Faculty Bibliography

BACKGROUND AND PURPOSE: Cognitive impairment is frequent among patients with mild traumatic brain injury despite the absence of detectable damage on conventional MR imaging. In this study, the quantitative MR imaging techniques DTI, DKI, and ASL were used to measure changes in the structure and function in the thalamus and WM of patients with MTBI during a short follow-up period, to determine whether these techniques can be used to investigate relationships with cognitive performance and to predict outcome. MATERIALS AND METHODS: Twenty patients with MTBI and 16 controls underwent MR imaging at 3T and a neuropsychological battery designed to yield measures for attention, concentration, executive functioning, memory, learning, and information processing. MK, FA, MD, and CBF were measured in the thalamus by using region-of-interest analysis and in WM by using tract-based spatial statistics. Analyses were performed comparing regional imaging measures of subject groups and the results of testing of their associations with neuropsychological performance. RESULTS: Patients with MTBI exhibited significant differences from controls for DTI, DKI, and ASL measures in the thalamus and various WM regions both within 1 month after injury and >9 months after injury. At baseline, DTI and DKI measures in the thalamus and various WM regions were significantly associated with performance in different neuropsychological domains, and cognitive impairment was significantly associated with MK in the thalamus and FA in optic radiations. CONCLUSIONS: Combined application of DTI, DKI, and ASL to study MTBI might be useful for investigating dynamic changes in the thalamus and WM as well as cognitive impairment during a short follow-up period, though the small number of patients examined did not predict outcome.

Objectives: To elucidate the effects of prolonged bisphosphonate (BP) exposure on the development of atypical fragility fractures and to define risk factors.Methods: Approval was obtained from the IRB. A retrospective chart analysis was performed on 51 patients with complete subtrochanteric or diaphyseal femoral fracture(s) from January 2005 to April 2011 while on BP for at least 3 years; 25 patients (mean age 67.52) had all available data. All fractures included in the study were low or no energy fractures. Relevant clinical and demographic data including age, gender, ethnicity, height, weight, comorbid medical conditions, and medications were collected. Imaging and laboratory data including calcium, alkaline phosphatase, 25-hydroxy vitamin D(25-OHD), intact parathyroid hormone(PTH), serum c-telopeptide(CTX), urine n-telopeptide(NTX), bone mineral density, radiography and MRI were obtained in all patients.Results: The majority of patients were Caucasian, on alendronate, had bilateral findings, and almost half had prodromal symptoms. 45.8% had a 25-OHD level that was suboptimal (less than 30 ng/ml). Mean BP duration was 9.84 years and mean bone densities were in the osteopenic, not osteoporotic, range.Conclusion: Certain characteristics in patients with atypical BP-related fracture include relatively young age, long duration of BP use, suboptimal 25-OHD and bone densities in non-osteoporotic ranges. All of these may be significant risk factors for insufficiency fracture development.

Since approximately 5-10% of the ~50,000 tuberous sclerosis complex (TSC) patients in the US are "MRI-negative," our goal was to test the hypothesis that they nevertheless exhibit metabolic abnormalities. To test this, we used proton MR spectroscopy to obtain and compare gray and white matter (GM and WM) levels of the neuronal marker, N-acetylaspartate (NAA), the glial marker, myo-inositol (mI), and its associated creatine (Cr), and choline (Cho) between two "MRI-negative" female TSC patients (ages 5 and 43 years) and their matched controls. The NAA, Cr, Cho and mI concentrations, 9.8, 6.3, 1.4, and 5.7mM, in the pediatric control were similar to those of the patients, whereas the adult patient revealed a 17% WM NAA decrease and 16% WM Cho increase from their published means for healthy adults - both outside their respective 90% prediction intervals. These findings suggest that longer disease duration and/or TSC2 gene mutation may cause axonal dysfunction and demyelination.

Purpose:To evaluate diagnostic performance of three nonenhanced methods: variable-refocusing-flip angle (FA) fast spin-echo (SE)-based magnetic resonance (MR) angiography (variable FA MR) and constant-refocusing-FA fast SE-based MR angiography (constant-FA MR) and flow-sensitive dephasing (FSD)-prepared steady-state free precession MR angiography (FSD MR) for calf arteries, with dual-injection three-station contrast material-enhanced MR angiography (gadolinium-enhanced MR) as reference.Materials and Methods:This prospective study was institutional review board approved and HIPAA compliant, with informed consent. Twenty-one patients (13 men, eight women; mean age, 62.6 years) underwent calf-station variable-FA MR, constant-FA MR, and FSD MR at 1.5 T, with gadolinium-enhanced MR as reference. Image quality and stenosis severity were assessed in 13 segments per leg by two radiologists blinded to clinical data. Combined constant-FA MR and FSD MR reading was also performed. Methods were compared (logistic regression for correlated data) for diagnostic accuracy.Results:Of 546 arterial segments, 148 (27.1%) had a hemodynamically significant (>/= 50%) stenosis. Image quality was satisfactory for all nonenhanced MR sequences. FSD MR was significantly superior to both other sequences (P < .0001), with 5-cm smaller field of view; 9.6% variable-FA MR, 9.6% constant-FA MR, and 0% FSD MR segmental evaluations had nondiagnostic image quality scores, mainly from high diastolic flow (variable-FA MR) and motion artifact (constant-FA MR). Stenosis sensitivity and specificity were highest for FSD MR (80.3% and 81.7%, respectively), compared with those for constant-FA MR (72.3%, P = .086; and 81.8%, P = .96) and variable-FA MR (75.9%, P = .54; and 75.6%, P = .22). Combined constant-FA MR and FSD MR had superior sensitivity (81.8%) and specificity (88.3%) compared with constant-FA MR (P = .0076), variable-FA MR (P = .0044), and FSD MR (P = .0013). All sequences had an excellent negative predictive value (NPV): 93.2%, constant-FA MR; 94.7%, variable-FA MR; 91.7%, FSD MR; and 92.9%, combined constant-FA MR and FSD MR.Conclusion:At 1.5 T, all evaluated nonenhanced MR angiographic methods demonstrated satisfactory image quality and excellent NPV for hemodynamically significant stenosis.(c) RSNA, 2013Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120859/-/DC1.

OBJECTIVE: To assess the role of apparent diffusion coefficient (ADC) measured with diffusion-weighted imaging (DWI) in predicting and assessing response of hepatocellular carcinoma (HCC) to transarterial chemoembolization (TACE). METHODS: Thirty-six patients with cirrhosis and untreated HCC who underwent TACE and MRI within 3 months before and after TACE were assessed. MRI included DWI and contrast-enhanced T1-weighted imaging. Two observers measured ADC of HCCs and liver parenchyma on pre- and post-TACE MRIs and measured degree of tumor necrosis on subtracted post-contrast images on post-TACE MRI. Pre-, post-TACE tumor ADC, and changes in tumor ADC (DeltaADC) were compared between lesions stratified by degree of tumor necrosis (measured on post-TACE MRI). RESULTS: Forty seven HCCs were evaluated (mean size 4.4cm, range 1.0-14.1cm). HCCs with poor and incomplete response to TACE (<50% necrosis on post-TACE MRI) had significantly lower pre-treatment ADC and lower post TACE ADC compared to HCCs with good/complete response (>/=50% necrosis): ADC pre-TACE 1.35+/-0.42 vs. 1.64+/-0.39x10mm/s (p=0.042); post-TACE ADC 1.34+/-0.36 vs. 1.92+/-0.47 (p=0.0008). There was no difference in DeltaADC values. CONCLUSION: This preliminary data suggests that pre-TACE tumor ADC can be used to predict HCC response to TACE.