Comparing visualization performance of liquid embolic agents using a novel injectable phantom.

Background: Radiographic visualization of liquid embolic agents (LEAs) during embolization procedures in neurovascular territory represents a crucial feature to ensure efficacy and safety for the patients during endovascular treatment of arteriovenous shunting lesions. Radiopacity of available LEAs varies significantly and limited methods are currently available for comparison. The purpose of this study was to compare the contrast resolution (CR) during injection under blank roadmap of various LEAs, as well as standard contrast material.

Methods: An injectable angiographic phantom was designed consisting of parallel tubings between 313 and 1000 micron. Under roadmap, eight radiopaque liquid agents were injected and analyzed: Onyx18^®, 34^® Squid^®12, 18, PHIL^®25% (PHIL^®25), PHIL^®30% (PHIL^®30).Trufill^TM (NBCA), 30% dilution and Omnipaque^®300. CR was evaluated as a contrast to noise ratio (CNR) and calculated as mean peak signal (Sa) minus mean background signal (Sb) divided by the standard deviation of the background signal (Std) $(CNR=\frac{Sa-Sb}{Std})$.

Results: Omnipaque 300 and NBCA were found to have the highest CR. PHIL^®25 demonstrated the lowest CNR (45% of Omnipaque CNR). Onyx 18 and 34 (Both around 82% of Omnipaque CNR) demonstrated higher CNR compared to Squid^®12 and 18 (52-55% of Omnipaque CNR). On average, at 500 micron there is a >70% reduction in CNR, and at 313 micron there is a 90% reduction in CNR compared to 1000 micron.

Conclusions: Significantly different CNR between most LEAs and iodinated contrast media was evident under roadmap conditions and should be considered prior to injection.