Radiation doses in extracorporeal shock wave lithotripsy

Patients undergoing lithotripsy on the Siemens Lithostar system are exposed to radiation in three modes: film radiography, electronic radiography and fluoroscopy. Radiation exposure techniques (kVp, field size, number of exposures and projection) were recorded for the first 125 patients undergoing treatment on a recently installed Lithostar unit at a Winnipeg hospital. These data were then used in conjunction with phantom-based radiation dose measurements to calculate entrance skin dose and total energy imparted for each patient. Values of 142 mGy and 53 mJ, respectively, were found. In the case of energy imparted, 20% of the total arose from film radiography, 30% from electronic radiography and the remaining 50% from fluoroscopy. The estimated effective dose-equivalent, HE, to the average patient undergoing lithotripsy was 0.75 mSv. This corresponds to an estimated radiation risk for the induction of fatal cancers and genetic defects (in the first two generations of offspring) of between 5 and 11 per million.