Computed Tomography (CT or CAT) Scan A CT scanner passes minimal x-rays through specific areas of the body by creating cross-sectional images on a computer.
CT scans use radiation. If you are pregnant or think you may be pregnant, please check with your doctor before scheduling the exam. We will discuss other options with you and your doctor.
How to Prepare If you are not scheduled to have a contrast dye (enhanced) scan, you can eat and take your prescribed medications as instructed prior to your study.
If your doctor orders a contrast enhanced exam, you may be asked not to eat anything three hours prior to your CT scan. The most common type of contrast enanced exam is the double contrast study that will require you to drink a contrast agent before your exam begins. The more oral contrast you are able to drink, the better the images are for the radiologist to visualize your digestive tract. If you are unable to receive the oral contrast by mouth, we may give it to you through a feeding tube or a nasal-gastric tube. In very rare cases, your exam may require you to receive the contrast rectally. The contrast agents aid the radiologist to better visualize vessels and organs in your body. Some patients should not have iodine-based contrast dyes. If you have multiple myeloma or kidney failure, please inform us in advance. We may be able to perform the scan without the contrast dye or may be able to perform an alternate study. Diabetics should eat a light breakfast or lunch three hours prior to the scan time. If you are taking Glucophage (an oral drug for diabetes), it should be discontinued prior to the study and for 48 hours thereafter.
All patients, except diabetics and those taking medications to reduce blood sugar, can take their prescribed medications. What To Expect
During the scan, you will either lie on your back or on your stomach within the scanner opening. The CT scanner opening is very wide and you will not feel confined within the space. You will be in the CT scanner for about 20 minutes while the scanning is being performed. During this time, it is important for you to hold still as motion makes the scanned images blurry. You will receive a second, iodine-based contrast intravenously (through a vein) once you are in the scan room. In order to get the best images of the organs and vasculature structures, it is important that you take both the oral and the IV contrasts. Before your scan, you will be asked to sign a consent form that will detail the risks and side-effects associated with the IV contrast. Please inform the receptionist when you schedule your scan if you have had an allergic reaction to the contrast dye in the past. We can give you medications that reduce the risk of side-effects. The IV contrast injected in the exam room for the contrast enhanced exam causes most patients to experience a warm sensation throughout the body that lasts a few minutes. However, please let the technologist know if you experience pain or discomfort at the injection site or elsewhere.
Regular CT scans will not cause any side-effects. The scan itself takes about five minutes on average. The radiologist will read your images the same day, and send a written report to your physician within 48 hours. Contact Information
If you have any questions about your CT scan, please contact:
Bea Mudge
CT Imaging Manager
Johns Hopkins Hospital
600 N. Wolfe Street
Baltimore, MD 21287
Phone: (410)614-9842 | 
