Faculty Bibliography

INTRODUCTION: Quantitative T2 mapping may provide an objective biomarker for occult nervous tissue pathology in relapsing-remitting multiple sclerosis (RRMS). We applied a novel echo modulation curve (EMC) algorithm to identify T2 changes in normal-appearing brain regions of subjects with RRMS (N = 27) compared to age-matched controls (N = 38). METHODS: The EMC algorithm uses Bloch simulations to model T2 decay curves in multi-spin-echo MRI sequences, independent of scanner, and scan-settings. T2 values were extracted from normal-appearing white and gray matter brain regions using both expert manual regions-of-interest and user-independent FreeSurfer segmentation. RESULTS: Compared to conventional exponential T2 modeling, EMC fitting provided more accurate estimations of T2 with less variance across scans, MRI systems, and healthy individuals. Thalamic T2 was increased 8.5% in RRMS subjects (p < 0.001) and could be used to discriminate RRMS from healthy controls well (AUC = 0.913). Manual segmentation detected both statistically significant increases (corpus callosum & temporal stem) and decreases (posterior limb internal capsule) in T2 associated with RRMS diagnosis (all p < 0.05). In healthy controls, we also observed statistically significant T2 differences for different white and gray matter structures. CONCLUSIONS: The EMC algorithm precisely characterizes T2 values, and is able to detect subtle T2 changes in normal-appearing brain regions of RRMS patients. These presumably capture both axon and myelin changes from inflammation and neurodegeneration. Further, T2 variations between different brain regions of healthy controls may correlate with distinct nervous tissue environments that differ from one another at a mesoscopic length-scale.

Purpose: Superior glenoid labral tears remain one of the most common causes of shoulder pain and loss of shoulder function. The clinical presentation for this group of patients can be non-specific. Thus imaging, in particular, MRI plays an important role in diagnosis. Currently, there is no consensus in terms of the most appropriate type of MRI to be used in this setting. The objective of this study was to evaluate the diagnostic accuracy of non-enhanced magnetic resonance imaging (MRI) and magnetic resonance arthrography (MRA) for diagnosis of superior labral tears in the shoulder. Materials and Methods: We performed a literature search (until August 2016) using PubMed (MEDLINE), Embase, ISIWeb of Science, Scopus, and national/international conference databases. The inclusion criteria consisted of original research studies that assessed the diagnostic accuracy of MRI, direct (d) MRA, and/or indirect (i) MRA for the detection of superior labral (SLAP) tears, while using arthroscopic findings as the reference standard. The methodological quality of each study was assessed with the use of the QUADAS 2 (Quality Assessment of Diagnostic Accuracy Studies) tool. Pooled sensitivities and specificities, and summary receiver-operating characteristic curves were calculated for each imaging strategy. Additional subgroup analyses compared 3 T and 1.5 T examinations of dMRI and MRA studies as well as low bias MRI and MRA studies. Study homogeneity was assessed visually on the basis of observed differences between study characteristics and methodologies, examination of the forest plots, and Cohran's Q tests of heterogeneity. Results: There were a total of 32 studies that met our inclusion criteria, including a total of 3525 total imaging examinations (1970 d-MRA, 1393 MRI, 162 iMRA). The sensitivities of dMRA, MRI, and iMRA for diagnosis of SLAP tear were 80.3% (CI 74.6-85.5), 62.9% (46.1-78.4), and 74.2 (66.1-81.6), respectively. The specificities of dMRA, MRI, and iMRA for diagnosis of SLAP tear were 90.7% (85.3-94.9), 90.8% (84.8-95.4), and 66.4 (51.0-79.6), respectively. The sensitivities of 3 T dMRA and 3 T MRI were 81.7% (71.6-89.9) and 79.4 (70.6-86.6). The specificities of 3 T dMRA and 3 T MRI were 94.3% (89.3-97.7) and 98.8% (95.8-99.8). The sensitivities of 1.5 T dMRA and 1.5 TMRI were 79.1% (68.9-87.7) and 81.2% (62.9-94.3). The specificities of 1.5 T dMRA and 1.5 T MRI were 83.6% (74.6-90.9) and 83.4% (78.9-87.3). The sensitivities of the low bias dMRA and low bias MRI were 83.2% (75.2-89.9) and 61.7 (40.7-80.7). The specificities of the low bias dMRA and low bias MRI were 90.6% (81.9-96.6) and 95.0% (85.1-99.7). No study heterogeneity was noted on the basis of observed differences between study characteristics, but it was noted upon examination of the forest plot for the pooled MRI sensitivities. Significance in departure from study homogeneity (p < .05) was seen for the dMRA and MRI pooled estimates. Conclusion: Overall, direct MR arthrography of the shoulder may be a better imaging option than non-contrast MRI for the diagnosis of a superior labral tear. 3 T MRI and 3 T dMRA may be better imaging options than their 1.5 T counterparts. These findings should be considered in the context of the degree of heterogeneity found in the available literature

PURPOSE: To compare the performance of non-contrast MRI with half-Fourier acquisition single-shot turbo spin echo (HASTE) vs. contrast-enhanced MRI/3D-MRCP for assessment of suspected choledocholithiasis in hospitalized patients. METHODS AND MATERIALS: 123 contrast-enhanced abdominal MRI/MRCP scans in the hospital setting for possible choledocholithiasis were retrospectively evaluated. Endoscopic retrograde cholangiopancreatography, intraoperative cholangiogram or documented clinical resolution served as the reference standard. Readers first evaluated the biliary tree using coronal and axial HASTE and other non-contrast sequences, and later reviewed the entire exam with post-contrast sequences and 3D-MRCP. Test performance for the image sets was compared for choledocholithiasis, acute hepatitis, cholangitis, and acute cholecystitis. Reader agreement, MRCP image quality, and confidence levels were also assessed. Clinical predictors of age and fever were tested for association with perceived need for contrast in biliary assessment. RESULTS: There were 27 cases of choledocholithiasis, 31 cases of acute hepatitis, 37 cases of acute cholecystitis, and 3 clinically diagnosed cases of acute cholangitis. Both the abbreviated and full contrast-enhanced/MRCP image sets resulted in high accuracy for choledocholithiasis (91.1-94.3% vs. 91.9-92.7%). There was no difference in sensitivity or specificity for either reader for any diagnosis between image sets (p > 0.40). 1 reader showed improved confidence (p < 0.001) with inclusion of MRCP and contrast-enhanced images, but neither confidence nor MRCP quality scores were associated with diagnostic accuracy. Patient age and fever did not predict the need for contrast-enhanced images. CONCLUSION: In hospitalized patients with suspected choledocholithiasis, performance of non-contrast abdominal MRI with HASTE is similar to contrast-enhanced MRI with 3D-MRCP, offering potential for decreased scanning time and improved patient tolerability.

RATIONALE AND OBJECTIVES: To evaluate uptake, patterns of use, and perception of digital breast tomosynthesis (DBT) among practicing breast radiologists. MATERIALS AND METHODS: Institutional Review Board exemption was obtained for this Health Insurance Portability and Accountability Act-compliant electronic survey, sent to 7023 breast radiologists identified via the Radiological Society of North America database. Respondents were asked of their geographic location and practice type. DBT users reported length of use, selection criteria, interpretive sequences, recall rate, and reading time. Radiologist satisfaction with DBT as a diagnostic tool was assessed (1-5 scale). RESULTS: There were 1156 (16.5%) responders, 65.8% from the United States and 34.2% from abroad. Of these, 749 (68.6%) use DBT; 22.6% in academia, 56.5% private, and 21% other. Participants are equally likely to report use of DBT if they worked in academics versus in private practice (78.2% [169 of 216] vs 71% [423 of 596]) (odds ratio, 1.10; 95% confidence interval: 0.87-1.40; P = 1.000). Of nonusers, 43% (147 of 343) plan to adopt DBT. No US regional differences in uptake were observed (P = 1.000). Although 59.3% (416 of 702) of DBT users include synthetic 2D (s2D) for interpretation, only 24.2% (170 of 702) use s2D alone. Majority (66%; 441 of 672) do not perform DBT-guided procedures. Radiologist (76.6%) (544 of 710) satisfaction with DBT as a diagnostic tool is high (score >/= 4/5). CONCLUSIONS: DBT is being adopted worldwide across all practice types, yet variations in examination indication, patient selection, utilization of s2D images, and access to DBT-guided procedures persist, highlighting the need for consensus and standardization.

PURPOSE: To assess the impact of patient race and age on the performance of apparent diffusion coefficient (ADC) values for assessment of prostate cancer aggressiveness. MATERIALS AND METHODS: 457 prostate cancer patients who underwent 3T phased-array coil prostate MRI including diffusion-weighted imaging (DWI; maximal b-value 1000 s/mm2) before prostatectomy were included. Mean ADC of a single dominant lesion was measured in each patient, using histopathologic findings from the prostatectomy specimen as reference. In subsets defined by race and age, ADC values were compared between Gleason score (GS) /= 4 + 3 tumors. RESULTS: 81% of patients were Caucasian, 12% African-American, 7% Asian-American. 13% were <55 years, 42% 55-64 years, 41% 65-74 years, and 4% >/=75 years. 63% were GS /= 4 + 3. ADC was significantly lower in GS >/= 4 + 3 tumors than in GS /= 4 + 3 as well as optimal ADC threshold was Caucasian: 0.73//=75 years, 0.79//=75 years than <55 years or 55-64 years (100.0% vs. 53.6%-73.3%; P < 0.001). CONCLUSION: Patients' race and age may impact the diagnostic performance and optimal threshold when applying ADC values for evaluation of prostate cancer aggressiveness.

Purpose To assess the determinants of technical failure of magnetic resonance (MR) elastography of the liver in a large single-center study. Materials and Methods This retrospective study was approved by the institutional review board. Seven hundred eighty-one MR elastography examinations performed in 691 consecutive patients (mean age, 58 years; male patients, 434 [62.8%]) in a single center between June 2013 and August 2014 were retrospectively evaluated. MR elastography was performed at 3.0 T (n = 443) or 1.5 T (n = 338) by using a gradient-recalled-echo pulse sequence. MR elastography and anatomic image analysis were performed by two observers. Additional observers measured liver T2* and fat fraction. Technical failure was defined as no pixel value with a confidence index higher than 95% and/or no apparent shear waves imaged. Logistic regression analysis was performed to assess potential predictive factors of technical failure of MR elastography. Results The technical failure rate of MR elastography at 1.5 T was 3.5% (12 of 338), while it was higher, 15.3% (68 of 443), at 3.0 T. On the basis of univariate analysis, body mass index, liver iron deposition, massive ascites, use of 3.0 T, presence of cirrhosis, and alcoholic liver disease were all significantly associated with failure of MR elastography (P < .004); but on the basis of multivariable analysis, only body mass index, liver iron deposition, massive ascites, and use of 3.0 T were significantly associated with failure of MR elastography (P < .004). Conclusion The technical failure rate of MR elastography with a gradient-recalled-echo pulse sequence was low at 1.5 T but substantially higher at 3.0 T. Massive ascites, iron deposition, and high body mass index were additional independent factors associated with failure of MR elastography of the liver with a two-dimensional gradient-recalled-echo pulse sequence. (c) RSNA, 2017.

OBJECTIVE: To develop a low-cost pedal ergometer compatible with ultrahigh (7 T) field MR systems to reliably quantify metabolic parameters in human lower leg muscle using phosphorus magnetic resonance spectroscopy. MATERIALS AND METHODS: We constructed an MR compatible ergometer using commercially available materials and elastic bands that provide resistance to movement. We recruited ten healthy subjects (eight men and two women, mean age +/- standard deviation: 32.8 +/- 6.0 years, BMI: 24.1 +/- 3.9 kg/m2). All subjects were scanned on a 7 T whole-body magnet. Each subject was scanned on two visits and performed a 90 s plantar flexion exercise at 40% maximum voluntary contraction during each scan. During the first visit, each subject performed the exercise twice in order for us to estimate the intra-exam repeatability, and once during the second visit in order to estimate the inter-exam repeatability of the time constant of phosphocreatine recovery kinetics. We assessed the intra and inter-exam reliability in terms of the within-subject coefficient of variation (CV). RESULTS: We acquired reliable measurements of PCr recovery kinetics with an intra- and inter-exam CV of 7.9% and 5.7%, respectively. CONCLUSION: We constructed a low-cost pedal ergometer compatible with ultrahigh (7 T) field MR systems, which allowed us to quantify reliably PCr recovery kinetics in lower leg muscle using 31P-MRS.

PURPOSE: To evaluate clinical applicability of fibroglandular tissue (FGT) segmentation on routine T1 weighted breast MRI and compare FGT quantification with radiologist assessment. METHODS: FGT was segmented on 232 breasts and quantified, and was assessed qualitatively by four breast imagers. RESULTS: FGT segmentation was successful in all 232 breasts. Agreement between radiologists and quantified FGT was moderate to substantial (kappa=0.52-0.67); lower quantified FGT was associated with disagreement between radiologists and quantified FGT (P