Introduction
A CAT scan, also known as a CT (computed tomography) scan, is a medical imaging technique that uses X-rays and computers to create cross-sectional images of the body (Source 1). CT stands for “computed tomography,” while CAT stands for “computed axial tomography.” But these two terms mean the same thing and refer to the same test (Source 2).
During a CAT scan, the person lies on a table that slides into a large tunnel-like machine. The machine rotates around the body and sends X-rays through from multiple angles. The X-rays are picked up by detectors which send the information to a computer. The computer compiles the data to create cross-sectional images or “slices” of the body. These image slices allow doctors to see more detailed images of organs, bones, tissues and blood vessels.
History
The development of CAT scanning began in the early 1970s by British engineer Sir Godfrey Hounsfield of EMI Laboratories and South African physicist Allan Cormack. Hounsfield built the first prototype CT scanner in 1971 and tested it on a preserved human brain. On October 1, 1971, the first scan of a live patient took place at Atkinson Morley Hospital in London using Hounsfield’s prototype scanner. This first patient scan took almost 5 hours to produce one image.
CAT scanning was developed to improve on existing imaging techniques like X-rays, which produced unclear overlapped 2D images. Hounsfield and Cormack wanted to find a way to generate clear, detailed 3D cross-sectional images of the body to better visualize organs and tissues for medical diagnosis. The invention of computed tomography (the technology behind CAT scans) made this possible and revolutionized radiology and medical imaging.
How CAT Scans Work
A CAT scan, also known as computed tomography (CT) scan, uses X-rays and a rotating X-ray device to create cross-sectional images of the body. The scanner itself is a large, box-like machine with a hole in the center for the patient to pass through while lying down on a motorized table.
The X-ray tube inside the scanner rotates around the patient’s body, taking images from different angles. As the X-ray beam passes through the body, it is absorbed in varying amounts depending on the density of structures and tissues. The attenuated X-rays are detected on the opposite side by X-ray detectors, which produce signals that are processed by the machine’s computer. Using algorithms, the signals are converted into cross-sectional images of the internal structures and organs. These images represent a slice through the body, like slices through a loaf of bread. [(see https://www.nibib.nih.gov/science-education/science-topics/computed-tomography-ct)l]
Multiple images are taken as the scanner rotates around the body. The images are then digitally combined together by the computer to produce highly detailed axial or transverse images. Modern scanners can complete a scan in just a few seconds.
Types of CAT Scans
There are several different types of CAT scans used for various medical imaging purposes. Some of the main types include:
CT Scan
CT scans, also known as computed tomography scans, are one of the most common types of CAT scans. They use X-rays and computers to produce cross-sectional images of the body (https://www.healthimages.com/types-of-ct-scans/). CT scans provide more detailed images than regular X-rays and are used to diagnose and monitor conditions affecting organs, tissues, bones and blood vessels.
PET Scan
PET scans, or positron emission tomography scans, involves injecting a radioactive tracer into the body that allows doctors to see how organs and tissues are functioning. PET scans are often used to detect cancer, heart problems and brain disorders (https://ipmcmed.com/radiology/ct-scan/types-of-ct-scan/).
SPECT Scan
SPECT scans (single photon emission computed tomography) are similar to PET scans but use a different radioactive tracer. SPECT scans produce 3D images that show how blood flows to tissues and organs. They are used to diagnose heart disease and stroke.
Cardiac CT Scan
Cardiac CT scans provide detailed images of the heart and its blood vessels. They can detect calcium buildup in the arteries and help diagnose heart disease and blocked arteries (https://www.atlanticmedicalimaging.com/radiology-services/ct/types-of-ct-scans/).
Uses and Applications
One of the primary uses of CAT scans in medicine is for diagnosis of abnormalities or diseases. The detailed images produced by CAT scans allow doctors to examine the body in slices, seeing bones, blood vessels, soft tissues, and organs more clearly than with a regular X-ray. This enables the detection of tumors, infections, injuries, bleeding, or other problems. CAT scans are routinely used to look for cancer, heart disease, liver disorders, kidney stones, spinal problems, musculoskeletal issues, and more. They provide a noninvasive way to get a comprehensive picture of what is going on inside the body.
In addition to diagnosis, CAT scans also help guide medical procedures by giving physicians an internal view of the body. Surgeons may use CAT scans to pinpoint the location of a tumor or other tissue before surgery. The scans also assist in needle biopsies, cyst aspirations, and abscess drainages by showing the exact site to target. Radiologists use CT images to guide the insertion of catheters or stents. CT scans are also used to assess the results of surgeries, biopsies or therapeutic procedures to determine their effectiveness.
Overall, CAT scans are a versatile diagnostic tool, allowing doctors to noninvasively peer inside a patient’s body for medical diagnosis and treatment planning.
Advantages
CAT scans have several key advantages that make them a popular diagnostic imaging tool. One of the main benefits is that CAT scans provide extremely detailed 3D images of the body. They can give doctors a comprehensive view of the structure and anatomy of organs, soft tissues, bone, and blood vessels (Mayo Clinic). This high level of detail allows doctors to detect small abnormalities that may not show up on other imaging tests.
Another advantage of CAT scans is that they are non-invasive. They don’t require incisions or inserting instruments into the body. This makes CAT scans a relatively safe and painless procedure for patients. The scan itself takes only 10-30 minutes to perform, which is faster than many other imaging techniques (RadiologyInfo.org). The speed of CAT scans combined with their detailed images make them well-suited for emergencies and situations where time is critical.
Overall, the key advantages of CAT scans are their ability to produce extremely detailed 3D images of the body’s anatomy quickly and without being invasive. This makes CAT scans one of the most useful and versatile diagnostic imaging tools available.
Limitations of CAT Scans
Though CAT scans provide detailed images of internal anatomy, there are some notable drawbacks and limitations to consider (FDA, Fred, 2004):
Expensive – CAT scans are much more expensive than regular x-rays. The scans require large, sophisticated machinery and specially trained technicians to operate them. This high-tech equipment and expert staff make CAT scans cost anywhere from $270 to $4800 depending on the body part being scanned (WebMD).
Radiation Exposure – While the radiation dose from a single scan is generally not harmful, repeated or excessive CAT scans can expose patients to unnecessarily high levels of radiation. This raises longer-term cancer risks, especially for children whose bodies are still developing (Fred, 2004).
Limited Soft Tissue Imaging – CAT scans are not as effective as MRI for imaging soft tissues. Though CT technology is improving, MRI still produces superior images of organs, tumors, cartilage, ligaments, and tendons (WebMD).
Interpreting CT Scan Results
Radiologists are medical doctors who specialize in interpreting medical images like CT scans. They carefully analyze the images looking for abnormalities or pathology. Radiologists will examine the size, shape, and brightness of structures, looking for anything unusual. They may compare images to previous scans to identify any changes over time.
Some findings on a CT scan that could indicate a problem include cysts, tumors, swelling, fluid accumulation, enlarged lymph nodes, kidney stones, liver lesions, and more. However, many things that look unusual on a CT scan turn out to be benign. Radiologists also consider clinical information and lab results when interpreting scans.
The radiologist will create a detailed written report summarizing the findings, impressions, and recommendations from the CT scan images (cite: How to Read Your Radiology Report). This radiology report allows physicians to determine the next steps in care and treatment.
CT scan images are created through a process called computed tomography reconstruction. Powerful computers process the raw data from the CT scanner and apply algorithms to generate cross-sectional “slice” images of the body. The computing power of modern scanners allows images to be reconstructed in a variety of planes.
Automated computer analysis can help identify certain abnormalities on a scan. But radiologists also rely heavily on their training and expertise when interpreting CT scans. Their ability to recognize subtle findings and put them in clinical context makes them vital to the process.
Patient Preparation
Proper patient preparation is important for getting high quality CT scan images. According to the Mayo Clinic (source), patients are often asked to refrain from eating or drinking anything for a few hours before the scan. This fasting helps prevent vomit aspiration during the scan and avoids potential artifacts from oral contrast or food material in the images.
Patients may also be asked to remove any metal objects like jewelry that could cause artifacts in the images. Removal of metal dental work is sometimes needed as well.
Some CT scans require ingestion or injection of a contrast dye beforehand. Oral contrast helps highlight the gastrointestinal tract while intravenous contrast enhances visualization of blood vessels and organs. The radiology staff provides instructions on how and when to take the contrast material. Rarely, patients can have an allergic reaction to the contrast dye so its use is determined on a case-by-case basis.
The Future of CAT Scans
CAT scan technology continues to rapidly advance and improve. Some key areas of innovation and development include:
Improved resolution: New CT scanners are achieving much higher resolution images, providing more detail and precision. For example, the latest scanners use smaller detectors and advanced image reconstruction to visualize structures down to the sub-millimeter level.
Lower radiation dose: Manufacturers are developing techniques like iterative reconstruction to maintain image quality while using less radiation. This makes CAT scans safer, especially for repeated imaging.
New applications: Photon-counting CT scanners are expanding capabilities into new frontiers like spectral imaging, dual energy scans, and functional imaging. This can reveal additional information about tissue composition, vascular flow, perfusion, and more (Source).
Overall, CAT scan technology is rapidly evolving to become faster, safer, and more versatile. This will increasingly expand their capabilities and usefulness for medical diagnosis and treatment.
