From the Guidelines
The average person can safely undergo 150-160 posteroanterior chest X-rays per year, equivalent to the natural background radiation of 3.0 millisieverts (mSv) per person per year in the United States, as stated in the 2018 ACC/HRS/NASCI/SCAI/SCCT expert consensus document 1.
Radiation Safety Considerations
When considering the number of X-rays a person can safely have in a year, it's essential to weigh the diagnostic benefits against the radiation risks for each examination. The ALARA principle (As Low As Reasonably Achievable) guides radiation safety, aiming to minimize exposure while maintaining diagnostic quality.
- Chest X-rays deliver about 0.02-0.06 mSv of radiation per exam, depending on the type of X-ray and body part examined.
- CT scans can deliver 2-10 mSv or more, significantly increasing the cumulative radiation exposure.
- Healthcare providers carefully consider the radiation risks, particularly for children, pregnant women, and those with certain medical conditions, who are more sensitive to radiation effects.
Patient Characteristics and Radiation Risk
The risk of radiation-caused cancer is not uniform across the population, and patient characteristics, such as age, gender, and comorbidities, modulate the risk associated with a particular radiation exposure 1.
- Children and young adults with a long life expectancy, particularly females, are at higher risk of radiation-induced cancer.
- Patients with shorter life expectancies and important comorbidities have a lower risk of radiation-induced cancer.
Minimizing Cumulative Exposure
To minimize cumulative radiation exposure, healthcare providers may consider alternative radiation-free options like ultrasound or MRI when appropriate or space X-rays throughout the year.
- The 2018 ACC/HRS/NASCI/SCAI/SCCT expert consensus document emphasizes the importance of assessing the radiation component when considering a proposed procedure's appropriateness 1.
- By carefully weighing the diagnostic benefits against radiation risks and following the ALARA principle, healthcare providers can ensure that patients receive the necessary imaging studies while minimizing the risk of radiation-induced harm.
From the Research
Radiation Safety and X-Ray Limitations
The question of how many X-rays can be done safely in a year without radiation ill effects is complex and depends on various factors, including the type of X-ray, the patient's condition, and the cumulative effective dose.
- The International Commission on Radiological Protection has alerted on the problems of using effective dose for risk estimation in individual patients, but has accepted its use for comparing relative radiation risks between different imaging modalities 2.
- Studies have shown that cumulative effective doses of 100 mSv or greater can increase the risk of radiation-induced cancer, but the exact number of X-rays that can be safely performed in a year is not well established 3, 4.
Cumulative Effective Dose and X-Ray Safety
- A study published in the European radiology journal found that a relatively low percentage of patients (0.5%) received a cumulative effective dose from CT computed tomography equal to or greater than 100 mSv, with most of them having an oncological disease 3.
- Another study published in the Chest journal found that 6.8% of patients in a mixed-use surgical ICU exceeded occupational exposure limits of 50 mSv, with CT imaging contributing the most to radiation exposure 4.
- The American College of Radiology recommends that patients should not receive more than 100 mSv of cumulative effective dose from medical imaging procedures in a year, but this limit is not universally accepted and may vary depending on the specific clinical situation 2, 3.
X-Ray Image Quality and Radiation Dose
- A study published in the Nihon Hoshasen Gijutsu Gakkai zasshi journal found that the image quality of X-rays improved as the radiation dose increased, but that there was a significant variation in radiation doses among institutions 5.
- Another study published in the American journal of surgery found that a chest X-ray and an abdominal computed tomography scan can identify most clinically significant thoracic injuries in trauma patients, rendering the thoracic CT scan useful in only a subset of patients 6.