Image-guided intravascular brachytherapy dose escalation

Purpose: Coronary stents reduce IVBT radiation dose with a single layer by 10-30%. However, the impact of multiple stent layers and stent expansion remains unexplored. Individualized dose adjustments considering variations in stent layers and expansion could improve radiation delivery effectiveness.

Methods: EGSnrc was used to compute the delivered vessel wall dose in various IVBT scenarios. Stent effects were modeled for the stent density of 25%, 50%, and 75% with 1, 2, and 3 layers respectively. Doses were calculated at 1.75 to 5.00 mm away from the source center, normalized to 100% at 2 mm.

Results: Dose fall-off increased with increasing stent density. With a single layer, the dose at 2 mm from source fell from 100% of prescription to 92%, 83% and 73% at 25%, 50% and 75% density, respectively. The computed dose to points with increasing radial distance from the source decreased progressively with increasing stent layers. With three layers, at 75% stent density, the dose at 2 mm from source center fell to 38%.

Conclusions: A schema for image-guided IVBT dose adjustment is described. While it would be an improvement over current standard of care, myriad factors remain to be addressed in a comprehensive effort to optimize IVBT.