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Abstract The displacement of the right coronary artery (RCA) origin with respiratory position was determined relative to the dome of the right hemidiaphragm in three orthogonal directions in eight healthy subjects. Both multiple breath‐hold and free‐breathing acquisitions were used, and motion correction factors for slice‐following applications were determined. The correction factors for all three directions showed considerable intersubject variability. The mean superior‐inferior factor was slightly less in free‐breathing than in breath‐holding (0.26 vs . 0.29, P = ns), and much less than the fixed value of 0.6 frequently implemented with slice‐following. The anterior‐posterior correction factors were uniformly low in free‐breathing, and significantly less than those obtained from breath‐holding (0.04 vs. 0.14, P < .05), while the mean left‐right correction factors were approximately 0.1 for both. It is concluded that subject variability in correction factors, together with within‐subject differences between breath‐holding and free‐breathing, is such that slice‐following should be performed with subject‐specific factors determined from free‐breathing acquisitions. Magn Reson Med 47:476–481, 2002. © 2002 Wiley‐Liss, Inc.
Keegan et al. (Wed,) studied this question.