Rapid hyperpolarized 3He diffusion MRI of healthy and emphysematous human lungs using an optimized interleaved-spiral pulse sequence.
PURPOSE: To develop and validate an interleaved-spiral diffusion pulse sequence capable of hyperpolarized (3)He MR imaging of the whole lung in less than 10 seconds. MATERIALS AND METHODS: Hyperpolarized (3)He diffusion measurements were performed in seven healthy volunteers and five patients with emphysema using an interleaved-spiral pulse sequence that provided 11 contiguous 15-mm thick coronal ADC maps, with an in-plane resolution of 3.9 mm, covering the whole lung in 5.5 seconds. The resulting means and SDs of ADC values were compared statistically to those from a gradient-echo pulse sequence with identical resolution and diffusion-weighting gradients that acquired five ADC maps in 10.5 seconds. RESULTS: High-quality diffusion-weighted interleaved-spiral images covering the whole lung were obtained, and showed no significant susceptibility-induced image degradation compared to corresponding gradient-echo images. On a subject-by-subject basis, the means and SDs of ADC values for the interleaved-spiral technique were not statistically different from those for the gradient-echo technique. The mean ADC values from the two techniques were highly correlated on a section-by-section basis (R = 0.99). CONCLUSION: The interleaved-spiral diffusion pulse sequence permits rapid acquisition of contiguous ADC maps covering the whole lung during a short breath-hold period, and provides ADC values that are statistically equivalent to those from standard gradient-echo techniques.