DOSIMETRY OF A RADIOACTIVE CORONARY BALLOON DILITATION CATHETER FOR TREATMENT OF NEOINTIMAL HYPERPLASIA

Recent reports suggest that intraluminal irradiation of coronary arter ies in conjunction with balloon angioplasty reduces proliferation of s mooth muscle cells and neointima formation, thereby inhibiting resteno sis. One possible irradiation technique is to inflate the balloon dili tation catheter with a radioactive solution. This has advantages over other proposed irradiation procedures, in that accurate source positio ning and uniform dose to the vessel wall are assured. Several high-ene rgy beta-minus emitters may be suitable for this application. We prese nt experimental measurements and analytical calculations of the dose d istribution around a 3-mm-diam by 20-mm-long balloon filled with Y-90- chloride solution. The dose rate at the surface of the balloon is appr oximately 0.14 cGy/s per mCi/ml (3.78x10(-11) Gy/s per Bq/ml), with th e dose decreasing to 53% at 0.5 mm, and <5% at 3.5-mm radial distance. Y-90 and other possible isotopes are currently available at specific concentrations greater than or equal to 50 mCi/ml (1.85x10(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 feasib ility studies. Issues of concern include incorporating the beta-emitte r into a suitable chemical form, and assessing organ and whole body do ses in the (<1 in 10(3)) event of balloon failure. (C) 1996 American A ssociation of Physicists in Medicine.