CT scan or CAT scan: How does it work?

A computerized tomography (CT) or computerized axial tomography (CAT) scan combines data from several X-rays to produce a detailed image of structures inside the body.

CT scans produce 2-dimensional images of a “slice” or section of the body, but the data can also be used to construct 3-dimensional images. A CT scan can be compared to looking at one slice of bread within a whole loaf.

CT scans are used in hospitals worldwide.

A CT scanner emits a series of narrow beams through the human body as it moves through an arc.

This is different from an X-ray machine, which sends just one radiation beam. The CT scan produces a more detailed final picture than an X-ray image.

The CT scanner’s X-ray detector can see hundreds of different levels of density. It can see tissues within a solid organ.

This data is transmitted to a computer, which builds up a 3-D cross-sectional picture of the part of the body and displays it on the screen.

Sometimes, a contrast dye is used because it can help show certain structures more clearly.

For instance, if a 3-D image of the abdomen is required, the patient may have to drink a barium meal. The barium appears white on the scan as it travels through the digestive system.

If images lower down the body are required, such as the rectum, the patient may be given a barium enema. If blood vessel images are the target, a contrast agent will be injected into the veins.

The accuracy and speed of CT scans may be improved with the application of spiral CT, a relatively new technology. The beam takes a spiral path during the scanning, so it gathers continuous data with no gaps between images.

CT is a useful tool for assisting diagnosis in medicine, but it is a source of ionizing radiation, and it can potentially cause cancer.

The National Cancer Institute advise patients to discuss the risks and benefits of CT scans with their doctors.

Share on PinterestA CT scan can detect abnormalities in the soft tissue.

It is useful for obtaining images of:

• soft tissues
• the pelvis
• blood vessels
• lungs
• brain
• abdomen
• bones

CT is often the preferred way of diagnosing many cancers, such as liver, lung, and pancreatic cancers.

The image allows a doctor to confirm the presence and location of a tumor, its size, and how much it has affected nearby tissue.

A scan of the head can provide important information about the brain, for instance, if there is any bleeding, swelling of the arteries, or a tumor.

A CT scan can reveal a tumor in the abdomen, and any swelling or inflammation in nearby internal organs. It can show any lacerations of the spleen, kidneys, or liver.

As a CT scan detects abnormal tissue, it is useful for planning areas for radiotherapy and biopsies, and it can provide valuable data on blood flow and other vascular conditions.

It can help a doctor assess bone diseases, bone density, and the state of the patient’s spine.

It can also provide vital data about injuries to a patient’s hands, feet, and other skeletal structures. Even small bones are clearly visible, as well as their surrounding tissue.

CT versus MRI

The main differences between CT and MRI are:

• A CT scan uses X-rays, but an MRI uses magnets and radio waves.
• Unlike an MRI, a CT scan does not show tendons and ligaments.
• MRI is better for examining the spinal cord.
• A CT scan is better suited to cancer, pneumonia, abnormal chest x-rays, bleeding in the brain, especially after an injury.
• A brain tumor is more clearly visible on MRI.
• A CT scan shows organ tear and organ injury more quickly, so it may be more suitable for trauma cases.
• Broken bones and vertebrae are more clearly visible on a CT scan.
• CT scans provide a better image of the lungs and organs in the chest cavity between the lungs.

The patient may need to abstain from food, and possibly drink, for a specific period before the scan.

On the day

In most places, the patient will need to undress, usually down to their underwear, and put on a gown that the health center will provide. Avoid wearing jewelry.

If the hospital does not provide a gown, the patient should wear loose-fitting clothes free of metal buttons and zippers.

Some patients may have to drink a contrast dye, or the dye may be given as an enema, or injected.This improves the picture of some blood vessels or tissues.

Any patient who has an allergy to contrast material should tell the doctor beforehand. Some medications can reduce allergic reactions to contrast materials.

As metal interferes with the workings of the CT scanner, the patient will need to remove all jewelry and metal fastenings.

During the scan

The patient will need to lie down on a motorized examination table that slides into a doughnut-shaped CT scanner machine.

In most cases, the patient will lie on their back, facing up. But, sometimes, they may need to lie facedown or sideways.

After one x-ray picture, the couch will move slightly, and then the machine will take another image, and so on. The patient needs to lie very still for the best results.

During the scan, everybody except for the patient will leave the room. An intercom will enable two-way communication between the radiographer and the patient.

If the patient is a child, a parent or adult might be allowed to stand or sit nearby, but they will have to wear a lead apron to prevent radiation exposure.

Share on PinterestThe doctor should explain why the scan is needed, any other options available, and the pros and cons of having a CT scan.

A CT scan involves a small, targeted dose of radiation.

These levels of radiation, even in people who have undergone several scans, has not proven to be harmful.

The chance of developing cancer as the result of a CT scan is thought to be less than 1 in 2,000.

The amount of radiation involved is estimated to be around the same as a person would be exposed to in a space of between several months and several years of natural exposure in the environment.

A scan is only given if there is a clear medical reason to do so. The results can lead to treatment for conditions that could otherwise be serious. When the decision is taken to perform a scan, doctors will ensure that the benefits outweigh any risk.

Problems that could possibly arise from radiation exposure include cancer and thyroid issues.

This is extremely unlikely in adults, and also unlikely in children. However, are more susceptible to the effects of radiation. This does not mean that health issues will result, but any CT scans should be noted on the child’s medical record.

In some cases, only a CT scan can show the required results. For some conditions, an ultrasound or MRI might be possible.

Can I have a CT scan if I am pregnant?

Any woman who suspects she may be pregnant should tell her doctor beforehand, because there is a risk that the x-rays could harm the fetus.

Citing the American College of Radiography, the American Pregnancy Association (APA) point out that “No single diagnostic x-ray has a radiation dose significant enough to cause adverse effects in a developing embryo or fetus. ”

However, the APA notes that CT scans are not recommended for pregnant women, “Unless the benefits clearly outweigh the risk.”

CT scans and breastfeeding

If a lactating, or breastfeeding, mother needs an iodinated intravenous dye for contrast, she should avoid breastfeeding for about 24 hours as may pass into the breast milk.

I have claustrophobia: Can I have a CT scan?

A patient who has claustrophobia should tell their doctor or radiographer beforehand. The patient may be given an injection or tablet to calm them down before the scan.

Your health care provider will usually be able to recommend a suitable facility for a scan. You can check if a radiologist is accredited by searching on the website of the American College of Radiology.

Computed Tomography (CT)

• What is a computed tomography (CT) scan?
• How does CT work?
• When would I get a CT scan?
• What is a CT contrast agent?
• Are there risks?
• What are examples of NIBIB-funded projects using CT?

What is a computed tomography (CT) scan?

The term “computed tomography,” or CT, refers to a computerized x-ray imaging procedure in which a narrow beam of x-rays is aimed at a patient and quickly rotated around the body, producing signals that are processed by the machine’s computer to generate cross-sectional images, or “slices. ” These slices are called tomographic images and can give a clinician more detailed information than conventional x-rays. Once a number of successive slices are collected by the machine’s computer, they can be digitally “stacked” together to form a three-dimensional (3D) image of the patient that allows for easier identification of basic structures as well as possible tumors or abnormalities.

How does CT work?

A CT machine. Credit: iStock

Unlike a conventional x-ray—which uses a fixed x-ray tube—a CT scanner uses a motorized x-ray source that rotates around the circular opening of a donut-shaped structure called a gantry. During a CT scan, the patient lies on a bed that slowly moves through the gantry while the x-ray tube rotates around the patient, shooting narrow beams of x-rays through the body. Instead of film, CT scanners use special digital x-ray detectors, which are located directly opposite the x-ray source. As the x-rays leave the patient, they are picked up by the detectors and transmitted to a computer.

Each time the x-ray source completes one full rotation, the CT computer uses sophisticated mathematical techniques to construct a two-dimensional image slice of the patient. The thickness of the tissue represented in each image slice can vary depending on the CT machine used, but usually ranges from 1-10 millimeters. When a full slice is completed, the image is stored and the motorized bed is moved forward incrementally into the gantry. The x-ray scanning process is then repeated to produce another image slice. This process continues until the desired number of slices is collected.

Image slices can either be displayed individually or stacked together by the computer to generate a 3D image of the patient that shows the skeleton, organs, and tissues as well as any abnormalities the physician is trying to identify. This method has many advantages including the ability to rotate the 3D image in space or to view slices in succession, making it easier to find the exact place where a problem may be located.

When would I get a CT scan?

CT scans can be used to identify disease or injury within various regions of the body. For example, CT has become a useful screening tool for detecting possible tumors or lesions within the abdomen. A CT scan of the heart may be ordered when various types of heart disease or abnormalities are suspected. CT can also be used to image the head in order to locate injuries, tumors, clots leading to stroke, hemorrhage, and other conditions. It can image the lungs in order to reveal the presence of tumors, pulmonary embolisms (blood clots), excess fluid, and other conditions such as emphysema or pneumonia. A CT scan is particularly useful when imaging complex bone fractures, severely eroded joints, or bone tumors since it usually produces more detail than would be possible with a conventional x-ray.

What is a CT contrast agent?

CT scan of the abdomen. Credit: iStock

As with all x-rays, dense structures within the body—such as bone—are easily imaged, whereas soft tissues vary in their ability to stop x-rays and therefore may be faint or difficult to see. For this reason, contrast agents have been developed that are highly visible in an x-ray or CT scan and are safe to use in patients. Contrast agents contain substances that can stop x-rays and are therefore more visible on an x-ray image. For example, to examine the circulatory system, an intravenous (IV) contrast agent based on iodine is injected into the bloodstream to help illuminate blood vessels. This type of test is used to look for possible obstructions in blood vessels, including those in the heart. Oral contrast agents, such as barium-based compounds, are used for imaging the digestive system, including the esophagus, stomach, and gastrointestinal (GI) tract.

Are there risks?

CT scans can diagnose possibly life-threatening conditions such as hemorrhage, blood clots, or cancer. An early diagnosis of these conditions could potentially be lifesaving. However, CT scans use x-rays, and all x-rays produce ionizing radiation. Ionizing radiation has the potential to cause biological effects in living tissue. This is a risk that increases with the number of exposures added up over the life of an individual. However, the risk of developing cancer from x-ray radiation exposure is generally small.

CT images of the heart and coronary artery. Credit: iStock

A CT scan in a pregnant woman poses no known risks to the baby if the area of the body being imaged isn’t the abdomen or pelvis. In general, if imaging of the abdomen and pelvis is needed, doctors prefer to use exams that do not use radiation, such as magnetic resonance imaging (MRI) or ultrasound. However, if neither of those can provide the answers needed, or there is an emergency or other time constraint, CT may be an acceptable alternative imaging option.

In some patients, contrast agents may cause allergic reactions, or in rare cases, temporary kidney failure. IV contrast agents should not be administered to patients with abnormal kidney function since they may induce a further reduction of kidney function, which may sometimes become permanent.

Because children are more sensitive to ionizing radiation and have a longer life expectancy, they have a higher relative risk for developing cancer from such radiation compared with adults. Parents may want to ask the technologist or doctor if their machine settings have been adjusted for children.

What are examples of NIBIB-funded projects using CT?

Imaging for acute ischemic stroke: Stroke, which can have lasting neurological injuries, is also a leading cause of death worldwide. To mitigate damage to the brain, patients may receive endovascular treatment, where the clot blocking the blood supply is either removed or dissolved. However, identifying patients who will benefit from endovascular therapy, such as those with only a small volume of irreversibly injured brain tissue, remains challenging, and time is a critically important factor for a successful clinical outcome.

Patient inside of a CT machine. Credit: iStock

NIBIB-funded researchers have developed an image reconstruction technique to more efficiently triage patients who present with symptoms of a stroke. This CT-based method can be used to rule out the presence of a hemorrhage; to find the site of the blood clot; and to identify the extent of damaged brain tissue. Such a technique could significantly shorten the time from the diagnosis of a stroke to the start of endovascular therapy, and could also guide the endovascular treatment. Following evaluation in animal models, researchers plan to validate this CT imaging technique in human studies.

Accounting for metal implants in CT imaging: Metal objects, such as implants and prostheses, can introduce ‘artifacts’ that may appear as streaks or shadows on a CT scan. These artifacts can obscure anatomical structures or affect calculations necessary for planning radiation therapy. While techniques exist to reduce such artifacts, they do not fully mitigate the artifacts and may even introduce new ones. In this project, NIBIB-funded researchers have developed an algorithm to reduce metal artifacts in CT imaging, without requiring knowledge of the implant material. The researchers plan to optimize their algorithm and then evaluate their technique as a potential method to improve radiation therapy planning for prostate cancer among those with hip protheses.

Leveraging CT images to guide treatments for COVID-19 and beyond: Artificial intelligence is increasingly being used with medical imaging, such as CT, to help improve diagnoses and guide treatment decisions. By using medical images and patient outcomes, clinicians can “train” machine learning-based technologies to recognize patterns and predict responses. During the COVID-19 pandemic, NIBIB created a collaborative imaging initiative called the Medical Imaging and Data Resource Center (MIDRC). This initiative collected and analyzed thousands of CT images from patients with COVID-19 for the development of artificial intelligence and machine learning tools to guide the treatment and monitoring of the disease. These datasets contribute to the development of algorithms for detection, prognosis, and optimization of therapy in acute COVID-19 patients and have the potential to contribute to the understanding of Post-Acute Sequelae of SARS-CoV-2 infection (PASC, otherwise known as “Long COVID”). Further, this initiative paves the way for new tools that leverage imaging for other medical conditions, such as cancer, liver disease, or other infectious diseases, among others.

For more information about CT, watch our video here.

Updated June 2022

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Cat Scanner – Identification of cat breeds on Android and iOS

See a cat, but don’t know its breed?

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Catch all cat breeds in Pokémon Go. Scan at least one cat of each breed, complete the challenges, earn virtual treats and become a true cat expert!

Compete against your friends or community members and climb to the top of our rankings!

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Let us know if the cat breed has been correctly identified. If not, you will receive useful tips to improve your own results. If you also indicate what breed of cat is in the picture, you will help us improve our software as the app automatically learns how to provide even more accurate results.

Suggest or vote for (unofficial) cat breeds you want us to add to the app in the future!

Get your premium upgrade!

With our premium version, the app will no longer show ads and your results will be available faster. What’s more, you can now choose whether to recognize your cat’s breeds fairly quickly or with greater accuracy. In the premium version, scanning cats is also possible offline, so you no longer need an active internet connection to identify their breeds. By purchasing our premium version as an option, you will also help support this app.

Find us on social networks!

On our social media channels, we bring you the most beautiful community cat pictures. You will also find many interesting facts about your favorite pet. Also, we will keep you updated on all the new added features of the Cat Scanner app in the future.

* Instagram
* Facebook
* Twitter

Just try it!

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Have you ever seen a cat and wondered what kind of cat it is? Maybe you even know the breed but can’t remember its name? Or do you have your own cat whose breed you still do not know? Well, you may know that you are a mixed breed, but what breeds are actually part of your favorite?

Before you consider getting an expensive DNA test, the Cat Scanner app will help you answer all these questions! Just scan the cat with the app and the cat’s breed will be automatically determined within seconds!

Disclaimer:

This app cannot turn your smart phone into a crazy spaceship that can extract your cat’s blood with a magic laser. The app gives educated predictions based on what it sees. On average, these predictions are fairly accurate. However, obviously the result can only be as good as the image/video you provide to the application. Moreover, it is impossible to correctly identify every cat. People tend to take it personally if their own favorite cat is not predicted correctly. If you give the app a chance, you’ll see that its overall performance is pretty decent. Instead of paying a bunch of money for a DNA test, you get this app for free. Enjoy!

‎App Store: Cat Scanner

Description

See a cat but don’t know its breed? Just take a picture and find out!

The Cat Scanner app reliably identifies your cat’s breed in just a few seconds! Apart from taking a photo, you can also record a video or upload an image from your gallery.

Are you a mixed breed?

No problem, the Cat Scanner app also recognizes mixed breeds! We will provide you with detailed data and interesting facts about the different breeds of your mixed breed cats.

Is there a cat nearby?

It doesn’t matter! The Cat Scanner app also recognizes people: Simply scan yourself, friends, family or those around you and find out which cat you like best!

——

NEW! Be part of our cat scanner community!

Share your results and compare with the community! Upload photos of your favorite cat to our Social Feed and share them with other cat lovers! Browse profiles and photos of other users, comment on our feline community posts and filter them by date or popularity!

In addition, you can easily share your messages with your friends by simply sending a photo directly from the Cat Scanner app.

——

Catch all cat breeds and become an expert!

Capture cats of all breeds with our Gamification feature, just like in Pokémon Go! Master the challenges, earn virtual treats and become a true cat expert! Compete against friends or users from the community and climb to the top of our rankings!

All cat breeds in the Cat Scanner app!

The Cat Scanner app currently recognizes about 60 different cat breeds, including all breeds officially recognized by the FIFe (International Federation) and even more! Our extensive database of information and photos of all cat breeds (including unofficial ones) is also available completely unscanned!

Give us your feedback on the Cat Scanner app!

Let us know if the cat’s breed has been correctly identified. If not, you will receive useful tips to improve your own results. If you also indicate what breed of cat is in the picture, you will help us improve our software as the app automatically learns how to provide even more accurate results. Also suggest or vote for (unofficial) cat breeds you want us to add to the app in the future!

Get your premium upgrade!

With our premium version, the app will no longer show ads and your results will be available faster. What’s more, you can now choose whether your cat breeds should be recognized quickly enough or with greater accuracy. With the premium version, scanning cats is also possible offline, so you no longer need an active internet connection to identify their breeds. By purchasing our premium version as an option, you will also help support this app.

——

Find us on social networks!

On our social media channels, we bring you the most beautiful community cat pictures. You will also find many interesting facts about your favorite pet. In addition, we will keep you updated on all new added features of the Cat Scanner app in the future.

* Instagram: https://www.instagram.com/catscanner_app
* Facebook: https://www.facebook.com/CatScanner
* Twitter: https://twitter.com/catscanner_app

——

Just try it!

Finding a cat is as easy as getting one! Despite the small size of the application, you will get all the features and be able to determine the breed of a cat or access our extensive database at any time! Before considering an expensive DNA test, simply scan your cat with the app and the cat breed will be automatically determined within seconds! Download the Cat Scanner app now!

Terms of Service:
https://scanner.siwalusoftware.com/terms-of-service

Mar 1 2023

Version 9.8.8

Bug fixes and improvements.

Ratings and reviews

ratings: 293

👍👍

The app accurately identified the breeds of my cats))👍👍👍👍

Does not recognize a cat correctly, even an ordinary one

He writes that Scottish cats are not an official breed and therefore he cannot recognize whether the Scots have not been an official breed for a long time ?! In 2004 it was registered, what’s the problem?! With an ordinary cat the same story …….

👎🏻

Does not scan, a window with a paid subscription opens immediately

The developer of Siwalu Software GmbH has indicated that, in accordance with the application’s privacy policy, data may be processed as described below. Detailed information is available in the developer’s privacy policy.

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Sensitive data may be used differently depending on your age, features involved, or other factors.