Dose conversion coefficients for interventional procedures

Effective dose (E) is a convenient quantity to estimate the stochastic risk of radiation applied to patients in interventional procedures and can be used for optimisation. Relatively long exposure times may cause deterministic effects. Hence it is necessary to know the (maximum local) doses in organs owing to the interventional procedure. In practice, organ doses cannot be measured directly. They are derived by applying a conversion coefficient to a measurable quantity, e.g. dose-area product (DAP) or entrance skin dose. For a number of interventional procedures, dose conversion coefficients (DCCs) can be found in the literature. Various DCCs are stated for nominally equal procedures, e.g. for percutaneous transluminal coronary angioplasty both 0.18 and 0.27 mSv Gy(-1) cm(-2) were reported to convert DAP to effective dose. Dependence of DCC on protocol and equipment parameters, as demonstrated through Monte Carlo simulation in this paper, makes it hazardous to simply adopt a literature value.