Faculty Bibliography

OBJECTIVE: The purpose of this study was to compare the reproducibility and diagnostic performance of 2D and 3D ROIs for prostate apparent diffusion coefficient (ADC) measurements. MATERIALS AND METHODS: The study included 56 patients with prostate cancer undergoing 3-T MRI including DWI (b = 50 and 1000 s/mm2) before radical prostatectomy. Histologic findings from prostatectomy specimens were reviewed to denote each patient's dominant tumor and a benign region with visually decreased ADC. Three readers independently measured the ADCs of both areas using an ROI placed on a single slice through the lesion (2D) and an ROI encompassing all slices through the lesion (3D). Readers repeated measurements after 3 weeks. Assessment included Bland-Altman analysis (coefficient of repeatability [CR] in which lower values indicated higher reliability) and ROC analysis. RESULTS: For intrareader variability, the CRs across readers for all ROIs were 9.9% for 2D and 9.3% for 3D. For tumor ROIs the CRs were 10.6% for 2D and 9.6% for 3D. For interreader variability, the CRs across readers for all ROIs were 17.1% for 2D and 20.5% for 3D and for tumor ROIs were 17.9% for 2D and 22.2% for 3D. For combined reader data, the AUCs for benign and malignant findings were 0.77 for 2D and 0.78 for 3D (p = 0.146). For differentiating Gleason score (GS) 3 + 3 from GS > 3 + 3 tumors, the AUCs were 0.92 for 2D and 0.92 for 3D ROIs (p = 0.649). For differentiating GS /= 4 + 3 tumors, the AUCs were 0.70 for 2D and 0.67 for 3D ROIs (p = 0.004). CONCLUSION: Use of a 3D ROI did not improve intrareader or interreader reproducibility or diagnostic performance compared with use of a 2D ROI for prostate ADC measurements. Interreader reproducibility of 2D ROIs was suboptimal nonetheless.

In patients with metallic hip implants, distortions, and other artifacts relating to the echo-planar imaging acquisition may render prostate diffusion-weighted imaging (DWI) nondiagnostic. Reduced field-of-view (rFOV) acquisition, using parallel transmission and focused excitation, is a novel DWI approach that reduces distortions and improves images quality. This article presents images from both standard and rFOV DWI acquisitions in 2 prostate cancer patients with hip implants, showing the effect of rFOV DWI for improving tumor localization. The findings have implications for the potential application of magnetic resonance imaging for guiding targeted biopsy and planning focal therapy in the growing population of patients with hip implants.

OBJECTIVE:The purpose of this study was to compare image quality and tumor assessment at prostate magnetic resonance imaging (MRI) between reduced field-of-view diffusion-weighted imaging (rFOV-DWI) and standard DWI (st-DWI). METHODS:A total of 49 patients undergoing prostate MRI and MRI/ultrasound fusion-targeted biopsy were included. Examinations included st-DWI (field of view [FOV], 200 × 200 mm) and rFOV-DWI (FOV, 140 × 64 mm) using a 2-dimensional (2D) spatially-selective radiofrequency pulse and parallel transmission. Two readers performed qualitative assessments; a third reader performed quantitative evaluation. RESULTS:Overall image quality, anatomic distortion, visualization of capsule, and visualization of peripheral/transition zone edge were better for rFOV-DWI for reader 1 (P ≤ 0.002), although not for reader 2 (P ≥ 0.567). For both readers, sensitivity, specificity, and accuracy for tumor with a Gleason Score (GS) of 3 + 4 or higher were not different (P ≥ 0.289). Lesion clarity was higher for st-DWI for reader 2 (P = 0.008), although similar for reader 1 (P = 0.409). Diagnostic confidence was not different for either reader (P ≥ 0.052). Tumor-to-benign apparent diffusion coefficient ratio was not different (P = 0.675). CONCLUSIONS:Potentially improved image quality of rFOV-DWI did not yield improved tumor assessment. Continued optimization is warranted.