Why Your Doctor May Order a CT Scan (And What to Expect)


A computed tomography (CT) scan, also known as a CAT scan, is a specialized X-ray procedure that uses computer processing to create cross-sectional images of the body (Mayo Clinic, 2022). A CT scan takes multiple X-ray images from different angles around the body, which a computer then compiles to produce cross-sectional views of the bones, blood vessels and soft tissues.

CT scans are an important and commonly used diagnostic imaging tool. They are typically used when a doctor needs a more detailed look inside the body than a regular X-ray can provide. CT scans allow doctors to see internal organs, blood vessels, bones and tissues in great detail to help diagnose cancers, infections, injuries, cardiovascular disease and other conditions (NIBIB, 2022).

Diagnosing Causes of Pain

A CT scan can be used to identify issues with organs, tissues, or bones that may be causing pain. The detailed images produced by a CT scan allow radiologists to pinpoint the exact location of pain and check for abnormalities or disease processes.

According to RadiologyInfo.org, an experienced radiologist can use a CT scan to diagnose many causes of abdominal pain or injury from trauma with very high accuracy. The high resolution of CT scans allows radiologists to see organs, tissues, muscles, fat, bones and blood vessels in great detail.

CT scans are considered one of the best methods for diagnosing the underlying cause of pain, as they can reveal issues like kidney stones, gallstones, appendicitis, diverticulitis, bowel obstructions, tumors, bleeding, or injuries that may be responsible for a patient’s symptoms.

Identifying Causes of Symptoms

A CT scan can help doctors identify underlying causes for symptoms such as shortness of breath, dizziness, weakness, and changes in thinking or behavior. The detailed images produced by a CT scan allow doctors to examine organs, tissues and blood vessels in the chest, abdomen or brain to pinpoint abnormalities or disease processes.

For example, if a patient is experiencing shortness of breath or dizziness, a CT scan of the chest can reveal blocked arteries, blood clots, fluid around the lungs, pneumonia, chronic lung disorders, or lung tumors (https://www.mayoclinic.org/tests-procedures/ct-scan/about/pac-20393675).

If a patient has weakness or changes in thinking or behavior, a CT scan of the brain can detect bleeding, brain tumors, stroke, or other brain disorders that may be responsible for the symptoms (https://www.webmd.com/cancer/what-is-a-ct-scan).

Checking for Cancer

CT scans are commonly used to screen for cancer and to identify the size and location of tumors if cancer is suspected or previously diagnosed (1). The detailed images produced by a CT scan allow doctors to detect even very small tumors in the body. This is advantageous compared to other imaging tests like X-rays or ultrasound, which are not as sensitive for finding cancer (2).

CT scans are particularly helpful for detecting cancers in the lungs, liver, kidneys, pancreas, adrenal glands, and pelvis (3). They can find tumors as small as a few millimeters in size. CT scans also assist in pinpointing the exact location of the cancer, which helps doctors determine if it has spread and aids in planning for surgery or other treatments. The scans provide clear visualization of the size and shape of tumors as well.

Overall, CT scans serve as an vital diagnostic tool for detecting, staging, and monitoring cancer. Their detailed images allow for early diagnosis and accurate mapping of tumor size and location, which leads to more effective treatment planning.


(1) https://www.cancer.org/cancer/diagnosis-staging/tests/imaging-tests/ct-scan-for-cancer.html

(2) https://www.cancercenter.com/diagnosing-cancer/diagnostic-imaging/ct-scans

(3) https://www.cancer.net/navigating-cancer-care/diagnosing-cancer/tests-and-procedures/computed-tomography-ct-scan

Monitoring Existing Conditions

A CT scan can be used to monitor existing medical conditions over time. It allows doctors to check on the status of known conditions and track any changes. Specifically, CT scans are commonly used for monitoring tumors, cancerous growths, and masses in the body.

If a patient already has a diagnosed tumor or mass, doctors will want to periodically check on it to see if it is stable, shrinking, or growing larger. Frequent CT scans at regular intervals (such as every few months or yearly) enable the medical team to closely track any changes in the size and shape of growths or masses (1).

This allows early detection if a mass begins to grow or spread. It also helps doctors evaluate how well treatment is working. Seeing that a tumor is shrinking over successive CT scans indicates that chemotherapy, radiation, or other therapies are being effective.

In addition to cancer, CT scans help monitor other conditions that involve abnormal growths or masses. This includes things like cysts, abscesses, inflammatory masses, and benign tumors. Being able to visualize the location and size of these masses over time is important for diagnosis and directing treatment.

Assessing Injuries

One of the most common reasons for getting a CT scan is to assess injuries, especially after an accident or trauma. CT scans can quickly find internal injuries and bleeding, as well as broken bones, which helps guide urgent treatment decisions.

For head injuries, CT scans can identify bleeding, skull fractures, bruising or damage to brain tissue and blood vessels (Hassan, 2010). This assists with determining the severity of a head injury and rules out serious conditions like hemorrhage or traumatic brain injury.

CT scans are also frequently used to check for internal bleeding or organ damage after abdominal trauma or injury (Andrawes, 2017). They can accurately pinpoint the location and extent of any bleeding, which guides decisions around surgery or other interventions.

For suspected broken bones, especially in the spine, pelvis or hips, CT scans give clear images to identify any fractures or displacements. This directs immobilization and other fracture treatment.

Guiding Medical Procedures

CT scans are often used to guide medical procedures such as biopsies, surgery, and radiation therapy Source. They provide detailed images that help doctors safely navigate to the correct area of the body. CT scans allow doctors to confirm the location of a tumor or other tissue that needs to be sampled or removed.

During biopsies, CT scans guide the radiologist or surgeon to insert the biopsy needle into the right spot. This ensures an accurate tissue sample is collected.

For surgeries, especially minimally invasive ones, CT scans let the surgeon view the anatomy and plan the operation. CT can also be used for live imaging during the procedure to show the position of surgical equipment and ensure accuracy.

With radiation therapy for cancer, CT simulations map the area to be treated. This allows delivery of higher radiation doses to the tumor while sparing surrounding healthy tissue. CT scans also ensure patients are positioned correctly for radiation therapy sessions.

Screening for Heart Disease

A cardiac CT scan is often used to screen for heart disease by checking for blockages or narrowing in the coronary arteries that bring blood to the heart. The scan creates detailed 3D images that can show calcium deposits and plaque buildup in the arteries, allowing doctors to assess the risk for heart attack or other cardiovascular problems. According to researchers at the University of Chicago Medicine, a cardiac CT scan is one of the best tests for detecting blockages before symptoms arise.

The scan is non-invasive and does not require entering the body. It also takes less time than other heart tests like a cardiac catheterization. During the scan, an iodine-based contrast dye is injected into the bloodstream to make the arteries more visible. The dye highlights any atherosclerotic plaques or calcification that may be blocking blood flow. The level of blockage and number of affected arteries can indicate the severity of coronary artery disease.

In addition to checking arteries, a cardiac CT provides detailed images of the structure and function of the heart. It can detect enlargement of chambers, valve problems, muscle damage, and other structural issues. Doctors may order cardiac CT scans on a routine basis for patients with risk factors like high cholesterol, smoking, obesity, or family history of heart disease. Catching problems early allows preventive treatment to reduce the chances of future heart attack or stroke.

When CT Scans Are Used

CT scans are often preferred over other imaging tests like X-rays or MRI in certain situations where it offers unique advantages:

Detecting cancers – CT scans can detect even small tumors in organs like the liver, lungs, pancreas and kidneys that may not show up on X-rays or ultrasound exams (https://www.mayoclinic.org/tests-procedures/ct-scan/about/pac-20393675). The detailed images allow doctors to confirm the presence of tumors and assess if they have spread.

Guiding biopsies – Doctors can use CT scans to pinpoint the exact location of a tumor or abnormal tissue and guide the placement of a needle for a biopsy (https://my.clevelandclinic.org/health/diagnostics/4808-ct-computed-tomography-scan). This ensures an accurate biopsy and minimal discomfort for the patient.

Checking for blood clots – CT angiography is ideal for diagnosing blood clots in the lungs (pulmonary embolism) as it provides clear images of the blood vessels (https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/ct-vs-mri-vs-xray). Clots that could be missed on X-rays are clearly visible on a CT scan.

Examining bones and joints – CT scans provide superior images of the bones and joints compared to X-rays, especially for complex areas like the pelvis, spine and hips. Orthopedic injuries like fractures are diagnosed quickly and accurately.

Checking for internal injuries – In emergency situations like trauma from accidents, CT scans can rapidly detect internal bleeding, organ damage or abdominal injuries that require immediate attention.


In conclusion, CT scans are an important medical imaging tool used for a variety of reasons. The key reasons for getting a CT scan are to diagnose causes of pain, identify causes of concerning symptoms, check for cancer, monitor existing conditions, assess injuries, guide medical procedures, and screen for heart disease. CT scans provide detailed images that can detect issues not visible on basic X-rays or physical exams. It’s critical to work with your doctor to determine if a CT scan is appropriate for your situation. While CT scans involve radiation exposure, the benefit often outweighs this risk when there is a medical need. By understanding the main uses of CT scans, you can have an informed discussion with your doctor about whether one might be helpful for your health concerns.

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