Faculty Bibliography

OBJECTIVE: The purpose of this study was to evaluate the utility of multiparametric MRI in localization of the index lesion of prostate cancer. MATERIALS AND METHODS: Fifty-one patients who underwent 3-T MRI of the prostate with a pelvic phased-array coil that included T2-weighted, diffusion-weighted, and dynamic contrast-enhanced sequences before prostatectomy were included. Six radiologists assessed all images to identify the lesion most suspicious of being the index lesion, which was localized to one of 18 regions. A uropathologist using the same 18-region scheme reviewed the prostatectomy slides to localize the index lesion. MRI performance was assessed by requiring either an exact match or an approximate match (discrepancy of up to one region) between the MRI and pathologic findings in terms of assigned region. RESULTS: The pathologist identified an index lesion in 49 of 51 patients. In exact-match analysis, the average sensitivity was 60.2% (range, 51.0-63.3%), and the average positive predictive value (PPV) was 65.3% (range, 61.2-69.4%). In approximate-match analysis, the average sensitivity was 75.9% (range, 65.3-69.6%), and the average PPV was 82.6% (range, 79.2-91.4%). The sensitivity was higher for index lesions with a Gleason score greater than 6 in exact-match (74.8% vs 15.3%, p < 0.001) and approximate-match (88.7% vs 36.1%, p = < 0.001) analyses and for index lesions measuring at least 1 cm in approximate-match analysis (80.3% vs 58.3%, p = 0.016). In exact-match analysis, 30.0%, 44.9%, and 79.1% of abnormalities found with one, two, and three MRI parameters represented the index lesion (p < 0.001). CONCLUSION: The sensitivity and PPV of multiparametric MRI for index lesion localization were moderate, although they improved in the setting of more aggressive pathologic features and a greater number of abnormal MRI parameters, respectively.

OBJECTIVE: The purpose of this study is to retrospectively compare 1D, 2D, and 3D measurements on CT for detection of growth of solid renal masses on active surveillance. MATERIALS AND METHODS: Forty solid renal masses measuring at least 1 cm in patients who underwent two CT studies at least 3 months apart were included. Two radiologists independently assessed the studies for interval growth using gestalt visual assessment and 1D, 2D, and 3D measurements. Prospective reports were also evaluated for indications of growth. The summation-of-areas technique was used to calculate volumes of lesions, which served as reference standard in determination of growth. Logistic regression analysis for correlated data was used to compare accuracy of methodologies for detection of lesion growth. Interreader agreement was assessed using kappa coefficients and intraclass correlation coefficients. RESULTS: The accuracy of gestalt visual, 1D, 2D, and 3D assessments for detection of interval growth was 72.5%, 70.0%, 82.5%, and 85% for reader 1 and 77.5%, 70.0%, 90.0%, and 95.0% for reader 2. These differences were significant or nearly significant (p = 0.003-0.054) for the greater accuracy of 2D or 3D measurements than for 1D measurements for reader 1 as well as the greater accuracy of 2D measurements than 1D measurements and 3D measurements than gestalt visual assessment or 1D measurements for reader 2. The accuracy of prospective reports for detection of growth was 65.0%. Reader agreement was fair for gestalt visual assessment (kappa = 0.31) and nearly perfect for 1D, 2D, and 3D measurements (intraclass correlation coefficient = 0.97-0.99). CONCLUSION: Our results show that 2D or 3D measurements may be preferable to 1D measurements on CT in assessment for growth of solid renal masses on active surveillance.

Purpose: To assess the feasibility of diffusional kurtosis (DK) imaging for distinguishing benign from malignant regions, as well as low- from high-grade malignant regions, within the peripheral zone (PZ) of the prostate in comparison with standard diffusion-weighted (DW) imaging. Materials and Methods: The institutional review board approved this retrospective HIPAA-compliant study and waived informed consent. Forty-seven patients with prostate cancer underwent 3-T magnetic resonance imaging by using a pelvic phased-array coil and DW imaging (maximum b value, 2000 sec/mm(2)). Parametric maps were obtained for apparent diffusion coefficient (ADC); the metric DK (K), which represents non-Gaussian diffusion behavior; and corrected diffusion (D) that accounts for this non-Gaussianity. Two radiologists reviewed these maps and measured ADC, D, and K in sextants positive for cancer at biopsy. Data were analyzed by using mixed-model analysis of variance and receiver operating characteristic curves. Results: Seventy sextants exhibited a Gleason score of 6; 51 exhibited a Gleason score of 7 or 8. K was significantly greater in cancerous sextants than in benign PZ (0.96 ± 0.24 vs 0.57 ± 0.07, P < .001), as well as in cancerous sextants with higher rather than lower Gleason score (1.05 ± 0.26 vs 0.89 ± 0.20, P < .001). K showed significantly greater sensitivity for differentiating cancerous sextants from benign PZ than ADC or D (93.3% vs 78.5% and 83.5%, respectively; P < .001), with equal specificity (95.7%, P > .99). K exhibited significantly greater sensitivity for differentiating sextants with low- and high-grade cancer than ADC or D (68.6% vs 51.0% and 49.0%, respectively; P ≤ .004) but with decreased specificity (70.0% vs 81.4% and 82.9%, respectively; P ≤ .023). K had significantly greater area under the curve for differentiating sextants with low- and high-grade cancer than ADC (0.70 vs 0.62, P = .010). Relative contrast between cancerous sextants and benign PZ was significantly greater for D or K than ADC (0.25 ± 0.14 and 0.24 ± 0.13, respectively, vs 0.18 ± 0.10; P < .001). Conclusion: Preliminary findings suggest increased value for DK imaging compared with standard DW imaging in prostate cancer assessment. Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12112290/-/DC1

OBJECTIVE: The objective of our study was to retrospectively compare the MRI features of retroperitoneal fibrosis (RPF) and lymphoma presenting as confluent retroperitoneal soft tissue. MATERIALS AND METHODS: MRI studies of 31 patients (18 men, 13 women; mean age, 58.4 +/- 15.8 [SD] years; 22 with RPF and nine with lymphoma) were evaluated. Two radiologists independently and in consensus evaluated all cases for an array of subjective imaging features. A third radiologist measured the size (i.e., the greatest dimension in the transverse plane) and apparent diffusion coefficient (ADC) value of the tissue. Features of RPF and lymphoma were compared using the Fisher exact test, Mann-Whitney test, and receiver operating characteristic (ROC) curve analysis. Interreader concordance was also calculated. RESULTS: The mean age of patients with lymphoma was significantly greater than that incases of RPF (72.4 +/- 13.3 [SD] vs 52.7 +/- 13.2 years, respectively; p = 0.003). The MRI features significantly more common in patients with RPF were pelvic extension (p = 0.004) and medial ureteral bowing (p < 0.001). The MRI features significantly more common in cases of lymphoma were predominantly suprarenal location, perirenal extension, anterior aortic displacement, heterogeneity, and the presence of additional nodes (p < 0.001-0.043). Size was significantly greater in patients with lymphoma than in those with RPF (mean +/- SD, 33.9 +/- 17.3 vs 11.0 +/- 5.7 mm; p < 0.001) and had an area under the curve (AUC) of 0.960; a size larger than 15 mm had sensitivity of 100% and specificity of 86.4% for the diagnosis of lymphoma. The ADC was significantly lower in lymphoma than in RPF (mean +/- SD, 0.92 +/- 0.17 vs 1.40 +/- 0.38 x 10(-3) mm(2)/s; p = 0.003) and had an AUC of 0.904. An ADC of 0.955 x 10(-3) mm(2)/s or less had sensitivity of 83.3% and specificity of 89.5% for the diagnosis of lymphoma. Interreader concordance for subjective features was very good to excellent (range, 80.6-100%). CONCLUSION: MRI features may be helpful in distinguishing between RPF and lymphoma.

Background The presence of muscularis propria invasion by bladder cancer is a key factor in prognosis and treatment decisions, although may be missed by biopsy due to sampling error. MRI has shown potential for detection of muscle invasion but has not specifically been evaluated for this purpose in the setting of bladder cancer patients without evidence of muscle invasion on initial biopsy. Purpose To evaluate the role of MRI in detection of muscularis propria invasion by bladder cancer following a pathologic diagnosis of non-invasive tumor. Material and Methods This retrospective study included 23 patients who underwent pelvic MRI following a pathologic diagnosis of bladder cancer without muscularis propria invasion and in whom additional histologic evaluation was performed following MRI. Two radiologists in consensus reviewed T2-weighted images to identify those cases suspicious for muscle invasion on MRI. The radiologists identified whether cases suspicious for invasion demonstrated disruption of the T2-hypointense muscularis layer of the bladder wall, peri-vesical fat stranding, and peri-vesical soft tissue nodularity. Findings were compared with pathologic results obtained after MRI. Results Suspicion was raised for muscle invasion in eight of 23 cases, four of which exhibited invasion on follow-up pathology. No case without suspicion on MRI exhibited invasion on follow-up pathology. Therefore, sensitivity and specificity were 100% and 79%, respectively. Among individual findings, muscularis disruption on T2WI exhibited sensitivity of 100% and specificity of 79%, peri-vesical fat stranding exhibited sensitivity and specificity of 50% and 84%, and peri-vesical soft tissue nodularity exhibited sensitivity and specificity of 25% and 100%. Conclusion MRI demonstrated high sensitivity for detection of muscle invasion in cases of bladder cancer without invasion on initial histologic assessment. Muscularis disruption on T2WI appeared to exhibit a better combination of sensitivity and specificity than did peri-vesical changes.

PURPOSE: To assess the utility of apparent diffusion coefficient (ADC) values obtained from diffusion-weighted imaging (DWI) in distinguishing high-grade bladder cancer with and without metastatic disease. MATERIALS AND METHODS: Seventeen patients with histologically confirmed high-grade bladder cancer who underwent pelvic magnetic resonance imaging (MRI) at 1.5T including DWI using b-values of 0, 400, and 800 sec/mm(2) were assessed. Histologic findings and follow-up imaging were used to establish the reference standard in terms of metastatic disease. Two radiologists independently recorded ADC of all lesions following a training session, with their results averaged. Mann-Whitney U-test, receiver operating characteristic (ROC) curve analysis and intraclass correlation coefficient (ICC) were used for data analysis. RESULTS: Metastatic disease was characterized as present or absent in eight and nine patients, respectively. ADC was significantly lower among cases with metastatic disease than among cases without metastatic disease, both within the entire cohort (1.07 +/- 0.18 x 10(-3) mm(2) /s vs. 1.45 +/- 0.22 x 10(-3) mm(2) /s; P = 0.002) and within the subset of patients with muscle-invasive tumor (1.06 +/- 0.19 x 10(-3) mm(2) /s vs. 1.45 +/- 0.23 x 10(-3) mm(2) /s; P = 0.017). Area under the ROC curve for identifying metastatic disease using ADC was 0.944, with optimal threshold of 1.21 x 10(-3) mm(2) /s, which was associated with a sensitivity of 87.5%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 90.0%. Interreader agreement for ADC was excellent (ICC = 0.91). CONCLUSION: In this preliminary study, ADC was significantly different between cases of high-grade urothelial carcinoma of the bladder with and without metastatic disease. These results may have value in assessing the metastatic potential of patients with localized high-grade tumors of the bladder. J. Magn. Reson. Imaging 2012;. (c) 2012 Wiley Periodicals, Inc.

PURPOSE: We identified histological differences between prostate cancer foci that are detected and missed using multiparametric magnetic resonance imaging.MATERIALS AND METHODS: A total of 49 patients who underwent multiparametric magnetic resonance imaging, including T2-weighted imaging, including diffusion weighted imaging and dynamic contrast enhanced imaging, before prostatectomy were enrolled in the study. One radiologist identified areas highly suspicious for tumor. One pathologist identified and categorized tumors in terms of size, Gleason score, solid tumor growth, intermixed benign glands, loose stroma, desmoplastic stroma and a high malignant epithelium-to-stroma ratio. Differences between detected and missed tumors were assessed using logistic regression analyses based on generalized estimating equations for correlated data. RESULTS: All histological features showed significant differences between detected and missed tumors on multiparametric magnetic resonance imaging (p<0.0001). Independent predictors of detection on multivariate analysis were size (OR 5.38, p=0.0077), Gleason score (OR 5.12, p=0.0094) and solid growth (OR 17.83, p<0.0001). Size, Gleason score and loose stroma were significant predictors of identification with diffusion weighted imaging on univariate analysis (p≤0.0245), while Gleason score (OR 17.05, p=0.0212) and solid growth (OR 34.90, p=0.0103) were independent predictors of identification with diffusion weighted imaging on multivariate analysis. Identification with T2-weighted imaging was associated with size and Gleason score (p≤0.01876). Identification with dynamic contrast enhanced imaging was associated with intermixed benign epithelium, loose stroma and a high malignant epithelium-to-stroma ratio (p≤0.0499). No combination of features served as independent predictors on multivariate analysis for T2-weighted imaging or dynamic contrast enhanced imaging. CONCLUSIONS: There are fundamental histological differences between detected and missed prostate tumors using magnetic resonance imaging. Insights into these differences may facilitate the prospective role of magnetic resonance imaging in counseling and treatment selection for patients with prostate cancer

OBJECTIVE: To assess the frequency, characteristics, and fate of arterioportal shunts in patients with hepatic steatosis and to compare this to the frequency in patients without liver disease. METHODS: Eighty-four patients with hepatic steatosis but no other known liver disease and who underwent 2 abdominal magnetic resonance imaging (MRI) examinations at least 1 year apart formed one study cohort. Eighty-four subjects without steatosis or other known liver disease and who also underwent 2 MRI examinations at least 1 year apart formed a control group. Two radiologists evaluated the initial study for the presence and characteristics of arterial enhancing foci not visible on other sequences and assessed the fate of these foci on the follow-up study. RESULTS: Of the patients with steatosis, 36.9% (95% confidence interval [CI], 26.6%-48.1%) demonstrated a total of 108 arterial enhancing foci, compared with 20 arterial enhancing foci in 13.1% of controls (95% CI, 6.7%-22.2%). Both the number of subjects with at least one arterial enhancing focus and the mean number per subject were significantly greater in the steatosis cohort (P < 0.001). The arterial enhancing foci were generally small and peripheral in location in both cohorts. On follow-up examination, all lesions disappeared, decreased in size, were stable, or increased slightly in size while remaining inconspicuous on other sequences. CONCLUSION: Findings consistent with arterioportal shunts were observed at an unexpectedly high frequency in the control group but at a significantly greater frequency in the steatosis group. All foci exhibited benign behavior on long-term follow-up. Future studies may assess for clinical implications of this finding in patients with hepatic steatosis.

Purpose: To retrospectively assess the relationships between a number of magnetic resonance (MR) imaging features and growth rate of solid renal masses in patients undergoing active surveillance. Materials and Methods: This retrospective study was institutional review board approved, with waiver of informed consent. This study was HIPAA compliant. Forty-four patients (mean age, 70 years +/- 13 [standard deviation]; 31 men, 13 women) with 47 solid renal masses measuring at least 1 cm who underwent two contrast material-enhanced MR imaging studies at least 3 months apart were included. The initial MR imaging study was evaluated independently by two radiologists for an array of imaging features, with differences resolved by consensus. Later, the two readers in consensus measured tumor volume on the first and last study to calculate tumor doubling time (DT). Associations between MR imaging features and DT were assessed by using generalized estimating equations and mixed model analyses. Interreader agreement was assessed with k coefficients. Results: kappa coefficients ranged from 0.62 to 0.92. Mean DT of the 47 masses was 530 days. Five (11%) masses decreased in size. Twenty-five of 47 masses were classified as slow growing on the basis of a DT of more than 2 years. There was significantly slower growth among masses showing homogeneity on T2-weighted images (P = .036) and a nearly significant slower growth rate among masses showing homogeneity on postcontrast images (P = .065) and hypointensity on T2-weighted images (P = .074). There was a significant correlation between initial volume and growth rate among lesions larger than 3 cm (r = 0.79, P = .041) but not among smaller lesions (r = -0.02, P = .911). Multivariate analysis identified age (odds ratio = 0.92, P = .015) and homogeneity on T2-weighted images (odds ratio = 4.47, P = .037) as independent predictors of slow growth. Conclusion: The results suggest MR imaging features may have a role in predicting growth rate of solid renal masses during active surveillance. (c) RSNA, 2012 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11111074/-/DC1.