Dual Energy Subtraction Angiography: A Simulation Study Using the Three Material Approach

Abstract

The purpose of this study was to evaluate a theoretical model describing the attenuation of X-rays under conditions found in angiographic applications and to develop a dual energy algorithm for either cancellation or enhancement of the visualization of soft tissue, bones, and iodine, which is used as a contrast agent, in the final image. Most dual energy reconstruction algorithms assume that the irradiated parts of the human body consist of two types of material. In the present study, the three-material approach is presented in order to remove from the final image not only one of the materials referred above, but also combinations of them by weighting subtraction of high and low energy images. The three-material algorithm was evaluated for a software phantom consisting of Plexiglas, hydroxyapatite - which simulate soft tissue and bone, respectively - and iodine, being irradiated in a variety of exposure conditions. Dual energy images are presented comparing the three-material with the two-material algorithm. Results showed that using the three-material approach, the weighting factors differ significantly than the two-material, thus leading to successful nullification of soft tissue and bones and high contrast Iodine visualization. Suggested recommendations for optimal dual energy imaging exposure conditions and implementation are also provided. The three-material approach for dual energy image reconstruction seems to be a more effective algorithm, when using the weighting subtraction, than the twomaterial technique. This method can be used in order to improve the existing techniques of dual energy angiography.