The CHARA Array is a six 1-m telescope optical/IR interferometric array located on Mount Wilson California, designed and built by the Center for High Angular Resolution Astronomy of Georgia State University. In this paper we describe the main elements of the Array hardware and software control systems as well as the data reduction methods currently being used. Our plans for upgrades in the near future are also described

Purpose To use 3D radial ultrashort echo time MRI to perform whole-lung oxygen-enhanced (OE) imaging in humans. Methods Eight healthy human subjects underwent two 3D radial UTE MRI acquisitions (TE = 0.08 ms): one while breathing 21% O2 and the other while breathing 100% O2. Scans were each performed over 5 minutes of free breathing, using prospective respiratory gating. For comparison purposes, conventional echo time (TE = 2.1 ms) images were acquired simultaneously during each acquisition using a radial “outward-inward” k-space trajectory. 3D percent OE maps were generated from these images. Results 3D OE maps showing lung signal enhancement were generated successfully in seven subjects (technical failure in one subject). Mean percent signal enhancement was 6.6% ± 1.8%, near the value predicted by theory of 6.3%. No significant enhancement was seen using the conventional echo time data, confirming the importance of UTE for this acquisition strategy. Conclusion 3D radial UTE MRI shows promise as a method for OE MRI that enables whole-lung coverage and isotropic spatial resolution, in comparison to existing 2D OE methods that rely on a less time-efficient inversion recovery pulse sequence. These qualities may help OE MRI become a viable low-cost method for 3D imaging of lung function in human subjects.

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1287-1297.

Background Magnetic resonance imaging (MRI) with 3He does not require ionizing radiation and has been shown to detect regional abnormalities in lung ventilation and structure in adult asthma, but the method has not been extended to childhood asthma. Measurements of regional lung ventilation and microstructure in childhood asthma could advance our understanding of disease mechanisms. Objective To determine whether 3He MRI in children can identify abnormalities related to diagnosis of asthma or prior history of respiratory illness. Methods Forty-four children aged 9-10 years were recruited from a birth cohort at increased risk of developing asthma and allergic diseases. For each subject a time-resolved three-dimensional (3D) image series and a 3D diffusion-weighted image were acquired in separate breathing maneuvers. The number and size of ventilation defects were scored, and regional maps and statistics of average 3He diffusion length were calculated. Results Children with mild to moderate asthma had lower average diffusion length, Xrmstrue¯ (p=0.004), increased regional standard deviation of diffusion length (p=0.03), and higher defect scores (p=0.03) than those without asthma. Children with histories of wheezing illness with rhinovirus infection prior to the third birthday had lower Xrmstrue¯ (p=0.01) and higher defect score (p=0.05). Conclusion MRI with 3He detected more and larger regions of ventilation defect and a greater degree of restricted gas diffusion in children with asthma compared to those without asthma. These measures are consistent with regional obstruction and smaller and more regionally variable dimensions of the peripheral airways and alveolar spaces.

In the last two decades, functional imaging of the lungs using hyperpolarized noble gases has entered the clinical stage. Both helium (3 He) and xenon (129Xe) gas have been thoroughly investigated for their ability to assess both the global and regional patterns of lung ventilation. With advances in polarizer technology and the current transition towards the widely available 129Xe gas, this method is ready for translation to the clinic. Currently, hyperpolarized (HP) noble gas lung MRI is limited to selected academic institutions; yet, the promising results from initial clinical trials have drawn the attention of the pulmonary medicine community. HP 129Xe MRI provides not only 3-dimensional ventilation imaging, but also unique capabilities for probing regional lung physiology. In this review article, we aim to (1) provide a brief overview of current ventilation MR imaging techniques, (2) emphasize the role of HP 129Xe MRI within the array of different imaging strategies, (3) discuss the unique imaging possibilities with HP 129Xe MRI, and (4) propose clinical applications.