Assessing Annual Radiation Exposure from Medical Imaging: Is It Too High?

Whether the annual examinations and radiation exposure exceed the standard limits?

Hello Dr.
Wang, I had a sarcoma last year and underwent radiation therapy.
For follow-up, I had MRI with contrast; subsequently, I had two PET scans and lung CTs.
At the beginning of this year, I had a lung CT, and in the middle of the year, I had a brain CT and a mammogram, along with a total of four MRIs with contrast this year.
Since I have mitral valve prolapse, my doctor suggested a myocardial perfusion scan, and I inquired with the nuclear medicine department about the radiation dose, which is approximately 10-15 millisieverts.
I would like to ask Dr.
Wang if the radiation exposure over the past two years is too high, especially since the heart, lungs, and breasts are all concentrated in the chest area.
Could this have any impact? My concern is that if the radiation is too high, I would like to ask the cardiologist to arrange for alternative tests.
Thank you for your assistance!

Miss Zhen, 30~39 year old female. Ask Date: 2021/08/10

Dr. Wang Yifen reply Radiology

Hello, MRI is a radiation-free examination, while positron emission tomography (PET), computed tomography (CT), and mammography involve radiation exposure.
Each imaging modality has its own advantages and disadvantages, and some examinations may not have alternative options.
The necessity for radiation-based examinations is determined by physicians based on medical expertise, adhering to the principle of "as low as reasonably achievable" (ALARA), which considers the justification and optimization of medical exposure without limiting the number or dose of radiation examinations.
Following your doctor's recommendations for radiation-related tests is based on the consideration that the health benefits outweigh the risks of radiation exposure.
If you have concerns, it is advisable to discuss them with your physician before undergoing the examination.
Do not avoid tests out of fear of radiation, as this may lead to missed opportunities for disease treatment.
Please take this into consideration, and I wish you peace and good health.

Reply Date: 2021/08/10

More Info

Hello! Thank you for your question regarding radiation exposure from medical imaging, especially in the context of your recent medical history. It's understandable to be concerned about the cumulative radiation dose from various imaging studies, particularly when you have undergone multiple procedures over a short period.

First, let's break down the radiation exposure from the imaging modalities you've mentioned:
1. MRI with Contrast: MRI (Magnetic Resonance Imaging) is generally considered safe as it does not use ionizing radiation. Instead, it uses strong magnetic fields and radio waves to create images of the body. The use of contrast agents in MRI does not add to radiation exposure, but it is important to monitor for any potential allergic reactions or kidney function issues, especially in patients with pre-existing conditions.

2. CT Scans: CT (Computed Tomography) scans do involve exposure to ionizing radiation. The amount of radiation from a CT scan can vary significantly depending on the type of scan and the area being imaged. For example, a chest CT typically delivers a dose of about 7-10 mSv, while a brain CT may deliver around 2 mSv. You mentioned having two lung CTs and one brain CT, which would contribute to your cumulative radiation exposure.

3. PET Scans: Positron Emission Tomography (PET) scans also involve radiation exposure, typically in the range of 5-25 mSv, depending on the specific protocol and the amount of radiotracer used.

4. X-rays: A standard chest X-ray delivers a much lower dose of radiation, approximately 0.1 mSv, while mammograms (breast X-rays) can deliver about 0.4 mSv.

Now, regarding your cumulative exposure over the past two years, it is essential to consider the total dose in the context of the medical necessity of these tests. The average annual background radiation exposure for a person is about 3 mSv, which includes natural sources of radiation from the environment.
Based on your description, if we estimate your exposure:
- MRI (4 times): 0 mSv (since MRI does not use ionizing radiation)
- Lung CT (2 times): approximately 14-20 mSv
- Brain CT (1 time): approximately 2 mSv
- Mammogram (1 time): approximately 0.4 mSv
- Heart scan (10-15 mSv)
This would bring your total estimated exposure to around 26-37 mSv over the two years, which is higher than the average but not excessively so, especially considering the medical necessity of these imaging studies for monitoring your health condition.

It's crucial to discuss your concerns with your healthcare provider, particularly regarding the heart scan. They can evaluate whether alternative imaging methods, such as echocardiography or cardiac MRI, could provide the necessary information without additional radiation exposure.
In summary, while your cumulative radiation exposure is higher than average, it is essential to weigh this against the medical benefits of the imaging studies you have undergone. Open communication with your healthcare team is vital to ensure that your imaging needs are met while minimizing unnecessary radiation exposure. Always feel free to ask about the necessity of each imaging study and potential alternatives. Your health and safety should always come first.

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