Knik Arm Crossing: The Economic Impact on Anchorage

Prepared for Department of Community Planning Municipality of AnchorageYe

Phase and amplitude correction for multi-echo water-fat separation with bipolar acquisitions

Purpose: To address phase and amplitude errors for multi-point water-fat separation with bipolar acquisitions, which efficiently collect all echoes with alternating read-out gradient polarities in one repetition. Materials and Methods: With the bipolar acquisitions, eddy currents and other system nonidealities can induce inconsistent phase errors between echoes, disrupting water-fat separation. Previous studies have addressed phase correction in the read-out direction. However, the bipolar acquisitions may be subject to spatially high order phase errors as well as an amplitude modulation in the read-out direction. A method to correct for the 2D phase and amplitude errors is introduced. Low resolution reference data with reversed gradient polarities are collected. From the pair of low-resolution data collected with opposite gradient polarities, the two-dimensional phase errors are estimated and corrected. The pair of data are then combined for water-fat separation. Results: We demonstrate that the proposed method can effectively remove the high order errors with phantom and in vivo experiments, including obliquely oriented scans. Conclusion: For bipolar multi-echo acquisitions, uniform water-fat separation can be achieved by removing high order phase errors with the proposed method. © 2010 Wiley-Liss, Inc

Robust multipoint water-fat separation using fat likelihood analysis

Fat suppression is an essential part of routine MRI scanning. Multiecho chemical-shift based water-fat separation methods estimate and correct for Bo field inhomogeneity. However, they must contend with the intrinsic challenge of water-fat ambiguity that can result in water-fat swapping. This problem arises because the signals from two chemical species, when both are modeled as a single discrete spectral peak, may appear indistinguishable in the presence of Bo off-resonance. In conventional methods, the water-fat ambiguity is typically removed by enforcing field map smoothness using region growing based algorithms. In reality, the fat spectrum has multiple spectral peaks. Using this spectral complexity, we introduce a novel concept that identifies water and fat for multiecho acquisitions by exploiting the spectral differences between water and fat. A fat likelihood map is produced to indicate if a pixel is likely to be water-dominant or fat-dominant by comparing the fitting residuals of two different signal models. The fat likelihood analysis and field map smoothness provide complementary information, and we designed an algorithm (Fat Likelihood Analysis for Multiecho Signals) to exploit both mechanisms. It is demonstrated in a wide variety of data that the Fat Likelihood Analysis for Multiecho Signals algorithm offers highly robust water-fat separation for 6-echo acquisitions, particularly in some previously challenging applications. © 2011 Wiley Periodicals, Inc

CHOICE THEORY: AN INVESTIGATION OF THE TREATMENT EFFECTS OF A CHOICE THEORY PROTOCOL ON STUDENTS IDENTIFIED AS HAVING A BEHAVIORAL OR EMOTIONAL DISABILITY ON MEASURES OF ANXIETY, DEPRESSION, LOCUS OF CONTROL AND SELF-ESTEEM

Existing research reveals that students who have a behavioral or emotional disability is a growing population within special education. Special education law and counseling organizations both agree that these students would likely benefit from counseling services at school. Research also reveals that this does not typically happen, that the interventions used in schools tend to have little beneficial effect and that these students are more likely than any other subgroup within public schools to drop out before graduating. This research was designed to assess what, if any, effect a tested treatment modality (Choice Theory) developed and used with children in juvenile detention centers has on students identified as having a behavioral or emotional disability in public school. This research utilized a true experimental design and assessed treatment outcomes on affective measures of Locus of Control, Anxiety, Depression and Self-Esteem in middle and high school aged students with a behavioral or emotional disability. Two groups of 15 students were randomly selected and randomly assigned to either a control or experimental group; the experimental group participated in a 6-week Choice Theory protocol. Both groups were administered the BASC-2 Self-Report at the beginning of the treatment and both groups completed the same instrument at the end of the protocol. Four two-way ANOVA's with one between subjects and one within subjects effects was used to examine differences between the groups on all four of the dependent variables. First, the measure of Locus of Control was examined and revealed a significant difference within subjects and between subjects effect. In addition, there was a significant interaction demonstrating that students in the experimental group experienced a greater sense of power over their internal world relative to external stimuli after the implementation of the protocol when compared to the control group. Second, the measure of Anxiety was examined and revealed no significant difference within subjects, or interaction, but there was a significant between subject effect. Third, the measure of Depression was examined and revealed that there was a significant difference both within and between subject effect as well as a significant interaction, revealing that students in the experimental group reported experiencing less depressive symptoms than did the control group after the implementation of the protocol. Last, the measure of Self-Esteem was examined and revealed that there was no significant within subject effect, but there was a significant between subjects effect and interaction, revealing that students in the experimental group reported more positive feelings of self worth and efficacy after the implementation of the protocol than did the student in the control group

The ISER MAP Economic Database Data Sources and Derivations A Companion to the Printed Tables

Ye

Noise analysis for 3-point chemical shift-based water-fat separation with spectral modeling of fat

Purpose: To model the theoretical signal-to-noise ratio (SNR) behavior of 3-point chemical shift-based water-fat separation, using spectral modeling of fat, with experimental validation for spin-echo and gradient-echo imaging. The echo combination that achieves the best SNR performance for a given spectral model of fat was also investigated. Materials and Methods: Cramér-Rao bound analysis was used to calculate the best possible SNR performance for a given echo combination. Experimental validation in a fatwater phantom was performed and compared with theory. In vivo scans were performed to compare fat separation with and with out spectral modeling of fat. Results: Theoretical SNR calculations for methods that include spectral modeling of fat agree closely with experimental SNR measurements. Spectral modeling of fat more accurately separates fat and water signals, with only a slight decrease in the SNR performance of the water-only image, although with a relatively large decrease in the fat SNR performance. Conclusion: The optimal echo combination that provides the best SNR performance for water using spectral modeling of fat is very similar to previous optimizations that modeled fat as a single peak. Therefore, the optimal echo spacing commonly used for single fat peak models is adequate for most applications that use spectral modeling of fat. © 2010 Wiley-Liss, Inc

Quantification of hepatic steatosis with 3-T MR imaging: Validation in ob/ob mice

Purpose: To validate quantitative imaging techniques used to detect and measure steatosis with magnetic resonance (MR) imaging in an ob/ob mouse model of hepatic steatosis. Materials and Methods: The internal research animal and resource center approved this study. Twenty-eight male ob/ob mice in progressively increasing age groups underwent imaging and were subsequently sacrificed. Six ob /+ mice served as control animals. Fat fraction imaging was performed with a chemical shift-based water-fat separation method. The following three methods of conventional fat quantification were compared with imaging: lipid extraction and qualitative and quantitative histologic analysis. Fat fraction images were reconstructed with single- and multiple-peak spectral models of fat and with and without correction for T2* effects. Fat fraction measurements obtained with the different reconstruction methods were compared with the three methods of fat quantification, and linear regression analysis and two-sided and two-sample t tests were performed. Results:Lipid extraction and qualitative and quantitative histologic analysis were highly correlated with the results of fat fraction imaging (r2 = 0.92, 0.87, 0.82, respectively). No significant differences were found between imaging measurements and lipid extraction (P = .06) or quantitative histologic (P = .07) measurements when multiple peaks of fat and T2* correction were included in image reconstruction. Reconstructions in which T2* correction, accurate spectral modeling, or both were excluded yielded lower agreement when compared with the results yielded by other techniques. Imaging measurements correlated particularly well with histologic grades in mice with low fat fractions (intercept, -1.0% ± 1.2 [standard deviation ]). Conclusion: MR imaging can be used to accurately quantify fat in vivo in an animal model of hepatic steatosis and may serve as a quantitative biomarker of hepatic steatosis. © RSNA, 2010