Dual energy bone subtraction in computed tomography angiography of extracranial-intracranial bypass: feasibility and limitations.

OBJECTIVES

To assess the feasibility of dual energy (DE)-CTA images with DE-bone removal (DEBR) for visualization of extra- to intracranial (EC/IC) arterial bypass compared to digital subtraction angiography (DSA).

MATERIALS AND METHODS

Prospectively, 24 patients underwent DE-CTA and DSA for evaluation of EC/IC-bypass. Using 5-point scales (0=poor to 4=excellent) two examiners rated image quality, quality of bone removal, and vessel integrity of bypass for three segments (extracranial, trepanation, intracranial) in CTA images with and without DEBR in comparison to DSA. Scores were evaluated by Friedmann's- and post-hoc Wilcoxon rank test.

RESULTS

Image quality was high in CTA with and without DEBR and DSA (3.78 ± 0.36, 3.78 ± 0.36, 3.27 ± 0.46). No significant bone remnants were present using DEBR. Mean scores of bypass visualization were not significantly different for the extra- and intracranial segments. However, in the trepanation segment pseudo-lesions of the bypass were present in DEBR-CTA (6 out 24 cases) with a negative effect on visualization scores compared to DSA (p < 0.05).

CONCLUSION

CTA with DEBR for assessment of EC/IC-bypass is feasible with reliable removal of cranial bones. Readers should be aware of a potential pitfall showing focal pseudostenosis/-occlusion of the bypass close to bone at the trepanation margin.