Internal dosimetry for radiation therapy in coronary arteries

Acute myocardial infarction, which occurs because of the occlusion of one or more coronary arteries, is the most common form of cardiovascular disease. Balloon angioplasty is often used to treat coronary artery occlusion and is less invasive than surgery involving revascularisation of the myocardium, thus promising a better quality of life for patients. Unfortunately, the rate of re-stenosis after balloon angioplasty is high (approximately 30-50% within the first year after treatment). Intravascular radiation therapy has been used with several types of radiation source, and researchers have observed some success in decreasing the rate of re-stenosis. In this paper theoretical radiation dose distributions for monoenergetic electrons (with discrete energies) and photons are calculated for blood vessels of diameter 1.5, 3.0 and 4.5 mm with balloon and wire sources using the radiation transport code MCNP4B. Stent sources employing 32P are also simulated. Advantages and disadvantages of the radionuclides and source geometries are discussed, as well as issues regarding possible benefits to the patients.