Faculty Bibliography

PURPOSE: The aim of this study was to determine if voxel-based histogram analysis of intravoxel incoherent motion imaging (IVIM) parameters can differentiate various subtypes of renal tumors, including benign and malignant lesions. SUBJECTS AND METHODS: A total of 44 patients with renal tumors who underwent surgery and had histopathology available were included in this Health Insurance Portability and Accountability Act-compliant, institutional review board-approved, single-institution prospective study. In addition to routine renal magnetic resonance imaging examination performed on a 1.5-T system, all patients were imaged with axial diffusion-weighted imaging using 8 b values (range, 0-800 s/mm). A biexponential model was fitted to the diffusion signal data using a segmented algorithm to extract the IVIM parameters perfusion fraction (fp), tissue diffusivity (Dt), and pseudodiffusivity (Dp) for each voxel. Mean and histogram measures of heterogeneity (standard deviation, skewness, and kurtosis) of IVIM parameters were correlated with pathology results of tumor subtype using unequal variance t tests to compare subtypes in terms of each measure. Correction for multiple comparisons was accomplished using the Tukey honestly significant difference procedure. RESULTS: A total of 44 renal tumors including 23 clear cell (ccRCC), 4 papillary (pRCC), 5 chromophobe, and 5 cystic renal cell carcinomas, as well as benign lesions, 4 oncocytomas (Onc) and 3 angiomyolipomas (AMLs), were included in our analysis. Mean IVIM parameters fp and Dt differentiated 8 of 15 pairs of renal tumors. Histogram analysis of IVIM parameters differentiated 9 of 15 subtype pairs. One subtype pair (ccRCC vs pRCC) was differentiated by mean analysis but not by histogram analysis. However, 2 other subtype pairs (AML vs Onc and ccRCC vs Onc) were differentiated by histogram distribution parameters exclusively. The standard deviation of Dt [sigma(Dt)] differentiated ccRCC (0.362 +/- 0.136 x 10 mm/s) from AML (0.199 +/- 0.043 x 10 mm/s) (P = 0.002). Kurtosis of fp separated Onc (2.767 +/- 1.299) from AML (-0.325 +/- 0.279; P = 0.001), ccRCC (0.612 +/- 1.139; P = 0.042), and pRCC (0.308 +/- 0.730; P = 0.025). CONCLUSIONS: Intravoxel incoherent motion imaging parameters with inclusion of histogram measures of heterogeneity can help differentiate malignant from benign lesions as well as various subtypes of renal cancers.

PURPOSE: To explore the feasibility of T1rho mapping of menisci at 3T in discriminating between patients with acute anterior cruciate ligament (ACL) injury and healthy controls. MATERIALS AND METHODS: Thirty-three subjects were included in the study and subdivided into two subgroups: 16 healthy controls (4 females, 12 males; mean age = 34.4 +/- 10.2 years, age range 24-63 years), 17 patients with ACL injury (3 females, 14 males; mean age = 29.8 +/- 10.8 years, age range 18-61 years). T1rho images from all subjects were acquired on a 3T MR scanner using a spin-lock-based 3D GRE sequence and computed for T1rho mapping. Clinical proton density (PD)-weighted fast spin echo (FSE) images in the sagittal (without fat saturation), axial, and coronal (fat-saturated) planes were also acquired for cartilage assessment using Whole-Organ MR Imaging Score (WORMS) grading. Mixed model two-way analysis of variance (ANOVA) was performed to determine whether there were any significant differences among subregional, compartmental, and whole structure T1rho values of meniscus between healthy controls and ACL-injured patients. RESULTS: Lateral posterior (29 +/- 8 msec) and medial central (25 +/- 7 msec) meniscus subregions in healthy controls had significantly lower T1rho values (P < 0.05) than the corresponding meniscus subregions in ACL-injured patients. Significantly lower meniscus T1rho values (P < 0.05) were also identified in lateral compartment in healthy controls (26 +/- 6 msec) than that of ACL-injured patients (33 +/- 4 msec). Subjects' total WORMS between healthy controls and ACL-injured patients had significant differences (P < 0.05). CONCLUSIONS: These preliminary results indicate that T1rho mapping is possibly feasible in detecting meniscus degeneration and may be useful in distinguishing ACL-injured patients. J. Magn. Reson. Imaging 2014. (c) 2014 Wiley Periodicals, Inc.

Despite the increasing development and applications of iron imaging, the pathophysiology of iron accumulation in multiple sclerosis (MS), and its role in disease progression and development of clinical disability, is poorly understood. The aims of our study were to determine the presence and extent of iron in T2 visible lesions and gray and white matter using magnetic field correlation (MFC) MRI and correlate with microscopic white matter (WM) injury as measured by diffusion tensor imaging (DTI). This is a case-control study including a series of 31 patients with clinically definite MS. The mean age was 39 years [standard deviation (SD) = 9.55], they were 11 males and 20 females, with a disease duration average of 3 years (range 0-13) and a median EDSS of 2 (0-4.5). Seventeen healthy volunteers (6 males and 11 females) with a mean age of 36 years (SD = 11.4) were recruited. All subjects underwent MR imaging on a 3T scanner using T2-weighted sequence, 3D T1 MPRAGE, MFC, single-shot DTI and post-contrast T1. T2-lesion volumes, brain volumetry, DTI parameters and iron quantification were calculated and multiple correlations were exploited. Increased MFC was found in the putamen (p = 0.061), the thalamus (p = 0.123), the centrum semiovale (p = 0.053), globus pallidus (p = 0.008) and gray matter (GM) (p = 0.004) of MS patients compared to controls. The mean lesional MFC was 121 s-2 (SD = 67), significantly lower compared to the GM MFC (<0.0001). The GM mean diffusivity (MD) was inversely correlated with the MFC in the centrum semiovale (p < 0.001), and in the splenium of the corpus callosum (p < 0.001). Patients with MS have increased iron in the globus pallidus, putamen and centrum with a trend toward increased iron in all the brain structures. Quantitative iron evaluation of WM and GM may improve the understanding of MS pathophysiology, and might serve as a surrogate marker of disease progression.

Purpose: To see if failure of arthroscopic shoulder stabilization can be predicted by the evaluation of bipolar bone loss on MRI Methods: A retrospective review of 39 consecutive patients (40 shoulders) who underwent arthroscopic capsulolabral repair for recurrent, traumatic, anterior shoulder instability was performed. There were a total of 40 MRIs from 39 patients (31males, 8 females, mean age 31.7 yrs.). Mean follow-up was 19 months. Pre-operative plain radiographs, MRI scans, operative reports, arthroscopic photos, and post-operative records were reviewed for each patient. Surgical failure was defined as recurrent shoulder dislocation and/or persistent apprehension during normal range of motion. Each preoperative MRI scan was evaluated for bipolar bone loss by one musculoskeletal radiologist using the on-track/off-track (OOT) method in which the glenoid track (GT) and Hill-Sachs interval (HSI) aremeasured. According to this technique, the GT is calculated as 0.83D-d in which "D" represents the diameter of the intact glenoid and "d" corresponds to the amount of glenoid bone loss. The HSI represents the width of the Hill-Sachs lesion plus the width of the intact bone bridge between the rotator cuff attachment and the lateral aspect of the Hill-Sachs lesion. All measurements were in millimeters. Lesions were considered "off-track" if the HSI exceeded the GT and "on-track" if the HSI was less than the GT. These findings were then compared to the corresponding post-operative outcomes. Statistical analysis was carried out using the Fisher exact test.
Result(s): Of the 40 shoulders evaluated, 6 were considered surgical failures (3 with recurrent dislocation and 3 with persistent apprehension). The OOT method correctly predicted 1 of these failures and falsely predicted 6 failures in shoulders that were clinically stable. There was no significant difference when comparing stable to unstable shoulders with regards to age, size of GTand HSI. Overall, the OOT method sensitivity was 16.7% (1/6), specificity 82.4% (28/34), positive predictive value 14.3% (1/7), negative predictive value 84.9% (28/33) and overall accuracy 72.5% (29/40).
Conclusion(s): MRI evaluation of bipolar (humeral and glenoid) bone loss using the on-track/off-track method is a moderately accurate and specific, but insensitive technique to predict surgical failure after arthroscopic capsulolabral repair for shoulder instability

Background: Mild cognitive impairment (MCI) is an intermediary state on the way to Alzheimer's disease (AD). Little is known about whole brain concentration of the neuronal marker, N-acetylaspartate (NAA) in MCI patients. Objective: To test the hypothesis that since MCI and AD are both neurodegenerative, quantification of the NAA in their whole brain (WBNAA) could differentiate them from cognitively-intact matched controls. Methods: Proton MR spectroscopy to quantify the WBNAA was applied to 197 subjects (86 females) 72.6 +/- 8.4 years old (mean +/- standard deviation). Of these, 102 were cognitively intact, 42 diagnosed as MCI, and 53 as probable AD. Their WBNAA amounts were converted into absolute concentration by dividing with the brain volume segmented from the MRI that also yielded the fractional brain volume (fBPV), an atrophy metric. Results: WBNAA concentration of MCI and AD patients (10.5 +/- 3.0 and 10.1 +/- 2.9 mM) were not significantly different (p = 0.85). They were, however, highly significantly 25-29% lower than the 14.1 +/- 2.4 mM of normal matched controls (p < 10-4). The fBPV of MCI and AD patients (72.9 +/- 4.9 and 69.9 +/- 4.7%) differed significantly from each other (4%, p = 0.02) and both were significantly lower than the 74.6 +/- 4.4% of normal elderly (2%, p = 0.003 for MCI; 6%, p < 10-4 for AD). ROC curve analysis has shown WBNAA to have 70.5% sensitivity and 84.3% specificity to differentiate MCI or AD patients from normal elderly versus just 68.4 and 65.7% for fBPV. Conclusion: Low WBNAA in MCI patients compared with cognitively normal contemporaries may indicate early neuronal damage accumulation and supports the notion of MCI as an early stage of AD. It also suggests WBNAA as a potential marker of early AD pathology.

Purpose: To demonstrate that sonographic morphologic properties of the supraspinatus tendon correlate with mechanical properties, as assessed quantitatively by shear-wave ultrasound elastography.
Material(s) and Method(s): This retrospective study included 36 patients who underwent sonographic evaluation of one or both shoulders on one or multiple dates from June 2013 through October 2014. A shoulder was excluded if the supraspinatus tendon contained calcifications or had undergone surgical repair for a tear. Each sonographic evaluation of each shoulder was regarded as a separate data point, totaling 76 sonographic evaluations of 36 patients. For each sonographic evaluation, the morphologic appearance of the proximal and distal supraspinatus tendon was graded (1 = normal or mild tendinosis without a tear, 2 = moderate or severe tendinosis without a tear, 3 = partial tear, 4 = full-thickness tear) by consensus of 2 musculoskeletal radiologists. In addition, for each sonographic evaluation, sample volumes were randomly placed within the proximal and distal supraspinatus tendon, viewed in the longitudinal dimension, to obtain shear-wave ultrasound elastography measurements. Finally, for 68 of the sonographic evaluations, on the same image used for sample volumes of the supraspinatus tendon, sample volumes were randomly placed within the deltoid muscle to obtain shear-wave ultrasound elastography measurements. Spearman rank correlations assessed the association between tendonmorphology grade and elastographymeasurements. Mann-Whitney tests compared elastography measurements between scans grouped by symptomatology or morphology grade. Bootstrap re-sampling procedures accounted for lack of statistical independence among scans of the same patient.
Result(s): Of the 36 patients, there were 21 males and 15 females (mean age 46, range 23-74). Of the 76 sonographic evaluations, there were 38 males and 38 females (mean age 44, range 23-74), 36 right and 40 left shoulders, and 21 symptomatic and 55 asymptomatic shoulders. The tendon morphology grade and elastography measurements were correlated in both the proximal (p < 0.001) and distal (p = 0.002) supraspinatus tendon. Comparing between grade 1 and grade >= 2 morphology, the elastography measurements differed significantly in both the proximal (p = 0.001) and distal (p = 0.012) supraspinatus tendon. Comparing between grade <= 2 and grade > 2 morphology, the elastography measurements also differed significantly in both the proximal (p = 0.002) and distal (p = 0.004) supraspinatus tendon. Interestingly, deltoid muscle elastography measurements also were associated with the morphology grade of the proximal (p = 0.004) and distal (p = 0.007) supraspinatus tendon; this measurement also differed significantly between asymptomatic and symptomatic scans (p = 0.001).
Conclusion(s): The sonographic morphologic properties of the supraspinatus tendon correlate with mechanical properties, as assessed by shear-wave ultrasound elastography. These findings indicate that shear-wave ultrasound elastography - a non-invasive, relatively inexpensive, and simple examination - can provide an objective measurement of tendon elasticity. Correlation of deltoid muscle elasticity with supraspinatus tendon morphology and symptomatology may be related to the two muscles being a force couple. Further research is needed to assess whether tendon elastography measurements correlate with the MRI morphologic appearance of the tendon and with intraoperative evaluation of tendon quality

Purpose: To see if 3D imaging could improve our understanding of rotator cuff tendon tear shapes on MRI.
Method(s): We performed a retrospective review of 1.5T/3T MR examinations, conducted over an 18-month period, of patients with arthroscopically proven full- thickness rotator cuff tears. Two orthopaedic surgeons reviewed the operative reports/arthroscopic photos for each patient, and characterized, in consensus, the shape of the tear based on a comparison of the tear's width (size) and length (retraction), and involvement of the rotator interval without measurements into the following categories: crescent, longitudinal, U or L-shaped longitudinal, and massive- type. Two musculoskeletal radiologists reviewed the pre-operative MR examination for each patient independently/blind to the arthroscopic findings. Initially, the readers characterized the shape of the tendon tears by reviewing the standard 2DMR sequences and using the same criteria as the surgeons used during their review of the scope images. Next, the readers measured and documented the width and length of each tendon tear using the 2D images. The shape of the tear was then classified based on a previously published MR-based system as either crescent, longitudinal, U or L-shaped, or massive. Four weeks after the initial imaging evaluation, 3DMR reconstructions of each tear were reviewed and the shape documented by each radiologist independently/blind to the arthroscopic results using the same system used by our orthopaedic colleagues. These results were then compared to the 2D imaging evaluations and arthroscopic findings. Statistical analysis included 95% confidence intervals, McNemar test, and intra-class correlation coefficients.
Result(s): A total of 34 patients were included in the study; 21 had crescent shaped tears and 13 had longitudinal tears during arthroscopy. Of the 13 longitudinal tears, 8 were subtyped as U-shaped, while 5 were described as L-shaped. 6 of the 13 longitudinal tears were additionally classified as massive-type. There was no significant difference when comparing the accuracy of the tear shape characterizations made on 2DMR imaging without measurements (pre) and with measurements (post). The accuracy for differentiating between crescent shaped, longitudinal, and massive tears was the same for reader 1, 70.6% (24/34; p=1) and more accurate using the post 2D data for reader 2 (67.6%(post) vs. 61.8%(pre), p=0.5). The accuracy for tear shape characterization between crescent and longitudinal using the 3D reconstructions for reader #1 was 97.1%(33/34) and 88.2% (30/34) for reader #2. When this characterization included subclassifying the longitudinal tears into U or-L shaped, the accuracy for reader #1 was 97.1% and 82.4% for reader #2. When further characterizing the longitudinal tears as massive or not, both readers had an accuracy of 76.9% (10/13). The overall accuracy of the 3D reconstructions was 82.4% (56/68), significantly different (p=0.021) from the post 2D accuracy (64.7%) and pre 2D accuracy (60.3%, p=0.001). The intraclass correlation coefficient for the 2D measurements of width and length were 0.81, moderate agreement, for width and 0.95, strong agreement, for length.
Conclusion(s): Our study has demonstrated that 3DMR reconstructions of the rotator cuff improve the accuracy of characterizing rotator cuff tear shapes compared to the current 2DMR imaging based techniques

The purpose of this study is to assess the repeatability of the quantification of pseudo-intracellular sodium concentration (C1) and pseudo-extracellular volume fraction (alpha) estimated in brain in vivo using sodium magnetic resonance (MRI) at 3 T. Eleven healthy subjects were scanned twice, with two sodium MRI acquisitions (with and without fluid suppression by inversion recovery), and two double inversion recovery (DIR) proton MRI. DIR MRIs were used to create masks of gray and white matter (GM, WM), that were subsequently applied to the C1 and alpha maps calculated from sodium MRI and a tissue three-compartment model, in order to measure the distributions of these two parameters in GM, WM or full brain (GM+WM) separately. The mean, median, mode, standard deviation (std), skewness and kurtosis of the C1 and alpha distributions in whole GM, WM and full brain were calculated for each subject, averaged over all data, and used as parameters for the repeatability assessment. The coefficient of variation (CV) was calculated as a measure of reliability for the detection of intra-subject changes in C1 and alphafor each parameter, while intraclass correlation (ICC) was used as a measure of repeatability. It was found that the CV of most of the parameters was around 10-20% (except for C1 kurtosis which is about 40%) for C1 and alpha measurements, and that ICC was moderate to very good (0.4 to 0.9) for C1 parameters and for some of the alpha parameters (mainly skewness and kurtosis). In conclusion, the proposed method could allow to reliably detect changes of 50% and above of the different measurement parameters of C1 and alphain neuropathologies (multiple sclerosis, tumor, stroke, Alzheimer's disease) compared to healthy subjects, and that skewness and kurtosis of the distributions of C1 and alphaseem to be the more sensitive parameters to these changes.

OBJECTIVE: The preferential delayed enhancement of the perilymphatic space enables detection of the non-enhancing endolymphatic hydrops present in patients with Meniere's disease. The aim of this study was to evaluate the diagnostic utility of delayed postcontrast 3D FLAIR images and a color map of fused postcontrast FLAIR and constructive interference steady state (CISS) images in the identification of endolymphatic hydrops in patients with clinically diagnosed Meniere's disease. STUDY DESIGN: Case control, blinded study. SETTING: Tertiary referral center. PATIENTS: Ten patients with Meniere's disease and five volunteer controls. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURE: Two neuroradiologists blinded to the clinical history independently evaluated for the presence of endolymphatic hydrops on the images of both inner ears for test and control subjects. Both the standard gray-scale FLAIR images and the fused color map images were independently reviewed. RESULTS: The gray-scale 3D FLAIR images demonstrated 68.2% sensitivity and 97.4% specificity, and the fused color map images demonstrated 85.0% sensitivity and 88.9% specificity in the identification of endolymphatic hydrops in Meniere's disease. There was significant correlation between the gray-scale 3D FLAIR images and fused color map images with the categorization of involvement (p = 0.002). Inter-evaluator reliability was excellent (kappa = 0.83 for gray-scale images, kappa = 0.81 for fused color map). CONCLUSION: Delayed 3D FLAIR and fused 3D FLAIR-CISS color map images of the inner ears after intravenous contrast administration are potentially useful diagnostic tools in the evaluation of patients with suspected Meniere's disease.