• Jiangsheng Yu, Masaru Ishii, Stephen Kadlecek, David A Lipson, Kiarash Emami, Timothy W Clark, Sheeva Rajaei, and Rahim R Rizi.
• Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA.
• J Magn Reson Imaging. 2007 May 1; 25 (5): 982-91.

PurposeTo develop and validate a new multiple regression technique for the separation of flip angle effect in pulmonary apparent diffusion coefficient (ADC) measurement.Materials And MethodsHyperpolarized (3)He MRI (HP (3)He MRI) ADC measurements were performed on phantom, pig, and human models. The diffusion-sensitization sequence is modified from a standard gradient echo (GRE) sequence with a nonlinear progression in the bipolar gradient amplitude with each image. In the self-diffusion phantom experiment, four images were acquired with base gradient factor b(0) = 0.15 second/cm(2); in the pig and human experiment, six images were acquired with base gradient factor b(0) = 1.4 second/cm(2).ResultsThe self-diffusion coefficient measured in the phantom experiment was 1.98 +/- 0.16 cm(2)/second. The measured uncertainty curve was consistent with the theoretically predicted curve. The measured in vivo ADC values (three coronal slices in the supine direction) were 0.20/0.16/0.13 cm(2)/second and 0.20/0.18/0.16 cm(2)/second for pig and human experiments, respectively.ConclusionWith the introduction of a nonlinear progression in the diffusion-sensitization gradients, the multiple regression technique is capable of separating the flip angle effect in ADC measurement. In addition, this technique can perform a rigorous measurement uncertainty analysis and provide the optimal scan parameters that yield best noise performance.(c) 2007 Wiley-Liss, Inc.

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