CT Scan Radiation: Safety and Accumulation Concerns

Computed Tomography (CT) radiation?

Hello, doctor.

1.
I would like to ask if the radiation exposure from a CT scan accumulates in the body.
I am scheduled for a head CT scan soon (which requires contrast media).

2.
I had an abdominal CT scan last October (also with contrast media), and my health insurance app shows that I currently have a cumulative dose of 12.2 millisieverts.
Is there any safety concern regarding this level?
3.
Is the recommendation to not exceed 100 millisieverts a lifetime limit? Thank you very much!

X, 20~29 year old female. Ask Date: 2022/10/18

Dr. Wang Yifen reply Radiology

Hello, radiation is a form of energy that causes exposure during examinations, but it does not accumulate in the human body afterward.
It is similar to how sunlight does not accumulate in the body after sun exposure.
It is important to be aware of the effects of radiation on the body, such as skin damage from sun exposure, which can lead to related subsequent reactions.
According to the International Commission on Radiological Protection's Report No.
60, when a person is exposed to a radiation dose of 100 millisieverts, their risk of developing cancer increases by 0.24% compared to someone who has not been exposed.
This means that if 100,000 people are simultaneously exposed to a dose of 100 millisieverts, approximately 240 of them may develop cancer as a result.
Additionally, information from the National Health Administration indicates that both men and women have about a 40% risk of being diagnosed with cancer at some point in their lives.
Therefore, among those 100,000 people, even if they do nothing, about 40,000 will still develop cancer.
Based on current scientific data, radiation exposure with an effective dose below 100 millisieverts is considered low-dose radiation and does not require special concern; however, exposure to a single organ exceeding 100 grays should be closely monitored.
Radiological examinations are determined by physicians based on medical necessity, adhering to the principles of justification and optimization of medical exposure, without limiting the number or dose of radiological examinations.
Following a doctor's instructions to undergo radiation-related examinations is based on the consideration that the health benefits outweigh the effects of radiation.
If there are any concerns, it is advisable to communicate with the physician before undergoing the examination.
One should not avoid examinations out of fear of radiation, as this may result in missing the opportunity for disease treatment.
Please refer to the above information, and I wish you peace and health.
Sources: 1.
"Afraid of Radiation, Better to Supplement the Brain" by Liao Yanpeng, First Edition.
Shih-Pao Culture, March 2016.
ISBN 978-957-13-6573-2 (Paperback) 2.
National Health Administration reference website: https://www.hpa.gov.tw/Pages/Detail.aspx?nodeid=127&pid=10357

Reply Date: 2022/10/18

More Info

When it comes to understanding the radiation exposure from CT scans, it is essential to consider several factors, including the nature of radiation, its accumulation in the body, and the associated risks.
1. Radiation Accumulation: The radiation exposure from CT scans does not accumulate in the body in the way that some substances do. Instead, ionizing radiation, which is what CT scans use, interacts with the body's tissues at the moment of exposure. Once the radiation has passed through the body, it does not remain or build up over time. However, it is important to note that the effects of radiation exposure can be cumulative in terms of risk. This means that while the radiation itself does not stay in your body, the potential risk of developing radiation-induced conditions, such as cancer, increases with each exposure over time.

2. Current Radiation Exposure: You mentioned that your total radiation exposure is currently 12.2 mSv. To put this into perspective, the average person is exposed to about 2-3 mSv of natural background radiation each year. A single abdominal CT scan typically exposes a person to about 8-10 mSv, while a head CT scan usually exposes about 2 mSv. Therefore, your current exposure is within a reasonable range, especially considering that medical imaging is often necessary for diagnosis and treatment. However, it is crucial to discuss with your healthcare provider whether the benefits of the upcoming head CT scan outweigh the risks, particularly since you have had previous scans.

3. Lifetime Radiation Limits: The recommendation to limit cumulative radiation exposure to 100 mSv over a lifetime is a guideline aimed at minimizing the risk of radiation-induced cancer. This limit is not a strict cutoff but rather a threshold that helps healthcare providers make informed decisions about the necessity of additional imaging studies. It is essential to understand that this recommendation is based on statistical risk assessments and does not mean that exceeding this limit will definitively result in harm. Individual risk can vary based on factors such as age, sex, genetic predisposition, and overall health.

In summary, while the radiation from CT scans does not accumulate in the body, the potential risks associated with repeated exposures can add up over time. Your current exposure of 12.2 mSv is within a safe range, but it is essential to weigh the necessity of any further scans against the potential risks. Always consult with your healthcare provider to ensure that any imaging studies are justified and that you are receiving the best possible care tailored to your individual health needs.
Additionally, if you have concerns about radiation exposure, you might want to discuss alternative imaging methods with your doctor, such as ultrasound or MRI, which do not involve ionizing radiation. These alternatives can sometimes provide the necessary diagnostic information without the associated risks of radiation exposure.

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