Faculty Bibliography

OBJECTIVES: We conducted a pilot study to identify whether MRI parameters are sensitive to hormone-induced changes in the breast during the natural menstrual cycle and whether changes could also be observed during an oral contraceptive (OC) cycle. MATERIALS AND METHODS: The New York University Langone Medical Center Institutional Review Board approved this HIPAA-compliant prospective study. All participants provided written informed consent. Participants were aged 24-31 years.We measured several non-contrast breast MRI parameters during each week of a single menstrual cycle (among 9 women) and OC cycle (among 8 women). Hormones were measured to confirm ovulation and classify menstrual cycle phase among naturally cycling women and to monitor OC compliance among OC users. We investigated how the non-contrast MRI parameters of breast fibroglandular tissue (FGT), apparent diffusion coefficient (ADC), magnetization transfer ratio (MTR), and transverse relaxation time (T2) varied over the natural and the OC cycles. RESULTS: We observed significant increases in MRI FGT% and ADC in FGT, and longer T2 in FGT in the luteal vs. follicular phase of the menstrual cycle. We did not observe any consistent pattern of change for any of the MRI parameters among women using OCs. CONCLUSIONS: MRI is sensitive to hormone-induced breast tissue changes during the menstrual cycle. Larger studies are needed to assess whether MRI is also sensitive to the effects of exogenous hormones, such as various OC formulations, on the breast tissue of young premenopausal women.

Diffusion tensor imaging (DTI) is highly sensitive in detecting brain structure and connectivity phenotypes in autism spectrum disorders (ASD). Since one of the core symptoms of ASD is reduced sociability (reduced tendency to seek social interaction), we hypothesized that DTI will be sensitive in detecting neural phenotypes that correlate with decreased sociability in mouse models. Relative to C57BL/6J (B6) mice, juvenile BALB/cJ mice show reduced sociability. We performed social approach test in a three-chambered apparatus and in-vivo longitudinal DTI at post-natal days 30, 50 and 70 days-of-age in BALB/cJ (n=32) and B6 (n=15) mice to assess the correlation between DTI and sociability and to evaluate differences in DTI parameters between these two strains. Fractional anisotropy (FA) and mean diffusivity (MD) values from in-vivo DTI data were analyzed from white matter (corpus callosum, internal and external capsule) and gray matter (cerebral cortex, frontal motor cortex, hippocampus, thalamus and amygdaloid) regions based on their relevance to ASD. A moderate but significant (p<0.05) negative correlation between sociability and FA in hippocampus and frontal motor cortex was noted for BALB/cJ mice at 30 days-of-age. Significant differences in FA and MD values between BALB/cJ and B6 mice were observed in most white and gray matter areas at all three time points. Significant differences in developmental trajectories of FA and MD values from thalamus and frontal motor cortex were also observed between BALB/cJ and B6, indicating relative under-connectivity in BALB/cJ mice. These results indicate that DTI may be used as an in-vivo, non-invasive imaging method to assess developmental trajectories of brain connectivity in mouse models of neurodevelopmental and behavioral disorders.

PURPOSE: To determine whether histogram analysis of diffusion-tensor (DT) magnetic resonance (MR) imaging metrics, including tensor shape measurements, can help determine the grades and subtypes of meningiomas. MATERIALS AND METHODS: The institutional review board approved this HIPAA-compliant study. Nine atypical, three anaplastic, and 39 typical meningiomas were retrospectively studied. The 39 typical meningiomas included one secretory meningioma and 11 fibroblastic, 11 transitional, 14 meningothelial, and two angiomatous meningiomas. DT imaging metrics, including fractional anisotropy, mean diffusivity, linear anisotropy coefficient, planar anisotropy coefficient (CP), spherical anisotropy coefficient (CS), and eigenvalue skewness (SK), as well as normalized signal intensity from contrast-enhanced T1- and T2-weighted images, were measured from the enhancing region of the tumor. Mean, variance, skewness, and kurtosis were extracted from the histograms. A two-level decision tree was designed, and a multivariate logistic regression analysis was used at each level to determine the best model for classification. RESULTS: Histogram skewness of SK and kurtosis of SK were significantly higher in atypical and anaplastic meningiomas than in typical meningiomas (P<.01). Among typical meningiomas, significant differences in histogram measures of CP and CS between fibroblastic meningiomas and other subtypes were observed (P<.01). The best model for differentiating atypical and anaplastic meningiomas from typical meningiomas consisted of mean and skewness of SK and kurtosis of T1 signal intensity, with an area under the receiver operating characteristic curve (AUC) of 0.946. The best model for differentiating fibroblastic meningiomas from other subtypes consisted of skewness of T2 signal intensity and kurtosis of CP (AUC, 0.970). CONCLUSION: Histogram analysis of DT imaging metrics can help determine the grades and subtypes of meningiomas, which can better assist in surgical planning.

The purpose of this study was to use high-resolution diffusion tensor imaging (DTI) to investigate the association between DTI metrics and sociability in BALB/c inbred mice. The sociability of prepubescent (30-day-old) BALB/cJ mice was operationally defined as the time that the mice spent sniffing a stimulus mouse in a social choice test. High-resolution ex vivo DTI data on 12 BALB/cJ mouse brains were acquired using a 9.4-T vertical-bore magnet. Regression analysis was conducted to investigate the association between DTI metrics and sociability. Significant positive regression (p < 0.001) between social sniffing time and fractional anisotropy was found in 10 regions located in the thalamic nuclei, zona incerta/substantia nigra, visual/orbital/somatosensory cortices and entorhinal cortex. In addition, significant negative regression (p < 0.001) between social sniffing time and mean diffusivity was found in five areas located in the sensory cortex, motor cortex, external capsule and amygdaloid region. In all regions showing significant regression with either the mean diffusivity or fractional anisotropy, the tertiary eigenvalue correlated negatively with the social sniffing time. This study demonstrates the feasibility of using DTI to detect brain regions associated with sociability in a mouse model system.

PURPOSE: : To compare image quality and lesion detection in postcontrast liver magnetic resonance imaging (MRI) between volumetric interpolated breath-hold examination (VIBE) sequences that achieve fat suppression via chemically selective fat saturation (FS-VIBE) and a 2-point Dixon water-fat separation method (Dixon-VIBE). MATERIALS AND METHODS: : Thirty patients underwent contrast-enhanced liver MRI at 1.5 T in which Dixon-VIBE was performed immediately after a delayed FS-VIBE. Two radiologists in consensus reviewed the sequences for a variety of qualitative and quantitative image quality measures and for lesion detection. RESULTS: : Dixon-VIBE received nearly perfect scores for strength and homogeneity of fat suppression that were significantly better than scores for FS-VIBE, with an associated significant improvement in liver-fat contrast (P < 0.0001 for all comparisons). Dixon-VIBE also received significantly better scores for sharpness of intrahepatic vessels (P = 0.0029) and overall image quality (P < 0.0001). Despite a slightly longer acquisition time for Dixon-VIBE, there was no significant difference in motion artifact (P = 0.3877). There was no significant difference for sensitivity, positive predictive value, or contrast relative to background liver for focal lesions (P = 0.448, P = 0.347, and P = 0.2312, respectively). CONCLUSIONS: : For postcontrast liver MRI, Dixon-VIBE demonstrated significantly improved fat suppression. Various assessments of lesion detection showed no significant difference between sequences

RATIONALE AND OBJECTIVES: The aim of this study was to assess the role of diffusion-weighted imaging in predicting progression-free survival in patients with head and neck squamous cell carcinoma (HNSCC) treated with induction chemotherapy. MATERIALS AND METHODS: Eighteen patients with HNSCC underwent diffusion-weighted imaging studies prior to treatment and within 3 weeks after completion of induction chemotherapy. Median apparent diffusion coefficient (ADC) values were computed from the largest cervical metastatic lymph node. Percentage changes in ADC values from pretreatment to posttreatment time points were compared between alive and dead patients using the Mann-Whitney U test. P values < .05 were considered statistically significant. RESULTS: A 22% increase in ADC was observed after induction chemotherapy in alive patients (n = 15), while patients who died from HNSCC (n = 3) demonstrated a 33% decrease in ADC. The difference in percentage change in ADC between alive and dead patients was significant (P = .039). CONCLUSIONS: ADC may be a useful marker in predicting progression-free survival in patients with HNSCC undergoing induction chemotherapy

The purpose of the study was to investigate the capability of (1)H MRS and MRI methods for detecting early response to radiation therapy in non-Hodgkin's lymphoma (NHL). Studies were performed on the WSU-DLCL2 xenograft model in nude mice of human diffuse large B-cell lymphoma, the most common form of NHL. Radiation treatment was applied as a single 15 Gy dose to the tumor. Tumor lactate, lipids, total choline, T(2) and apparent diffusion coefficients (ADC) were measured before treatment and at 24 h and 72 h after radiation. A Hadamard-encoded slice-selective multiple quantum coherence spectroscopy sequence was used for detecting lactate (Lac) while a stimulated echo acquisition mode sequence was used for detection of total choline (tCho) and lipids. T(2)- and diffusion-weighted imaging sequences were used for measuring T(2) and ADC. Within 24 h after radiation, significant changes were observed in the normalized integrated resonance intensities of Lac and the methylenes of lipids. Lac/H(2)O decreased by 38 +/- 15% (p = 0.03), and lipid (1.3 ppm, CH(2))/H(2)O increased by 57 +/- 14% (p = 0.01). At 72 h after radiation, tCho/H(2)O decreased by 45 +/- 14% (p = 0.01), and lipid (2.8 ppm, polyunsaturated fatty acid)/H(2)O increased by 970 +/- 36% (p = 0.001). ADC increased by 14 +/- 2% (p = 0.003), and T(2) did not change significantly. Tumor growth delay and regression were observed thereafter. This study enabled comparison of the relative sensitivities of various (1)H MRS and MRI indices to radiation and suggests that (1)H MRS/MRI measurements detect early responses to radiation that precede tumor volume changes.

The purpose of this study was to investigate the effects of cardiac pulsation in diffusion tensor imaging (DTI) of the rat brain. DTI data were acquired either with or without different cardiac gating delays. For each case, two sets of identical DTI data were acquired for a bootstrap analysis to measure the uncertainty in estimating mean diffusivity (MD), fractional anisotropy (FA) and the primary eigenvector direction. The 95% confidence interval of the primary eigenvectors was substantially reduced (21-25%) when cardiac gating with triggering delay of 70 ms ( approximately half of R-R peak duration) was used in comparison to studies without gating or when gating with a triggering delay of 0 ms was used. Standard deviations of MD and FA estimates were also reduced by 12-26% and 13-24%, respectively. For voxels with mean FA values larger than 0.15 and smaller than 0.95, the decrease in CI and standard deviations of MD and FA by cardiac gating with triggering delay of 70 ms were significant (p < 0.05). These results demonstrate the importance of cardiac gating in acquisition of in vivo high resolution DTI data.

BACKGROUND AND PURPOSE: Tumor microenvironment, including blood flow and permeability, may provide crucial information regarding response to chemoradiation therapy. Thus, the objective of this study was to investigate the efficacy of pretreatment DCE-MR imaging for prediction of response to chemoradiation therapy in HNSCC. MATERIALS AND METHODS: DCE-MR imaging studies were performed on 33 patients with newly diagnosed HNSCC before neoadjuvant chemoradiation therapy by using a 1.5T (n = 24) or a 3T (n = 9) magnet. The data were analyzed by using SSM for estimation of K(trans), v(e), and tau(i). Response to treatment was determined on completion of chemoradiation as CR, with no evidence of disease (clinically or pathologically), or PR, with pathologically proved residual tumor. RESULTS: The average pretreatment K(trans) value of the CR group (0.64 +/- 0.11 minutes(-1), n = 24) was significantly higher (P = .001) than that of the PR (0.21 +/- 0.05 minutes(-1), n = 9) group. No significant difference was found in other pharmacokinetic model parameters: v(e) and tau(i), between the 2 groups. Although the PR group had larger metastatic nodal volume than the CR group, it was not significantly different (P = .276). CONCLUSIONS: These results indicate that pretreatment DCE-MR imaging can be potentially used for prediction of response to chemoradiation therapy of HNSCC.

The purpose of this study was to investigate the effect of gadolinium (III) diethyltriaminepenta-acetic acid (Gd-DTPA) mixed with a fixative on the image contrast between the white and gray matter of the perfusion-fixed mouse brain. A series of microscopic MRI (microMRI) studies using different concentrations of Gd-DTPA were performed at multiple time points to determine the optimal Gd-DTPA concentration and fixation time necessary to maximize the contrast-to-noise ratio between the white and gray matter with relatively short scan time using a three-dimensional gradient-echo pulse sequence. On the basis of the experimental results, high-resolution (39 microm isotropic) images with excellent contrast-to-noise ratio ( approximately 50) were acquired in less than 2 h of scan time after the specimen had been soaked in 10 mM Gd-DTPA for 4 days. Excellent correlation was noted between microMRI and histology in that the microMRI clearly depicted brain regions that were also observed by the Kluver-Barrera stain. The enhanced contrast between the white and gray matter obtained by the proposed microMRI method may facilitate the development of microMRI-based morphological phenotyping methods for mouse models of neurological disorders.