What is a CT Scan (Computed Tomography)?

A CT scan (Computed Tomography) uses a series of X-rays to create image “slices” of the body. This type of study is also called a CAT scan (Computerized Axial Tomography). CT scans of organs, bone, soft tissue and blood vessels provide greater internal image clarity than conventional x-ray exams.

A CT diagnostic scan has the patient lying on a table with a doughnut-shaped scanning device at one end. This device contains an X-ray that takes images from different orientations and creates cross-sectional images of the body area surrounded by the device. The image slices can then be reformatted into two-dimensional and sometimes three-dimensional images that are “read” by an HDI Radiologic Physician and your doctor.

CT Scans are commonly used to detect:

  • Broken bones
  • Cancers and brain tumors
  • Internal bleeding and brain injury
  • Skull fractures and enlarged brain cavities
  • Malformations of the skull
  • Diseases and strokes
  • Heart disease and more

CT exams and radiation safety

Although CT examinations improve health care and are an essential part of diagnosis and treatment planning, there are some radiation risks associated with this imaging procedure.

Women should always inform their physician and HDI Technologist prior to a test if they suspect they might be pregnant.

Inform your physician and technologist of any allergies you might have, especially to medications or iodine. Allergic reactions to any contrast materials that may be used are extremely rare, but in the instance of a reaction, HDI is well equipped to deal with them.

Children should have a CT exam only if it is essential for making a diagnosis. They should not have repeated CT exams unless absolutely necessary given their increased sensitivity to radiation and exams should always be administered using a lower radiation dose.

To learn more about X-ray radiation, visit radiologyinfo.org.


If you take medications, please check with your primary care physician or HDI Technologist before your exam appointment about maintaining your regular dose schedule. If you have a known allergy to contrast material or “dye”, your doctor may prescribe medications to reduce the rare risk of an allergic reaction. These medications generally need to be taken 12 hours prior to administration of contrast material. To avoid unnecessary delays, contact your medical provider before the exact time of your exam.

Food and drink

Unless you are instructed otherwise by the HDI staff or your physician, you should not eat or drink (other than water) for 4 hours prior to your test. If you are told not to withhold oral food and fluids, be sure to drink plenty of clear fluids before your exam.

When to arrive

If you are having a CT scan of your abdomen or pelvis, plan to arrive at High Desert Imaging one hour before your scheduled appointment. This allows time for you to ingest the oral contrast material prior to your exam that will help highlight body areas for imaging. For scans performed in areas other than the abdomen, you’ll need to arrive 10 minutes prior to your appointment.

What to wear

Wear comfortable clothing, like sweats. Be sure to avoid clothing containing metal found in eyelets, rivets, zippers or buttons. Also be conscious of metal in any undergarments worn as it can interfere with the quality of the imaging. You may be asked to remove jewelry, eyeglasses, hearing aids or any dentures and any metal objects or clothing if necessary and gowns are available if needed.

Diabetic conditions

If you have diabetes and are on insulin, please continue to take your insulin as prescribed, but drink extra fruit juices during the six to eight hour fast from solid foods before your exam. If you are taking medications, such as Glucophage (Metformin), you should take the prescribed dose as normally done on the day of the test, but discontinue the next doses for 48 hours AFTER your CT exam, notifying your physician of this instruction. If you need a substitute medication, please consult your doctor.

Contrast agents

Depending on the body part being scanned, you may be given a contrast medium. This dye may be given orally as a drink, through an intravenous (IV) line, or through injection. The contrast travels through your bloodstream and helps create a clearer picture of specific parts of your body. Contrast agents highlight your organs and blood vessels for better interpretation of images. If your exam requires oral contrast, you must pick up the contrast from HDI at least one day prior to your exam.

Please notify your doctor and HDI Technologist if you have ever had an allergic reaction to a contrast material administered for a medical imaging procedure. Contrast materials used today contain a lower iodine content that greatly reduces the chance of an allergic reaction and most of the discomfort associated with injection.

You may have a higher risk for a complication due to a contrast if you:

  • Are over 60 years of age
  • Had a previous allergic reaction to contrast dye
  • Have a serious heart condition or disease
  • Have diabetes or lupus
  • Have severe kidney disease, especially if due to diabetes
  • Are receiving dialysis
  • Have severe allergies to any drugs or foods
  • Have unstable asthma that requires treatment
  • Have sickle cell disease, polysythemia, or multiple myeloma

If you have any of the conditions below, speak with your doctor and HDI Technologist. You may need a blood test beforehand to make sure the contrast will be safe for you.


Inform your HDI Technologist if you have a pacemaker. Pacemakers won’t hinder the use of CT scanning (as opposed to an MRI) so long as the scanner isn’t taking images repeatedly over the area of the pacemaker in the upper chest. This is usually not an issue for cardiac CT exams.


A CT examination is painless but will require you to remain completely still for a period of 5-10 minutes which may cause some discomfort. You may be asked to hold your breath during part of the scan because the motion created by breathing can blur the images. Given the CT scanner’s donut shape, you will not be enclosed in the scanner at any time. The exam table may be raised, lowered, or tilted to create the correct angle for the x-rays. You can expect to hear whirring or clicking sounds from the machine as it captures images. Your HDI Radiologic Technologist will communicate with you to ensure your comfort throughout the testing procedure.


The CT scanner resembles a large donut. The exam table will slide back and forth through the large hole in the center of the machine as the scanner rotates around you. At first, the table will move through the scanner quickly, which helps the technologist confirm that your body is in the right position. After that, the table will move more slowly through the scanning process.

Length of scan

Each CT scan performed by HDI is individualized and tailored to your needs. In general, the actual image capture portion of the exam lasts only a few minutes with most examinations lasting approximately 15-20 minutes total.

After your CT Scan

There are no restrictions after having a CT scan and you can go about your normal activities. To help eliminate the contrast medium from your body, drink plenty of water or decaffeinated or non-alcoholic beverages. Your kidneys help filter the iodine that is in the contrast out of your body. If you have kidney disease or diabetes, you should be closely monitored for kidney problems after your CT scan. Please talk with your health care provider prior to your test to reduce health risks.

Scan Results 

HDI prides itself on delivering superior studies and rapid results from your medical imaging procedure. Diagnostic exams are typically read within 24 hours and the results will be sent to your primary care physician who will explain them to you in detail. We’ll also provide a DVD of your exam images for your personal records.

If you have further questions about HDI CT scanning procedures, please use our online contact form or call us at 775.621.5800.