Dose Rate Calculations from Radioactive Vascular Stents: DPK versus exact MC approach

Vascular stents activated with radioactive isotopes are planned to be used in clinical practice to prevent restenosis in human coronary arteries after balloon angioplasty. Medical stents are cylindrical meshes and their complex geometry is usually treated for energy dose calculation with approximate dose point kernel(DPK) approach. The important point missed in the DPK approach is the absence of the stent material and, hence, the absence of energy absorption inside the stent. We have performed a comparison between DPK and exact Monte Carlo calculations for some simplified stent models. It appears that DPK approximation significantly overestimates pike dose values especially for the case of gamma-emitting sources. We suggest DPK kernel normalization, which minimizes the difference at relatively far distances, while significant discrepancies near the stent surface still remain.