Dedicated to improving the understanding of radiation risks from medical imaging. Calculate your dose and estimate cancer risk from studies including CT scans, x-rays, nuclear scans and interventional procedures.

• Background
• Methods
• Team
• References

Background

It is currently estimated that 62 million CT scans are obtained in the United States each year.¹  While debated, a recent study suggests that radiation exposure from medical imaging may be responsible for 1-3% of cancers worldwide.² In light of recent media coverage focusing on the increased risk of cancer from CT scans, patients and physicians have become more concerned about the increased use of medical imaging.  Patients are asking their primary care providers and emergency room physicians for information about their risk. In 2004, Lee et al. concluded that “patients are not given information about the risks, benefits and radiation dose for a CT scan”.³  Additionally, this study found that both patients and physicians were “unable to provide accurate estimates of CT doses”.³

While the need for education in this area has clearly been established, there are no widely available resources that provide information to both patients and health care providers about the increased risk of cancer from medical imaging. X-RayRisk.com is an educational website that focuses on estimating this risk. One of the site’s main features is a web based calculator that allows users to track their imaging history and estimate their personal risk, while providing answers to frequently asked questions.

There are no published studies that prove the direct causality between medical imaging and increased cancer risk. Current data on radiation exposure and cancer risk is based on data from survivors of atomic bombs, nuclear accidents and the early use of x-rays.  The assumed increased risk of cancer from low dose medical exposure (CT scans and x-rays) is based on individuals exposed to high doses (atomic bombs and nuclear accidents). The theory that the increased risk holds true at these lower doses is called the linear no threshold model, and is generally accepted in the scientific community.

Great effort has been made throughout the medical community to ensure patient safety while providing quality diagnostic images. It is important to realize that in a properly performed individual exam, the potential health benefits almost always outweigh the potential risks of radiation exposure. Simply put, patients should not hesitate having a study if it is medically indicated. This site aims to provide accurate information for patients and health care providers to facilitate well-informed discussions about the increased risk of cancer from low dose radiation exposure.

The American College of Radiology (ACR) and the International Atomic Energy Agency (IAEA) both recommend hospitals monitor radiation exposure. It may be some time before all hospitals have the ability to track individual exposure. This site allows patients to log-in, create their own imaging record and generate an X-ray Risk Report with information about cancer risk.

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Methods

A committee of scientists and educators gathered by the National Research Council and organized by the National Academy of Sciences published their report on the Health Risks From Exposure to Low Levels of Ionizing Radiation in 2006.  Table 1 was adapted from their Biological Effects of Ionizing Radiation (BEIR) VII Phase 2 Report⁴.  The table estimates the number of additional cases of cancer attributable to a single dose of 0.1Gy (100 mSv) for different age groups.  Data is based on the incidence of all cancer types. Data was plotted (Graph 1), exponential curves were drawn through the data points and formulas derived.  Table 2 was adapted from Mettler et al and lists average adult doses for various medical imaging studies⁵. The conversion factors used to Convert Your Dose from Dose Length Product (mGy · cm) to Effective Dose (mSv) were 0.0022 mSv/mGy · cm for Head CT, 0.0054 mSv/mGy · cm for Neck CT and 0.0180 mSv/mGy · cm for Body CT.⁸ The Risk Calculator can also be used to convert Dose Length Product (DLP in mGy · cm) to Effective Dose (ED in mSv).

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Team

The content of this website has been reviewed by our medical team.

Mike Hanley, MD Founder and Editor Dr. Hanley graduated from the University of Virginia School of Medicine and is currently completing his residency in Radiology at the Medical University of South Carolina.

Jay Koonce, MD Contributing Editor Dr. Koonce graduated from the University of Tennessee College of Medicine and is currently completing his residency in Radiology at the Medical University of South Carolina.

Marques Bradshaw, MD Contributing Editor Dr. Bradshaw graduated from Duke University School of Medicine, completed his residency in Nuclear Medicine at Vanderbilt University School of Medicine and is currently completing his residency in Radiology at the Medical University of South Carolina.

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References