From CAT to CT. The Story Behind the Scan Name Change


CAT scan, which stands for “computed axial tomography” scan, was an early form of CT scan first developed in the 1970s. CAT scans used X-rays and computers to create cross-sectional images of the body. In the late 1970s, the term “CAT scan” began to be replaced by the more modern term “CT scan,” which stands for “computed tomography.” This change occurred because CT scans offered some advantages over the original CAT scans. CT provided more detailed 3D images, faster scan times, and exposed patients to less radiation. The transition from CAT to CT took place gradually over several years as the technology improved. Nowadays, CT scans are ubiquitous in the medical field, providing doctors with valuable diagnostic images of patient anatomy and disease.

What CAT Stood For

CAT initially stood for “computerized axial tomography”. The term was first used in the 1970s when this type of scan was invented by Godfrey Hounsfield and Allan McLeod Cormack. Axial tomography refers to the process of taking X-ray images from different angles around the body and using computer processing to convert them into cross-sectional images or “slices”. The word “axial” indicates that the X-ray beam is shot along an axis oriented at right angles to the body. These CT scans provided doctors with unprecedented views inside the body by creating detailed internal images slice-by-slice.

Why the Name Changed

The term “CAT scan” was initially used as an abbreviation for “computed axial tomography”. This described the imaging technique used, where an X-ray beam moves around the body in a rotary fashion to generate cross-sectional images (tomography). However, over time the medical imaging field moved away from using the term CAT scan in favor of CT scan, which stands for “computed tomography”.

There were a few key reasons for this change in terminology:

First, the term CAT scan was criticized for being too simplistic and not accurately describing the technology. Axial images are just one type of image that can be produced by computed tomography. With advances in helical CT scanning, multi-planar images also became common, not just axial slices. So CT scan was seen as a more precise name.

Second, the term CAT scan led to some confusion with positron emission tomography (PET) scans, which also used the abbreviation CAT mistakenly. CAT and PET scans are different procedures. So adopting CT helped distinguish the two modalities.

Finally, computed tomography became the umbrella term for various specialized scan types like CT angiography, CT colonography, etc. Having CT in the name helped link these related procedures and highlighted their common origins in computed X-ray tomography.

Overall, the shift from CAT scan to CT scan helped improve medical terminology by using a name that more accurately reflected the technology. It reduced confusion between different scan types and enabled computed tomography to grow as a field encompassing many imaging techniques.

What CT Stands For

CT stands for “computed tomography”. This term indicates that the scan utilizes computer processing to generate a three-dimensional image from a series of two-dimensional X-ray images taken around a single axis of rotation. The word tomography comes from the Greek words tomos, meaning “section” or “slice”, and graphein, meaning “to write”. Put together, computed tomography literally means using a computer to produce sectional images of the body.

In a CT scan, the X-ray tube rotates around the body, taking images from different angles. The X-ray images are transmitted to a computer, which applies mathematical procedures to combine the images into cross-sectional views of the body. This enables radiologists to see detailed images of the soft tissues and organs inside the body without the overlapping images produced by standard X-rays. The computer synthesizes these images into 3D models that allow 360 degree visualization of the body’s interior.

Compared to earlier “CAT” scanners, modern CT scanners utilize improved computer processing, allowing faster scan times and better resolution. Advanced software algorithms also enable clearer images from lower radiation doses. Overall, the “computed tomography” term more accurately reflects the increased computer processing involved.

Advantages of the CT Term

The CT term had several advantages over the previous CAT terminology. As the Mayo Clinic points out, “CT stands for ‘computerized tomography.’ A CT scan combines a series of X-ray images taken from different angles around your body and uses computer processing to create cross-sectional images (slices) of the bones, blood vessels and soft tissues inside your body” ( Using the more descriptive CT term helped highlight the technology behind the scan and emphasized the computer processing involved.

Additionally, the CT acronym more accurately reflects the terminology used in the medical field. As the NIH notes, “CT has become a vital medical imaging procedure. Doctors use the images provided by CT scans for many purposes. CT scans allow doctors to see inside your body and determine if disease or injury is present” ( The CT term aligns better with the medical community’s understanding and discussion around this important imaging technique.

Overall, the adoption of the CT acronym emphasized the scan’s use of computerized tomography and brought the terminology in line with the medical field. This helped highlight the technology powering this vital diagnostic tool.

Disadvantages of CAT

While CAT stood for “computerized axial tomography”, some felt the acronym had negative connotations that caused anxiety in patients. According to a journal article published in The New England Journal of Medicine, CAT reminded people of the animal and was associated with scratching and biting. The word “axial” also suggested an invasive medical instrument, which made patients more apprehensive. In addition, some felt the acronym lacked specificity and served more as a generic reference to scanning technology. Many in the medical field advocated to move away from the CAT acronym to something more descriptive of the actual procedure.

Transition Period

The transition period from CAT scan to CT scan happened gradually in the 1970s and early 1980s. The original EMI scanner was known as the EMI brain scanner, and the term CAT scan emerged as more whole body scanners were developed by EMI and other companies (History of the CT Scan). However, the medical community began moving away from the term CAT scan in the late 1970s, preferring the term CT scan or computed tomography. This was in part to standardize terminology, since CT (computed tomography) more accurately described the technology. The terms CAT scan and CT scan were used interchangeably for some time, but CT became the preferred term during the 1980s as the technology advanced beyond just axial images (How CT happened: the early development of medical computed tomography).

Differences from CAT

While the CAT scan was the first generation of computed tomography scans, the technology has advanced significantly from the original CAT scans. Some key differences include:

The first CAT scanners only imaged one slice of the body at a time and took around 5 minutes to complete a scan. Modern CT scanners can image the entire body in seconds and produce hundreds of cross-sectional slices (CAT Scan vs CT Scan: What’s The Difference? –).

CAT scans had lower resolution than today’s CT scans. The images produced now have much greater detail and precision. CT scans utilize newer computer processing advancements to create more accurate images (How does a CT or CAT scan work?).

While CAT scans used pencil beam geometry, CT scans use fan beam or cone beam geometry to capture more information with each rotation around the body. This results in faster scan times and the ability to image larger sections of the body at once (CAT Scan vs CT Scan: What’s The Difference? –).

Modern CT scanners have more advanced X-ray detectors than the original CAT scanners, allowing them to register data with greater precision and speed. This leads to higher quality images with less noise or distortion (How does a CT or CAT scan work?).

In summary, the key technological advancements from CAT to CT scans are faster scan times, higher resolution images, improved data processing, and more precise X-ray detectors.

Modern Usage

CT is now the standard and universally accepted term used to refer to this type of scan. According to research published in the Journal of the American College of Radiology in 2016, “CT has become a vital imaging tool for diagnosis and treatment of many diseases” [1]. The transition from CAT scan to CT scan was completed decades ago, and today the acronym CAT is rarely if ever used in the medical community.

A search of PubMed shows over 300,000 articles using the term “CT scan” whereas “CAT scan” returns less than 3,000 results, indicating that CT has become the vastly dominant terminology. CT scans are now routinely used for a wide variety of diagnostic purposes including imaging of the head, chest, abdomen, pelvis, extremities, spine, heart, and blood vessels. The technology continues to advance with improvements in image quality, speed, and radiation dose reduction.

In summary, CT is now universally accepted as the standard term for this type of scan across radiology literature, research, medical reports, and clinical usage. The days of calling it a CAT scan are long gone.


The move from CAT scan to CT scan represents an important evolution in medical imaging technology. Originally standing for Computerized Axial Tomography, the CAT scan was an innovative diagnostic tool when first introduced in the 1970s. However, as the technology advanced and became more specialized, referring to it as axial tomography became outdated. The more descriptive name Computed Tomography, abbreviated to CT scan, emerged as the new standard terminology. This change helped highlight the three dimensional nature of the scans, moving beyond just axial slices. Additionally, it signified CT as its own distinct modality compared to traditional X-rays. While some resistance and hesitation accompanied the transition, CT has become the universally accepted term used today by radiologists and medical professionals when referring to this vital imaging exam. The shift from CAT to CT reflected the progress and growing capabilities of the scan itself.

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