Can the unenhanced phase be eliminated from dual-phase CT angiography for chest pain? Implications for diagnostic accuracy in acute aortic intramural hematoma.

Objective: The purposes of this study were to retrospectively assess the frequency of acute aortic intramural hematoma and evaluate whether the elimination of the unenhanced imaging acquisition series from the dual-phase MDCT angiography (CTA) protocol for chest pain might affect diagnostic accuracy in detecting intramural hematoma and justify the reduced radiation dose.

Materials And Methods: From October 2006 to November 2012, 306 patients (mean age, 65.0 years) with acute chest pain underwent emergency CTA with a 64-MDCT scanner. Two experienced cardiovascular radiologists, blinded to the diagnosis, assessed the images in two different sessions in which enhanced (single-phase CTA) and combined unenhanced and contrast-enhanced (dual-phase CTA) findings were evaluated. Sensitivity, specificity, and accuracy along with 95% CIs were calculated. Surgical and pathologic diagnoses, including findings at clinical follow-up and any subsequent imaging modality, were used as reference standards.

Results: Thirty-six patients were suspected of having intramural hematoma; 16 patients underwent both surgery and transesophageal echocardiography (TEE), and the remaining 20 underwent TEE. Single-phase CTA showed a higher number of false-negative and false-positive results than dual-phase CTA. With intramural hematoma frequency of 12% (95% CI, 8.38-15.91%), sensitivity, specificity, and accuracy were 94.4% (81.3-99.3%), 99.3% (97.4-99.9%), and 98.7% (96.7-99.6%) for combined dual-phase CTA and 68.4% (51.4-82.5%), 96.3% (93.2-98.2%), and 92.8% (89.3-95.4%) for single-phase CTA. Dual-phase was significantly better than single-phase CTA with respect to sensitivity (p=0.002), specificity (p=0.008), overall accuracy (p<0.001), and interrater agreement (p=0.001).

Conclusion: The frequency of acute aortic intramural hematoma is similar to that previously reported. The acquisition of unenhanced images during the chest pain dual-phase CTA protocol significantly improves diagnostic accuracy over single-phase CTA.