Enlarged coronary arteries. Coloured 3-D computed tomography (CT) scan of a heart with enlarged coronary arteries (orange/red). These vessels supply oxygenated blood directly to the heart muscle. The swollen arteries may have resulted from a blockage within the vessel, which can cause angina, or a symptom of high blood pressure (hypertension). This image was produced using a multi-slice CT scanner, which uses a thin X-ray beam to scan around the patient to collect image 'slices'. Contrast agent, injected into the blood stream, allows the CT scanner to detect the blood vessels, a technique known as cardiac angiography. A computer reconstructs the slices into coloured 3-D images of the body. This image was created using OsiriX medical imaging software.