Dynamic 3HE MRI of the Lungs

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DESCRIPTION (provided by applicant): Small airway disease is a significant cause of morbidity and mortality. Chronic obstruction pulmonary disease (COPD) and asthma affect 40 million Americans and cost 23 billion dollars in direct health care expenditure annually. If detected early, disease progression can be slowed or halted by the removal of causative factors, and implementation of specific treatments. Means of assessing therapeutic response of the small airways are necessary to effectively apply these new treatments, but current methods of assessing lung function are limited. Clinical examination is not sensitive, is often non-specific, and identifies disease on a global but not regional basis. Pulmonary function tests (PFTs) similarly only identify global deficiencies and are insensitive to small airway disease, indeed 75% of the airways are not assessed with screening spirometry. High resolution CT can identify regional anatomic airway changes if present, but these are usually non-specific and do not necessarily reflect the degree of functional change. Many causes of airway dysfunction, such as asthma, may be occult to CT. MRI of helium-3 (3HeMRI) is a recently developed method of visualizing lung air spaces and airways. The subject inhales He that has been hyperpolarized to generate a large magnetic moment and an 3 MR image of the gas in acquired. HeMRI is exquisitely sensitive to areas of decreased air flow. However, 3 although He images have been acquired dynamically during inhalation and exhalation, no optimum method 3 has yet emerged for combining volumetric dynamic imaging with airflow quantification. The overarching goal of this proposal is to develop multiecho methods of assessing lung function using magnetic resonance imaging of inhaled hyperpolarized helium, He. SPECIFIC AIM 1: To determine the feasibility of using novel Shifted k- 3 space Imaging (SKIM) sequences for two- and three-dimensional dynamic parallel imaging. Hypothesis 1.1: Undersampled SKIM acquisitions have the same, if not higher, signal-to-noise ratios as conventional fully- sampled spin-warp acquisitions. Hypothesis 1.2: Any artifacts introduced by undersampled SKIM sequences have negligible effects on image quality. Hypothesis 1.3: Volumetric dynamic functional imaging of the lungs can be performed by combining SKIM and parallel imaging. SPECIFIC AIM 2: To determine the feasibility of using a new phase contrast approach for characterizing gas flow. Studies will be performed in flow phantoms and normal volunteers. Hypothesis 2.1: The proposed phase contrast approach can map gas flow velocities in 3He flow phantom studies with an encoding velocity (Venc) of 100 cm/s. Hypothesis 2.2: This approach can be used to map airflow velocities in the trachea, main stem bronchus and right and left bronchi in normal humans. The two aims of this proposal are essential to achieve our ultimate goal of developing a sensitive, reliable method of detecting decreased gas flow in the diseased lung. This proposal would represent the first method developed for flow and functional assessment of the lungs and as such will permit quantitative assessment of the whole lung function. Small airway disease is a significant cause of morbidity and mortality. If detected early, disease progression can be slowed or halted by the removal of causative factors, and implementation of specific treatments. However, current methods of assessing lung function are limited. Our proposal would represent the first method developed for flow and functional assessment of the lungs and will permit quantitative assessment of the whole lung function.