THE DOSE DISTRIBUTION PRODUCED BY A P-32 SOURCE FOR ENDOVASCULAR IRRADIATION

Purpose: Percutaneous transluminal coronary angioplasty (PTCA) is one of the most common therapies for obstructive coronary artery disease, Unfortunately, subsequent restenosis after percutaneous balloon angiop lasty occurs in 30-50% of patients and remains one of the major unsolv ed problems of contemporary cardiology, The study of endovascular irra diation has been greatly stimulated by the discovery that the process of restenosis may be impaired by irradiation, The objective of this st udy was to examine a custom-made commercial P-32 wire and to determine whether the present source presentation is suitable for this applicat ion. Methods and Materials: Measurements of the dose distribution arou nd a 3 mm long P-32 source With an activity of 0.414 GBq (11.2 mCi) we re made by using LiF thermoluminescent dosimeters and a scintillation detector, The source had the dimensions of 0.3 mm in diameter and 3 mm in length, and was first encapsulated by a plastic tube and then enca psulated in a specially manufactured Ni-Ti wire with a diameter of 0.4 mm and a length of 2.6 m. The detector size effect is removed from th e measurements calculation, Loevinger's equation for the dose distribu tion around a P-32 source was used for the calculations. Results: The dose rate at a radial distance of 1.5 mm was 53 cGy/s per GBq (1.96 cG y/s per mCi) and fell off rapidly perpendicularly to the axis of the s ource in an approximately exponential manner, from 53-5.3 cGy/s per GB q (similar to 2 to 0.2 cGy/s per mCi) as radial distances increased fr om 0.2 to 0.4 g/cm(2) (1.5 to 3.5 mm away from the center of the sourc e), The treatment length parallel along the wire could be as long as 2 4 mm for eight source dwell positions with the average dose rate of 59 cGy/s per GBq (2.2 cGy/s per mCi) and a variation of +/-2.3% at a rad ial distance of 1.5 mm. Conclusions: Our experiments show that the dos e distribution is ideal for endovascular irradiation, The source was i ncorporated in the end of a flexible cable and with a half-life of 14. 3 days is suitable for endovascular irradiation. Copyright (C) 1996 El sevier Science Inc.