Songfan Xu1, Geon-Ho Jahng2, Norbert Schuff3, Dieter J. Meyerhoff3, Michael W. Weiner3
1Department of Medical Research Center, Kyung-Hee University, Seoul, Korea; 2Radiology, East West Neo Medical Center, Kyung Hee University, Seoul, Korea; 3Radiology, CIND, Veterans Affairs Medical Center, UCSF, San Francisco, CA, USA
DTI studies can be confounded by local background gradients that may relate to brain abnormalities. We studied DTI maps of patients with Alzheimers disease (AD), mild cognitively impairment (MCI) and cognitive normal (CN) subjects by comparing between maps derived from either positive or negative polarities of diffusion gradients or from geometric diffusion means that minimize background gradients. We found that background gradients were significantly enhanced in AD when compared to MCI or CN subjects, implying that AD pathology may contribute to local background gradients. Background gradients need to be considered when interpreting DTI data in AD.