Image quality and lesion detectability using different simulated activities of 68Ga-PSMA-11

Ziel/Aim:

To evaluate the feasibility of reducing administered tracer activities for ⁶⁸Ga-PSMA11 below the recommended range in the EANM/SNMMI procedure guideline (1.8 – 2.2 MBq/kgBW) maintaining high image quality.

Methodik/Methods:

⁶⁸Ga-PSMA-11 PET/CT was performed in eleven prostate cancer (PC) patients. PET data were acquired in list-mode (3 min per bed position) and reconstructed using the 3 min full acquisition, 2 min and 1 min to generate 3/3, 2/3 and 1/3 of injected activities referenced as standard dose (1.9 ± 0.1 MBq/kgBW), low-dose (1.3 ± 0.1 MBq/kgBW) and very-low dose (0.6 ± 0.0 MBq/kgBW). Overall image quality was assessed on a five-point-scale and detectability of focal PSMA-positive lesions were compared to reference standard by three readers.

Ergebnisse/Results:

Subjective image quality declined with computational decreasing simulated tracer activities (mean score standard dose: 4.1 ± 0.4, low-dose: 3.4 ± 0.7, very low-dose: 1.9 ± 0.4, respectively). Mean scores for image quality were statistically significant different between the three activity groups. In total, 21 lesions suggestive for PC were present and correctly identified in 100%, 100% and 95% on standard dose, in 95%, 81% and 90% on low-dose and in 71%, 76% and 59% on very low-dose images, for reader 1, reader 2 and reader 3 respectively.

Schlussfolgerungen/Conclusions:

Reduction of ⁶⁸Ga-PSMA-11 activities below the recommended range in the EANM/SNMI procedure guideline is not feasible without substantial negative impact on image quality and lesion detectability.