These are specialists of medicine who are highly trained to read and interpret X-rays of the body. These physicians are referred patients either as outpatients or in the hospital to help in the medical or surgical evaluation of patients. They prepare reports to the referring physic to help them diagnosis and treatment plan. Additional techniques of evaluation include ultrasound, CAT or MRI-scans. In addition, special invasive procedures may be performed in which dyes may be injected into arteries or veins to allow better visualization of body structures. The radiologist also provides interventional care and may catheterize arteries, perform angioplasty to expand and dilate the vessel lumens to improve blood flow. Some radiologists are especially trained to place thing needles into abnormalities detected by the X-ray and take very small samples for diagnostic purposes.