Contribution of 5th minute and 2nd hour images to standard imaging in (68Ga)PSMA 11 PET/CT.

Abstract

To investigate the superiority or contribution of 5th minute pelvic and 2nd hour whole body Gallium68-prostate-specific membrane antigen-HBED-CC [(68Ga)PSMA 11] Positron Emission Tomography/Computed Tomography (PET/CT) images to 1st hour imaging in patients with prostate cancer (PCa). A total of 63 patients diagnosed with PCa who underwent (68Ga)PSMA 11 PET/CT between April 2019 and June 2019 and who had 5th minute and 1st and 2nd hour images were included in the study. Early (5th minute) pelvic region and 1st and 2nd hour full body images were obtained from all patients. The regions of interest (ROI) were drawn from the background tissues and the physiological uptake sites in a way to include the same lesions from primary and metastatic lesions in all three imagings, and SUVmax values, and tumor-background ratio (TBR) were calculated. The mean age of the patients was 69.81 ± 8.78 (min/max: 51/91) years. In the 5th minute images, prostate gland and bed were easier to evaluate, because of low bladder activity. However, lymph node evaluation was more difficult due to high vascular activity. In the prostate gland, lymph nodes and bone metastases, both SUVmax values and TBR rates increased with time from the 5th minute (p < 0.001). At the 2nd hour, some lesions became more visible, while decreased activity was observed in some lesions. However, none of the patients required a change in the stage or treatment. In conclusion, the 5th minute pelvic images in (68Ga)PSMA 11 PET/CT were helpful in visual evaluation of the prostate gland and bed, while 2nd hour images showed high SUVmax and TBR rates in malignant lesions. As the SUVmax values of benign lesions were found to be lower in the 2nd hour, when compared to the 1st hour, it was thought that the 2nd hour imaging could be used in the additional imaging for suspicious lesions without the need for very long waiting times.