Motion artifacts on chest computed tomogram

Double-contour artifacts mainly attributable to heart motion occur on chest CT when scan time was 1.0 sec, which is difficult to differentiate from bona fide lesions resulting from aortic dissection or bronchiectasis. These artifacts, usually seen on full-scan CT images, become unclear on reconstructed half-scan images. This study was thus carried out to compare the frequency of these artifacts on the full- and reconstructed half-scan CT images from 25 patients with no diagnosis of aortic dissection or bronchiectasis. Double-contour artifacts at the ascending aorta were depicted in 38 of 50 full-scan CT images (76%), and 31 of these (82%) became unclear on each reconstructed half-scan image. Double-contour artifacts of the pulmonary vessels were also shown in 20 of 75 full-scan CT images (33%) in the left lung fields and in 5 of 75 ones (7%) in the right lung fields. Blurring of the contour of the ascending aorta was depicted in 19 of 50 reconstructed half-scan images (38%), and 10 of these (53%) appeared normal in the corresponding full-scan images. Half-scan chest CT images seemed to be reasonable to obviate double-contour artifacts experienced on full-scan CT images; however, the noise levels on recontructed half-scan CT images were higher than the corresponding full-scan images. Thus a comparison of full-scan and reconstructed half-scan images in chest CT should be made to differentiate double-contour artifacts from bona fide lesions. (N.K.)