Personnel exposure during gamma endovascular brachytherapy

Purpose: The use of 192 Ir brachytherapy for the treatment of in-stent restenosis of the coronary arteries has shown promising clinical results. This paper investigates the radiation exposure of catheterization laboratory staff associated with the performance of this procedure. Methods and Materials: Cath lab staff were monitored using personal monitors (shielded against fluoroscopic x-rays) during the performance of eleven cases using nominal 10 GBq 192 Ir sources. Staff positions in the lab were simultaneously tracked by video cameras. Direct measurements were also made using a survey meter. Treatments were administered in a conventional cardiac-catheterization-laboratory. Results: The dosimeter readings were analyzed in combination with the radiation survey and time motion survey. Brachytherapy procedural times for the cardiologist, oncologist, physicist, and angiographic assistants were, respectively, 26 ± 24, 401 ± 132, 486 ± 148, and 7 ± 13 s per case (mean ± standard deviation). Readings of the personnel monitors were low. Credible upper limits of the respective doses are estimated to be less than 10, 10, 7, and 5 μSv per procedure. Auxiliary shields reduced the dose to individuals located outside of the catheterization laboratory to less than 0.5 μSv per procedure. Conclusions: The average radiation dose received by laboratory personnel during a representative 192 Ir endocoronary brachytherapy procedure is estimated to be less than 0.1% of the NCRP recommended annual radiation worker's Maximum Permissible Dose (1% of the general public's MPD). This level is justifiable as long as the use of 192 Ir benefits patients by producing an improved clinical outcome relative to the use of a less penetrating radionuclide or the application of alternative therapies. Further optimization of the delivery procedure is expected to reduce staff dose.