Comparison of split bolus dual energy CT and standard multiphase CT in assessing vascular invasion in patients with...

To compare the image quality, definition of vascular invasion and radiation dose of split bolus dual energy CT (DECT) with standard multiphase CT in biliary malignancies.

This prospective study performed from December 2020 to November 2022 included 88 patients of biliary malignancies randomized into two groups and scanned on rapid-switching dual energy CT scanner. Group 1 (n = 43, mean age: 54.6 years, 12 males) underwent the standard multiphase protocol (MPP; arterial, venous phases), while group 2 (n = 45, mean age: 52.6 years, 20 males) underwent split bolus dual-energy protocol (SBP; split-bolus phase). The mean attenuation, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of tumor, liver and hepatic vessels were measured and compared between the two groups along with dose-length product. Two readers independently assessed image quality and vascular invasion (5-point Likert scale) in each phase and inter-reader agreement was compared within groups. Mann Whitney U-test and kappa statistics were used for comparison.

The mean attenuation, CNR and SNR of arteries were significantly higher in the arterial phase of group 1 and significantly lower in the venous phase of group 1 than the SBP of group 2 (p < 0.001). The quantitative parameters of veins and tumor between venous phase (group 1) and SBP (group 2) were comparable. Good-to-strong inter-reader agreement (k = 0.45 to 0.75) for image quality for both protocols was observed. For hepatic arterial invasion, the SBP had significantly higher inter-reader agreement compared to the arterial phase of MPP (p < 0.001). The SBP had a 37% lower radiation dose than the MPP (p < 0.001).

The image quality of SBP was non-inferior to the standard MPP for biliary malignancies. However, SBP showed significantly better inter-observer agreement for arterial invasion indicating better assessment of vascular involvement with significantly lower radiation dose.

Biliary malignancies are better defined in the venous phase in which arteries are indistinct, making arterial invasion assessment tough. SBP overcomes this by clearly depicting arteries and tumor in the same phase for confident assessment.