The Inner Workings. How CAT Scans See What’s Inside You

Introduction to CAT Scans

A CAT scan, also known as a CT or computed tomography scan, is a specialized X-ray procedure that takes cross-sectional images of the body (1). CAT scans use a rotating X-ray machine and advanced computing technology to create detailed images that can detect many medical conditions.

During a CAT scan, the patient lies still on a table while the X-ray tube rotates around the body. As this rotation occurs, the table moves slowly through the scanning ring, allowing multiple X-ray beams from many angles to pass through the area being examined. The X-rays are detected and digitally recorded, and a computer uses complex mathematical processes to create cross-sectional images of the internal organs and tissues (2).

CAT scans were first developed in the 1970s by Godfrey Hounsfield and Allan Cormack (3). Their pioneering work allowed medical imaging technology to advance from simple X-rays to detailed 3D views inside the body. Over the years, CAT scan technology has improved dramatically, allowing for faster scan times, reduced radiation exposure, and greatly enhanced image quality.


What is a CAT Scan?

CAT scan stands for computed axial tomography scan. It is a special type of X-ray that takes cross-sectional images of the body (How do CAT scans work? | A Level Physics – YouTube). CAT scans allow doctors to see inside the body in detail without having to perform exploratory surgery.

Unlike a regular X-ray that takes one image from one angle, a CAT scan takes multiple images from different angles around the body. A computer then combines these images to produce cross-sectional views of the internal organs and tissues (CAT Scans / X-Rays – tom reilly). This allows doctors to see a 3D visualization of the inside of the body.

Because CAT scans provide more detailed images than regular X-rays, doctors can use them to diagnose issues and injuries to organs, blood vessels, bones and tissues. CAT scans are one of the most common ways for doctors to get comprehensive views inside the body in a non-invasive manner.

Why are CAT Scans Used?

CAT scans, also known as CT scans or computed tomography scans, are primarily used to help diagnose diseases and conditions in the body (Mayo Clinic, 2022). The scans provide detailed images of bones, blood vessels, soft tissues, and organs, allowing doctors to detect abnormalities and tumors that may not be visible on basic X-rays or physical exams.

According to the Mayo Clinic, CT scans are often used to diagnose conditions such as (Mayo Clinic, 2022):

  • Cancer
  • Heart disease
  • Lung nodules and lesions
  • Abdominal pain or injury
  • Musculoskeletal disorders
  • Spinal injuries

Overall, CAT scans provide a non-invasive way for doctors to see inside the body and diagnose a wide range of diseases and conditions. The detailed images produced by CAT scans allow doctors to detect even small tumors and abnormalities, which can lead to earlier diagnosis and more effective treatment.

Common Uses of CAT Scans

CAT scans are frequently used by doctors to help diagnose various health conditions affecting different parts of the body. Some of the most common uses of CAT scans include:

Diagnosing cancer – CAT scans allow doctors to detect tumors, determine their exact location, size and spread. This imaging test is commonly used to diagnose cancers affecting lungs, colon, liver, kidneys, ovaries and other organs.

Detecting heart disease – Cardiac CAT scans help identify plaque buildup in arteries, check for calcium deposits, analyze heart anatomy and function, and diagnose coronary artery disease.

Identifying lung conditions like pneumonia – CAT scans provide detailed images of lung tissue, airways, blood vessels and lymph nodes. This assists diagnosis of pneumonia, chronic obstructive pulmonary disease (COPD), lung abscesses, cystic fibrosis and other lung problems.

Finding kidney stones – CAT scans accurately locate kidney stones in the kidneys and urinary tract. The images pinpoint the stone’s size and position, allowing doctors to determine treatment options.

Checking for appendicitis – When appendicitis is suspected, a CAT scan can confirm an inflamed appendix. The scan provides crucial information about the severity of the condition to help doctors decide on surgery or antibiotic treatment.

CAT Scan Procedure

During the procedure, the patient lies still on a table that slides into a large, donut-shaped scanner. The scanner consists of an x-ray tube that rotates around the body and takes cross-sectional images from different angles. As the table moves through the scanner, the x-ray tube rotates and sends narrow beams of x-rays through the body. Detectors on the opposite side of the scanner measure the amount of radiation absorbed by different tissues.

The computer then takes all of these cross-sectional x-ray images and assembles them together into highly detailed 3D models. This allows radiologists to examine different parts of the anatomy layer by layer. The images generated from a CT scan provide more detailed information than typical x-rays and allow doctors to view tissues, organs, bones and blood vessels inside the body.


Preparing for a CAT Scan

Proper preparation is important before undergoing a CAT scan. According to the Mayo Clinic (, patients will need to refrain from eating or drinking anything for a few hours beforehand. This is to prevent food or drink from interfering with the images. Patients may be advised to avoid eating for 4 hours before the scan, and only drink clear liquids like water or juice in the 2 hours leading up to the test.

Patients will also need to remove any metal objects like jewelry or eyeglasses beforehand, as these can cause artifacts in the images ( Some CAT scans require drinking a contrast material that contains iodine, which helps enhance the images. For scans involving IV contrast, a radiology nurse will insert an IV line and inject the contrast dye into the bloodstream.

During the CAT Scan

During the CT scan, you will need to lie still on the table and breathe normally. The table will slide back and forth through the center of the scanner, which looks like a large donut. You may hear buzzing or clicking noises as the scanner’s internal parts move and take images. The actual CT scanning process takes between 10-30 minutes, depending on the part of the body being imaged and the number of images required. Some patients report feeling a bit warm during the scan due to the equipment. It is important to relax, lie still, and follow any breathing instructions from the technologist to get the clearest images possible.

According to the Mayo Clinic, “CT scans are painless and, with newer machines, take only a few minutes. The whole process typically takes about 30 minutes.” [1] WVU Medicine also notes, “There will be no side effects after your CT scan. You can resume all normal activities.” [2]



After the CAT Scan

Once the CAT scan is complete, patients can typically resume normal activities immediately. No special care is needed after the procedure.

Patients can eat and drink normally after the scan. There are no diet restrictions or fasting requirements.

The CAT scan images will be read by a radiologist, a medical doctor who specializes in the interpretation of medical images. The radiologist will analyze the images to identify any areas of concern.

After reading the scan, the radiologist will put together a report for the ordering physician. This report will describe the radiologist’s findings, including notation of any abnormalities. The ordering physician will then go over the radiology report with the patient to discuss treatment options if needed.

Patients typically receive the results of their CAT scan within a few days. However, timing can vary based on the medical provider. Those who undergo a CAT scan in the emergency room may get results more rapidly.

CAT Scan Risks

As with most medical procedures, there are some risks associated with getting a CAT scan. The main risk is exposure to radiation from the x-rays used to generate the scan images. According to, CAT scans use low levels of radiation, but repeated or accumulated exposure over time could potentially cause cancer. However, the benefits of detecting medical conditions often outweigh this small cancer risk.

Some patients may have allergic reactions to the contrast material containing iodine that is sometimes used in CAT scans. However, these allergic reactions are very rare. The contrast agents used can also affect kidney function in some cases, but this is quite unlikely in patients with normally functioning kidneys according to Dr. Bruce on the Adam Carolla Show.


In summary, CAT scans, or computed tomography scans, are an essential medical imaging technique used to create detailed pictures of the body’s internal structures. They work by using X-rays and a computer to create cross-sectional images or “slices” of the area being scanned. Some key points about CAT scans covered in this article include:

CAT scans are commonly used to examine the brain, spine, heart, abdomen and chest, detect tumors, infections or internal injuries, and diagnose conditions like cancer, heart disease and liver disorders. The scans provide more detailed images than regular X-rays.

Before a CAT scan, patients may be asked to avoid food or drinks for a period of time. An IV contrast material may be used to enhance the visibility of certain tissues. During the scan, the patient lies still on a table that moves through the scanner. After the test, patients can resume normal activities.

While CAT scans involve some radiation exposure, the benefits usually outweigh the low risks. The amount of radiation is minimized by using the lowest possible dose needed for quality images.

Looking ahead, advances in CAT scan technology will allow for even faster scan times, reduced radiation doses, and improved image quality. New techniques like spectral CT scans can better differentiate tissues and provide additional diagnostic information. As the technology continues to progress, CAT scans are sure to remain an indispensable tool for medical diagnosis and treatment planning.

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