18F-DCFPyL-PSMA radiotracer. Concordance with biopsy results or final histopathology was recorded. Results: Mean absolute differences in SUVmax at 60 vs. 90, 60 vs. 120, and 90 vs. 120 min uptake periods were 3.23 (SD 4.76), 4.53 (SD 7.33), and 3.24 (SD 4.56), respectively. This represents a statistically significant systematic increase in SUVmax (p-value < 0.001) with increasing uptake period. The interval between the uptake period of 60 vs. 120 min represented the largest SUVmax change of 29.98%. Conclusions: The SUVmax is a dynamic variable significantly affected by uptake period. Our study supports image acquisition at 120 min following injection of 18F-DCFPyL radiotracer. Further studies are needed to determine if this acquisition period can be applied to other Fluorine-18 based PSMA radiotracers.