Abstract: A method and apparatus for dynamic stereotactic radiotreatment and prevention of restenosis. A stent is implanted in a coronary artery, following percutaneous transluminal coronary angioplasty. Subsequent restenosis is minimized by external irradiation of the stent by ionizing radiation such as gamma rays. The fact that the stent is significantly more opaque to x-rays than the surrounding tissue is exploited to track the stent using fluoroscopy, so that the ionizing radiation can be aimed accurately at the stent. Preferably, the fluoroscopic imaging and the irradiation of the stent are synchronized with the patient's cardiac cycle. The external irradiation may be performed hours or days after implanting the stent, for prevention of restenosis, or weeks or months after implanting the stent, for treatment of restenosis, and may be fractionated.