Diffusion‐weighted MRI of the lung with hyperpolarized helium‐3: A study of reproducibility

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Abstract
Purpose To determine the reproducibility of several parameters of the ADC measurement by calculating the scan-to-scan intrasubject variability. Materials and Methods Measurements were performed using a gradient-echo sequence with a bipolar gradient for diffusion weighting (b = 3.89 sec/cm2). Five patients with pulmonary emphysema, and six healthy-lung volunteers were included in the study. Images were acquired after inspiration of 3He during a single inspiratory breath-hold. To assess the reproducibility, the measurement was performed twice (time between measurements = 20 minutes) without repositioning the subjects. Analysis was performed on the basis of region-of-interest (ROI) analysis and global lung ADC histograms. Results The mean ADC of a ROI varied by 5.1% between two measurements for volunteers and by 6.1% for patients. In the global evaluation, the 75th percentile demonstrated the best reproducibility (2%), while other parameters showed variations up to 12%. Only the variation of the standard deviation (SD) and the measure of homogeneity of the ADC map showed a significant difference between patients and volunteers. Conclusion Diffusion-weighted imaging (DWI) is a well-reproducible method for assessing the lung microstructure. J. Magn. Reson. Imaging 2005;21:765–774.