Time Dependence of 3He Diffusion in the Human Lung: Measurement in the Long-time Regime Using Stimulated Echoes
Wang c, Miller G, Altes T, de lange E, Mugler, III J
University of Virginia
A stimulated-echo-based technique was developed for measuring the long-time-scale apparent diffusion coefficient (ADC) of hyperpolarized 3He in the lung. Computer simulations and phantom studies were used to validate our method. In ten healthy subjects, we found that the long-time-scale global ADC decreased substantially with increasing diffusion time. ADC maps in healthy subjects were uniform. In two COPD subjects, global ADC values at all diffusion times and the means of ADC maps were both significantly elevated compared to healthy subjects. In addition, regional elevation of ADC values was far more conspicuous on long-time-scale ADC maps than on short-time-scale ADC maps.