Introduction
CAT scans, also known as CT (computed tomography) scans, are imaging tests used to detect diseases, injuries, and other conditions by taking detailed pictures of the inside of the body (“CT Scan (CAT Scan): Purpose, Procedure, Risks, Side …,” 2023). They create cross-sectional images of the body using computer-processed combinations of multiple X-ray measurements taken from different angles. The rapid beam rotation and sophisticated computing create detailed “slices” of the body which a specialist is able to analyze. The primary purpose of a CAT scan is to noninvasively detect abnormalities in the body, such as tumors, bleeding, blood clots, swelling, etc.
Medical Reasons
Doctors may order a CT or CAT scan for a variety of medical reasons. Some common reasons include:
- Head injury – CT scans are often used to check for bleeding, swelling, or skull fractures after a head injury. They can detect traumatic brain injuries that may not show up well on a regular X-ray (Source).
- Cancer diagnosis – CT scans are often used to detect tumors, determine the stage of cancer, and monitor the effectiveness of cancer treatments like chemotherapy and radiation (Source).
- Infection – CT scans can be used to detect the location of infections like appendicitis, diverticulitis, abscesses, osteomyelitis, and sinusitis (Source).
- Blood clot – CT angiography scans are used to detect blood clots in the lungs (pulmonary embolism) or legs (deep vein thrombosis) (Source).
CAT scans provide detailed images that can help doctors diagnose many conditions that may not be evident on regular X-rays or physical exams.
Preparation
Proper preparation is important before a CAT scan to ensure the scan goes smoothly and provides useful results. According to the University of Connecticut Health Center, patients should not eat or drink anything for 2-4 hours prior to the scan if contrast material will be used. The stomach must be empty to help the contrast material work effectively. Patients scheduled for a scan without contrast can eat and drink normally before the test.
Mayo Clinic also recommends refraining from eating or drinking for a few hours beforehand. Cleveland Clinic advises patients not to eat for four hours prior and to only drink clear liquids like water or juice in the two hours leading up to the scan. These fasting guidelines help ensure the abdomen is free of food and stool, allowing for clearer scan images.
Additionally, patients may be instructed to drink a contrast material solution over the course of an hour before the scan to help enhance the images. Comfortable loose fitting clothing should be worn, and any metal objects like jewelry should be removed prior to the scan.
Procedure
During a CT scan, you’ll need to lie still on a table while the machine rotates around you. The table will slide in and out of the large, donut-shaped scanner as the scan is performed. The technologist will leave the room and operate the CT scanner from another room with a window and intercom to see and hear you. You’ll be able to communicate with the technologist if you have any concerns during the test.
You may receive a contrast material by mouth or through an intravenous (IV) line before or during your CT scan. The contrast material allows your blood vessels, organs and tissues to be seen more clearly. Some CT scans are done without contrast. The type of CT scan you’re getting will determine if you need the contrast material.
The table will move slowly through the scanner as the machine’s X-ray beam rotates around you. The X-ray detector on the opposite side of the scanner will record the images. Scans are usually done in sequences, so the scanner may move from your abdomen to your chest and back several times. You’ll hear buzzing and clicking noises during the CT scan. The procedure is generally painless, though you may feel uncomfortable from lying still for several minutes.
A full body CT scan usually takes about 30 minutes. The scanning itself takes only 10 to 15 minutes or less. The additional time is for moving you into position and taking images from different angles. Time will also be needed before and after the test to get you ready and then remove the IV line and any contrast materials, if used.
After the CT scan, you can resume your normal activities, including driving. The results will go to a radiologist who will interpret the CT scan images and send a report to your doctor. Your doctor will then discuss the results with you.
Risks
There are some risks associated with getting a CT scan, the main one being exposure to radiation from the X-rays used during the scan. According to the Mayo Clinic, the amount of radiation exposure from a CT scan is higher than conventional X-rays. However, the risk of getting cancer from the radiation exposure of one CT scan is still low.
Repeated or multiple CT scans do carry a higher risk of cancer down the line. A 2009 study from Brigham and Women’s Hospital cited by Harvard Health estimated the potential increased cancer risk from multiple CT scans in over 30,000 patients. The FDA also notes that the main risks of CT scans come from incidental findings leading to unnecessary follow-up tests that have their own risks.
Steps can be taken to minimize radiation exposure from CT scans when they are medically necessary. This includes using alternative imaging exams like MRI or ultrasound when possible. The lowest radiation dose necessary should be used for CT scans. Protective shielding can also be used to limit exposed areas.
Results
According to Cleveland Clinic, CT scan results typically take 24-48 hours to receive. For non-emergency situations, results can take 1-2 days or longer depending on factors like radiologist availability.
In an emergency situation, results may be expedited and available more quickly to assist with urgent medical decision making, according to KidsHealth. The radiologist analyzes the images from the CT scanner and generates a report that is shared with the ordering physician. The physician then reviews the radiology report and discusses the results with the patient, providing context on the findings.
Patients are advised not to assume that “no news is good news” when awaiting CT scan results. It’s important to follow up with your physician’s office if you do not receive results within the expected timeframe. The radiology report contains highly technical terminology, so it is helpful to discuss the results directly with your doctor who can explain the findings and recommended next steps in understandable terms.
Children
There are special considerations when children need CAT scans. While CAT scans provide important diagnostic information, there are concerns about radiation exposure for children. According to the National Cancer Institute, the risks from radiation exposure from medical imaging like CAT scans are small for an individual child, but repeated or excessive CAT scans should be avoided when possible (https://www.cancer.gov/about-cancer/causes-prevention/risk/radiation/pediatric-ct-scans).
To protect children, doctors follow special pediatric protocols to optimize image quality at the lowest radiation dose. They may also use alternative imaging exams when possible that don’t use ionizing radiation, like MRI or ultrasound (https://kidshealth.org/en/parents/getting-ct-scan.html). The risk versus benefit is carefully considered before ordering pediatric CAT scans.
Radiation exposure is a greater concern for infants and younger children because they are more sensitive to radiation and have more remaining years of life during which cancer could potentially develop. So doctors especially avoid unnecessary CAT scans for babies and young children when other exams could provide the needed information (https://www.radiologyinfo.org/en/info/pedia-ct). With appropriate precautions and judicious use, CAT scans are a safe, useful imaging tool for children.
During Pregnancy
Getting a CT scan during pregnancy does carry some risk of exposing the developing fetus to radiation. However, the amount of radiation used in normal CT imaging has never been shown to cause harm to an unborn child (https://www.radiologyinfo.org/en/info/safety-ct-pregnancy).
Precautions should be taken to minimize radiation exposure when getting a CT scan while pregnant. The lowest dose possible should be used, especially for abdominal and pelvic scans which expose the fetus to more direct radiation. Multiple scans should also be avoided if possible (https://americanpregnancy.org/healthy-pregnancy/is-it-safe/ct-scan-during-pregnancy/).
The radiologist and technician should be informed of the pregnancy so they can take appropriate precautions. Lead shielding may also be used to cover the abdomen and pelvis area. Getting a CT scan in the early stages of pregnancy or limiting the area scanned can also reduce risk (https://blog.radiology.virginia.edu/medical-imaging-while-pregnant-how-safe-is-it/).
Overall, the benefits of getting a medically necessary CT scan generally outweigh the small potential risk to the fetus. However, precautions should be taken and the scan limited to the area of interest when possible.
Alternatives to CAT Scans
In some cases, other imaging tests may be used as alternatives to CAT scans. Some examples include:
- MRI scan – An MRI uses strong magnetic fields and radio waves to produce detailed images of organs and tissues. MRIs do not use ionizing radiation like CAT scans, so they may be preferable in certain situations, like imaging the brain or musculoskeletal system. However, MRIs cannot be done in patients with metal implants or pacemakers (Use of Ultrasound as an Alternative to CT).
- Ultrasound – Ultrasound uses sound waves to produce images of internal organs and tissues. It is commonly used to image the abdomen, pelvis, heart, blood vessels, and during pregnancy. Ultrasound does not use ionizing radiation and is lower cost than CAT scans, but does not produce as detailed images (Use of Ultrasound as an Alternative to CT).
- X-ray – Plain x-rays produce images of bones and some dense tissues. They involve lower radiation exposure than CAT scans, but do not give as detailed images of soft tissues. X-rays may be used to image the chest, abdomen, bones, joints, and teeth (CT Scan Versus MRI Versus X-Ray).
The choice of imaging test depends on the specific area and information needed. Doctors consider the benefits versus risks of radiation exposure, image quality, and cost when determining if alternatives to a CAT scan are appropriate.
Conclusions
In summary, CAT scans are a critical medical imaging tool used to help doctors diagnose and monitor a wide range of conditions affecting the head, spine, chest, abdomen, blood vessels, and bones. Some of the top reasons a doctor may order a CAT scan include evaluating symptoms like headaches or dizziness, detecting tumors or cancers, looking for internal injuries after trauma, finding the cause of chronic pain, and monitoring known conditions like heart disease or multiple sclerosis.
Though CAT scans involve radiation exposure, the benefits generally outweigh this risk when used appropriately. Proper preparation like avoiding food and medications beforehand can help ensure a clear scan. The scan itself only takes a few minutes, though total appointment time is longer. While the results are immediately available to the ordering doctor, it may take some time to go over the full report with your physician.
Pregnant women and children require special consideration when ordering CAT scans. Alternatives like ultrasounds or MRIs may be preferred when possible. Overall, CAT scans are an invaluable tool when ordered judiciously by your doctor to help diagnose and manage many medical conditions.