Quantitative Methods for Evaluating Ventilation on Hyperpolarized Gas MRI PDF Download

Author: Katherine Josephine Carey
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Languages : en
Pages : 0

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Book Description
Magnetic Resonance Imaging (MRI) is an attractive modality for imaging the pulmonary system at relatively high resolution, especially for longitudinal disease assessment. HP gas MRI provides a means of visualizing pulmonary gas distribution directly, using either HP 3He or HP 129Xe. By using specialized equipment to excite the gases into hyperpolarized states, the net magnetic moment of the gas is temporarily increased, enabling ventilation imaging over a 12-20 second breath-hold. Visualization and quantification of inhaled gas allows for direct functional information while imaging lung structure with conventional MRI in the same study. Functional metrics derived from ventilation patterns, such as the ventilation defect percent (VDP) have been previously established as markers of disease instability in obstructive lung diseases. In this work, we first apply HP gas MRI in asthma to assess regional structure-function relationships with other quantitative imaging modalities. Then we assess VDP as a biomarker in two longitudinal studies, one during a period of disease instability, where we show that VDP is a biomarker of persistent obstructive change reflecting disease progression and provide evidence for VDP as a longitudinal biomarker of asthma instability. We then extend HP gas MRI to study restrictive lung disease in Idiopathic Pulmonary Fibrosis (IPF), first establishing areas of high ventilation as a biomarker of disease stability and providing evidence that ventilation provides information about disease stability following treatment. Finally, we present a case study establishing the feasibility of using HP gas MRI as a longitudinal marker of response to radiation therapy. Overall, this dissertation presents original work establishing VDP as a biomarker of airway obstruction and a longitudinal marker of disease stability in asthma that can benefit drug development by enriching populations with unstable disease and monitoring therapy response. Moreover, this work establishes an initial understanding of ventilation biomarkers in restrictive lung diseases, an area little studied heretofore. Using these results and techniques for further validation of imaging-based asthma phenotypes and the development of ventilation biomarkers in other pulmonary disorders has the potential to improve drug development and support clinical therapy management by better targeting treatment and monitoring their disease stability and progression.