Faculty Bibliography

AIM: To evaluate the performance of normalised apparent diffusion coefficient (ADC) values for prostate cancer assessment when performed by independent observers blinded to histopathology findings. MATERIALS AND METHODS: Fifty-eight patients undergoing 3 T phased-array coil magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI; maximal b-value 1000 s/mm2) before prostatectomy were included. Two radiologists independently evaluated the images, unaware of the histopathology findings. Regions of interest (ROIs) were drawn within areas showing visually low ADC within the peripheral zone (PZ) and transition zone (TZ) bilaterally. ROIs were also placed within regions in both lobes not suspicious for tumour, allowing computation of normalised ADC (nADC) ratios between suspicious and non-suspicious regions. The diagnostic performance of ADC and nADC were compared. RESULTS: For PZ tumour detection, ADC achieved significantly higher area under the receiver operating characteristic curve (AUC; p=0.026) and specificity (p=0.021) than nADC for reader 1, and significantly higher AUC (p=0.025) than nADC for reader 2. For TZ tumour detection, nADC achieved significantly higher specificity (p=0.003) and accuracy (p=0.004) than ADC for reader 2. For PZ Gleason score >3+3 tumour detection, ADC achieved significantly higher AUC (p=0.003) and specificity (p=0.005) than nADC for reader 1, and significantly higher AUC (p=0.023) than nADC for reader 2. For TZ Gleason score >3+3 tumour detection, ADC achieved significantly higher specificity (p=0.019) than nADC for reader 1. CONCLUSION: In contrast to prior studies performing unblinded evaluations, ADC was observed to outperform nADC overall for two independent observers blinded to the histopathology findings. Therefore, although strategies to improve the utility of ADC measurements in prostate cancer assessment merit continued investigation, caution is warranted when applying normalisation to improve diagnostic performance in clinical practice.

OBJECTIVE: The purpose of this study was to retrospectively investigate associations between baseline CT findings in suspected acute appendicitis and subsequent hospital resource utilization. MATERIALS AND METHODS: One hundred thirty-eight patients (76 male and 62 female patients; mean [+/- SD] age, 40 +/- 21 years) who were admitted for suspected acute appendicitis and underwent baseline CT were included. A single radiologist reviewed CT examinations for appendiceal-related findings. Linear and logistic regressions were performed to identify independent predictors of payer and hospital resource utilization. Combined performance of identified independent factors for predicting outcomes was determined. RESULTS: Greater age, lower Charlson comorbidity index (CCI), lesser appendiceal wall thickness, absence of loculated fluid collection, and absence of periappendiceal fluid were significant independent predictors of inpatient surgery (joint sensitivity, 92.7%; specificity, 65.8%). Smaller appendiceal diameter, absence of periappendiceal fluid, and laparoscopic surgery were significant independent predictors of same-day discharge (joint sensitivity, 79.1%; specificity, 64.2%). Greater CCI, greater wall thickness, and presence of periappendiceal fluid were significant independent predictors of repeat abdominopelvic CT (joint sensitivity, 82.5%; specificity, 68.1%). Presence of an appendicolith was the only significant predictor of repeat emergency department visit within 30 days (sensitivity, 61.2%; specificity, 68.8%) and the only significant predictor of repeat inpatient admission within 30 days (sensitivity, 63.6%; specificity, 68.5%). Greater appendiceal diameter and presence of free air were significant predictors of inpatient costs, and predicted costs were as follows: $8047 + ($745 x appendiceal diameter) if free air was absent; and $-39,261 + ($4426 x appendiceal diameter) if free air was present. However, costs were poorly predicted when greater than $45,000. Sex, WBC count, and payer category were not independent predictors, relative to CT findings, of any outcome. CONCLUSION: Admission CT findings serve as independent predictors of hospital resource utilization in suspected acute appendicitis.

PURPOSE: To compare boundaries of prostate tumors on MRI and histologic assessment from radical prostatectomy (RP) using detailed software-assisted co-registration, in order to define an optimal treatment margin to achieve complete tumor destruction during image-guided focal ablation. METHODS: 33 patients who underwent 3T MRI before RP were included. A radiologist traced lesion borders on MRI and assigned a suspicion score (SS) from 2-5. 3D reconstructions were created from high-resolution digitalized slides from RP specimens and co-registered to MRI using advanced software. Tumors were compared between histology and MRI using the Hausdorff Distance (HD) and stratified by MRI-SS, Gleason Score (GS), and lesion diameter. Cylindrical volume estimates of treatment effects were used to define the optimal treatment margin. RESULTS: 46 histologically confirmed cancers underwent 3D software-based registration with MRI. MRI underestimated tumor sizes, with the maximal discrepancy between MRI and histologic boundaries for a given tumor averaging 1.99+/-3.1mm (18.5% of the MRI diameter). Boundary underestimation was larger for MRI-SS>/=4 lesions (+3.49+/-2.1mm; p<0.001) and GS>/=7 lesions (+2.48+/-2.8mm; p 0.035). On average, a simulated cylindrical treatment volume based on the MRI boundary missed 14.8% of the tumor volume compared with a simulated cylindrical volume based on the histologic boundary. A simulated treatment volume based on a 9mm treatment margin achieved complete histologic tumor destruction in 100% of patients. CONCLUSION: MRI underestimates histologically-determined tumor boundaries, especially for high MRI-SS and high GS lesions. A 9mm treatment margin around an MRI-visible lesion consistently ensures treatment of the entire histologic tumor volume during focal ablative therapy.

PURPOSE: The aim of this study was to compare coregistration of the bladder wall, bladder masses, and pelvic lymph nodes between sequential and simultaneous PET and MRI acquisitions obtained during hybrid F-FDG PET/MRI performed using a diuresis protocol in bladder cancer patients. METHODS: Six bladder cancer patients underwent F-FDG hybrid PET/MRI, including IV Lasix administration and oral hydration, before imaging to achieve bladder clearance. Axial T2-weighted imaging (T2WI) was obtained approximately 40 minutes before PET ("sequential") and concurrently with PET ("simultaneous"). Three-dimensional spatial coordinates of the bladder wall, bladder masses, and pelvic lymph nodes were recorded for PET and T2WI. Distances between these locations on PET and T2WI sequences were computed and used to compare in-plane (x-y plane) and through-plane (z-axis) misregistration relative to PET between T2WI acquisitions. RESULTS: The bladder increased in volume between T2WI acquisitions (sequential, 176 [139]mL; simultaneous, 255 [146]mL). Four patients exhibited a bladder mass, all with increased activity (SUV, 9.5-38.4). Seven pelvic lymph nodes in 4 patients showed increased activity (SUV, 2.2-9.9). The bladder wall exhibited substantially less misregistration relative to PET for simultaneous, compared with sequential, acquisitions in in-plane (2.8 [3.1]mm vs 7.4 [9.1]mm) and through-plane (1.7 [2.2]mm vs 5.7 [9.6]mm) dimensions. Bladder masses exhibited slightly decreased misregistration for simultaneous, compared with sequential, acquisitions in in-plane (2.2 [1.4]mm vs 2.6 [1.9]mm) and through-plane (0.0 [0.0]mm vs 0.3 [0.8]mm) dimensions. FDG-avid lymph nodes exhibited slightly decreased in-plane misregistration (1.1 [0.8]mm vs 2.5 [0.6]mm), although identical through-plane misregistration (4.0 [1.9]mm vs 4.0 [2.8]mm). CONCLUSIONS: Using hybrid PET/MRI, simultaneous imaging substantially improved bladder wall coregistration and slightly improved coregistration of bladder masses and pelvic lymph nodes.

The contemporary management of prostate cancer (PCa) has been criticized as fostering overdetection and overtreatment of indolent disease. In particular, the historical inability to identify those men with an elevated PSA who truly warrant biopsy, and, for those needing biopsy, to localize aggressive tumors within the prostate, has contributed to suboptimal diagnosis and treatment strategies. This article describes how modern multi-parametric MRI of the prostate addresses such challenges and reduces both overdiagnosis and overtreatment. The central role of diffusion-weighted imaging (DWI) in contributing to MRI's current impact is described. Prostate MRI incorporating DWI achieves higher sensitivity than standard systematic biopsy for intermediate-to-high risk tumor, while having lower sensitivity for low-grade tumors that are unlikely to impact longevity. Particular applications of prostate MRI that are explored include selection of a subset of men with clinical suspicion of PCa to undergo biopsy as well as reliable confirmation of only low-risk disease in active surveillance patients. Various challenges to redefining the standard of care to incorporate solely MRI-targeted cores, without concomitant standard systematic cores, are identified. These include needs for further technical optimization of current systems for performing MRI-targeted biopsies, enhanced education and expertise in prostate MRI among radiologists, greater standardization in prostate MRI reporting across centers, and recognition of the roles of pre-biopsy MRI and MRI-targeted biopsy by payers. Ultimately, it is hoped that the medical community in the United States will embrace prostate MRI and MRI-targeted biopsy, allowing all patients with known or suspected prostate cancer to benefit from this approach.

While initial implementations of prostate MRI suffered from suboptimal performance in tumor detection, technological advances over the past decade have allowed modern multi-parametric prostate MRI (mpMRI) to achieve high diagnostic accuracy for detection, localization, and staging and thereby impact patient management. A particular emerging application of mpMRI is in the pre-biopsy setting to allow for MRI-targeted biopsy, for instance, through real-time MRI/ultrasound fusion, which may help reduce the over-detection of low-risk disease and selectively detect clinically significant cancers, in comparison with use of standard systematic biopsy alone. mpMRI and MRI-targeted biopsy are spreading beyond the large academic centers to increasingly be adopted within small and community practices. Aims of this review article are to summarize the hardware and sequences used for performing mpMRI, explore patient specific technical considerations, delineate approaches for study interpretation and reporting [including the recent American College of Radiology Prostate Imaging Reporting and Data System (PI-RADS) version 2], and describe challenges and implications relating to the widespread clinical implementation of mpMRI.

OBJECTIVE: The apparent diffusion coefficient (ADC) values for benign central zone (CZ) of the prostate were compared with ADC values of benign peripheral zone (PZ), benign transition zone (TZ), and prostate cancer, using histopathologic findings from radical prostatectomy as the reference standard. MATERIALS AND METHODS: The study included 27 patients with prostate cancer (mean [+/- SD] age, 60.0 +/- 7.6 years) who had 3-T endorectal coil MRI of the prostate performed before undergoing prostatectomy with whole-mount histopathologic assessment. Mean ADC values were recorded from the ROI within the index tumor and within benign CZ, PZ, and TZ, with the use of histopathologic findings as the reference standard. ADC values of the groups were compared using paired t tests and ROC curve analysis. RESULTS: The ADC of benign CZ in the right (1138 +/- 123 x 10(-6) mm(2)/s) and left (1166 +/- 141 x 10(-6) mm(2)/s) lobes was not significantly different (p = 0.217). However, the ADC of benign CZ (1154 +/- 129 x 10(-6) mm(2)/s) was significantly lower (p < 0.001) than the ADCs of benign PZ (1579 +/- 197 x 10(-6) mm(2)/s) and benign TZ (1429 +/- 180 x 10(-6) mm(2)/s). Although the ADC of index tumors (1042 +/- 134 x 10(-6) mm(2)/s) was significantly lower (p = 0.002) than the ADC of benign CZ there was no significant difference (p = 0.225) between benign CZ and tumors with a Gleason score of 6 (1119 +/- 87 x 10(-6) mm(2)/s). In 22.2% of patients (6/27), including five patients who had tumors with a Gleason score greater than 6, the ADC was lower in benign CZ than in the index tumor. The AUC of ADC for the differentiation of benign CZ from index tumors was 72.4% (sensitivity, 70.4%; specificity, 51.9%), and the AUC of ADC for differentiation from tumors with a Gleason score greater than 6 was 76.7% (sensitivity, 75.0%; specificity, 65.0%). CONCLUSION: The ADC of benign CZ is lower than the ADC of other zones of the prostate and overlaps with the ADC of prostate cancer tissue, including high-grade tumors. Awareness of this potential diagnostic pitfall is important to avoid misinterpreting the normal CZ as suspicious for tumor.

PURPOSE: To determine the frequency and characteristics of recommendations for additional imaging and/or intervention (RAIs) in abdominal CT and MRI interpretations that might be avoided through comprehensive comparison with all available prior examinations. METHODS: A total of 1,006 RAIs in abdominopelvic CT and MRI reports were retrospectively evaluated. Reports and images from each patient's prior imaging examinations, including those of all relevant body parts and modalities, were reviewed to determine if the RAI could have been avoided based on prior imaging. Frequency and characteristics of such "avoidable" RAIs were evaluated. RESULTS: A total of 41 of 1,006 (4.1%) RAIs were avoidable. The key prior examination that established the RAI as avoidable was a different modality in 53.7% (22 of 41) and on a different body area in 41.5% (17 of 41) of cases, including chest imaging in 31.7% (13 of 41). A total of 83.3% (5 of 6) adrenal RAIs, and 80.0% (4 of 5) liver RAIs were avoidable based on prior chest imaging. The key finding was present on the prior images but was not described in the report in 46.3% (19 of 41) of cases. A greater number of prior examinations were available in cases of avoidable RAIs (mean, 12.2 +/- 16.7) than in those of nonavoidable RAIs (mean, 5.7 +/- 9.5) (P < .001). CONCLUSIONS: A small fraction of RAIs can be avoided by performing a thorough evaluation of all prior imaging examinations, including different modalities and body parts. Nearly half of the key prior examinations did not report the finding, highlighting the importance of directly reviewing relevant images, particularly chest imaging for evaluation of indeterminate upper-abdominal findings. Configuration of PACS for optimized selection and display of relevant examination reports and images may facilitate such comparisons.

PURPOSE: The aim of this study was to evaluate use of the microblogging social network Twitter by academic radiology departments (ARDs) in the United States. METHODS: Twitter was searched to identify all accounts corresponding with United States ARDs. All original tweets from identified accounts over a recent 3-month period (August to October 2014) were archived. Measures of account activity, as well as tweet and link content, were summarized. RESULTS: Fifteen ARDs (8.2%) had Twitter accounts. Ten (5.5%) had "active" accounts, with >/=1 tweet over the 3-month period. Active accounts averaged 711 +/- 925 followers (maximum, 2,885) and 61 +/- 93 tweets (maximum, 260) during the period. Among 612 tweets from active accounts, content most commonly related to radiology-related education (138), dissemination of departmental research (102), general departmental or hospital promotional material (62), departmental awards or accomplishments (60), upcoming departmental lectures (59), other hospital-related news (55), medical advice or information for patients (38), local community events or news (29), social media and medicine (27), and new departmental or hospital hires or expansion (19). Eighty percent of tweets (490 of 612) included 315 unique external links. Most frequent categories of link sources were picture-, video-, and music-sharing websites (89); the ARD's website or blog (83); peer-reviewed journal articles (40); the hospital's or university's website (34), the lay press (28), and Facebook (14). CONCLUSIONS: Twitter provides ARDs the opportunity to engage their own staff members, the radiology community, the department's hospital, and patients, through a broad array of content. ARDs frequently used Twitter for promotional and educational purposes. Because only a small fraction of ARDs actively use Twitter, more departments are encouraged to take advantage of this emerging communication tool.

PURPOSE: To determine multi-parametric MRI features that can help differentiate malignant omental caking from benign omental thickening in the setting of portal hypertension. METHODS: We identified 19 patients with an abnormal omentum on MRI and an available reference standard: 11 patients with portal hypertension and benign omental thickening (9 male, 2 female, mean age 58 +/- 6 years) and 8 patients with metastatic omental caking (4 male, 4 female, mean age 61 +/- 13 years). Criteria for benign omental thickening were no evidence of malignancy for at least 24 months of follow-up (n = 7), negative ascites cytology (n = 2), or absence of malignancy on pathologic analysis of liver explant (n = 2). Criteria for omental malignancy were positive omental biopsy (n = 6) or ascites cytology (n = 2). Two radiologists (R1 and R2) evaluated characteristics of the thickened omentum on MRI. RESULTS: Findings occurring with significantly higher frequency in malignant omental caking were hyperintensity on high b-value diffusion-weighted imaging (DWI) (R1 88% vs. 0%, R2 88% vs. 0%), hyperenhancement (R1 75% vs. 0%, R2 75% vs. 0%), and convex outer omental contour (R1 88% vs. 0%, R2 75% vs. 9%) (all p /= 0.058). CONCLUSION: Abnormal signal on DWI, hyperenhancement, and convex outer contour are helpful MRI features to differentiate malignant from benign omental thickening.