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X-rays - what patients need to know

» What are X rays and what do they do?

X rays are a form of electromagnetic radiation that can penetrate or pass through the human body and produce shadow-like images of bones and some organs. The images can reveal signs of disease and injury.
X rays are used in medicine in procedures such as:

  • radiography, which produces a still X ray image;
  • fluoroscopy, which  enables the observation of motion within the body and certain diagnostic and treatment procedures;
  • computed tomography, which produces more detailed still images.

The body absorbs some of the X rays’ energy. The very low radiation doses absorbed during imaging procedures generally produce no adverse effects, but it is still recommended to reduce the doses as much possible. Very large radiation doses are used in radiation oncology or therapy to stop the multiplication of cancer cells.

» How safe are X rays?

Adverse effects from radiation dose absorbed in diagnostic practice are rare. For example, the radiation dose absorbed from a simple X ray examination such as a chest X ray (radiograph) or an X ray of the skull, abdomen, pelvic region, arms, shoulder or knees is quite low and is smaller than that received annually from natural sources. Even at these low levels of radiation exposure, it cannot be excluded that the dose could cause cancer or genetic effects. There is no practical evidence of such effects from any human studies to date, but the theoretical possibility cannot be ruled out.

» Which procedures are associated with higher radiations doses?

Computed tomography (CT) and interventional procedures such as angiography and cardiac catheterisation are associated with higher doses of radiation, about 100 to 1000 times more than a chest X ray.

» What are the possible effects of radiation on my health?

Most diagnostic investigations will not have an adverse effect. Procedures with higher doses such as CT, interventional procedures or multiple exposures could lead to biological effects in some cases. A higher absorbed dose means a higher risk for adverse effects – the relationship is almost linear. Adverse effects could include skin redness, infertility, cataracts and hair loss. There are no reports of radiation exposure in diagnostic and interventional procedures causing infertility or cataracts. Patients undergoing interventional procedures that require fluoroscopy that lasts one hour or more could in very rare cases experience radiation induced skin injuries (erythema). Diagnostic X rays and nuclear medicine examinations lead to a slightly increased risk of cancer. This risk increases with the magnitude of the dose and with the number of procedures.

» How much radiation is acceptable?

There are no prescribed limits on radiation doses to patients. This means that no amount of radiation is considered too much for a patient when the procedure is justified by the doctor. The doctor will consider the benefits versus the risks. Several international organizations have established guidelines and recommendations based on scientific data. Every effort should be made to reduce the patient’s exposure to radiation. A principle known as ALARA – As Low as Reasonably Achievable – guides practices. An examination that serves no medical purpose is inappropriate, no matter how small the dose.

» How do I know if the X ray facility is safe to perform the procedure?

X ray equipment should be maintained by qualified staff and periodically tested. Radiation safety includes management of the doses patients are exposed to. Some organizations and agencies accredit facilities that fulfil safety related criteria.

» How will I know if I am getting the radiation dose that is needed and no more?

The following principles are helpful:

  • Each examination should be justified. Benefits and risks of the intended examination or procedure should be considered, and the possibility of using other methods that do not involve radiation exposure should be explored. This is the principle of justification;
  • Once justified, the examination should be performed with minimal radiation dose. This requires achieving adequate image quality while keeping the exposure as low as reasonably achievable. This is the principle of optimization and ALARA;
  • The radiation dose could be compared with regional, national or international reference levels that indicate approximate dose levels for different medical procedures;
  • Unnecessary repeat examinations should be avoided. Repeat examinations are sometimes needed to monitor progress, particularly with cancer treatment.

» Can I avoid unnecessary repeat investigations?

You can help avoid unnecessary repeat investigations by ensuring that your doctor has access to the results of earlier X rays. Even if this is not possible, it is essential to tell your doctor when the previous examination took place. Not all repeat investigations can be avoided - some are needed to determine a treatment’s effectiveness, for example.

» Do I become radioactive after an X ray procedure?

No.

X rays do not induce radioactivity.

Appropriateness and special situations

» How does my doctor select the most appropriate investigation/procedure?

Doctors are trained to determine the appropriate investigations for common medical conditions. They may use referral criteria such as those produced by the American College of Radiology, the European Society of Radiology and the Royal College of Radiologists. Doctors take medical histories, examinations, other test results and the radiation dose into account when they decide on an investigation method. Where possible, doctors choose alternative tests that do not expose patients to radiation.

» What alternative investigations 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  useful for examining the pelvis and abdomen, particularly in pregnancy, and  for the breast, testes and soft tissues of the neck and limbs. Where available, MRI is increasingly used for scanning the head, spine and joints. 

» How do doses and risk from nuclear medicine compare to X rays?

Most diagnostic investigations in nuclear medicine expose the patient to a small dose of radiation similar to the range of doses received from X ray investigations.

» Can I undergo X ray investigations while I am pregnant?

Yes, but with certain precautions. 

The aim is to minimize  the unborn child’s radiation exposure. An unborn child is considered to be more sensitive than adults or children to potential adverse radiation effects. For many investigations such as X ray examinations of the head (including dental X rays), the chest and limbs, the dose to an unborn child would be very low as the patient’s pelvic region is not exposed to the X ray beam. 
All medically justified procedures can be conducted. 

Doctors may consider delaying  procedures that would put the pelvic region and the unborn child in the direct path of the X ray beam, particularly fluoroscopy or CT investigations. If the procedure is essential to the mother’s health, the doctors take special actions to keep the dose to the unborn child as low as possible. For example, pregnant patients can have their pelvic regions’ shielded during the procedure as an added precaution.