In this edition of the AMI blog, Dr. Ajay Viswambharan, a board certified radiologist at Atlantic Medical Imaging, answers some of the commonly asked questions about CT scans (CAT scans).
What is a CAT scan?
Computerized tomography (CT), also known as CAT scan, is a non-invasive, painless medical test that helps physicians diagnose and treat medical conditions. CT imaging uses special x-ray equipment to produce multiple images of the inside of the body and a computer to join them together in cross-sectional views of the area being studied.
CT scans of internal organs, bone, soft tissue, and blood vessels provide greater clarity than conventional x-ray exams. Using specialized equipment and expertise to create and interpret CT scans of the body, radiologist can more easily diagnose problems such as cancers, cardiovascular disease, infectious disease, trauma, and musculoskeletal disorders.
How does a CAT scan work?
In many ways, CT scanning works very much like an x-ray examination. In a conventional x-ray exam, a small bursts of radiation is aimed at and passes through the body, recording an image on photographic film or a special image recording plate. Bones appear white on the x-ray; soft tissue shows up in shades of gray and air appears black. However, unlike conventional x-rays, CT scanning provides very detailed images of many types of tissues as well as the lungs, bones, and blood vessels.
Advancements in imaging technology now allow new CT scanners to obtain multiple slices in a single rotation. These scanners, called "multi-slice CT" or "multi-detector CT", allow thinner slices to be obtained in a shorter period of time, resulting in more detail, additional view capability and shorter patient exam time. This is beneficial for all patients but especially children, the elderly and critically ill.
What should I expect during the exam?
A CT exam usually takes between 10 and 30 minutes depending on the type of exam. Most CT exams are painless, fast and easy. With spiral CT, the amount of time that the patient needs to lie still is reduced.
The technologist begins the CT exam by positioning you on the exam table. You will be asked to lay very still and at times hold your breath. Next, the table will move quickly through the scanner to determine the correct starting position for the scans. Then, the table will move slowly through the machine as the actual CT scanning is performed.
You will be alone in the exam room during the CT scan, however, the technologist will be able to see, hear and speak with you at all times. With pediatric patients, a parent may be allowed in the room but will be required to wear a lead apron to prevent radiation exposure.
Is there any preparation for the CAT scan?
The CT exam may require the use of a contrast material to enhance the visibility of certain tissues and blood vessels. The contrast material can be administered via IV (intravenous) or orally. With an intravenous contrast material, you will feel a slight pin prick when a needle is inserted into your vein. You may have a warm, flushed sensation during the injection of the contrast materials and a metallic taste in your mouth that lasts for a few minutes. Occasionally, a patient will develop itching and hives, which can be relieved with medications. If you become light-headed or experience difficulty breathing, you should notify the technologists or nurse, as it may indicate a more severe allergic reaction. With oral contrast, you will be ask to drink the contrast agent prior to the exam.
Continue to check back for more information on low dose CT scans from Dr. Viswambharan.