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.

BACKGROUND: Obtaining diagnostic coronary CT angiography with low radiation exposure in patients with irregular heart rhythms such as atrial fibrillation (AF) remains challenging. OBJECTIVE: We evaluated image quality and inter-reader variability with the use of prospective electrocardiographic (ECG)-triggered sequential dual-source acquisition at end systole for coronary artery disease (CAD) evaluation in patients with AF. METHODS: Thirty consecutive patients with AF who underwent prospective ECG-triggered sequential dual-source acquisition were evaluated. Images were reconstructed every 50 milliseconds from 250 to 400 milliseconds after the R wave. Two independent, blinded readers evaluated the coronaries for image quality on a 5-point scale (worst to best) and stenosis on 5-point semiquantitative (none to severe) and binary scales (>50% or <50%). Diagnostic image quality was graded for each reconstruction. RESULTS: Eleven patients (37%) had significant (>/=50% stenosis) CAD. Average heart rate was 82 +/- 20 beats/min and variability range was 71 +/- 22 beats/min. Mean effective radiation dose was 6.5 +/- 2.4 mSv. Diagnostic image quality was noted in 97.9% of 304 coronary segments with median image quality of 3.0. The 300-millisecond reconstruction phase provided the highest image quality; 70% of patients showed diagnostic image quality. Combination of all phases (250-400 milliseconds) performed significantly better than single or other phase combinations (P < 0.0005 for all comparisons). Inter-reader variability for stenosis detection was excellent, with 98.4% concordance by using a binary scale (50% stenosis cutoff). CONCLUSIONS: Prospective ECG-triggered sequential dual-source CT acquisition with the use of end-systolic acquisition provides diagnostic image quality with potentially low radiation doses for evaluation of CAD in patients with AF. Use of multiple end-systolic phases over a 150-millisecond window improves diagnostic image quality.

OBJECTIVES: Progression of an incomplete atypical femoral fracture (IF) to a complete fracture in patients on long term bisphosphonate (BP) therapy can be catastrophic. We aimed to determine the frequency and imaging features of IF in asymptomatic patients on long-term BP therapy and to identify distinguishing clinical and laboratory markers in the subset of patients who develop these fractures. MATERIAL AND METHODS: From August 2009 to March 2011, 220 femoral radiographs in 110 asymptomatic patients (101 women, 9 men, age 47-94) were reviewed by 2 radiologists. All patients were on BP therapy for at least 3years and had no history of hip/thigh pain or recent trauma. MRI was performed when a fracture was suspected on radiographs. Bone mineral density, serum calcium, 25-hydroxy vitamin D, intact parathyroid hormone, serum c-telopeptide and urine n-telopeptide were obtained in all patients. RESULTS: Two of 110 patients (1.82%, confidence interval of 0.6% to 6.3%) had 3 IFs. Both patients, age 50 and 57, were Caucasian, active and on BP for 8years. MRI confirmed radiographic findings in both patients. Both women had T-scores in the osteopenic range at 2 sites and osteoporotic range at 1 site. CONCLUSION: The 1.82% frequency of IF in asymptomatic patients on long term BP therapy is higher than that suggested in the literature. Statistical differences between fracture and non-fracture groups were not presented as the patient population was too small to draw any significant conclusions.

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.

OBJECTIVE. The purpose of this study was to use measured glomerular filtration rate (GFR), the reference standard of renal function, to assess the deleterious effect of iodinated contrast media on renal function. Such an effect has been traditionally defined as a greater than 0.5-mg/dL increase in serum creatinine concentration or a 25% or greater increase 24-72 hours after the injection of iodinated contrast medium. SUBJECTS AND METHODS. This pilot investigation was focused on the consequences of clinically indicated IV injection of iodinated contrast media; intraarterial injection was excluded. One hundred thirteen patients with normal serum creatinine concentrations were enrolled in an approved protocol. At random, as chosen by one of the investigators, patients underwent imaging with one of three monomeric agents (iopamidol 300, iopromide 300, iohexol 300) and one dimeric agent (iodixanol 320). Measured GFR was determined immediately before CT and approximately 3 and 72 hours after the contrast injection for the CT examination. Iodinated contrast medium, a glomerular filtrate with no tubular excretion or reabsorption, was the GFR marker. Measured GFR was determined by x-ray fluorescence analysis with nonisotopic iodinated contrast media. RESULTS. Monomeric and dimeric contrast agents in diagnostic CT volumes (based on bodyweight and imaging protocol) did not induce a significant change in measured GFR (95% confidence by Wilcoxon test), suggesting that use of the evaluated contrast media will not lead to more than a 12% variation. CONCLUSION. The three monomeric agents studied and the one dimeric agent were equivalent in terms of lack of a significant effect on measured GFR when administered to patients with a normal GFR.

There are no established biomarkers for mild traumatic brain injury (mTBI), in part because post-concussive symptoms (PCS) are subjective and conventional imaging is typically unremarkable. To test whether diffuse axonal abnormalities quantified with three-dimensional (3D) proton magnetic resonance spectroscopic imaging (1H-MRSI) correlated with patients' PCS, we retrospectively studied 26 mTBI patients (mean Glasgow Coma Scale score of 14.7), 18-56 years old, 3 - 55 days post injury and 13 controls. All were scanned at 3 Tesla with T1-and T2-weighted MRI and 3D 1H-MRSI (480 voxels over 360 cm3, ~30% of the brain). On scan day patients completed a symptom questionnaire and those indicating at least one of the most common acute/subacute mTBI symptoms (headache, dizziness, sleep disturbance, memory deficits, blurred vision) were grouped as PCS-positive. Global gray- and white matter (GM/WM) absolute concentrations of N-acetylaspartate (NAA), choline (Cho), creatine (Cr) and myo-inositol (mI) in the PCS-positive and PCS-negative patients were compared to age- and gender-matched controls using two-way analysis of variance. The results showed that the PCS-negative group (n=11) and controls (n=8) did not differ in any GM or WM metabolite level. The PCS-positive patients (n=15), however, had lower WM NAA than the controls (n=12): 7.0+/-0.6 mM (mean+/- standard deviation) versus 7.9+/-0.5mM (p=0.0007). Global WM NAA, therefore, showed sensitivity to the TBI sequelae associated with common PCS in individuals with mostly normal neuroimaging as well as GCS scores. This suggests a potential biomarker role in a patient population in which objective measures of injury and symptomatology are currently lacking.

PURPOSE: To evaluate the performance of diffusion tensor imaging (DTI) in the evaluation of chronic exertional compartment syndrome (CECS) as compared to T(2) -weighted (T2w) imaging. MATERIALS AND METHODS: Using an Institutional Review Board (IRB)-approved, Health Insurance Portability and Accountability Act (HIPAA)-compliant protocol, spectral adiabatic inversion recovery (SPAIR) T2w imaging and stimulated echo DTI were applied to eight healthy volunteers and 14 suspected CECS patients before and after exertion. Longitudinal and transverse diffusion eigenvalues, mean diffusivity (MD), and fractional anisotropy (FA) were measured in seven calf muscle compartments, which in patients were classified by their response on T2w: normal (<20% change), and CECS (>20% change). Mixed model analysis of variance compared subject groups and compartments in terms of response factors (post/pre-exercise ratios) of DTI parameters. RESULTS: All diffusivities significantly increased (P < 0.0001) and FA decreased (P = 0.0014) with exercise. Longitudinal diffusion responses were significantly smaller than transversal diffusion responses (P < 0.0001). Nineteen of 98 patient compartments were classified as CECS on T2w. MD increased by 3.8 +/- 3.4% (volunteer), 7.4 +/- 4.2% (normal), and 9.1 +/- 7.0% (CECS) with exercise. CONCLUSION: DTI shows promise as an ancillary imaging method in the diagnosis and understanding of the pathophysiology in CECS. Future studies may explore its utility in predicting response to treatment. J. Magn. Reson. Imaging 2013;. (c) 2013 Wiley Periodicals, Inc.

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.