Radiation Exposure from CT Scans and PET Imaging: Risks and Safety

Q: Radiation Exposure from CT Scans and PET Imaging: Risks and Safety

Dear cf user： Hello, regarding your question, here is a comprehensive response： <br>1. <br>Will undergoing multiple tests in a short period increase cancer risk? The answer is no; the likelihood of increased cancer risk is almost negligible. <br>The effects of radiation on the hu

The radiation dose from a computed tomography (CT) scan?

Hello, I saw a message the other day stating that 1.
One PET scan is equivalent to 100 mammograms.
2.
The cancer risk from one full-body CT scan is 1 in 1,000.
Since I underwent the following procedures last month within a month: 1.
Chest CT scan (without contrast), 2.
Chest CT scan (with contrast), 3.
Full-body PET scan, 4.
Small bowel imaging (barium swallow), and the final conclusion from these examinations was that there were no issues, I would like to ask the following:
1.
Does undergoing multiple scans in a short period increase the risk of cancer? I have read online that radiation can increase the incidence of leukemia and other cancers.

2.
What is the radiation dose for each of the four examinations mentioned? Does the dosage accumulate? What is the acceptable radiation dose for the human body? Am I at risk of receiving excessive radiation exposure, and how long should I wait before undergoing similar examinations again?
3.
My previous white blood cell count has been between 4,200 and 4,800 (in previous years).
Two months ago, it was 4,700, but a few days ago, it was 6,000.
Is this related to the scans I underwent? Now that the examinations are complete, are there any dietary or lifestyle adjustments I can make to mitigate the side effects (excessive radiation exposure)? I am concerned about having received too much radiation exposure.

Sincerely.

cf, 30~39 year old female. Ask Date: 2005/09/30

Dr. Wu Bin'an reply Radiology

Dear cf user: Hello, regarding your question, here is a comprehensive response:
1.
Will undergoing multiple tests in a short period increase cancer risk? The answer is no; the likelihood of increased cancer risk is almost negligible.
The effects of radiation on the human body are as follows: The body's tissues and organs are composed of numerous cells, and if exposed to a large amount of radiation, cells may exhibit the following damage responses: (1) Low-dose radiation may not affect cellular metabolism or delay its normal cycle, and after a period, can self-repair and return to normal.
Generally, diagnostic radiology and nuclear medicine examinations involve low-dose radiation, which is less hazardous than smoking.
(2) High-dose short-term exposure or low-dose long-term exposure can damage cells, causing them to lose their ability to divide and reproduce, ultimately leading to cell death.
(3) If damaged cells divide abnormally, changes in the genetic material (DNA) of germ cells can affect offspring, and abnormal development of individual cells may lead to tumor formation.
(4) If the energy is very high, irradiated cells may swell and rupture immediately.
The Atomic Energy Commission stipulates: the annual effective dose for the general public is 5 mSv, and the annual dose limit for individual organs or tissues is 50 mSv.
For example, a single chest X-ray has a dose of 1 mSv; after accounting for background radiation of 2.0 mSv over the year, one can safely undergo approximately 48 chest X-rays.
In fact, there are many sources of low-dose radiation in our environment that we are exposed to over the long term, allowing our body cells to often self-repair.
Essentially, there is no significant impact on the body, and there will be no sequelae.
X-ray examinations are classified as low-dose radiation tests, and according to literature reports, they are considered safe.
It is a common misconception that radiation can kill cancer cells while also harming normal tissues; excessive radiation exposure can lead to leukemia or other conditions, which arises from a misunderstanding of X-ray examinations.
2.
Generally, the effective dose for whole-body FDG PET scans is about 11.6 mSv, and when combined with the effective dose from a chest CT scan (without contrast and with contrast) and small bowel imaging (with barium), the total effective dose should be less than 20 mSv, which is well below the Atomic Energy Commission's limit of 50 mSv for individual organs or tissues.
Therefore, you have not received excessive radiation exposure.
Based on your description, since the final conclusion from these examinations was that there are no issues and only outpatient follow-up is needed, it is recommended that you do not need to undergo similar examinations in the short term (3 to 6 months).
3.
Your previous white blood cell counts have been between 4200 and 4800 (over the past few years), with a check two months ago showing 4700, and a recent check showing 6000, all within the normal range and unrelated to these examinations.

Reply Date: 2005/09/30

More Info

Radiation exposure from medical imaging, particularly from CT scans and PET scans, is a significant concern for many patients. Understanding the risks associated with these procedures is essential for informed decision-making regarding your health.

1. Understanding Radiation Risks: It is true that exposure to ionizing radiation, such as that from CT scans and PET scans, can increase the risk of developing cancer over time. The risk is generally considered low, especially at doses below 100 millisieverts (mSv). For context, a single chest CT scan typically exposes a patient to about 6-7 mSv, while a full-body PET scan can expose a patient to approximately 9-21 mSv, depending on the specific protocol used. The risk of cancer from a single CT scan is estimated to be about 1 in 1,000, while the cumulative risk from multiple scans can increase, albeit still remaining relatively low.

2. Cumulative Radiation Exposure: The radiation dose from each imaging procedure does indeed accumulate. For the procedures you mentioned, here are the approximate radiation doses:
- Chest CT without contrast: ~6-7 mSv
- Chest CT with contrast: ~6-7 mSv (the contrast agent itself does not add significant radiation)
- Whole-body PET scan: ~9-21 mSv (including the CT component)
- Barium swallow (small bowel study): ~1-3 mSv
Adding these together, your total radiation exposure from these four procedures could range from approximately 22 to 38 mSv. While this is above the average annual background radiation exposure (which is about 3 mSv), it is still below levels that are typically considered to pose a significant risk for immediate health effects.

3. Safe Radiation Levels and Future Imaging: The International Commission on Radiological Protection (ICRP) suggests that doses below 100 mSv are unlikely to cause any significant health effects. However, it is essential to balance the need for imaging with the potential risks. If you have had multiple scans in a short period, it may be prudent to discuss with your healthcare provider the necessity of any future imaging and whether alternative methods (like MRI or ultrasound) could be used instead, which do not involve ionizing radiation.

4. White Blood Cell Count: Your recent increase in white blood cell count from 4,700 to 6,000 could be due to various factors, including stress, infection, or inflammation, rather than directly related to the imaging procedures. Radiation exposure does not typically cause an immediate increase in white blood cell counts; rather, it can have more long-term effects on bone marrow and blood cell production. If you have concerns about your blood counts, it would be wise to follow up with your healthcare provider for further evaluation.

5. Lifestyle Adjustments: To mitigate any potential effects of radiation exposure, consider adopting a healthy lifestyle. This includes:
- Eating a balanced diet rich in fruits and vegetables, which can help support your immune system.

- Staying hydrated and maintaining a healthy weight.

- Engaging in regular physical activity.

- Avoiding smoking and limiting alcohol consumption.

In conclusion, while the radiation exposure from your recent imaging studies is a valid concern, the risk of developing cancer from these doses remains low. It is crucial to maintain open communication with your healthcare provider about your imaging needs and any potential alternatives. Regular monitoring of your health and lifestyle adjustments can also contribute positively to your overall well-being.

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