AORTIC MOTION - A POTENTIAL PITFALL IN CT IMAGING OF DISSECTION IN THE ASCENDING AORTA

Objective: Artefacts complicate the diagnosis of thoracic aortic disse ction by CT. Aortic compliance and cardiac motion may be responsible b ut the precise cause of these artefacts remains unclear. Materials and Methods: Fifty consecutive clinical thoracic CT examinations performe d on a Siemens Somatom Plus scanner (8 mm slice thickness, 1 s scan ti me) were reviewed (mean patient age 56 years). For each examination, t he presence, position, and displacement of motion artefact from the ao rtic wall were noted at three ascending aortic levels. Cine ultrafast CT on 10 volunteers (mean age 49 years) was used to assess aortic moti on for the same three levels (8 mm slice thickness, 50 ms scan time). Digital subtraction of consecutive cine CT allowed the position of the aortic wall throughout the cardiac cycle to be tracked. Results: Curv ilinear motion artefacts were seen in the ascending aorta in 17 conven tional CT scans, occurring left anterior and right posterior in all bu t one and maximally at the aortic root (mean amplitude 3.5 mm). Ultraf ast CT, however, showed no motion artefact and no significant change i n aortic area with systole. Aortic motion in the sagittal-oblique plan e at the ascending aorta was confirmed. Conclusion: Motion artefacts s imulating ascending aortic dissection occur frequently on conventional CT. Their position is predictable and is related to systolic aortic m otion from the left anterior to the right posterior position.