Among the challenges cardiac CT must overcome are imaging stents and bypass grafts, according to Koen Nieman, MD, PhD, of the Department of Cardiology Thoraxcenter at Erasmus Medical Center in Rotterdam, Netherlands, at the Society of Cardiovascular CT meeting in July in Arlington, Va. Other speakers at the meeting added to the list of challenges such as the current required used of beta blockers that are not effective on all patients, the small number of qualified readers available on call, its long learning curve, its use of a substantial amount of radiation (8-21 mSv) and iodinated contrast.
   
Nieman detailed difficulties in imaging stents and bypass grafts, as well as surgical materials such as vascular clips, anastosnosis markers, surgical wires, sutures and pacemaker clips. Patient and anatomic motion coupled with calcium bring on blooming artifacts that make reading difficult or impossible. Stents complicate that further because their metal is very attenuating and can cause beam hardening and shadowing. The size and type of the stent or graft is the most important foreteller of imaging success, with larger stents and grafts easier to visualize. Three to four millimeter stents are the threshold to visualization. Strut thickness and knowing the type and location of the stent are optimum. Three-D is useful in graft evaluation, he said.
   
Among the improvements Neiman said would contribute to more successful imaging are thinner stent struts, improved CT technology for more optimized image quality, dedicated filtering, non-metal stents, Dual Source CT, and flat panel CT technology, although he noted that is “still a ways off.” He sees future potential for CCTA in LM and graft intervention.