Speed is especially beneficial for children, the elderly, and critically ill — anyone who finds it difficult to stay still, even for the brief time necessary to obtain images. For children, the radiologist will adjust the CT scanner technique to their size and the area of interest to reduce the radiation dose. The technologist begins by positioning you on the CT exam table, usually lying flat on your back.
They may use straps and pillows to help you maintain the correct position and remain still during the exam. Many scanners are fast enough to scan children without sedation. In special cases, children who cannot hold still may need sedation.
Motion may cause blurring of the images and degrade image quality the same way that it affects photographs. The exam may use contrast material, depending on the type of exam. If so, it will be swallowed, injected through an intravenous line IV or, rarely, administered by enema. 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 for the actual CT scan. Depending on the type of CT scan, the machine may make several passes. The technologist may ask you to hold your breath during the scanning. Any motion, including breathing and body movements, can lead to artifacts on the images. This loss of image quality can resemble the blurring seen on a photograph taken of a moving object. When the exam is complete, the technologist will ask you to wait until they verify that the images are of high enough quality for accurate interpretation by the radiologist.
The CT examination is usually completed within 30 minutes. The portion requiring intravenous contrast injection usually lasts only 10 to 30 seconds. CT exams are generally painless, fast, and easy. Multidetector CT reduces the amount of time that the patient needs to lie still. Though the scan is painless, you may have some discomfort from remaining still for several minutes or from placement of an IV. If you have a hard time staying still, are very nervous, anxious, or in pain, you may find a CT exam stressful.
The technologist or nurse, under the direction of a doctor, may offer you some medication to help you tolerate the CT exam. If the exam uses iodinated contrast material, your doctor will screen you for chronic or acute kidney disease. The doctor may administer contrast material intravenously by vein , so you will feel a pin prick when the nurse inserts the needle into your vein. You may feel warm or flushed as the contrast is injected.
You also may have a metallic taste in your mouth. This will pass. You may feel a need to urinate. However, these are only side effects of the contrast injection, and they subside quickly.
If you swallow oral contrast material, you may find the taste mildly unpleasant. However, most patients can easily tolerate it. If you receive an enema, you can expect to experience a sense of abdominal fullness. You may also feel an increasing need to expel the liquid. If so, be patient; the mild discomfort will not last long.
When you enter the CT scanner, you may see special light lines projected onto your body. These lines help ensure that you are in the correct position on the exam table. With modern CT scanners, you may hear slight buzzing, clicking and whirring sounds.
These occur as the CT scanner's internal parts, not usually visible to you, revolve around you during the imaging process. You will be alone in the exam room during the CT scan, unless there are special circumstances.
For example, sometimes a parent wearing a lead shield may stay in the room with their child. However, the technologist will always be able to see, hear and speak with you through a built-in intercom system.
With pediatric patients, a parent may be allowed in the room but may need to wear a lead apron to minimize radiation exposure. After a CT exam, the technologist will remove your intravenous line.
They will cover the tiny hole made by the needle with a small dressing. You can return to your normal activities immediately. A radiologist , a doctor specially trained to supervise and interpret radiology exams, will analyze the images. The radiologist will send an official report to the doctor who ordered the exam. You may need a follow-up exam. If so, your doctor will explain why. Sometimes a follow-up exam further evaluates a potential issue with more views or a special imaging technique. It may also see if there has been any change in an issue over time.
Follow-up exams are often the best way to see if treatment is working or if a problem needs attention. There is no conclusive evidence that radiation at small amounts delivered by a CT scan causes cancer.
Large population studies have shown a slight increase in cancer from much larger amounts of radiation, such as from radiation therapy. Thus, there is always concern that this risk may also apply to the lower amounts of radiation delivered by a CT exam.
When a CT scan is recommended by your doctor, the expected benefit of this test outweighs the potential risk from radiation. You are encouraged to discuss the risks versus the benefits of your CT scan with your doctor or radiologist, and to explore whether alternative imaging tests may be available to diagnose your condition. Soft-tissue details in areas such as the brain, gallbladder , internal pelvic organs, and joints such as knees and shoulders can often be better evaluated with magnetic resonance imaging MRI.
Website by Baseline Works. CT Sinuses — most commonly done to check for a deviated septum or sinusitis or polyps. CT Scans That May Require IV Contrast If you are scheduling one of these studies you should check your prescription or with your referring physician as to whether you will need to have a contrast injection.
The following CT scans are either sometimes or always done with IV contrast and will require preparation: CT Head — usually done to detect infarction, the source of headaches, seizures, dizziness, tumors, stroke, TIA, hemorrhage and trauma to the bones CT Neck Soft Tissue — done to detect mass, tumor, foreign object, gland lesion, infection or abscess.
CT Extremities — most often done to diagnose mass, fractures, injury to the ligament and dislocations. CT Spine — done to assess injury or abnormalities in the cervical, thoracic or lumbar spine CT Chest — usually performed to detect acute and chronic changes in the lungs, such as fibrosis, emphysema, and tumors CT Urogram — evaluates the kidneys, ureters, and bladder for stones, blockages and cancers or stenosis.
CT Stone Search — evaluates kidneys, ureters, and bladder for stones. Has mostly replaced the more crude and less accurate Intravenous Pyelogram All CTA scans — specialized CTs designed to look at blood vessels in a specific body region. Patients who are allergic to or sensitive to medications should notify their doctor.
You will need to let your doctor know if you have ever had a reaction to contrast media, or kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast. Patients with kidney failure or other kidney problems should notify their doctor. In some cases, the contrast media can cause kidney failure, especially if the person is dehydrated or already has underlying kidney disease.
There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure. Certain factors or conditions may interfere with the accuracy of a CT scan of the abdomen. These factors include, but are not limited to, the following:. If you are having a computed tomography angiography CTA or virtual colonoscopy with Johns Hopkins radiology, you will be given specific instructions when you make your appointment.
Other options will be discussed with you and your doctor. If so, a gown will be provided for you. A locker will be provided to secure personal belongings. Please remove all piercings and leave all jewelry and valuables at home. The contrast media improves the radiologist's ability to view the images of the inside of the body. Some patients should not have an iodine-based contrast media. If you have problems with your kidney function, please inform the access center representative when you schedule the appointment.
You may be able to have the scan performed without contrast media or have an alternative imaging exam. You will be asked to sign a consent form that will detail the risks and side-effects associated with contrast media injected through a small tube places in a vein called an intravenous IV line.
The most common type of CT scan with contrast is the double contrast study that will require you to drink a contrast media before your exam begins in addition to the IV contrast. The more contrast you are able to drink, the better the images are for the radiologist to visualize your digestive tract.
IV contrast will not be administered if you have had a severe or anaphylactic reaction to any contrast media in the past. If you had mild to moderate reactions in the past, you will likely need to take medication prior to the CT scan.
These plans will be discussed with you in detail when you schedule your exam. Any known reactions to a contrast media should be discussed with your personal physician.
If your doctor ordered a CT scan with contrast, do not eat anything three hours prior to your CT scan. You are encouraged to drink clear liquids. You may also take your prescribed medications prior to your exam.
Depending on your oral medication for diabetes, you may be asked to discontinue use of the medication for 48 hours after the CT scan. If you have a CT scan with Johns Hopkins radiology, detailed instructions will be given following your examination. CT scans may be performed on an outpatient basis or as part of your stay in a hospital.
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