DIAGNOSIS OF AORTIC DISSECTION - VALUE OF HELICAL CT WITH MULTIPLANARREFORMATION AND 3-DIMENSIONAL RENDERING

OBJECTIVE. Twenty-three patients with suspected aortic dissection were evaluated in this preliminary study of helical CT to determine the us efulness of axial sections, multiplanar reformation, and three-dimensi onal (3D) rendering in assessing the presence of dissection and the ex tent of intimal flap. MATERIALS AND METHODS. Patients were referred fo r helical CT scanning because of chest pain or an abnormal chest radio graph. Scans were performed during bolus injection of nonionic contras t material at 2.0-2.5 ml/sec using a mean scan delay of 47 sec, Axial scans with 5-mm collimation were obtained in all patients. They extend ed from the great vessels to the distal thoracic aorta just above the hiatus. Delayed nonhelical sections were obtained through the upper ab domen. Multiplanar reformations and 3D models were reconstructed from the helical data in 13 patients and were compared to axial sections in 7 patients who proved to have documented dissection. The efficacy of CT was determined using surgery, angiography, or clinical outcome to e stablish the diagnosis. RESULTS. Of the 23 patients studied, axial sec tions resulted in 15 true-negative, 7 true-positive, and 1 false-posit ive interpretation. In three of seven patients with dissection, it was difficult to determine the extent of the intimal flap on axial sectio ns; multiplanar reformation or 3D views clarified the relevant anatomy in all 3 cases. Among the 3D display methods, ray-sum projection view s were superior to surface model or maximum-intensity-projection views . CONCLUSION. If studies of larger numbers of patients confirm our pre liminary findings, multiplanar reformation and 3D rendering of helical CT scans will be a valuable addition to axial display of CT studies u sed to detect aortic dissection and to determine the extent of the int imal flap.