Dosimetry of a radioactive coronary balloon dilatation catheter for treatment of neointimal hyperplasia.

Abstract

Recent reports suggest that intraluminal irradiation of coronary arteries in conjunction with balloon angioplasty reduces proliferation of smooth muscle cells and neointima formation, thereby inhibiting restenosis. One possible irradiation technique is to inflate the balloon dilitation catheter with a radioactive solution. This has advantages over other proposed irradiation procedures, in that accurate source positioning and uniform dose to the vessel wall are assured. Several high-energy beta-minus emitters may be suitable for this application. We present experimental measurements and analytical calculations of the dose distribution around a 3-mm-diam by 20-mm-long balloon filled with 90Y-chloride solution. The dose rate at the surface of the balloon is approximately 0.14 cGy/s per mCi/ml (3.78 x 10(-11) Gy/s per Bq/ml), with the dose decreasing to 53% at 0.5 mm, and < 5% at 3.5-mm radial distance. 90Y and other possible isotopes are currently available at specific concentrations > or = 50 mCi/ml (1.85 x 10(9) Bq/ml), which enables the delivery of 20 Gy in less than 5 min. The dosimetric and radiation safety advantages of this system warrant further feasibility studies. Issues of concern include incorporating the beta-emitter into a suitable chemical form, and assessing organ and whole body doses in the (< 1 in 10(3)) event of balloon failure.