Cervical and Cranial Computed Tomographic Angiography With Automated Bone Removal

OBJECTIVE: In supraaortic vessels, bone subtracted maximum intensity projections make the evaluation of computed tomographic angiography (CTA) datasets easier and faster. Dual energy CT can be used for bone removal without user interaction. The purpose of this study was to compare the results of conventional and dual energy-based bone removal. MATERIALS AND METHODS: Dual energy CT angiography of the supraaortic vessels was acquired in 30 patients at 140 and 80 kVp tube potential simultaneously. Thick images of 0.75 mm were reconstructed from both datasets, and an additional weighted average dataset using information from both tubes was calculated. Two readers independently assessed vessel delineation, completeness of bone removal, and vessel preservation, as well as adequacy for diagnostic evaluation after dual energy-based bone removal (DEBR) and conventional bone removal (CoBR). The Student t test and Wilcoxon rank sum test were applied to test differences between data for significance. Cohen's kappa-test was used to calculate the interobserver agreement. RESULTS: Of dual energy datasets DEBR 88.3% were rated as adequate for diagnostic evaluation compared with only 6.7% with CoBR, P < 0.001. Of DEBR (35%) contained all vessels and no bony structures, whereas all diagnostic CoBR still contained residual bone and showed partial vessel truncations. Vessel delineation was rated significantly better with DEBR. DEBR profited from stronger vascular enhancement, whereas it had no significant influence on CoBR. Reading times were 173 +/- 55 seconds with DEBR and 253 +/- 12 seconds with CoBR, P < 0.001, which corresponds to a reduction of 32%. Comparison of dual energy CTA versus single energy CTA showed a dose reduction of 29.0% to 43.7%. CONCLUSIONS: Dual Energy-based bone removal can remove bony structures from supraaortic CTA datasets without time-consuming user interaction. This leads to a significant reduction of reading time, radiation dose and improved vessel delineation.