Reducing emission time in prostate cancer patients undergoing Ga-68-PSMA PET/CTon a digital system

Ziel/Aim Ga-68-PSMA-PET allows for a superior detection of prostate cancer tissue, especially in the context of low tumor burden. Digital PET/CT bears the potential of reducing emission time or administered activity due to its higher sensitivity. Our aim was to evaluate a fast acquisition protocol with regard to its lesion detection and quantification in the clinical setting.

Methodik/Methods 20 prostate cancer patients underwent Ga-68-PSMA-PET/CT on a digital Siemens Biograph Vision PET/CT system with standard (3 min per bed position) and reduced emission time (1 min per bed position). Each dataset was reconstructed using 4 different reconstruction algorithms. The images were anonymized and read centrally on a per-region basis (prostate bed, pelvic lymph nodes, extrapelvic soft-tissue incl. lymph nodes, bone lesions) by a blinded reader in random order. Accuracy was defined as the percentage of correctly classified regions in short emission time PSF+TOF reconstructed images using the corresponding standard images as reference. SUVs (max. one per region) were compared using images reconstructed with the TOF reconstruction algorithm.

Ergebnisse/Results The vast majority of 80 regions were correctly classified in the short emission time data; accuracy reached 98 %. Two nodal lesions (each ≤4 mm) were not identified (influencing staging in one case). Mean ± standard deviation ratio between SUV_max measured with reduced and standard emission time was 1.03±0.13.

Schlussfolgerungen/Conclusions In this preliminary study, lesion detection and quantification was reproducible with high accuracy using the short emission time. However, in rare cases accurate assessment of small lesions can be hampered. SUV_max did not deviate substantially. Our results suggest that a reduction of administered Ga-68-PSMA activities would maintain diagnostic accuracy.