Fluctuant tonus of the coronary arteries possibly documented by repeated multidetector row computed tomography Ikuko Anan,1 Kenichi Hongo,1 Makoto Kawai,1 Kazuo Ogawa,1 Toru Sakuma,2 Kunihiko Fukuda,2 Ikuo Taniguchi,1 Michihiro Yoshimura1 1Division of Cardiology, Department of Internal Medicine, 2Department of Radiology, The Jikei University School of Medicine, Tokyo, Japan Objective: Recent advances in multidetector row computed tomography (MDCT) have made it possible to diagnose coronary stenosis with high sensitivity. However, coronary arterial tonus has not been considered when reading MDCT. We hypothesized that MDCT can document fluctuant tonus of the coronary arteries. Methods: The study population consisted of 39 consecutive patients who underwent MDCT twice in our institution with 64-row dual-source MDCT. Measurements were performed with stretched multiplanar reconstruction images using the full width at half maximum method. The coronary arteries were measured at each segment, and the same measurement was performed in the ascending aorta and the left internal thoracic artery (ITA). The percent diameter changes between the first and second measurements were examined in each segment of the coronary arteries and compared with those in the aorta or the ITA. Results: The average percent diameter changes were statistically equivalent between the coronary arteries and the aorta or the ITA. On the other hand, the percent diameter changes in distribution were significantly larger in the coronary arteries than those in the aorta or the ITA. This suggests that the diameter of the coronary arteries is liable to show variation compared to that of other arteries. Conclusion: This study confirmed for the first time that coronary arteries can fluctuate substantially and that these changes can be documented by MDCT. Changes in coronary arterial tonus should therefore be considered when reading MDCT. Keywords: coronary spastic angina, coronary arterial tonus, false positive study