What is a CT Scan?

CT is a diagnostic tool used to look at various parts of the body, especially those made of bone (including joints), air (including lungs and the nose), and soft tissue structures- particularly those with a blood supply. CT scanning is used commonly in people, and is used extensively at Willows. It uses X-rays to produce an image, these are the same X-rays that produce the X-ray images that you may well be familiar with (called radiographs).

CT works by using a continuous beam of X-rays which spin around in a doughnut shaped support called a gantry. The ‘tube head’, which produces the X-ray beam, can spin very quickly, taking as little as 0.35 seconds with our Siemens 64 slice scanner, to completely circle around the patient. While this is happening, the patient, can be moved through the gantry by electronically moving the table top. Each revolution of the X-ray tube around the patient in the scanner builds up slices of X-ray images.

After this information is obtained, powerful computers use complex software to produce images that can be recognise and interpreted. Interpretation of the hundreds of slices of information, obtained for every patient, takes considerable time and expertise, exclusively undertaken by our team of Board-Certified Specialist Radiologists.

CT scanning has a number of advantages over both conventional X-ray radiography and other imaging techniques:

• Interpretation: CT scanning removes superimposition of overlying structures as it produces slices which are cross sections of the patient, making interpretation of complex parts of the body a lot easier.
• Abnormalities: A CT scan allows the slices to be added together electronically to give much thicker slices. In this way, we often see small abnormalities that might otherwise have been missed.
• ‘Surgeon’s Eye View: The slices from a CT scan can be electronically stacked up in any direction, allowing the radiologist to manipulate the images and effectively reconstruct the tissues. This can often help surgeons to understand disease better, as they can have a more three dimensional ‘surgeon’s eye view’ of the abnormalities.
• Speed and Detail: The 64 slice scanner is incredibly quick and has the advantage of ECG gating which can build up very detailed pictures of the heart and the tiny vessels (called coronary arteries) that support it. This is very important for imaging patients with cardiac disease that is difficult to identify on ultrasound.

CT scanning is particularly useful for looking at injected contrast agent within the body. A contrast agent is a liquid that can be injected into a patient and then watched on the CT scan as it passes around the arteries and veins, and into the organs that the blood vessels supply. The fast speed of the CT scanner enables the contract agent to be tracked.

In addition, the contrast agent has to be delivered to the body quickly so that a ‘bolus’ or discrete ‘package’ of the contrast is present, rather diffusing slowly into the body. Willows has a pressure injector linked to the CT scanner, which means that contrast can be injected into a vein very quickly while the patient is being scanned. The combination of fast scanner and pressure injector means that even small blood vessel abnormalities can be seen, and the contrast tracked as it passes through the internal organs.