Measurement of pulmonary structure and function parameters with hyperpolarized 3He magnetic resonance imaging
Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States. The established technique of computed tomography can detect and stage the disease with limited sensitivity and is not suitable for long-term studies due to radiation exposure. In recent years, hyperpolarized 3He (HP 3He) MRI has been studied extensively as a promising tool to assess pulmonary structural and functional parameters. This work focuses on the application of this technique to study pulmonary ventilation and perfusion disorders, with an emphasis on COPD. Two hypotheses are proposed and tested in this thesis. The first hypothesis is that microscopic changes in lung structure induced by COPD cause associated function deteriorations, and HP 3He MRI is capable of quantifying this correlation. To this end, a simultaneous measurement technique is developed for the co-registered measurement of apparent diffusion coefficient (ADC), partial pressure of oxygen (pO2) and oxygen depletion rate (R). In this technique, a mathematical model on signal evolution is proposed and the multiple regression method is applied to extract the values of ADC, pO2 and R from a series of acquired signals. Measurement uncertainty expressions are derived and the key scan parameters are optimized to reduce the noise-induced uncertainty. The technique was first tested on a phantom model, and then on an in-vivo normal pig experiment. A case study was performed on a COPD patient, which showed that, in a region-of-interest ADC was 29% higher while oxygen depletion rate was 61% lower than the corresponding global average values. The second hypothesis is that HP 3He MRI can not only be applied to measure ventilation disorders, but also capable of detecting perfusion defects, such as pulmonary emboli (PE). To test this hypothesis, Gadolinium (Gd) is injected to modify the magnetic susceptibility gradient between lung tissue and air, and this modification is recorded through the phase of the HP 3He MRI signal. A double-echo based method is proposed for the automatic co-registration of lung perfusion and ventilation images. The in-vivo animal experiment showed a significant phase shift followed by the perfusion-induced susceptibility change. ^
Engineering, Biomedical|Engineering, Electronics and Electrical
"Measurement of pulmonary structure and function parameters with hyperpolarized 3He magnetic resonance imaging"
(January 1, 2008).
Dissertations available from ProQuest.