Faculty Bibliography

Purpose:To assess diagnostic sensitivity of radial T1-weighted gradient-echo (radial volumetric interpolated breath-hold examination [VIBE]) magnetic resonance (MR) imaging, positron emission tomography (PET), and combined simultaneous PET and MR imaging with an integrated PET/MR system in the detection of lung nodules, with combined PET and computed tomography (CT) as a reference.Materials and Methods:In this institutional review board-approved HIPAA-compliant prospective study, 32 patients with tumors who underwent clinically warranted fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT followed by PET/MR imaging were included. In all patients, the thorax station was examined with free-breathing radial VIBE MR imaging and simultaneously acquired PET data. Presence and size of nodules and FDG avidity were assessed on PET/CT, radial VIBE, PET, and PET/MR images. Percentage of nodules detected on radial VIBE and PET images was compared with that on PET/MR images by using generalized estimating equations. Maximum standardized uptake value (SUVmax) in pulmonary nodules with a diameter of at least 1 cm was compared between PET/CT and PET/MR imaging with Pearson rank correlation.Results:A total of 69 nodules, including 45 FDG-avid nodules, were detected with PET/CT. The sensitivity of PET/MR imaging was 70.3% for all nodules, 95.6% for FDG-avid nodules, and 88.6% for nodules 0.5 cm in diameter or larger. PET/MR imaging had higher sensitivity than PET for all nodules (70.3% vs 61.6%, P = .002) and higher sensitivity than MR imaging for FDG-avid nodules (95.6% vs 80.0%, P = .008). There was a significantly strong correlation between SUVmax of pulmonary nodules obtained with PET/CT and that obtained with PET/MR imaging (r = 0.96, P < .001).Conclusion:Radial VIBE and PET data acquired simultaneously with PET/MR imaging have high sensitivity in the detection of FDG-avid nodules and nodules 0.5 cm in diameter or larger, with low sensitivity for small non-FDG-avid nodules.(c) RSNA, 2013.

Objective: To determine the accuracy of MR imaging for the evaluation of the subscapularis tendon as well as define imaging findings that will increase accuracy. MATERIALS AND METHODS: Retrospective review of the MR and operative (OR) reports of 286 patients was conducted and reviewed for the presence/degree (partial (PT)/full-thickness (FT)) of tearing; only PT articular tears were included. The presence of a supraspinatus tear and time interval between surgery and MRI were also documented. All of the PT tears called on MRI were also reviewed to see if there was a statistically significant association between certain imaging characteristics and the presence of a tear in surgery. Statistical analysis included 95 % confidence intervals, Fisher's exact, and exact Mann-Whitney tests. RESULTS: A total of 244 patients were included in the study with a total of 25 subscapularis tears, 16 PT and nine FT, and 219 intact tendons in arthroscopy; 20/25 tears and 200 intact sensitivity of 80%, specificity of 91%, accuracy of 90%, positive predictive value of 51%, and negative predictive value of 98 %. There was a significant association between the presence of a PT tear during arthroscopy and fluid-like signal within the tendon on more than one imaging plane (p<0.001) with an accuracy of 90%. CONCLUSIONS: This study reflects a musculoskeletal radiology section's experience with the diagnosis of subscapularis tendon pathology, demonstrating that MRI could be used to accurately evaluate the subscapularis tendon. An understanding of certain imaging pitfalls and the presence of fluid-like signal on multiple imaging planes should increase the diagnostic accuracy of the radiologist evaluating the subscapularis tendon for the presence of a tear.

BACKGROUND AND PURPOSE: The spinal cord is a site of predilection for MS lesions. While diffusion tensor imaging is useful for the study of anisotropic systems such as WM tracts, it is of more limited utility in tissues with more isotropic microstructures (on the length scales studied with diffusion MR imaging) such as gray matter. In contrast, diffusional kurtosis imaging, which measures both Gaussian and non-Gaussian properties of water diffusion, provides more biomarkers of both anisotropic and isotropic structural changes. The aim of this study was to investigate the cervical spinal cord of patients with MS and to characterize lesional and normal-appearing gray matter and WM damage by using diffusional kurtosis imaging. MATERIALS AND METHODS: Nineteen patients (13 women, mean age = 41.1 +/- 10.7 years) and 16 controls (7 women, mean age = 35.6 +/- 11.2-years) underwent MR imaging of the cervical spinal cord on a 3T scanner (T2 TSE, T1 magnetization-prepared rapid acquisition of gradient echo, diffusional kurtosis imaging, T2 fast low-angle shot). Fractional anisotropy, mean diffusivity, and mean kurtosis were measured on the whole cord and in normal-appearing gray matter and WM. RESULTS: Spinal cord T2-hyperintense lesions were identified in 18 patients. Whole spinal cord fractional anisotropy and mean kurtosis (P = .0009, P = .003), WM fractional anisotropy (P = .01), and gray matter mean kurtosis (P = .006) were significantly decreased, and whole spinal cord mean diffusivity (P = .009) was increased in patients compared with controls. Mean spinal cord area was significantly lower in patients (P = .04). CONCLUSIONS: Diffusional kurtosis imaging of the spinal cord can provide a more comprehensive characterization of lesions and normal-appearing WM and gray matter damage in patients with MS. Diffusional kurtosis imaging can provide additional and complementary information to DTI on spinal cord pathology.

OBJECTIVE. The objective of this study was to compare the performance of different methodologies for interpretation of dynamic contrast-enhanced MRI (DCE-MRI) in localization of peripheral zone prostate cancer. MATERIALS AND METHODS. Forty-three men (mean age, 59 +/- 8 years) with biopsy-proven prostate cancer who underwent prostate MRI including DCE-MRI before prostatectomy were included. Two observers independently reviewed DCE-MRI data using three methodologies: qualitative, in which kinetic curves of signal intensity versus time were generated for foci showing rapid enhancement on subtracted contrast-enhanced images; semiquantitative, in which a biexponential heuristic model was used to generate color-coded maps depicting maximum slope and washout of contrast enhancement; and quantitative, in which a Tofts model was used to generate color-coded influx rate transfer constant (K(trans)) and efflux rate transfer constant (Kep) maps. Findings were stratified by whether suspicious foci showed evidence of washout with each method and compared with histopathologic results in each sextant. RESULTS. There was similar accuracy for the semiquantitative and quantitative models for both observers irrespective of requiring evidence of washout. For the more experienced observer, requiring washout resulted in lower sensitivity and higher specificity for the qualitative and semiquantitative models. Also for the more experienced observer, use of either a semiquantitative or quantitative model provided greater sensitivity compared with a qualitative model when requiring washout. There was no association between tumor detection and Gleason score for any DCE-MRI methodology for either reader. CONCLUSION. For the experienced reader, sensitivity for peripheral zone tumor was increased by use of either a semiquantitative or quantitative model compared with a qualitative model and decreased by requiring washout. We failed to identify a difference in performance between semiquantitative and quantitative models.

PURPOSE: To compare tumor detection on acquired diffusion-weighted (DW) images and apparent diffusion coefficient (ADC) maps, obtained using b-values of 1000 s/mm(2) and 2000 s/mm(2) , using radical prostatectomy as the reference. MATERIALS AND METHODS: In all, 29 prostate cancer patients who underwent 3T magnetic resonance imaging (MRI) including DW imaging using b-values of 1000 s/mm(2) and 2000 s/mm(2) were included. Two radiologists independently evaluated four image sets during different sessions and recorded the location and diameter of the dominant lesion: DW images acquired using b-values of 1000 s/mm(2) and 2000 s/mm(2) and ADC maps calculated using maximal b-values of 1000 s/mm(2) and 2000 s/mm(2) . Findings were correlated with the location and diameter of the dominant lesion at prostatectomy. Tumor-to-PZ contrast was also calculated, unblinded to pathology. RESULTS: Both readers achieved significantly higher sensitivity for DW images obtained using a b-value of 2000 s/mm(2) than 1000 s/mm(2) (P < 0.001), although there was no difference in sensitivity between ADC maps calculated using the two b-values (P >/= 0.309). Tumor-to-PZ contrast was higher for DW images using a b-value of 2000 s/mm(2) (P = 0.067), although it was not different between the two corresponding ADC maps (P = 0.544). For both readers, correlations with tumor diameters were higher for either ADC map (r = 0.59-0.73) than for either acquired DW image set (r = 0.03-0.57). CONCLUSION: Use of a b-value of 2000 s/mm(2) compared with a b-value of 1000 s/mm(2) resulted in improved tumor sensitivity and higher tumor-to-PZ contrast on the acquired DW images, although performance of the ADC maps corresponding with the two b-values was similar. Correlation with tumor size was greater for either ADC map than for either acquired DW image set. J. Magn. Reson. Imaging 2013;. (c) 2013 Wiley Periodicals, Inc.

AIM: To investigate diagnostic accuracy of high, low and mixed voltage dual energy computed tomography (DECT) for detection of prior myocardial infarction (MI). METHODS: Twenty-four consecutive patients (88% male, mean age 65 +/- 11 years old) with clinically documented prior MI (> 6 mo) were prospectively recruited to undergo late phase DECT for characterization of their MI. Computed tomography (CT) examinations were performed using a dual source CT system (64-slice Definition or 128-slice Definition FLASH, Siemens Healthcare) with initial first pass and 10 min late phase image acquisitions. Using the 17-segment model, regional systolic function was analyzed using first pass CT as normal or abnormal (hypokinetic, akinetic, dyskinetic). Regions with abnormal systolic function were identified as infarct segments. Late phase DE scans were reconstructed into: 140 kVp, 100 kVp, mixed (120 kVp) images and iodine-only datasets. Using the same 17-segment model, each dataset was evaluated for possible (grade 2) or definite (grade 3) late phase myocardial enhancement abnormalities. Logistic regression for correlated data was used to compare reconstructions in terms of the accuracy for detecting infarct segments using late myocardial hyperenhancement scores. RESULTS: All patients reported prior history of documented myocardial infarction, with most occurring more than 5 years prior (n = 18; 75% of cohort). Fifty-five of 408 (13%) segments demonstrated abnormal wall motion and were classified as infarct. The remaining 353 segments were classified as non-infarcted segments. A total of 1692 segments were analyzed for late phase enhancement abnormalities, with 91 (5.5%) segments not interpretable due to artifact. Combined grades 2 and 3 compared to grade 3 only enhancement abnormalities demonstrated significantly higher sensitivity and similar specificity for detection of infarct segments for all reconstructions evaluated. Evaluation of different voltage acquisitions demonstrated the highest diagnostic performance for the 100 kVp reconstruction which had higher diagnostic accuracy (87%; 95%CI: 80%-90%), sensitivity (86%-93%; 95%CI: 54%-78%) and specificity (90%; 95%CI: 86%-93%) compared to the other reconstructions. For sensitivity, there were significant differences noted between 100 kVp vs 140 kVp (P < 0.0005), 100 kVp vs mixed (P < 0.0001), and 100 kVp vs iodine only (P < 0.005) using combined grade 2 and grade 3 perfusion abnormalities. For specificity, there were significant differences noted between 100 kVp vs 140 kVp (P < 0.005), and 100 kVp vs mixed (P < 0.01) using combined grades 2 and 3 perfusion abnormalities. CONCLUSION: Low voltage acquisition CT, 100 kVp in this study, demonstrates superior diagnostic performance when compared to higher and mixed voltage acquisitions for detection of prior MI.

Purpose:To assess the potential use of sodium magnetic resonance (MR) imaging of cartilage, with and without fluid suppression by using an adiabatic pulse, for classifying subjects with versus subjects without osteoarthritis at 7.0 T.Materials and Methods:The study was approved by the institutional review board and was compliant with HIPAA. The knee cartilage of 19 asymptomatic (control subjects) and 28 symptomatic (osteoarthritis patients) subjects underwent 7.0-T sodium MR imaging with use of two different sequences: one without fluid suppression (radial three-dimensional sequence) and one with fluid suppression (inversion recovery [IR] wideband uniform rate and smooth truncation [WURST]). Fluid suppression was obtained by using IR with an adiabatic inversion pulse (WURST pulse). Mean sodium concentrations and their standard deviations were measured in the patellar, femorotibial medial, and lateral cartilage regions over four consecutive sections for each subject. The minimum, maximum, median, and average means and standard deviations were calculated over all measurements for each subject. The utility of these measures in the detection of osteoarthritis was evaluated by using logistic regression and the area under the receiver operating characteristic curve (AUC). Bonferroni correction was applied to the P values obtained with logistic regression.Results:Measurements from IR WURST were found to be significant predicators of all osteoarthritis (Kellgren-Lawrence score of 1-4) and early osteoarthritis (Kellgren-Lawrence score of 1 or 2). The minimum standard deviation provided the highest AUC (0.83) with the highest accuracy (>78%), sensitivity (>82%), and specificity (>74%) for both all osteoarthritis and early osteoarthritis groups.Conclusion:Quantitative sodium MR imaging at 7.0 T with fluid suppression by using adiabatic IR is a potential biomarker for osteoarthritis.(c) RSNA, 2013.

PURPOSE: To assess the utility of diffusion-weighted imaging (DWI) findings as an indirect marker of side-specific risk of extracapsular extension (ECE) of prostate cancer. MATERIALS AND METHODS: Fifty-one patients underwent 3T magnetic resonance imaging (MRI) before prostatectomy. Radiologists 1 and 2 (4 and 1 years experience) assessed each side for ECE using T2-weighted imaging (T2WI) and evaluated apparent diffusion coefficient (ADC) maps for the presence of apparent tumor in each lobe and to measure peripheral zone ADC. A uropathologist measured the extent of any ECE. RESULTS: In all, 28/102 lobes had ECE, of which 12 measured 1 mm and 2 mm. Side-specific accuracies for detection of ECE for readers 1 and 2 were respectively: T2WI 68.6% and 74.5%; presence of apparent tumor on ADC map 66.7% and 60.8%; ADC value 75.5% and 69.6%. For ECE >2 mm, both readers achieved 100% sensitivity based on apparent tumor on ADC map or ADC values and 80% sensitivity using T2WI. For detection of ECE