Dosimetry for an Sr90/Y90 source train used for intravascular radiation of a hemodialysis graft.

OBJECTIVE: Vascular access for hemodialysis is often achieved with an arterial-venous graft (AVG). Brachytherapy is being explored for prevention of stenosis within these grafts. The objective was to develop treatment planning (TP) capability for dialysis implants. MATERIALS AND METHODS: Fluoroscopic images are used to identify position of sources and irradiated vessel. An Sr(90)/Y(90) beta source, jacketed in a CO(2)-filled balloon, is used to irradiate the AVG. A single-seed Sr(90) dose kernel was generated using Monte Carlo. The single-seed dose kernel was employed to calculate the dose surrounding the implant accounting for the path length of the beta particles through the gas-filled balloon. RESULTS: Dose distributions are displayed superimposed on the fluoroscopic image of the AVG. Dose-area histograms were also generated. CONCLUSION: TP for dialysis implants can be performed using radiographic localization of the graft. The TP tools could be used to correlate clinical outcome with dose delivery.

Monte Carlo dose characterization of a new 90Sr/90Y source with balloon for intravascular brachytherapy.

Beta emitting source wires or seeds have been adopted in clinical practice of intravascular brachytherapy for coronary vessels. Due to the limitation of penetration depth, this type of source is normally not applicable to treat vessels with large diameter, e.g., peripheral vessel. In the effort to extend application of its beta source for peripheral vessels, Novoste has recently developed a new catheter-based system, the Corona 90Sr/90Y system. It is a source train of 6 cm length and is jacketed by a balloon. The existence of the balloon increases the penetration of the beta particles and maintains the source within a location away from the vessel wall. Using the EGSnrc Monte Carlo system, we have calculated the two-dimensional (2-D) dose rate distribution of the Corona system in water for a balloon diameter of 5 mm. The dose rates on the transverse axis obtained in this study are in good agreement with calibration results of the National Institute of Standards and Technology for the same system for balloon diameters of 5 and 8 mm. Features of the 2-D dose field were studied in detail. The dose parameters based on AAPM TG-60 protocol were derived. For a balloon diameter of 5 mm, the dose rate at the reference point (defined as r0 = 4.5 mm, 2 mm from the balloon surface) is found to be 0.01028 Gy min(-1) mCi(-1). A new formalism for a better characterization of this long source is presented. Calculations were also performed for other balloon diameters. The dosimetry for this source is compared with a 192Ir source, commonly used for peripheral arteries. In conclusion, we have performed a detailed dosimetric characterization for a new beta source for peripheral vessels. Our study shows that, from dosimetric point of view, the Corona system can be used for the treatment of an artery with a large diameter, e.g., peripheral vessel.