Quantifying Lung Water Density with Ultrashort Echo Time Yarn-Ball MRI

• Author / Creator

  Meadus, William Q

• Pulmonary edema (PE) involves an excess of extravascular lung water (EVLW) due to an imbalance in fluid filtration which results in hypoxia and respiratory distress. Cardiogenic pulmonary edema is a primary clinical feature and therapeutic target in acute heart failure. Current methods in measuring EVLW are lacking, so this study aimed to provide quantitative imaging of water density in the lung parenchyma through MRI. This thesis illustrates a novel Yarn-Ball (YB) ultrashort TE (UTE) k-space trajectory along side an automated image processing approach. Efficiency optimized UTE-YB k-space trajectories were designed for breath-hold and free-breathing acquisitions. These provide full torso spatial coverage with minimal T1 and T2* weighting at 3T. A composite of all solid tissues surrounding the lungs (muscle, liver, heart, blood-pool) was used for the lung water density signal referencing and B1-inhomogeneity correction which results in relative water density based images. Automated region-growing based lung segmentation isolates relevant lung parenchyma voxels for final relative lung water density (rLWD) values. Acquisition-time matched 3D radial acquisitions were compared to YB. Sponge phantom experiments were used to validate absolute water density quantification. Phantom experiments showed excellent agreement between sponge wet weight and imaging-derived water density. Breath-hold (13 seconds) and free-breathing (∼2 minutes) YB acquisitions in volunteers (2.5 mm isotropic resolution) had negligible artifacts and good lung parenchyma SNR (>10:1). Whole lung average rLWD values were 28.6±3% (automated analysis) with good test/re-test reproducibility (ICC=0.87-0.99). Radial acquisitions with matched durations had significantly reduced fully sampled fields of view resulting in prominent undersampling artifacts. Quantitative lung water density imaging with an optimized YB acquisition is possible in breath-hold or short free-breathing studies and may prove invaluable in the measurement and tracking of PE.

• Subjects / Keywords

  • MRI
  • Lung Water Density
  • Ultrashort Echo Time
  • Pulmonary Edema
  • Yarn-Ball MRI

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-nkkx-4c58

• License

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