Clinical aspects of the apparent diffusion coefficient in 3He MRI: Results in healthy volunteers and patients after lung transplantation

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Abstract
Purpose To measure the apparent diffusion coefficient (ADC) after inhalation of hyperpolarized 3He in healthy volunteers and lung transplant recipients, and demonstrate the gravity dependence of ADC values. Materials and Methods Six healthy volunteers, 10 patients after single-lung transplantation, and six patients after double-lung transplantation were examined at 1.5T during inspiration and expiration. The inhalation of 300 mL of hyperpolarized 3He was performed with a computer-controlled delivery device. A two-dimensional fast low-angle shot (FLASH) sequence measured the 3He diffusive gas movement. From these data the ADC was calculated. Results The mean ADC was 0.143 cm2/second in healthy individuals, 0.162 cm2/second in transplanted healthy lungs, and 0.173 cm2/second in rejected transplanted lungs, whereas it was 0.216 cm2/second in native fibrotic lungs and 0.239 cm2/second in emphysematous lungs. The difference in mean ADC values among healthy lungs, healthy transplanted lungs, and native diseased lungs was significant (P < 0.001). In inspiration the healthy volunteers showed higher ADC values in the anterior than in the posterior parts of the lungs. In expiration this gradient doubled. Conclusion An anterior–posterior (A/P) gradient was found in inspiration and expiration in healthy lungs. Healthy, transplanted, and native diseased lungs had significantly different mean ADC values. From our preliminary results, 3He MRI appears to be sensitive for detecting areas of abnormal ventilation in transplanted lungs. J. Magn. Reson. Imaging 2007;25:1152–1158.