X-rays: Medical and dental X-rays
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Safety and regulations
Medical and dental X-rays can provide valuable information on a patient's medical or dental condition. They're both subject to requirements under the:
About medical X-rays
Diagnostic X-rays can provide a doctor with important information about a medical condition in an adult or child.
Like many medical tests, X-rays have risks as well as benefits. Your doctor is trained to determine whether the benefits of receiving an X-ray outweigh the risks. The risk of not having a needed X-ray can be much greater than the risk from any exposure to the radiation.
Types of medical X-rays
2D X-ray imaging/radiography (general planar imaging)
This type of exam provides a 2D picture of the inside of a patient's body. It's used for many applications, including to:
- determine if an arm or leg is broken
- diagnose health problems of the cardiovascular, respiratory or digestive system
The dual-energy X-ray absorptiometry (DEXA or DXA) scan is a specialized type of planar imaging that gives information about a patient's bone density. It uses X-ray beams of different energies to evaluate bone density.
This type of 2D imaging produces a movie-like image by repeating X-rays over time. It's often used during diagnostic procedures or interventions where it's important to keep track of something moving in the body in real-time, such as:
- inserting a catheter
- placing a stent to open an artery
- viewing a barium enema for gastrointestinal tract analysis
- monitoring the flow of contrast agents to identify narrowed or blocked arteries
This is a specific-type of imaging technique that uses X-rays to provide a couple of 2D pictures of the internal structure of the breast. The X-rays can show abnormal growths or changes in breast tissue before they can be found by any other method, including breast self-examination.
Tomosynthesis is another technique that creates a 3D picture of the internal breast structure. It takes multiple 2D pictures of the breast from different angles.
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Computed tomography (CT)/CAT scan
A CT scan gives a detailed 3D picture of the inside of a patient's body. The patient lies down on the exam table, which is moved in and out of a large donut-like ring. An X-ray generator and detector inside the ring rotate around the patient to get pictures from many angles.
These pictures produce a 3D picture, which allows physicians to see parts of the body that might otherwise be hidden with planar imaging, such as a blood clot or cancer in the brain.
A cone-beam CT device that rotates around a stationary patient can also perform a CT scan.
Health risks of medical X-rays
There are many medical conditions and situations where medical X-rays are used to diagnose or monitor patients. Health professionals are trained to only prescribe medical imaging exams when necessary and appropriate. They also make efforts to optimize the amount of information when X-rays are needed. This means only using the lowest dose of radiation needed to obtain the necessary medical information.
For this reason, there is no limit on the number of medical X-ray exams or the total dose a person may receive over time. The medical benefit to the patient far outweighs the radiation risks from a clinically appropriate X-ray exam.
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Diagnostic X-rays and pregnancy
X-rays during pregnancy may have potential risks to an unborn child. Doctors are in the best position to weigh the risks against the benefits. If an X-ray is necessary, technologists will use special techniques to reduce the level of radiation and risk to the unborn child.
Informing your doctor if you are or might be pregnant allows them to take any appropriate precautions.
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About dental X-rays
X-rays are used in dental health care to diagnose conditions that are difficult to identify by sight. They're also used to help plan a course of treatment.
The X-ray source (generator) of all dental X-ray devices is positioned outside of the head. The image receptor is positioned either:
- inside the mouth (intra-oral) or
- outside of the head opposite the X-ray source (extra-oral)
This uses a detector inside of the mouth to get a 2D picture of a few upper and lower teeth at a time.
This type of X-ray detects problems in the jaw and skull. Common extra-oral X-ray devices include:
- panoramic X-rays, which provide a single 2D picture of all the teeth in both jaws by scanning the device around the front of the head
- much like how your camera can obtain a wide-view photograph in panorama mode
- cone-beam computed tomography (CBCT) devices, which create a 3D image by taking pictures as they rotate around the patient's head
- cephalometric X-rays, which provide a 2D picture of the jaw and head, similar to general planar imaging medical X-rays
Health risks of dental X-rays
Since the radiation dose is low for each exposure, the risk of harm from dental X-rays is generally low. However, since a large number of people in Canada receive dental X-rays each year, it's important to decrease risks for the population as a whole.
Health Canada's Safety Code 30 and guidance by the Canadian Dental Association indicate that a dental X-ray should be performed:
- based on a clinical examination and
- for obtaining diagnostic information, providing safe and efficient treatment or monitoring treatment
Health care professionals should not perform routine or screening exams without doing a clinical exam first. When a patient changes dentists, the new dentist should try to obtain previous X-ray information rather than take new X-rays.
Learn more about:
- Safety Code 30
- CDA position on control of X-radiation in dentistry (Canadian Dental Association)
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