Artifacts in the ascending aorta on computed tomography: another measure of aortic distensibility?

Effects of Heart Rate on Motion Artifacts of the Aorta on Non-ECG-Assisted 0.5-Sec Thoracic MDCT

OBJECTIVE

Our aim was to evaluate the effects of heart rate on aortic motion artifacts on 0.5-sec non-ECG-assisted thoracic MDCT.

MATERIALS AND METHODS

A total of 124 non-ECG-assisted thoracic MDCT scans with satisfactory simultaneous ECG data were reviewed. Scans were grouped according to patient heart rates (beats per minute [bpm]: group A, 46-55; B, 56-65; C, 66-75; D, 76-85; E, 86-95; and F > 95). The groups were compared regarding the presence, locations, and spatial distributions of pulsation artifact, number of slices affected, maximum amplitude of pulsation, continuity of artifact, and the presence of superior vena cava (SVC) pseudoflaps.

RESULTS

Of the 124 scans, 114 (91.9%) had aortic motion artifacts, with prevalence ranging from 85.3% (66-75 bpm) to 100% (65 bpm or less). Of the 114 motion artifacts, all affected the ascending aorta, 105 (92.1%) involved the left anterior and right posterior aspects of the aortic circumference, and 106 (93%) were associated with SVC pseudoflaps. Group B had significantly greater numbers of images with artifacts (p < 0.001-0.006), greater artifact amplitudes (p < 0.001-0.002), and a higher continuity trend for the artifacts (p = 0.003-0.194) than did the other five groups.

CONCLUSION

Aortic motion artifacts are frequently seen on thoracic MDCT, especially in patients with heart rates of 65 bpm or less. The presence of a SVC pseudoflap is helpful for distinguishing artifacts from dissection. If aortic disease is suspected, then measures to reduce motion artifact, such as ECG-gating, should be considered.

Fast CT for aortic dissection

Results were evaluated in 81 patients with suspected acute aortic dissection who were examined on a fast CT system capable of a 1 s data acquisition time. 17 patients had Type A and nine had Type B dissections. Radiological assessment provided 78 confident reports and expressed some uncertainty about the diagnosis in three patients. Overall sensitivity for aortic dissection was 96.2% and specificity was 96.4%. When 78 confident reports alone were considered, both sensitivity and specificity reached 100%. Reconstruction of data at 100 ms intervals allowed discrimination between artefacts in the ascending aorta and Type A dissections. CT can often be used as the single investigation prior to surgery for acute Type A dissections.

Radiological evaluation of the ascending aorta following repair of type A dissection

A patient with persistent chronic dissection proximal to an aortic interposition graft for repair of a type A dissection prompted us to review the computed tomographic (CT) findings in 14 other such patients 5-47 months after surgery. No other case of proximal aortic dissection was identified although dilatation of the aortic root proximal to the graft was present in 8 patients (57%). Persistent dissection distal to the graft in 11 patients (79%) was in keeping with that reported by other workers. Chronic dissection proximal to the surgical repair of a dissection seems a rare although important complication.