Department of Radiology and Medical Imaging, University of Virginia Health System, 1215 Lee St, Box 800170, Charlottesville, VA 22908.
The objective of our study was to evaluate the diagnostic performance of dual-source dual-energy CT (DECT) in the detection of endoleaks after thoracic endovascular aortic repair for thoracic aortic aneurysm and to investigate if a double-phase (arterial and dual-energy late delayed phase) or a single-phase (dual-energy late delayed phase) acquisition can replace the standard triphasic protocol.
All DECT examinations performed for evaluation after thoracic endovascular aortic repair during a 30-month period were retrospectively reviewed. An initial single-source unenhanced acquisition was followed by a single-source arterial phase acquisition and a dual-energy 300-second late delayed phase acquisition. "Virtual noncontrast images" were generated from the dual-energy acquisition. Two independent and blinded radiologists evaluated the cases during three reading sessions: session A (triphasic protocol: standard unenhanced, arterial phase, and late delayed phase), session B (virtual noncontrast and late delayed phase), and session C (virtual noncontrast, arterial phase, and late delayed phase). The diagnostic accuracies of sessions B and C were calculated using session A as the reference standard. Contrast-to-noise ratios and effective radiation doses were calculated.
Forty-eight patients (mean age, 66 years; age range, 19-84 years) underwent 74 triple-phase CT examinations. The single-phase studies (session B) were characterized by 85.7% sensitivity, 100% specificity, 100% negative predictive value (NPV), and 94.6% positive predictive value (PPV). The dual-phase study (session C) revealed 100% sensitivity, 100% specificity, 100% NPV, and 100% PPV. The use of the dual-phase protocol and single-phase protocol resulted in a radiation exposure reduction of 19.5% and 64.1%, respectively.
Virtual noncontrast and late delayed phase images reconstructed from a single DECT acquisition can replace the standard triphasic protocol in follow-up examinations after thoracic endovascular aortic repair, thereby providing a significant dose reduction.