In cases of bleeding or vascular malformations, occlusion devices can be used, which may prevent dangerous surgery. Because these invasive procedures require the insertion of catheters or other instruments into the body, they entail a certain amount of discomfort and also carry more risk than noninvasive studies. Possible complications include bleeding at the site where the instrument is inserted, an allergic reaction to the contrast medium, occlusion or perforation of a blood vessel, and in rare instances, a stroke or heart attack. For this reason, invasive procedures are usually carried out in a hospital or other clinical setting where nursing and other emergency medical services are readily available. They also should be performed by a physician and staff who have had special training in the procedures.
Invasive procedures tend to be more costly than other imaging studies.
Because of this and their increased risk of complications, doctors generally order them only after other tests have failed to provide the necessary information. And there are instances in which the information they yield cannot be obtained any other way. For example, cardiac catheterization and arteriography are essential preliminary tests performed before coronary bypass surgery. In a growing number of invasive procedures, a radiologist may double as a therapist. For example, in cases in which a patient may require long-term intravenous therapy, a radiologist may be asked to insert an infusion catheter that can be used to administer antibiotics or cancer chemotherapy.