Faculty Bibliography

Utilization of abdominopelvic MR imaging continues to increase in volume and gain widespread clinical acceptance. Many factors such as diaphragmatic respiratory motion, bulk patient motion, and the need for large volumetric coverage while maintaining clinically feasible scan times have proven challenging for body applications of MRI. However, many advances in MR acquisition, including non-Cartesian T1-weighted and T2-weighted acquisitions, advanced Dixon sequences, and 3-dimensional volumetric T2-weighted imaging have helped to mitigate some of the issues which have hampered abdominopelvic MR. This article will summarize these advances in T1-weighted and T2-weighted imaging, with an emphasis on clinical applications and implementation.

PURPOSE: Dynamic FDG imaging for prostate cancer characterization is limited by generally small size and low uptake in prostate tumors. Our aim in this pilot study was to explore feasibility of simultaneous PET/MRI to guide localization of prostate lesions for dynamic FDG analysis using a graphical approach. METHODS: Three patients with biopsy-proven prostate cancer underwent simultaneous FDG PET/MRI, incorporating dynamic prostate imaging. Histology and multiparametric MRI findings were used to localize tumors, which in turn guided identification of tumors on FDG images. Regions of interest were manually placed on tumor and benign prostate tissue. Blood activity was extracted from a region of interest placed on the femoral artery on PET images. FDG data were analyzed by graphical analysis using the influx constant Ki (Patlak analysis) when FDG binding seemed irreversible and distribution volume VT (reversible graphical analysis) when FDG binding seemed reversible given the presence of washout. RESULTS: Given inherent coregistration, simultaneous acquisition facilitated use of MRI data to localize small lesions on PET and subsequent graphical analysis in all cases. In 2 cases with irreversible binding, tumor had higher Ki than benign using Patlak analysis (0.023 vs 0.006 and 0.019 vs 0.008 mL/cm per minute). In 1 case appearing reversible, tumor had higher VT than benign using reversible graphical analysis (0.68 vs 0.52 mL/cm). CONCLUSIONS: Simultaneous PET/MRI allows localization of small prostate tumors for dynamic PET analysis. By taking advantage of inclusion of the femoral arteries in the FOV, we applied advanced PET data analysis methods beyond conventional static measures and without blood sampling.

OBJECTIVE: Prostate tumors occasionally have unusual manifestations on multiparametric MR images that can present a diagnostic dilemma and result in a false-negative interpretation. This article presents examples of such "hiding places" of prostate tumors, four in the peripheral zone and four in the central gland. CONCLUSION: The provided pointers in multiparametric MRI assessment can aid the radiologist in achieving an accurate diagnosis of tumor in the eight scenarios described.

PURPOSE: To retrospectively assess the utility of whole-lesion apparent diffusion coefficient (ADC) metrics in characterizing the Gleason 4 component of Gleason 7 prostate cancer (PCa) at radical prostatectomy. MATERIALS AND METHODS: Seventy patients underwent phased-array coil 3T-magnetic resonance imaging (MRI) before prostatectomy. A uropathologist mapped locations and Gleason 4 percentage (G4%) of Gleason 7 tumors. Two radiologists independently reviewed ADC maps, aware of tumor locations but not G4%, and placed a volume-of-interest (VOI) on all slices including each lesion on the ADC map to obtain whole-lesion mean ADC and ADC entropy. Entropy reflects textural variation and increases with greater macroscopic heterogeneity. Performance for characterizing Gleason 7 tumors was assessed with mixed-model analysis of variance (ANOVA) and logistic regression. RESULTS: Among 84 Gleason 7 tumors (G4% 5%-85%, median 30%; 59 Gleason 3+4, 25 Gleason 4+3), ADC entropy was significantly higher in Gleason 4+3 than Gleason 3+4 tumors (R1: 5.27 +/- 0.61 vs. 4.62 +/- 0.78, P = 0.001; R2: 5.91 +/- 0.32 vs. 5.57 +/- 0.56, P = 0.004); mean ADC was not significantly different between these groups (R1: 0.90 +/- 0.15*10-3 cm2 /s vs. 0.98 +/- 0.21*10-3 cm2 /s, P = 0.075; R2: 1.06 +/- 0.19*10-3 cm2 /s vs. 1.14 +/- 0.16*10-3 cm2 /s, P = 0.083). The area under the receiver operating characteristic (ROC) curve (AUC) for differentiating groups was significantly higher with ADC entropy than mean ADC for one observer (R1: 0.74 vs. 0.57, P = 0.027; R2: 0.69 vs. 0.61, P = 0.329). For R1, correlation with G4% was moderate for ADC entropy (r = 0.45) and weak for mean ADC (r = -0.25). For R2, correlation with G4% was moderate for ADC entropy (r = 0.41) and mean ADC (r = -0.32). For both readers, ADC entropy (P = 0.028-0.003), but not mean ADC (P = 0.384-0.854), was a significant independent predictor of G4%. CONCLUSION: Whole-lesion ADC entropy outperformed mean ADC in characterizing Gleason 7 tumors and may help refine prognosis for this heterogeneous PCa subset. J. Magn. Reson. Imaging 2014. (c) 2014 Wiley Periodicals, Inc.

PURPOSE: To retrospectively compare standard and BLADE T2-weighted imaging (T2WI) sequences of the prostate in terms of image quality and tumor assessment. METHODS: 49 prostate cancer patients (64 +/- 6 years) who underwent 3 T phased-array coil MRI before prostatectomy were included. T2WI was acquired using standard rectilinear and BLADE techniques. Two readers (R1, R2) independently localized the dominant lesion using T2WI alone and using multi-parametric imaging; recorded presence of extraprostatic extension (EPE) in each lobe; and scored lesion conspicuity and absence of motion artifact (1-5 scale; 5 = highest quality). A third reader, unblinded to pathology, placed ROIs to record tumor-to-peripheral-zone contrast. Standard and BLADE T2WI were compared using paired Wilcoxon tests. RESULTS: BLADE showed a trend toward improved motion artifact for R1 (3.4 +/- 1.3 vs. 2.9 +/- 1.5; p = 0.054) but not R2 (4.0 +/- 1.0 vs. 3.9 +/- 1.1; p = 0.880). Dominant lesions showed significantly lower conspicuity using BLADE for R1 (2.8 +/- 2.0 vs. 3.2 +/- 2.0; p = 0.011) but not R2 (2.3 +/- 1.6 vs. 2.4 +/- 1.7; p = 0.353), and significantly lower tumor-to-peripheral-zone contrast using BLADE (0.35 +/- 0.13 vs. 0.42 +/- 0.15; p