The safety of receiving X-rays is not determined by a simple number, but by balancing medical necessity with the total amount of radiation exposure. X-rays are a form of electromagnetic radiation used to create images of the body’s internal structures, providing physicians with valuable diagnostic information. Like all medical procedures, X-rays carry benefits and a minimal risk from the radiation involved. Safety, therefore, focuses on carefully managing the cumulative dose a patient receives over time. The medical community employs a system of measurement and guiding principles to ensure this balance is maintained.
Understanding Radiation Dose and Measurement
Doctors and physicists use a standardized measurement for radiation exposure known as the effective dose to manage risk. This dose quantifies the overall biological risk to the entire body, taking into account that different tissues have varying sensitivities. The unit of measurement for this effective dose is the millisievert (mSv), which allows for the comparison of risk across different types of procedures and sources of radiation.
The effective dose delivered by medical imaging varies significantly. A standard chest X-ray delivers a low dose (around 0.05 to 0.1 mSv), equivalent to about 10 days of natural background radiation exposure. In contrast, a computed tomography (CT) scan, which uses many X-ray beams to create detailed cross-sectional images, delivers a much higher dose. A CT scan of the abdomen and pelvis, for example, can result in an effective dose ranging from 6 mSv to 10 mSv, comparable to several years of natural background radiation. This wide variation is why total radiation exposure, rather than the count of procedures, dictates safety discussions. Medical professionals track this cumulative effective dose to ensure exposure remains within an acceptable range for the diagnostic benefit received.
The Principle Guiding X-Ray Frequency
Because the dose varies widely between procedures, there is no fixed, universal limit on the number of X-rays a person can have in a year. Frequency is governed by the “As Low As Reasonably Achievable” (ALARA) principle. This principle dictates that radiation exposure must be minimized while still achieving the intended diagnostic objective.
ALARA requires physicians to first justify every examination by confirming that the diagnostic information gained outweighs the potential radiation risk. If an X-ray is necessary, the procedure must be optimized, meaning the lowest possible radiation dose is used to produce an acceptable image quality. This justification and optimization process determines how often an X-ray is performed.
Radiology departments apply ALARA using techniques such as:
- Minimizing the time of exposure.
- Maximizing the distance between the patient and the source when feasible.
- Using protective shielding, such as lead aprons.
Doctors maintain detailed records of a patient’s imaging history to monitor their total cumulative exposure, ensuring medical necessity is the primary driver for every request.
Comparing Common Medical and Environmental Exposures
To put the risks of medical imaging into perspective, they are compared to the radiation exposure people experience daily from natural and environmental sources. All individuals are constantly exposed to natural background radiation from cosmic rays, radioactive materials in the earth and soil, and gases like radon. The average American receives a natural background dose of approximately 3 mSv per year.
Many common X-ray procedures deliver a dose that is only a small fraction of this annual background exposure. A single chest X-ray, for example, is equivalent to the dose received from natural sources over about 10 days. Even flying on a commercial airplane increases exposure, as a cross-country flight can result in a small dose of about 0.035 mSv due to reduced atmospheric shielding. This comparison shows that while medical imaging adds to a person’s total radiation dose, routine diagnostic procedures deliver doses equivalent to what the body encounters naturally over a few weeks or months. Higher-dose procedures like a CT scan must be weighed against the life-saving information they provide.
Special Safety Considerations for Vulnerable Groups
Heightened precautions are taken when considering X-ray procedures for specific populations, particularly children and pregnant individuals, due to their increased sensitivity to radiation. For pediatric patients, their tissues are still developing, and they also have a longer life expectancy, which increases the potential time for radiation effects to manifest. Doctors address this by practicing dose optimization, using lower radiation settings tailored to the child’s smaller size and employing alternative imaging methods like ultrasound or magnetic resonance imaging (MRI) whenever possible.
For pregnant individuals, the primary concern is the potential exposure to the developing fetus, which is most sensitive to radiation effects between weeks 2 and 15 of gestation. X-rays of the abdomen, pelvis, or lower back are avoided unless the procedure is critical to the mother’s immediate health. If an X-ray is necessary, the medical team minimizes the dose, such as by carefully shielding the abdomen with a lead apron. The radiation dose from most common non-abdominal X-rays (e.g., teeth, chest, or extremities) is considered very low and unlikely to pose a risk to the fetus.