cost around $1,000 to 3,000 each (us 2004 dollars), the drug coated ones being the more expensive. advances in catheter-based physical treatments interventional procedures have been plagued by restenosis due to the formation of endothelial tissue overgrowth at the lesion site. restenosis is the body's response to the injury of the vessel wall from angioplasty and to the stent as a foreign body. as assessed in clinical trials during the late 1980 and 1990s, using only balloon angioplasty (poba, plain old balloon angioplasty), up to 50% of patients developed significant restenosis; but that percentage has dropped to the single to lower two-digit range with the introduction of drug-eluting stents. sirolimus, paclitaxel, and everolimus are the three drugs used in coatings which are currently fda approved in the united states. as opposed to bare metal, drug-eluting stents are covered with a medicine that is slowly dispersed with the goal of suppressing the restenosis reaction. the key to the success of drug coating has been (a) choosing effective agents, (b) developing ways of adequately binding the drugs to the stainless surface of the stent struts (the coating must stay bound despite marked handling and stent deformation stresses), and (c) developing coating controlled release mechanisms that release the drug slowly over about 30 days. one of the newest innovations in coronary stents is the development of a dissolving stent. abbott laboratories has used a dissolvable material, polylactic acid, that will completely absorb within 2 years of being implanted. alternative approaches angiography (left) and ct (middle and right) of chronic total occlusion lesions at the left anterior descending coronary artery (lad) and right coronary artery (rca). ct angiography can act as a less invasive alternative to catheter angiography. instead of a catheter being inserted into a vein or artery, ct angiography involves only the injection of a ct-visible dye into the arm or hand via an iv line. ct angiography lowers the risk of arterial perforation and catheter site infection. it provides 3d images that can be studied on computer, and also allows measurement of heart ventricle size. infarct area and arterial calcium can also be observed (however those require a somewhat higher radiation exposure). that said, one advantage retained by catheter angiography is the ability of the physician to perform procedure such as balloon angioplasty or insertion of a stent to improve blood flow to the artery. radiation dosage angiography imaging in coronary angiograms is performed via fluoroscopy using x-rays, which pose a potential for increasing the patient's risk of radiation-induced cancer. the risk increases with the exposure time, consisting of 1) time guiding the probe into and out of the heart and 2) time illuminating the contrast agent to perform the angiogram. absorbed radiation is also a function of body mass index, with obese patients having twice the dose of normal-weight patients; exposure to the operator was also doubled. coronary angiograms can be done either transradial (through the wrist) or transfemoral (through the groin). the transradial route results in somewhat greater patient and operator exposure. overall, patient exposure can range from 2 millisieverts (equivalent of about 20 chest x-ray plates) to 20 millisieverts. for a given patient, exposure can vary within an institution and between institutions by up to 121%. radiation exposure to the operator can be reduced by the use of protective equipment. exposure to the patient can be reduced by minimizing fluoroscopy time.