39 research outputs found
Motion robust MR fingerprinting scan to image neonates with prenatal opioid exposure
Background: A noninvasive and sensitive imaging tool is needed to assess the
fast-evolving baby brain. However, using MRI to study non-sedated babies faces
roadblocks, including high scan failure rates due to subjects motion and the
lack of quantitative measures for assessing potential developmental delays.
This feasibility study explores whether MR Fingerprinting scans can provide
motion-robust and quantitative brain tissue measurements for non-sedated
infants with prenatal opioid exposure, presenting a viable alternative to
clinical MR scans. Assessment: MRF image quality was compared to pediatric MRI
scans using a fully crossed, multiple reader multiple case study. The
quantitative T1 and T2 values were used to assess brain tissue changes between
babies younger than one month and babies between one and two months.
Statistical Tests: Generalized estimating equations (GEE) model was performed
to test the significant difference of the T1 and T2 values from eight white
matter regions of babies under one month and those are older. MRI and MRF image
quality were assessed using Gwets second order auto-correlation coefficient
(AC2) with its confidence levels. We used the Cochran-Mantel-Haenszel test to
assess the difference in proportions between MRF and MRI for all features and
stratified by the type of features. Results: In infants under one month of age,
the T1 and T2 values are significantly higher (p<0.005) compared to those
between one and two months. A multiple-reader and multiple-case study showed
superior image quality ratings in anatomical features from the MRF images than
the MRI images. Conclusions: This study suggested that the MR Fingerprinting
scans offer a motion-robust and efficient method for non-sedated infants,
delivering superior image quality than clinical MRI scans and additionally
providing quantitative measures to assess brain development
MR fluoroscopy in vascular and cardiac interventions (review)
Vascular and cardiac disease remains a leading cause of morbidity and mortality in developed and emerging countries. Vascular and cardiac interventions require extensive fluoroscopic guidance to navigate endovascular catheters. X-ray fluoroscopy is considered the current modality for real time imaging. It provides excellent spatial and temporal resolution, but is limited by exposure of patients and staff to ionizing radiation, poor soft tissue characterization and lack of quantitative physiologic information. MR fluoroscopy has been introduced with substantial progress during the last decade. Clinical and experimental studies performed under MR fluoroscopy have indicated the suitability of this modality for: delivery of ASD closure, aortic valves, and endovascular stents (aortic, carotid, iliac, renal arteries, inferior vena cava). It aids in performing ablation, creation of hepatic shunts and local delivery of therapies. Development of more MR compatible equipment and devices will widen the applications of MR-guided procedures. At post-intervention, MR imaging aids in assessing the efficacy of therapies, success of interventions. It also provides information on vascular flow and cardiac morphology, function, perfusion and viability. MR fluoroscopy has the potential to form the basis for minimally invasive image–guided surgeries that offer improved patient management and cost effectiveness
Normalized T1 Magnetic Resonance Imaging for Assessment of Regional Lung Function in Adult Cystic Fibrosis Patients - A Cross-Sectional Study
Background: Cystic fibrosis (CF) patients would benefit from a safe and effective tool to detect early-stage, regional lung disease to allow for early intervention. Magnetic Resonance Imaging (MRI) is a safe, non-invasive procedure capable of providing quantitative assessments of disease without ionizing radiation. We developed a rapid normalized T1 MRI technique to detect regional lung disease in early-stage CF patients.
Materials and Methods: Conventional multislice, pulmonary T1 relaxation time maps were obtained for 10 adult CF patients with normal spirometry and 5 healthy non-CF control subjects using a rapid Look-Locker MRI acquisition (5 seconds/imaging slice). Each lung absolute T1 map was separated into six regions of interest (ROI) by manually selecting upper, central, and lower lung regions in the left and right lungs. In order to reduce the effects of subject-to-subject variation, normalized T1 maps were calculated by dividing each pixel in the absolute T1 maps by the mean T1 time in the central lung region. The primary outcome was the differences in mean normalized T1 values in the upper lung regions between CF patients with normal spirometry and healthy volunteers.
Results: Normalized T1 (nT1) maps showed visibly reduced subject-to-subject variation in comparison to conventional absolute T1 maps for healthy volunteers. An ROI analysis showed that the variation in the nT1 values in all regions was <= 2% of the mean. The primary outcome, the mean (SD) of the normalized T1 values in the upper right lung regions, was significantly lower in the CF subjects [.914 (.037)] compared to the upper right lung regions of the healthy subjects [.983 (.003)] [difference of .069 (95% confidence interval .032-.105); p=.001). Similar results were seen in the upper left lung region.
Conclusion: Rapid normalized T1 MRI relaxometry obtained in 5 seconds/imaging slice may be used to detect regional early-stage lung disease in CF patients
Application of the Concurrent Subspace Design Framework to Aircraft Brake Component Design Optimization
The Concurrent Subspace Design (CSD) framework has been used to conduct a preliminary design optimization of an aircraft landing gear subsystem. The application required the implementation of the MDO framework with existing industrial analysis software. The CSD framework employs artificial neural networks to provide approximations to the design space, which are the means of coordinating design decisions in the individual disciplines. This approach was applied to the design of an aircraft brake actuation system which contains continuous and discrete design variables. The results demonstrate that the mixed CSD framework was able to efficiently identify improved designs. This study also demonstrated that the CSD framework can be exploited using existing engineering analysis methods
Reproducible MRI measurement of adipose tissue volumes in genetic and dietary rodent obesity models
Purpose: To develop ratio MRI [lipid/(lipid+water)] methods for assessing lipid depots and compare measurement variability with biological differences among lean controls (spontaneously hypertensive rats [SHRs]), dietary obese rats (SHR-DOs), and genetic/dietary obese rats (SHROBs). Materials and Methods: Images with and without chemical shift-selective (CHESS) water suppression were processed using a semiautomatic method that accounts for relaxometry, chemical shift, receive coil sensitivity, and partial volume. Results: Partial volume correction improved results by 10\% to 15\%. Over six operators, volume variation was reduced to 1.9 mL from 30.6 mL for single-image-analysis with intensity inhomogeneity. For three acquisitions on the same animal, volume reproducibility was <1\%. SHROBs had six times more visceral and eight times more subcutaneous adipose tissue than SHRs. SHR-DOs had enlarged visceral depots (three times larger than those in SHRs). SHROBs had significantly more subcutaneous adipose tissue, indicating a strong genetic component to this fat depot. Liver ratios in SHR-DO and SHROB were higher than in SHR, indicating elevated fat content. Among SHROBs, evidence suggested a phenotype SHROB{*} having elevated liver ratios and visceral adipose tissue volumes. Conclusion: Effects of diet and genetics on obesity were significantly larger than variations due to image acquisition and analysis, indicating that these methods can be used to assess accumulation/depletion of lipid depots in animal models of obesity