The double-fissure sign: a motion artifact on thin-section CT scans

A motion artifact has been observed that may affect the number of fine interstitial lines seen at thin-section (1.5-mm-collimation) computed tomography (CT) for the evaluation of interstitial lung disease. In 14 of 42 patients, one or both major fissures appeared as two parallel lines rather than as a single line. This was more common in the left lung base. Using a phantom, the authors were able to reproduce the phenomenon by simulating cardiac motion. Therefore, this motion may lead to an artifactual increase in the number of interstitial lines.