Radiation Redux for Coronary CT Angiography: How Low Can We Go?

Abstract

647 construction is computationally intensive and thus for many years was not suitable for CT because of the inability to reconstruct images based on the large amount of CT projection data in a timely fashion. With advancements in computing power, iterative reconstruction techniques can now be applied to CT and, in fact, a blend of both iterative reconstruction and FBP may be used. This issue of the American Journal of Roentgenology features two articles by Leipsic et al. [2, 3] on the use of iterative reconstruction for coronary CTA, a technique with substantial implications for radiation dose reduction. The first article explores different blends of FBP and iterative reconstruction. With adaptive statistical iterative reconstruction (ASIR, GE Healthcare), the vendor implementation of iterative reconstruction used in the authors’ study, it has been recognized that CT images reconstructed with 100% ASIR, which allows the largest reduction of noise and radiation, can manifest a “plastic” quality that is displeasing to interpreters. The authors found that the best image quality scores were obtained using 40% or 60% ASIR. In the second article, they assessed 574 patients from three institutions, of whom 331 underwent scanning with FBP reconstruction and the remainder with ASIR using similar gating, kVp, and scan length. There was a 27% reduction in radiation dose without an adverse effect on signal, noise, and signal-to-noise ratio. There are some limitations to the study, including the use of only a single interpreter and the lack of blinding to the type of protocol. These studies signal an important advance in managing radiation dose for patients undergoing coronary CTA. A major advantage of iterative reconstruction is that it is supplemental to other radiation reduction techniques, and thus it is not necessary to compromise on the choice of protocol. Moreover, in patients with borderline image quality due to noise for Radiation Redux for Coronary CT Angiography: How Low Can We Go?