Abstract

Purpose: The aim of this study was to quantitatively assess the conspicuity of extravasated contrast-enhanced blood on 40 keV virtual monoenergetic images (VMI) and quantitative iodine density images at various slow bleeding rates in an arterial phase GI bleeding phantom.

Methods: Peristaltic extravasation of simulated contrast-enhanced blood (CT number: 400 HU at 120 kVp; viscosity: 3.5 Centipoise) at bleeding rates 0.04-0.36 mL/min was investigated. The conspicuity of extravasated contrast of SECT and 40 keV VMI of DECT was measured based on their respective CT attenuations and CNRs. Quantitative iodine density of DECT was measured to corroborate the findings of 40 keV VMI.

Results: At the bleeding rate of 0.36, 0.16, 0.09, 0.07, and 0.04 mL/min, the CNRs of 40 keV VMI were 8.66±3.71, 6.56±2.35, 6.77±2.10, 5.27±1.46, and 6.50±0.21, respectively, compared to 4.95±2.20, 4.21±0.85, 5.35±1.87, 3.83±0.95, and 4.72±0.93, respectively, for SECT. However, with the decrease of bleeding rate from 0.36 to 0.04 mL/min, the CNRs of 40 keV VMI decreased by 24.9%, compared to a decline of merely 4.6% of SECT. The average iodine density of extravasated contrast was 1.2 mg/cm3.

Conclusion: 40 keV VMI images significantly improve the conspicuity of GI bleeding in a phantom model. The significant loss of CNR at bleeding rates <0.36 mL/min, when compared with SECT, warrants attention and further study to assess DECT’s efficacy at slow GI bleeding patients. Iodine density quantification can be used to objectively measure contrast extravasation.