Faculty Bibliography

Cerebral perfusion was evaluated in 87 subjects prospectively enrolled in three study groups-healthy controls (HC), patients with insulin resistance (IR) but not with diabetes, and type 2 diabetes mellitus (T2DM). Participants received a comprehensive 8-hour clinical evaluation and arterial spin labeling magnetic resonance imaging (MRI). In order of decreasing significance, an association was found between cerebral blood flow (CBF) and sex, waist circumference, diastolic blood pressure (BP), end tidal CO2, and verbal fluency score (R2=0.27, F=5.89, P<0.001). Mean gray-matter CBF in IR was 4.4 mL/100 g per minute lower than in control subjects (P=0.005), with no hypoperfusion in T2DM (P=0.312). Subjects with IR also showed no CO2 relationship (slope=-0.012) in the normocapnic range, in contrast to a strong relationship in healthy brains (slope=0.800) and intermediate response (slope=0.445) in diabetic patients. Since the majority of T2DM but few IR subjects were aggressively treated with blood glucose, cholesterol, and BP lowering medications, our finding could be attributed to the beneficial effect of these drugs.Journal of Cerebral Blood Flow & Metabolism advance online publication, 15 October 2014; doi:10.1038/jcbfm.2014.173.

PURPOSE: To evaluate the precision of measures of bone volume and bone volume fraction derived from high-resolution 3T MRI of proximal femur bone microarchitecture using non-uniformity correction. METHODS: This HIPAA compliant, institutional review board approved study was conducted on six volunteers (mean age [Formula: see text] years), and written informed consent was obtained. All volunteers underwent a 3T FLASH MRI hip scan at three time points: baseline, second scan same day (intra-scans), and third scan one week later (inter-scans). Segmentation of femur images and values for total proximal femur volume ([Formula: see text]), bone volume ([Formula: see text]), and bone volume fraction (BVF) were calculated using in-house developed software, FireVoxel. Two types of non-uniformity corrections were applied to images (N3 and BiCal). Precision values were calculated using absolute percent error (APE). Statistical analysis was carried out using one-sample one-sided t test to observe the consistency of the precision and paired t test to compare between the various methods and scans. RESULTS: No significant differences in bone volume measurements were observed for intra- and inter-scans. When using non-uniformity correction and assessing all subjects uniformly at the level of the lesser trochanter, precision values overall improved, especially significantly ([Formula: see text]) when measuring bone volume, [Formula: see text]. [Formula: see text] values using the combination of N3 or BiCal with CLT had a significant consistent APE values of less than 2.5 %, while BVF values were all consistently and significantly lower than 2.5 % APE. CONCLUSION: Our results demonstrate the precision of high-resolution 3D MRI measures were comparable to that of dual-energy X-ray absorptiometry. Additional corrections to the analysis technique by cropping at the lesser trochanter or using non-uniformity corrections helped to improve precision. The high precision values from these MRI scans provide evidence for MRI of the proximal femur as a promising tool for osteoporosis diagnosis and treatment.

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.

OBJECTIVE: To evaluate the agreement in volumes of prostate tumors determined on multiparametric MRI (mpMRI) and histologic assessment, using detailed software-assisted co-registration. MATERIALS AND METHODS: 37 patients who underwent 3T mpMRI (T2WI, DWI/ADC, DCE) were included. A radiologist traced the borders of suspicious lesions on T2WI and ADC and assigned a suspicion score (SS) from 2-5; a uro-pathologist traced borders of tumors on histopathologic photographs. Software was used to co-register MRI and 3D digital reconstructions of RP specimens and compute imaging and histopathologic volumes. Agreement in volumes between MRI and histology was assessed using Bland-Altman plots and stratified by tumor characteristics. RESULTS: Among 50 tumors, mean difference and 95% limits of agreement on MRI relative to histology were -32% (-128% to +65%) on T2WI and -47% (-143% to +49%) on ADC. For all tumor subsets, volume under-estimation was more marked on ADC maps (mean difference ranging from -57% to -16%) than T2WI (mean difference ranging from -45% to +2%). 95% limits of agreement were wide for all comparisons, with lower 95% limit ranging between -77% and -143% across assessments. Volume under-estimation was more marked for tumors with Gleason score >/=7 or MRI SS 4 or 5. CONCLUSION: Volume estimates of PCa using MRI tended to substantially under-estimate histopathologic volumes, with wide variability in extent of under-estimation across cases. These findings have implications for efforts to use MRI to guide risk assessment.

OBJECTIVE. The purpose of this article is to evaluate differences in texture measures on apparent diffusion coefficient (ADC) maps between low- and high-stage clear cell renal cell carcinomas (RCCs). MATERIALS AND METHODS. In this retrospective study, 61 patients with clear cell RCC at pathologic examination and who underwent preoperative MRI with diffusion-weighted imaging were included. Clear cell RCCs were clinically staged on review of preoperative MRI by a board-certified radiologist blinded to the pathologic findings. Whole lesions were segmented on ADC maps by two readers independently, from which first-order texture features (i.e., mean and skewness) and second-order texture features (i.e., cooccurrence matrix measures) were calculated. Texture metrics were compared between low- and high-stage clear cell RCC. RESULTS. In 61 patients, there were 62 clear cell RCCs (33 low stage [stages I and II] and 29 high stage [stages III and IV]) at pathologic examination. Staging accuracy of qualitative interpretation was 100% for low-stage lesions and 37.9% (11/29) for high-stage lesions. There was no statistically significant difference in mean ADC between high- and low-stage clear cell RCCs (1.77 x 10(-3) vs 1.80 x 10(-3) mm(2)/s; p = 0.7). However, high-stage clear cell RCCs were larger (6.96 +/- 2.93 vs 3.49 +/- 1.57 cm; p < 0.0001) and had statistically significantly (p