Comparison of MRI sequences in whole-body PET/MRI for staging of patients with high-risk prostate cancer

OBJECTIVE. The purpose of this study is to investigate the diagnostic value of various MRI sequences used for whole-body (WB) 18F-fluorocholine (FCH) PET/MRI staging of patients with high-risk prostate cancer (PCa). SUBJECTS AND METHODS. This analysis is based on data from a prospective study that included 58 patients with untreated high-risk PCa who underwent integrated WB FCH PET/MRI (n = 10) or FCH PET/CT and WB MRI (n = 48). Metastatic sites were recorded. The standard of reference was histopathologic findings or clinical and imaging follow-up, or both. For each MRI sequence (Dixon T1-weighted, turbo inversion recovery magnitude, WB DWI, and gadolinium-enhanced T1-weighted volumetric interpolated breath-hold examination [VIBE]), acquisition time was recorded, and conspicuity of metastatic lesions was qualitatively assessed by two radiologists using a 4-point ordinal scale (0-3). RESULTS. Total WB acquisition times were 1 minute 25 seconds for Dixon T1-weighted, 15 minutes 7 seconds for turbo inversion recovery magnitude, 16 minutes 33 seconds for WB DWI, and 1 minute 28 seconds for gadolinium-enhanced T1-weighted VIBE. The lesion detection rates were 88.3% (68/77) for Dixon T1-weighted, 94.8% (73/77) for turbo inversion recovery magnitude, 95.2% (40/42) for WB DWI, and 97.4% (75/77) for gadolinium-enhanced T1-weighted VIBE sequences. Moderate or high conspicuity scores were assigned to 62.3% (48/77) of lesions for Dixon T1-weighted, 88.3% (68/77) of lesions for turbo inversion recovery magnitude, 90.5% (38/42) of lesions for WB DWI, and 92.2% (71/77) of lesions for gadolinium-enhanced T1-weighted VIBE sequences. Conspicuity of metastases on gadolinium- enhanced T1-weighted VIBE and WB DWI sequences was higher than that on Dixon T1-weighted sequences (p < 0.0001 and p = 0.0011, respectively). CONCLUSION. Metastases from prostate cancer are best detected at DWI or gadolinium- enhanced T1-weighted VIBE sequences. The most time-efficient sequence with the highest lesion detection rate and conspicuity is gadolinium-enhanced T1-weighted VIBE.