Concerns About Radiation Exposure: Your X-Ray and CT Scan Risks

Concern about excessive radiation exposure?

Hello Dr.
Wang,
I would like to ask you a question.
In March of this year, I had a chest X-ray, and on October 8, I had an abdominal X-ray in the emergency department.
On October 19, I underwent a chest CT scan (CT of the thorax) at my own expense, with the report indicating an Effective Dose of 0.25 mSv.
On November 2, due to the need for surgery, I had another chest X-ray at a different hospital (I forgot to transfer the chest CT report because it was urgent).
Originally, I was scheduled for a biennial breast ultrasound and mammogram at the end of November, but after researching online, I found that the annual radiation dose limit for the general public is not to exceed 1 mSv/year.
I started to worry whether my radiation exposure this year has exceeded that limit, and I am considering canceling the mammogram.
I would appreciate your advice on this matter.
Thank you for your time!

Li Juan, 40~49 year old female. Ask Date: 2020/11/04

Dr. Wang Yifen reply Radiology

Hello, the following is an explanation by Committee Member Liao Yan-Peng of the Public Affairs Committee of the Radiological Society of the Republic of China regarding the regulations on annual radiation dose limits:
1.
Why is the annual dose limit for "the general public" set at 1 millisievert (mSv)? This limit ensures that over a lifetime exposure remains below 50 mSv (considering an adult aged 20 years plus 50 years to age 70).
Based on our current understanding of radiation, this is an absolutely safe limit.
2.
Why is the occupational exposure dose limit for "radiation workers" set at 100 mSv over five years? This is based on two factors: (1) there is no evidence of probabilistic effects below a cumulative dose of 100 mSv; (2) using the linear no-threshold (LNT) model for estimation, the risk of death at 100 mSv is comparable to the mortality rates of other occupations.
In other words, workers below this limit are practically safe for their health and theoretically do not exceed the risks associated with other professions.
3.
Medical radiation is not subject to these radiation dose limits.
Diagnostic radiation, except for interventional procedures, generally does not exceed 100 mSv, thus "the benefits of diagnosis far outweigh the risks of radiation." Even in interventional procedures, the doses are usually insufficient to be fatal and provide significant medical benefits; therefore, there is a global consensus that these should not be restricted.
The regulation you found regarding the annual radiation dose limit for the general public not exceeding 1 mSv/year refers to "non-medical radiation" exposure.
Theoretically, only doses exceeding 100 mSv have statistical significance, so all single exposures below 100 mSv in medical procedures are not a cause for concern.
Following your doctor's advice to undergo radiation-related examinations is based on the consideration that the health benefits outweigh the effects of radiation.
If you have concerns, it is advisable to communicate further with your physician before undergoing examinations.
Do not avoid examinations out of fear of radiation, as this may result in missed opportunities for disease treatment.

Please take this into consideration, and I wish you peace and health.

Reply Date: 2020/11/04

More Info

Dear Patient,
Thank you for reaching out with your concerns regarding radiation exposure from your recent medical imaging procedures. It's completely understandable to have apprehensions about the cumulative effects of radiation, especially with the increasing awareness of its potential risks. Let’s break down your situation and provide some clarity.

From your description, you have undergone several imaging studies this year, including a chest X-ray in March, an abdominal X-ray in October, a CT scan of the chest on October 19, and another chest X-ray on November 2. The effective dose from the CT scan was noted to be 0.25 mSv.
To put this into perspective, the average background radiation exposure for a person is about 2-3 mSv per year, depending on geographic location and lifestyle factors. The radiation dose from a single chest X-ray typically ranges from 0.1 to 0.2 mSv, while a CT scan can deliver a dose of approximately 7-10 mSv, depending on the area being scanned and the specific protocol used.

Now, let’s calculate your cumulative radiation exposure for this year based on the information provided:
1. March Chest X-ray: Approximately 0.1 to 0.2 mSv
2. October Abdominal X-ray: Approximately 0.1 to 0.2 mSv (assuming similar dose as chest X-ray)
3. October CT Scan: 0.25 mSv
4. November Chest X-ray: Approximately 0.1 to 0.2 mSv
Adding these together, your total estimated exposure could be around 0.6 to 0.85 mSv. This is well below the annual limit of 1 mSv that you mentioned, which is a guideline for occupational exposure rather than a strict limit for the general public.
It’s important to note that while radiation exposure does accumulate over time, the risk of developing cancer from low doses of radiation is relatively low. The increase in cancer risk from exposure to radiation is often described in terms of a linear no-threshold model, meaning that even small doses can theoretically contribute to risk, but the actual increase in risk from the doses you’ve received is minimal.

Regarding your upcoming mammogram, it is crucial to weigh the benefits of the screening against the risks of radiation exposure. Mammograms are essential for early detection of breast cancer, and the radiation dose from a mammogram is typically around 0.4 mSv, which would still keep you within a safe range for the year.
If you have concerns about the cumulative radiation exposure, I recommend discussing these with your healthcare provider. They can help assess your individual risk factors and the necessity of the mammogram based on your personal and family medical history. It’s essential not to avoid necessary screenings due to fear of radiation, as early detection can significantly improve outcomes.

In summary, your cumulative radiation exposure this year appears to be within safe limits, and the benefits of a mammogram generally outweigh the risks associated with the radiation dose. However, open communication with your healthcare provider is key to making informed decisions about your health.

Wishing you good health and peace of mind.

Best regards,
Doctor Q&A Teams

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