Faculty Bibliography

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: Our aim in this study was to evaluate the effect of the radiologist, technologist, and other examination-related factors on the frequency of recommendations for additional imaging (RAI) during sonographic (US) interpretation. METHODS: We retrospectively reviewed 719 US reports from a single academic medical center for the presence of RAI. All studies had been interpreted by one of three abdominal radiologists. Examinations were performed at an outpatient radiology facility with no onsite radiologist (n = 299) or at an inpatient emergency department or hospital-based outpatient setting that had an onsite radiologist (n = 420). Possible associations between the frequency of RAI and the presence of an onsite radiologist, location of the examination, body part or region imaged, patient age, technologist performing the exam, and radiologist reading the exam were evaluated. RESULTS: There were significant differences between each pair of radiologists in terms of overall frequency of RAI (p < 0.001) (radiologist 1: 12.0% [22/184]; radiologist 2: 21.6% [78/361]; and radiologist 3: 45.5% [79/174]). In addition, there were statistically significant differences in the frequency of RAI among studies scanned by the 10 different US technologists (13.6%-40.0%, p = 0.03). However, other factors such as patient age, patient sex, US unit, patient location, and radiologist location were not associated with the frequency of RAI (p = 0.15-0.93). CONCLUSIONS: The individual radiologist and technologist influenced the frequency of RAI for US examinations, whereas other examination-related factors did not. The observed substantial variability in RAI between radiologists and technologists warrants further study, with consideration of strategies to optimize RAI within US reports. (c) 2015 Wiley Periodicals, Inc. J Clin Ultrasound, 2015.

PURPOSE: Diffusional kurtosis imaging is an advanced diffusion MRI method that yields, in addition to conventional diffusion information, non-Gaussian diffusion effects, which may allow a more comprehensive characterization of tissue microstructure. The purpose of this study is to use diffusional kurtosis to assess white matter integrity in patients with hydrocephalus and to determine whether changes in kurtosis correlate with the severity of hydrocephalus and leukoaraiosis, a commonly seen comorbidity in hydrocephalus. METHODS: 26 patients with imaging evidence of hydrocephalus and 26 age- and sex- matched subjects with normal ventricular size were retrospectively analyzed. Standard diffusion tensor imaging and diffusional kurtosis metrics were compared between the two groups. Correlation between kurtosis and severity of hydrocephalus and presence and severity of leukoaraiosis was determined. RESULTS: Hydrocephalus patients relative to controls demonstrated statistically significant decrease in all kurtosis metrics in most brain regions studied. The severity of hydrocephalus was associated with greater decrease in kurtosis in the corpus callosum. There was more leukoaraiosis in the hydrocephalus group, and severity of leukoaraiosis was associated with decrease in kurtosis. After controlling for the degree of leukoaraiosis, kurtosis was still decreased in hydrocephalus relative to the controls. CONCLUSION: Diffusional kurtosis imaging detects microstructural changes in the white matter of patients with hydrocephalus. Our results suggest that hydrocephalus plays a role in altering white matter integrity.

BACKGROUND: Rapid and accurate diagnosis of appendicitis, particularly with respect to the presence or absence of perforation, is essential in guiding appropriate management. Although many studies have explored sonographic findings associated with acute appendicitis, few investigations discuss specific signs that can reliably differentiate perforated appendicitis from acute appendicitis prior to abscess formation. OBJECTIVE: The purpose of our study was to identify sonographic findings that improve the specificity of US in the diagnosis of perforated appendicitis. Our assessment of hepatic periportal echogenicity, detailed analysis of intraperitoneal fluid, and formulation of select constellations of sonographic findings expands upon the literature addressing this important diagnostic challenge. MATERIALS AND METHODS: We retrospectively reviewed 116 abdominal US examinations for evaluation of abdominal pain in children ages 2 to 18 years from January 2008 to September 2011 at a university hospital pediatric radiology department. The study group consisted of surgical and pathology proven acute appendicitis (n = 51) and perforated appendicitis (n = 22) US exams. US exams without a sonographic diagnosis of appendicitis (n = 43) confirmed by follow-up verbal communication were included in the study population as the control group. After de-identification, the US exams were independently reviewed on a PACS workstation by four pediatric radiologists blinded to diagnosis and all clinical information. We recorded the presence of normal or abnormal appendix, appendicolith, appendiceal wall vascularity, thick-walled bowel, dilated bowel, right lower quadrant (RLQ) echogenic fat, increased hepatic periportal echogenicity, bladder debris and abscess or loculated fluid. We also recorded the characteristics of intraperitoneal fluid, indicating the relative quantity (number of abdominal regions) and quality of the fluid (simple fluid or complex fluid). We used logistic regression for correlated data to evaluate the association of diagnosis with the presence versus absence of each US finding. We conducted multivariable analysis to identify constellations of sonographic findings that were predictive of perforated appendicitis. RESULTS: The individual US findings of abscess/loculated fluid, appendicolith, dilated bowel and increased hepatic periportal echogenicity were significantly associated with perforated appendicitis when compared with acute appendicitis (P < 0.01). The sonographic observation of increased hepatic periportal echogenicity demonstrated a statistically significant association with perforated appendicitis compared with acute appendicitis (P < 0.01). The presence of complex fluid yielded a specificity of 87.7% for perforated appendicitis compared with the acute appendicitis group. The US findings of >/=2 regions or >/=3 regions with fluid had specificity of 87.3% and 99.0%, respectively, for perforated appendicitis compared with the acute appendicitis group. Select combinations of sonographic findings yielded high specificity in the diagnosis of perforated appendicitis compared with acute appendicitis. These constellations yielded higher specificity than that of each individual finding in isolation. The constellation of dilated bowel, RLQ echogenic fat, and complex fluid had the highest specificity (99.5%) for perforated appendicitis (P < 0.01). CONCLUSION: Our study demonstrates that identification of select constellations of findings using abdominal sonography, in addition to focused US examination of the right lower quadrant, can improve sonographic diagnosis of perforated appendicitis in the pediatric population.

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: 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 compare fitting methods and sampling strategies, including the implementation of an optimized b-value selection for improved estimation of intravoxel incoherent motion (IVIM) parameters in breast cancer. METHODS: Fourteen patients (age, 48.4 +/- 14.27 years) with cancerous lesions underwent 3 Tesla breast MRI examination for a HIPAA-compliant, institutional review board approved diffusion MR study. IVIM biomarkers were calculated using "free" versus "segmented" fitting for conventional or optimized (repetitions of key b-values) b-value selection. Monte Carlo simulations were performed over a range of IVIM parameters to evaluate methods of analysis. Relative bias values, relative error, and coefficients of variation (CV) were obtained for assessment of methods. Statistical paired t-tests were used for comparison of experimental mean values and errors from each fitting and sampling method. RESULTS: Comparison of the different analysis/sampling methods in simulations and experiments showed that the "segmented" analysis and the optimized method have higher precision and accuracy, in general, compared with "free" fitting of conventional sampling when considering all parameters. Regarding relative bias, IVIM parameters fp and Dt differed significantly between "segmented" and "free" fitting methods. CONCLUSION: IVIM analysis may improve using optimized selection and "segmented" analysis, potentially enabling better differentiation of breast cancer subtypes and monitoring of treatment. Magn Reson Med, 2014. (c) 2014 Wiley Periodicals, Inc.

PURPOSE: To retrospectively compare standard and BLADE T2-weighted imaging (T2WI) sequences of the prostate in terms of image quality and tumor assessment. METHODS: 49 prostate cancer patients (64 +/- 6 years) who underwent 3 T phased-array coil MRI before prostatectomy were included. T2WI was acquired using standard rectilinear and BLADE techniques. Two readers (R1, R2) independently localized the dominant lesion using T2WI alone and using multi-parametric imaging; recorded presence of extraprostatic extension (EPE) in each lobe; and scored lesion conspicuity and absence of motion artifact (1-5 scale; 5 = highest quality). A third reader, unblinded to pathology, placed ROIs to record tumor-to-peripheral-zone contrast. Standard and BLADE T2WI were compared using paired Wilcoxon tests. RESULTS: BLADE showed a trend toward improved motion artifact for R1 (3.4 +/- 1.3 vs. 2.9 +/- 1.5; p = 0.054) but not R2 (4.0 +/- 1.0 vs. 3.9 +/- 1.1; p = 0.880). Dominant lesions showed significantly lower conspicuity using BLADE for R1 (2.8 +/- 2.0 vs. 3.2 +/- 2.0; p = 0.011) but not R2 (2.3 +/- 1.6 vs. 2.4 +/- 1.7; p = 0.353), and significantly lower tumor-to-peripheral-zone contrast using BLADE (0.35 +/- 0.13 vs. 0.42 +/- 0.15; p