Early GA-68-PSMA PET/MR acquisition decreases the halo-artifact around the bladder and kidneys: Lesion detectability rate and PET metrics evaluation.

Objectives: Bladder and kidneys halo-artifact in 68Ga-PSMA PET/MR affects image quality and PET metric measurements of nearby lesions. Our aim was to determine if PET/MR performed immediately after 68Ga-PSMA injection reduces the artifact incidence and to compare lesion detectability and PET metrics between early-PET/MR and same-day PET/CT.

Methods: The study was IRB approved and written informed consent was obtained from all patients. 42 patients were enrolled (mean age 68.6±8.1years), 21 patients (group 1) performed whole-body (WB) PET/CT followed by WB-PET/MR (late-PET/MR), whereas 21 patients (group 2) underwent prostate-PET/MR and WB-PET/MR (early-PET/MR) followed by WB-PET/CT. Halo-artifact incidence was compared between groups. Lesion detectability and PET metrics were compared in group 1 between PET/CT and late PET/MR and in group 2 between prostate PET/MR, early PET/MR and PET/CT. Pearson's correlation, Bland-Altman plot, Kappa and student's t-tests were used for statistical analysis.

Results: Bladder halo-artifact was seen in 19/21 (90.5%) patients in group 1 and in 3/21 (14.3%, p=0.00) and 2/21(9.5%, p=0.00) patients in group 2 (early and prostate-PET/MR, respectively). Kidneys halo-artifact was present in 19/21 (90.5%) and 5/21(23.8%) patients in group 1 and group 2, respectively (p=0.00). In group 1, 27 and 13 lesions were found on PET/CT and late-PET/MR, respectively (K=0.33, CI=0.09-0.57). In group 2, 61 and 63 lesions were found on early-PET/MR and PET/CT, respectively (K=0.95, CI= 0.89-1.0) with very good correlation between PET metrics measurements (r=0.91; p=0.001). Limits of agreement was of -0.55:2.92 for MTV and -5.7:7.0 for SUVpeak; and -2.2:3.2 for MTV and -4.9:9.8 for SUVpeak; in group 1 and group 2; respectively.

Conclusion: Early-PET/MR decreases the incidence of halo-artifact with very good lesion detectability agreement and PET metrics correlation compared to same-day PET/CT. Research Support: NA