DIFFUSION CORRECTED RECONSTRUCTIONS OF PARTIAL PRESSURE OF OXYGEN

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Pulmonary compliance  defined as the change in volume of the lung per unit change in pressure  is one of the fundamental parameters used in the analysis of lung mechanics, and knowledge of this parameter is important for the study and diagnosis of pulmonary diseases. Hyperpolarized (HP) 3He MRI measures of regional oxygen tensions provide important insight into lung function under physiologic and pathophysiologic conditions. This stems from the unique correlation between the lungs steady state oxygen tensions and its ventilation perfusion ratios; a similar relationship exists between the lungs the oxygen degradation rate and local alveolar perfusion. Thus these measures are of great interest to pulmonologists and physiologists. Current HP oxygen measurement techniques assume that diffusion of the HP gas during the measurement cycle affects the measured signal intensity negligibly. We show that under many conditions this assumption is false and severely degrades measurement accuracy; we present the first direct oxygen reconstruction algorithm for measuring regional oxygen tensions in the presence of a diffusing HP contrast agent. Numerical simulations and experimental results are presented as well.