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CT Imaging

General Radiography (x-rays)

Selected CT Screening Procedures

CT Cardiovascular Disease Screening - Cardiac Calcium Exam
CT Lung Cancer Screening
CT Colon Cancer Screening-Virtual Colonoscopy

CT (Computed Tomography) scans are performed on a sophisticated machine that focuses a narrow x-ray beam to generate images of anatomical structures within the body.

CT scans provide high resolution imaging detail of internal organs, blood vessels, lymph nodes, and musculoskeletal structures from head to toe. More specifically, CT imaging uses a ring shaped x-ray detector to obtain x-ray images of the body at multiple angles around the body. Using complex mathematical reconstructions, a computer is then able to create a cross-sectional image (tomogram) of the body, much like a slice through the body. The computer generates multiple images, slices that could be stacked up to recreate the whole region scanned. The interpreting radiologist then reviews the images at a digital workstation, dictating a report which is provided to the ordering physician.

Some types of CT scans can be done with little or no preparation on the part of the patient. In other instances, the patient may be required to drink a liquid containing a contrast dye to better outline the stomach, intestines, or colon during the scan. In other types of CT scans, a patient may receive an IV injection of iodinated contrast material, which can be extremely helpful in the evaluation of selected internal organs. The exact type of preparation necessary varies with each type of CT scan.

Frequently Asked Questions (FAQs) about CT Scans:

What does the equipment look like?

The CT scanner is a ring of imaging equipment inside a square block-like housing which contains electronics, the x-ray generator and detectors, and the mechanical instrumentation to move the imaging components. The apparatus is relatively like a square doughnut. The patient lays on a cart or table which slides into the x-ray ring, but the ring is relatively thin and open at both ends so it should not present any problems for claustrophobic patients.

How long will my CT exam take?

The CT scan itself usually takes 10 to 15 minutes. If you receive IV contrast, it may take slightly longer.

What should I expect during the procedure?

While the unit is scanning the images, the CT gantry rotates in a circle to allow the x-ray tube to image from all angles. There is whirring and clicking in the CT unit while the tube is rotating for the pictures. The table will slowly slide through the ring to allow the machine to cover the necessary segment of the body. If iodinated IV contrast is used, this may cause a warm flushing feeling through the body and occasionally a metallic taste in the mouth, both of which are experienced only momentarily.

How much radiation do I get from a CT scan?

New CT scanning machines are designed to expose to radiation only the small part of your body that is being examined. The amount of radiation you receive is comparable to the same amount you get for plain x-rays of the abdomen or spine, depending on what areas are to be imaged. One of our goals is to perform each CT scan with as little radiation as possible while still obtaining the images needed to make a diagnosis

What if I am pregnant?

If so, we do not recommend this test since there is exposure to radiation. If you are not sure, but think you may be pregnant, be sure to inform the technologist of this possibility before proceeding.

How do I prepare for a CT scan?

As noted above, your examination may or may not require any pre-procedure preparation.

If you have a known allergy to iodine or iodinated IV contrast (dye), please call the facility where your examination is scheduled, and ask to speak with one of the radiology nurses at least one day before your CT scan. For CT studies, in which you will receive either IV or oral contrast, please do not eat or drink anything except for the oral liquid contrast for 3 hours prior to the study.

I am allergic to X-ray dye. What do I do?

If your CT study requires iodinated intravenous (IV) contrast (dye), you should speak with a radiology nurse the day before the study. Usually the study can be safely done with contrast even if you have an iodine-allergy history. Generally, we recommend treating you the night before and the morning of your study with several medications designed to decrease your chance of an allergic reaction. These medicines often include common histamine-blockers like Benadryl and Tagamet, and potent anti-inflammatory steroid medications. While allergic reactions to IV contrast can occur, trained physicians and nurses with necessary medications and equipment are always available to treat any reaction.

How do I know if I am allergic to the X-ray contrast (X-ray dye)?

True allergic reactions to the X-ray contrast are very rare, in the range of 1 in 50,000. If your CT exam requires IV contrast, we will ask you to fill out a questionnaire about other allergies you may have. People who have asthma or who have a history of multiple food or drug allergies may be at a mildly increased risk of being allergic to the x-ray contrast. We commonly treat those people with the medicines described above.

Some of my relatives are allergic to X-ray dye. Does that mean that I am more likely to be allergic?

In general, no. We do not routinely "pre-treat" patients for possible IV contrast reaction in the instance of those who have relatives who have such an allergy.

I have diabetes. Does this matter?

If so, we recommend that your doctor obtain a blood test to show the status of your kidney function before you have the CT exam. If you take Glucophage or Glucovance for Type II diabetes, and we administer iodinated IV contrast for the exam, we will ask you to withhold your medication for 48 hours after the exam. You may resume your medication after your doctor checks a blood test to show that your kidneys function has not changed.

I have kidney disease or poorly functioning kidneys. Does this matter?

If so, we recommend that your doctor obtain a blood test to show the status of your kidney function before you have the CT exam if it is anticipated that you will require iodinated IV contrast.

I have asthma requiring daily use of an inhaler. Does this matter?

If so, we recommend that you bring your inhaler with you, as you may be asked to use it immediately before your scan is performed if it is anticipated that you will require iodinated IV contrast.

How do I prepare for my CT scan of the head, neck, chest, or extremities?

Generally, no specific pre-procedure preparation is needed, although patients are advised not to eat or drink anything for approximately 3 hours prior to the scan if iodinated IV contrast dye is to be administered.

How do I prepare for my CT scan of the abdomen or pelvis?

You may need to drink a liquid containing a contrast dye before the study. You may pick up this drink at any one of our sites of service. Drink one 8-ounce glass the night before your study. The next day, usually starting about 3 to 5 hours before the exam, slowly drink the rest of the contrast—about 6 to 8 ounces every 30 minutes until the study starts. It is better to drink small amounts frequently rather than large amounts at once.

When will my doctor get the test results?

Our radiologists look at all of you CT images and compare the study with any previous exams you may have had. Our typed report is available to your doctor usually within one day.


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