Aortic intramural hematoma : can unenhanced phase be eliminated from dual-phase chest pain CT angiography protocol- implications on diagnostic accuracy

PURPOSE. To evaluate whether the elimination of unenhanced imaging acquisition series from dual-phase chest pain CT angiography protocol may affect diagnostic accuracy in the detection of Intramural Hematoma (IMH), and justify the reduced radiation dose. METHOD AND MATERIALS. From October 2006 to February 2011, 37 patients (20 males, 17 females ; mean age 65.0 years) with acute chest pain underwent emergency multi-detector CT angiography (MDCTA) and subsequent Transesophageal Echocardiography (TEE) and/or surgery for IMH. All patients underwent MDCTA with a 64-slice scanner (Somaton Definition, Siemens, Germany).Two experienced Emergency Radiologists blind-tested with regard to the diagnosis, assessed the images in two different sessions in which enhanced (single-phase MDCTA) , and combined unenhanced and enhanced (dual-phase MDCTA) findings were separately evaluated.Sensitivity, specificity and accuracy of both modalities, along with 95%CIs, were calculated by using TEE and surgical confirmation as reference standards. RESULTS. Single-phase MDCTA showed a higher number of false negative, and false positive results than did dual-phase MDCTA. For the detection of aortic IMH, the sensitivity, specificity and accuracy, respectively, were 85%, 93% and 92% for combined dual-phase MDCTA , and 51%, 77%,and 69% for single-phase MDCTA. CONCLUSION. The acquisition of unenhanced images during dual-phase chest pain MDCTA protocol provides additional benefit in terms of diagnostic accuracy over single-phase CT , and warrants the increased radiation dose. CLINICAL RELEVANCE/APPLICATION Our results suggest that unenhanced phase should not be eliminated from dual-phase chest pain MDCTA protocol.