Friedrich D. Knollmann MD, PhD, Presenter: Nothing to Disclose

Iclal Ocak MD, Abstract Co-Author: Nothing to Disclose

In the work up of acute aortic syndromes, non contrast CT  prior to aortic CTA  is a widely accepted standard. The scientific evidence for this practice stems from single row CT with thick slices and without EKG synchronisation. The non contrast series is required to diagnose intramural aortic hematoma (IMH), wihch may escape detection, or be difficult to differentiate from atherothrombotic wall changes, on the CTA series. With increasing concerns regarding radiation exposure, the incremental benefit of the non contrast series should be analysed.

A data base search of imaging reports from the last ten years was performed to identify all CT reports on aortic syndrome, aortic dissection, and IMH.  Images underlying the reports that discussed IMH were reviewed, and the patients'  further course observed. The CTA series were reviewed by two expert readers, who were presented with the non contrast series only in a second step. The incremental diagnostic benefit of the non contrast series was assessed by comparing the diagnostic confidence after reading the CTA series only with that after inclusion of  the non contrast series.

Over a ten year period, 1206 reports considered aortic dissection, while only 102 discussed a possible diagnosis of an IMH. Of these, 20 were confirmed,  including 4 studies that were evaluated as false positive in retrospect, and displayed either postoperative mediastinal hematoma, or aortic dissection. None of the 20 studies had a normal CTA portion, but the non contrast series increased the confidence in 10. In one case, the non contrast series was essential to identify IMH and arrive at the diagnosis of a penetrating aortic ulcer. No follow up study of those who were initially diagnosed as normal evolved into any aortic complications subsequently.

In the era of thin slice multi detector row CT, the vast majority of patients presenting with a suspicion of an acute aortic syndrome has normal CT findings, and no cases of an IMH could be found in our series that showed normal findings on the CTA series. Substantial savings in radiation dose could be achieved if patients with a suspected acute aortic syndrome were examined with a single CTA series, and only patients with suspicious CTA findings re assessed later.  

The routine use of a non contrast CT series preceding CTA for evaluating possible acute aortic syndromes has a low incremental diagnostic yield.

Knollmann, F, Ocak, I, Role of the Noncontrast CT Series in Acute Aortic Syndromes.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11006204.html