The Monte Carlo-Based Dosimetry of Beta Emitters for Intravascular Brachytherapy
Intravascular brachytherapy (IVBT) is a new radiotherapy modality to prevent restenosis (re-blockage of the coronary artery) following interventional coronary angioplasty. It is estimated that the restenosis rate may drop from {approx}35 to 40% to well below 10% if radiation is delivered to the obstruction site during or after angioplasty. In traditional brachytherapy, the dose is typically specified at 1 cm from the source, and the effects of low-energy photons and secondary electrons are essentially ignored. In IVBT, however, the entire lesion may be 1 to 3 mm in thickness. A better understanding of dosimetry in the millimetre range will help in the development of optimum clinical devices and their efficacious use in different institutions using different radionuclides and devices. The actual treatment geometry consists of an encapsulated train of seeds, a guide wire, and a stent in a curved vessel. The source is a cylindrical train of 12 source seeds, each having dimensions of 0.64 mm in diameter and 2.5 mm in length, and proximal/distal gold markers. Each seed contains {sup 90}Sr/Y mixed with fired ceramic encapsulated in a 0.04-mm stainless steel wall. The Monte Carlo simulations are carried out for the trained source geometries in the linear and curved vessels with and without a stent. The stent structure is approximately modeled as a set of tori with a rotational radius of 1.92 mm from the source axis and a circular radius of 0.08 mm in cross section. Five tori are equally spaced for each seed. The stent shadows 31% of the total area of the source surface. The total activity of 70 mCi (2.59 x 10{sup 9} Bq) was chosen from manufacturer data. The corresponding mass fraction of {sup 90}Sr/Y in the source ceramic is negligible and was not explicitly included in the MCNP simulations. All tallies were multiplied with 5.83 mCi/seed x 3.7 x 10{sup 7} s/mCi for one active seed, and then the tallies that made contributions to the dose in a voxel of interest were summed over to obtain the actual dose for the total activity.
- Research Organization:
- Purdue University, West Lafayette, IN (US); Medical College of Ohio, Toledo, OH (US)
- Sponsoring Organization:
- US Department of Energy (US)
- OSTI ID:
- 785342
- Report Number(s):
- ISSN 0003-018X; CODEN TANSAO; ISSN 0003-018X; CODEN TANSAO; TRN: AH200132%%119
- Resource Relation:
- Conference: 2001 Annual Meeting, Milwaukee, WI (US), 06/17/2001--06/21/2001; Other Information: Transactions of the American Nuclear Society, volume 84; PBD: 17 Jun 2001
- Country of Publication:
- United States
- Language:
- English
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