What Is an X-ray and What Is It Used For?
X-ray is a form of electromagnetic radiation that can penetrate or pass through the human body and produce shadow-like images of bones and some organs. These images can reveal signs of disease and injury.
X-rays are used in medicine for procedures such as:
radiography, which produces a still X-ray image;
fluoroscopy, which allows observation of movement within the body and enables certain diagnostic and therapeutic procedures;
and computed tomography, which produces more detailed still images.
The body absorbs some of the energy from X-rays. The very low doses of radiation absorbed during imaging procedures generally do not cause any side effects, but it is still recommended that doses be kept as low as possible. In radiation oncology or therapy, very high doses of radiation are used to stop cancer cells from multiplying.
How Safe Is an X-ray?
The side effects of the radiation dose absorbed during diagnostic procedures are rare. For example, the radiation dose absorbed from a simple X-ray examination, such as a chest X-ray (radiography) or an X-ray of the skull, abdomen, pelvic region, arms, shoulders, or knees, is quite low and smaller than the annual dose received from natural sources. Even at these low levels of radiation exposure, the dose may theoretically cause cancer or genetic effects. There is no practical evidence from human studies of such effects to date, but the theoretical possibility cannot be dismissed.
Which Procedures Are Associated with Higher Radiation Doses?
Computed tomography (CT) and interventional procedures such as angiography and cardiac catheterization are associated with radiation doses that are about 100 to 1000 times higher than a chest X-ray.
What Are the Potential Effects of Radiation on My Health?
Most diagnostic investigations will not have adverse effects. Higher dose procedures, such as CT, interventional procedures, or multiple exposures, may lead to biological effects in some cases. A higher absorbed dose means a higher risk of side effects — the relationship is almost linear. Adverse effects may include skin redness, infertility, cataracts, and hair loss. No diagnostic and interventional procedures have been reported to cause infertility or cataracts. Patients undergoing interventional procedures requiring fluoroscopy lasting one hour or longer may, in very rare cases, experience radiation-induced skin injuries (erythema). Diagnostic X-rays and nuclear medicine examinations slightly increase the risk of cancer.
How Much Radiation Is Acceptable?
There is no predetermined limit for radiation doses for patients. This means that no amount of radiation is considered too much for a patient if the procedure is justified by the doctor. The doctor will weigh the risks against the benefits. Several international organizations have developed guidelines and recommendations based on scientific data. Every effort should be made to minimize the patient’s exposure to radiation. The principle of ALARA – As Low As Reasonably Achievable – guides practices. No examination that does not serve a medical purpose is appropriate, no matter how small the dose.
How Do I Know If the X-ray Facility Is Safe for the Procedure?
X-ray equipment must be maintained by qualified personnel and tested periodically. Radiation safety involves managing the doses to which patients are exposed. Some institutions and organizations accredit facilities that meet safety criteria.
How Do I Know If I’m Receiving the Correct Radiation Dose?
The following principles are helpful:
Every examination must be justified. The benefits and risks of the intended examination or procedure should be considered, and the possibility of using alternative methods that do not involve radiation exposure should be explored. This is the justification principle;
Once justified, the examination should be performed with the minimum radiation dose. This requires obtaining sufficient image quality while keeping the exposure as low as reasonably achievable. This is the optimization principle and ALARA;
The radiation dose can be compared to regional, national, or international reference levels that show approximate dose levels for different medical procedures;
Unnecessary repeat examinations should be avoided. Sometimes repeat examinations are necessary to monitor progress, especially in cancer treatment.
Can I Avoid Unnecessary Repeat Examinations?
You can help avoid unnecessary repeat examinations by ensuring that your doctor has access to the results of previous X-rays. Even if this is not possible, it is important to inform your doctor when the previous examination was done. Not all repeat examinations can be avoided — for example, some are needed to determine the effectiveness of treatment.
How Does My Doctor Choose the Most Appropriate Examination/Procedure?
Doctors are trained to identify appropriate examinations for common medical conditions. When deciding on a research method, doctors consider medical histories, examinations, other test results, and radiation doses. Whenever possible, doctors choose alternative tests that do not expose patients to radiation.
What Alternative Examinations Are Available That Do Not Use X-rays or Radioactivity?
Ultrasound and magnetic resonance imaging (MRI) do not use X-rays or radioactivity. Ultrasound is especially useful for examining the pelvis and abdomen during pregnancy, as well as the breast, testes, and soft tissues in the neck and limbs. MRI is increasingly used to scan the head, spine, and joints when possible.
How Do the Doses and Risks of Nuclear Medicine Compare to X-rays?
Most diagnostic investigations in nuclear medicine expose the patient to a small radiation dose similar to that of X-ray investigations.
Can I Have an X-ray Examination While Pregnant?
Yes, but with certain precautions.
The goal is to minimize the unborn child’s exposure to radiation. It is accepted that an unborn child is more sensitive to potential adverse radiation effects than adults or children. For many examinations, such as X-rays of the head (including dental X-rays), chest, and limbs, the dose to the unborn child will be very low, as the pelvic region is not exposed to the X-ray beam.
All medically justified procedures can be performed.
Doctors may consider delaying procedures that would place the pelvic region and unborn child in the direct path of the X-ray beam, especially for fluoroscopy or CT scans. If the procedure is necessary for the mother’s health, doctors will take special precautions to keep the dose to the unborn child as low as possible. For example, pregnant patients can have their pelvic areas shielded during the procedure as an extra precaution.