Different Spiral CT protocol types and their significance in the diagnosisof aortic dissections: results of a prospective study.

Purpose: Development of an optimized Spiral CT protocol type for the diagno sis of aortic dissections. Material and Methods: 121 consecutive CT examina tions applying 5 different protocol types were blindly read by two experien ced radiologists and then compared with: (a) 45 biplane transesophageal ech ocardiographies (TEE), (b) 52 transthoracic echographies (TTE), (c) 52 oper ative findings and, furthermore, related to the clinical course over at lea st six months in 79 patients. Results: The sensitivity of the spiral comput ed tomography for detection of dissection was 97% (biplane TEE: 88%), the s pecificity 100% (biplane TEE: 91%). In 15% dissections with atypical origin and entries (mid-portion of the aortic arch, distal thoracic aorta, etc.) were found. The optimal CT-protocol was the one with a combination of two s eparate but adjacent spiral scans achieving high spatial resolution for the aortic arch and enough spatial resection for the residual aorta (1. helica l scan 3 mm collimation, pitch 2. 2. helical scan 5 mm collimation and pitc h 2, 130 ml contrast medium at 5 ml/s) with a classification accuracy of 10 0%, visualization of entries of 100%, reentries of 100% (40% direct, 60% in direct). The identification of the ostia of the aortic branches were: supra aortic 93%, visceral 100%, left renal artery 100%, right renal artery 93%, iliac 64%. The CT angiography, designed as aortic arch angiography, showed a good contrast in the aortic arch vessels (79-86%) and the visceral vessel s too (91%). Conclusion: Thoracic CT angiography can be used as gold standa rd in the primary evaluation of aortic dissections.