Brief Answer:
There is no safe limit, every CT scan increases the relative risk of cancer

Detailed Answer:
Hi XXXX,
Thanks for writing in to us.

I have read through your query in detail.
Please find my observations below.

1. Any exposure to radiation from CT scan carries a small relative risk of adverse radiation effects. This adverse radiation effect is both dose dependent and non dose dependent. The relative risk also depends on the gender, height and weight and age of the patient.

2. There is no practical limit regarding the number of CT scan tests that might be safe for an individual. There are also many types of scans and each of them will expose the patient to a different dose depending on the purpose and part scanned. However the relative risk of a person who has undergone CT scans in the past might be calculated mathematically and the increased risk to the development of cancer is known.

3. The contrast used is a non ionic iodine containing compound which is given in the veins. If kidney function tests are normal then there is no reason to worry. Should there be abnormal kidney function then the use of contrast has to be justified and precautions taken.

4. The number of CT scans also depends on the disease and medical condition of the patient. A person who is getting treated for cancer has to get more number of CT scans done to regularly follow up on the disease condition and this is for the benefit of the patient.

5. In the absence of abnormal kidney function, two CT scans of any one part of the body can be safely done in a year without much increased relative risk of developing cancer. However it does not mean that two CT scans be done every year due to the cumulative effects of radiation exposure. If you have got CT scans done recently then please tell me the area scanned and how many times and I will calculated the increased relative risk due to the scans.

Hope this answers your question. Please feel free to correct any oversight in my interpretation of your problems and discuss them in detail as per your requirements.

Hope your query is answered.
Do write back if you have any doubts.

Regards,
Dr.Vivek

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Brief Answer:
Contrast injection is washed out of your system within 3 days

Detailed Answer:
Hi XXXX,
Thanks for writing back with an update.

1. The 5 CT scans you had have given you a radiation dose of approximately 70 mSv which is an increased cancer risk of 0.14 percent. It means that there are 99.85 percent chances that it will not cause another cancer due to radiation exposure. Therefore you are relatively safe and considering the benefit to risk, the CT scans are justified in the follow up of kidney cancer.

2. From the contrast injection point of view, it stays in the system for 3 days and after that it gets washes out. If your other kidney is functioning well and the serum creatinine is within acceptable limits then there is no risk of any adverse reaction to contrast use after 6 weeks. There is no health concern if contrast given after 6 weeks in any case.

3. In earlier days we used ionic contrast which had a higher rate of adverse reactions. Now the contrast used is non ionic which is safe and most patients tolerate it without any side effects. Even in people with kidney function reduced, this contrast might be used with precautions.

Hope your query is answered.
Do write back if you have any doubts.

Regards,
Dr.Vivek

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Brief Answer:
Welcome

Detailed Answer:
Hi A.B. XXXXXXX
Welcome and thanks for sending in your query.

Should you have any more health queries and would like me to answer them then please mention "Query Id 206125 DR XXXXXXX CHAIL, RADIOLOGIST" in your query and the moderators will direct it to me. I will reply back to you at the earliest.

Wishing you good health.

Regards,
XXXXX

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