Assessing Radiation Exposure from Recent Medical Imaging Procedures

Radiation issues

During a health check-up, a shadow was found in the lungs.
In mid-February, follow-up X-rays (both frontal and lateral views) were taken, along with a non-contrast CT scan of the lungs (which took about 20 to 30 minutes).
At the end of February, a contrast-enhanced chest CT was performed, and the biopsy results confirmed a diagnosis of stage 1 malignant tumor.
On March 9, a whole-body PET scan was conducted, revealing an SUV value of 4.2, suspected to be in the ascending colon area.
A colonoscopy showed no issues, but a CT scan of the abdomen is needed.

Is the amount of radiation absorbed so far above the safety threshold? Should the abdominal CT be delayed, and if so, for how long? If the abdominal CT is performed soon, what methods can be used to reduce radiation exposure? Thank you.

Otter, 20~29 year old female. Ask Date: 2019/03/27

Dr. Wang Yifen reply Radiology

1.
According to the American Society of Radiologic Technologists, the radiation dose from a frontal and lateral X-ray is approximately 0.1 millisieverts, while two chest CT scans can amount to about 14 millisieverts, a full-body PET scan delivers around 14.1 millisieverts, and an abdominal CT scan has a radiation dose of about 8 millisieverts, totaling approximately 36 millisieverts.
The International Commission on Radiological Protection (ICRP) report 103 states that doses below 100 millisieverts (whether single or multiple exposures) do not cause clinical functional impairment.
The use of radiation in the medical field is increasing, and to achieve diagnostic or therapeutic purposes, it is important to follow the physician's recommendations for radiation-related examinations or treatments, considering that the health benefits outweigh the effects of radiation.
If there are concerns, it is advisable to communicate with the physician before proceeding with the examination.
2.
To reduce the harm of radiation to the human body, minimizing unnecessary radiation exposure is key.
However, if examinations are necessary due to medical conditions, one can enhance the body's immunity and resistance to radiation by drinking a glass of orange juice or taking vitamin C before undergoing low-dose X-ray imaging, or by drinking a glass of milk to prevent calcium loss.
This can help mitigate the potential harm from radiation exposure.
Wishing you safety and good health.

Reply Date: 2019/03/27

More Info

When evaluating the radiation exposure from recent medical imaging procedures, it is essential to understand the types of imaging tests performed, the associated radiation doses, and the cumulative effects of these exposures. Based on the information provided, you have undergone several imaging studies, including chest X-rays, a non-contrast CT scan, a contrast-enhanced chest CT, and a whole-body PET scan.
To quantify your radiation exposure, let's break down the approximate doses for each procedure:
1. Chest X-ray (front and side): Each standard chest X-ray typically delivers about 0.1 mSv. Therefore, two X-rays would amount to approximately 0.2 mSv.

2. Non-contrast Chest CT: A standard chest CT without contrast usually delivers around 7 mSv.

3. Contrast-enhanced Chest CT: This type of CT scan generally has a similar radiation dose to a non-contrast CT, so you can estimate it at about 7 mSv as well.

4. Whole-body PET scan: The radiation dose for a PET scan is approximately 10-15 mSv, depending on the specific protocol used.

Adding these together gives you a cumulative radiation exposure of approximately:
- Chest X-rays: 0.2 mSv
- Non-contrast Chest CT: 7 mSv
- Contrast-enhanced Chest CT: 7 mSv
- Whole-body PET scan: 10-15 mSv
Total cumulative exposure: 24.2 to 29.2 mSv.

The International Commission on Radiological Protection (ICRP) suggests that doses below 100 mSv are generally not associated with significant health risks, particularly in the context of medical imaging. Your cumulative exposure, while notable, is still below this threshold. However, it is understandable to be concerned about the potential risks associated with repeated imaging, especially in the context of a recent cancer diagnosis.

Regarding the abdominal CT scan you mentioned, it is crucial to weigh the necessity of the scan against the potential risks of additional radiation exposure. If the abdominal CT is deemed necessary for diagnostic purposes, it may be advisable to proceed, but there are strategies to minimize radiation exposure:
1. Low-Dose CT (LDCT): If available, request a low-dose CT scan, which uses less radiation than standard CT scans.

2. Radiation Shielding: Ensure that appropriate shielding is used during the scan to protect other parts of your body from unnecessary exposure.

3. Alternative Imaging: Discuss with your physician the possibility of using alternative imaging modalities that do not involve ionizing radiation, such as MRI or ultrasound, if they can provide the necessary information.

4. Delay the Scan: If the abdominal CT is not urgent, consider delaying it to allow for a longer interval since your last imaging studies. This can help reduce cumulative exposure.

In conclusion, while your cumulative radiation exposure from recent imaging is significant, it remains within generally accepted safety limits. It is essential to maintain open communication with your healthcare provider regarding the necessity of further imaging and to explore options for minimizing radiation exposure. Your health and safety should always be the top priority, and your physician can help guide you through the decision-making process regarding any further imaging studies.

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