Objective: Our aim is to assess if there is a relationship between maximum standardized uptake (SUVmax) and apparent diffusion coefficient (ADC) values of reactive and metastatic lymph nodes, also to compare ADC values of reactive and metastatic lymph nodes in prostate cancer patients.

Materials and Methods: We have retrospectively investigated 20 patients diagnosed with prostate cancer who underwent Ga-68 PSMA PET/MR imaging. Three metastatic and three reactive lymph nodes classified according to the level of PSMA Ga-68 uptake in PET/MR were chosen for each patient. SUVmax and ADCmean values were calculated for each lymph node separately. SPSS version 22 was used for statistical analysis.

Results: A total of 120 lymph nodes in 20 prostate cancer patients were assessed. There was a moderate negative correlation between SUVmax values and ADCmean values of metastatic lymph nodes (p=0.009, r=-0.333). However, there was no significant correlation between SUVmax values and ADCmean values of reactive lymph nodes. ADCmean values of metastatic lymph nodes were significantly lower than those of reactive lymph nodes (p=0.0001).

Conclusion: PET/MR, which combines both advantages of PET and MRI, is an important tool for the diagnosis and management of prostate cancer. We have found that SUVmax values of metastatic lymph nodes were inversely correlated with ADCmean values and combination of both parameters may increase the diagnostic accuracy of Ga-68 PSMA PET/MR in the detection of lymph node metastasis.

Keywords : prostate cancer, lymph node metastasis, Ga-68 PSMA, positron emission tomography