A computerized tomography (CT or CAT) is a non-invasive method of diagnosing diseases that could otherwise not be diagnosed without surgery or autopsy.
The computerized tomography (CT scan) is also known as a CAT – axial computerized tomography or CAT scan. [1]
What is CT Scan (CAT scan, Computed Tomography) and how it works
The tomograph is a device that uses a combination of X-rays that are processed by computer software and can render parts or the whole human body in 3D images, thus allowing doctors to see in detail internal organs, blood vessels or bone structure. [2]
Etymologically, the word tomography has its roots in the Greek word “tomos” which means “section” or “slice” and “graphos” which means “writing”. This procedure was independently invented by two researchers – Godfrey Hounsfield, EMI Laboratories in England [3] and Allan Cormack – Tufts University, Massachusetts [4]. For this discovery that marked modern medicine, the two received the Nobel Prize in 1979. [5]
Curious about what a CT scan looks like in Medicai?
Using our embeddable DICOM Viewer, you can easily view your CT scans anywhere online (on the web, in the mobile application). Your CT scans are stored in your Medicai workspace, in the Medicai cloud PACS.
What is the difference between a CT scan – computerized tomography – and MRI – magnetic resonance imaging?
The main difference between the two methods of examination is the technology used. In the case of an MRI, a combination of a magnetic field and a radio wave is used to obtain an image of the organs or other structures in the body. In contrast, a CT uses X-rays to do this. [6]
In some situations, it may also be necessary to use iodine-based contrast agents to better highlight certain areas, organs or structures, such as the main vascular system, tumors or other pathological entities.
The contrast substance can be administered intravenously (in the arm) or introduced to other parts of the body – intrarectal, intra-articular or administered orally. The contrast substance can be administered orally (on the mouth) to allow a better delimitation of the anatomical formations called handles (which are located in the large and small intestine) from the other structures that surround them and also to be able to verify and better visualize the inside of the digestive tract.
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What is the operating principle of CT Scan?
The X-ray machine emits X-radiation that crosses the body. These rays are absorbed by tissues differently, depending on their density. Thus, each tissue and each area will react differently, and the colored image in shades of gray that they produce will be cast beyond the body, on a special plate, either photographic or electronic, the final result being the x-ray we all know.
In the case of a CT-Scan the device is more complex. The patient is seated on a table and is easily inserted into the device. A device that emits X-rays is constantly rotating around and transmits real time information to the computer, which in turn performs a series of complex mathematical calculations and then displays the final image on the device screen. Thus, images of the sections are obtained in any plane of the desired area – 3D organs can be recreated or the bone can be removed for a better visibility of the other tissues.
Because the examination is very precise, the patient is asked to remain very still throughout the examination, which usually only lasts a few minutes. The procedure is not painful, and usually does not involve other preparations, unless it’s necessary to use contrast substance. In this situation, the patient must come to the clinic an hour or 90 minutes before the examination, in order for the administered substance to have time to reach the target area (for example in the entire intestine and in all its handles).
Depending on the area examined, it is possible to ask the patient not to consume food or drink for 4 hours before surgery.
What areas or parts of the child can be examined with the help of a CT?
This procedure is very comprehensive, allowing a full body scan and can cover all segments – head, chest, abdomen, cervical area, pelvis, arms and legs. Also, organs such as heart, lungs, liver, pancreas, kidneys, stomach, intestines, bladder, adrenal glands, spinal cord, blood vessels and bone system can be checked. [7]
What is the range of CT exams?
CT head – imaging different structures of the brain when there are symptoms indicating tumors, strokes, different abnormalities of blood vessels or intracranial bleeding, as well as enlarged lymph nodes and enlarged glands. This large group of head computerized tomography includes: cerebral angio-CT / neck region, frontal bone CT, skull / cerebral CT, internal ear CT, mastoid CT, sinus CT, temporal bone CT.
Abdominal CT – provides a detailed visualization of the abdominal and pelvic organs, such as liver, pancreas, kidney, spleen, adrenal glands, but also the stomach and intestines. Included here: Angio-CT abdomen, CT abdomen, CT abdomen and pelvis, Colo-CT (virtual colonoscopy).
Spine CT – is used to correctly identify the causes of pain in the back, neck, arms or legs. It enables the correct diagnosis of disc hernias or the narrowing of the spinal canal (spinal stenosis). Also with the help of a computerized tomography, spinal fractures or cracks can be detected. There are several types of CT included in this area: cervical spine CT, dorsal spine CT, lumbar spine CT, spine segment CT.
Limbs CT – allows to obtain a clear and detailed image of the limbs to correctly identify the causes of afflictions in these areas: arms, shoulders, elbows, wrist joint, hand joint, legs, hip, knee, ankles, foot. This category includes: Limb Angio-CT, arm / forearm CT, joint (shoulder, elbow, knee, ankle) CT, 3D Reconstruction.
Chest CT – focused on the chest area and internal organs located here: heart, lungs, respiratory tract, etc. This category includes: chest angio CT , chest CT and High-resolution CT.
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What are the risks of a CT scan?
Such a medical examination involves, like any other medical procedure, certain risks, some of them common, others specific to it. Many of these are related to the general condition of the patient and the medical situation they are in.
The doctor, along with the patient, will analyze each situation prior to the tomography and will compare the benefits and the risks of performing the examination and only afterwards will make the best possible decision.
The patient also has the obligation to inform the doctor about any illness or extra information – for example, if a patient is pregnant.
Irradiation.
Among the most frequently asked questions about the risks of a CT scan are radiation related.
Every human being is exposed during life to different sources of irradiation, the sun being for example one of the largest.
Computerized tomography and radiography, because they are based on X-rays, expose the person to an extra dose of radiation. [8] This is not a big dose, but it is not recommended to carry out a large number of such examinations.
The amount of radiation is strictly dosed so that it is optimal to give correct and conclusive images, without the level being higher than necessary.
The risk associated with too high and prolonged exposure to these radiation is the increased likelihood of developing cancer. This is why before each tomography the advantages of its accomplishment and the risks of not doing it are put into balance.
Pregnant women need to be more careful, because the fetus is more sensitive to these radiation than the adult. A CT scan can be performed on a pregnant woman if the situation requires it and the benefits are much greater than this potential risk.
Contrast substance.
The contrast substance is a iodized pharmaceutical substance that, due to its properties, helps in better visibility of the tissues, especially those in the abdomen or blood vessels. It is generally given orally (drank) or intravenously. It is naturally eliminated – usually through the urine – within a few hours of administration. It is not radioactive.
The risks associated with the use of the contrast substance consist of adverse reactions that it can generate. In rare cases, of 1%, these reactions occur in the form of nausea, vomiting, hives, headaches. Usually they pass very quickly after the administration of the substance. In very rare cases – 0.01% – 1 case per 10,000 patients – the reactions may be more severe, manifesting themselves in the form of anaphylactic shock and requiring the intervention of specialized doctors. However, these reactions cannot be predicted. [9]
This is why it is very important that when a doctor recommends using this kind of substance, a patient answers very diligently and accurately to each question in order to prevent unwanted consequences.
Frequently Asked Questions:
What does a CT scan detect?
A CT scan, also known as a CAT scan (Computed Axial Tomography), is a powerful medical imaging technique utilized in hospitals to detect a wide array of medical conditions. This imaging method employs a CT scanner, which takes detailed cross-sectional images of the body's internal structures using X-ray technology and computer processing. There are various types of CT scans, including the spiral CT, which provides faster and more detailed images by rotating continuously around the patient.
Radiologists, who are medical professionals specializing in interpreting medical images, analyze the results of the CT scan to diagnose conditions. This imaging technique can detect a multitude of medical conditions, ranging from bone fractures, tumors, and infections to blood clots, heart disease, and internal injuries. CT scans are particularly valuable for identifying abnormalities in the brain, chest, abdomen, and pelvis.
The scan procedure involves the patient lying on a table that slides into the CT scanner. The machine then rotates around the patient, capturing multiple images from different angles. These images are compiled to create a comprehensive view of the targeted area.
One of the considerations during a CT scan is radiation exposure. Although the levels of radiation used are generally safe, they are higher than those in standard X-rays. Hence, the radiologist and other medical professionals ensure that the benefits of the scan outweigh the risks of radiation exposure.
In summary, CT scans are a vital tool in radiology, enabling the detection and diagnosis of a vast range of medical conditions through detailed imaging of the body's internal structures.
How long does a CT scan take?
The duration of a CT scan, or computed tomography scan, can vary depending on several factors, including the type of exam being performed, the specific area of the body being imaged, and the need for any additional preparations or procedures. Here are some details:
- General Time Frame: A typical tomography scan usually takes between 10 to 30 minutes. This includes the time spent on preparation and positioning as well as the actual time inside the CT machine.
- Type of Exam: The duration can differ based on the specific type of imaging required. For instance:
- A standard CT scan of the head, chest, or abdomen generally takes about 10 to 15 minutes.
- More complex scans, such as those involving detailed imaging of soft tissues, blood vessels, or detection of artery disease, may take longer.
- Preparation Time: Some exams may require special preparation, such as drinking a contrast solution or receiving an intravenous (IV) injection of contrast material. These preparations can add an additional 15 to 30 minutes to the overall process.
- CT Machine Efficiency: Modern CT machines are designed to capture detailed information rapidly. Advanced technology, such as spiral (helical) CT scanners, can complete scans more quickly by continuously rotating around the patient.
- Radiologist Review: After the scan, radiologists will need some time to review the CT images and provide a detailed interpretation. This review is separate from the actual scan time and can take from a few minutes to an hour, depending on the complexity of the exam and the findings.
- Special Considerations: For patients undergoing radiation therapy planning or those with specific conditions like cancer or artery disease, the CT scan might be part of a more extended session that includes additional imaging and planning.
In summary, while the actual scan inside the CT machine might only take a few minutes, the entire process of a computed tomography scan, including preparation and post-scan review, generally takes between 10 to 30 minutes. The exact duration depends on the type of exam and the specific imaging requirements. The result of the CT scan consists of a series of standardized medical images, which can be saved locally or in a cloud PACS for later analysis or comparison with other studies using a DICOM viewer.
References :
[1] https://www.webmd.com/cancer/what-is-a-ct-scan#1
[2] https://www.healthline.com/health/ct-scan
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5144463/
[4] https://www.britannica.com/biography/Allan-MacLeod-Cormack
[5] https://www.nobelprize.org/prizes/medicine/1979/summary/
[6] https://www.medicinenet.com/ct_scan_vs_mri/article.htm
[7] https://patient.info/treatment-medication/ct-scan#nav-1
[8] https://www.mayoclinic.org/tests-procedures/ct-scan/expert-answers/ct-scans/faq-20057860
[9] https://www.radiologyinfo.org/en/info.cfm?pg=safety-contrast#safety-benefits-risks
