Exposure For Those Under 15 Can Triple Leukaemia, Brain Ailment Prospect: Study

New Delhi: Children subjected to CT scans with high radiation doses face a three-time increased risk of leukaemia and brain cancer during their lifetime.

In the most conclusive evidence till date, a study published in the Lancet on Wednesday says radiation exposure received from two to three CT scans of the head in childhood (aged under 15 years) — giving a cumulative dose of around 60 milli-Grays (mGy) can triple the risk of later developing brain cancer.

On the other hand, around 5 to 10 such scans (cumulative dose around 50 mGy) could triple the risk of developing leukaemia.

The authors from the Newcastle University studied close to 180,000 patients who underwent a CT scan between 1985 and 2002 from 70% of the UK’s hospitals.

A total of 74 from 178,604 patients were diagnosed with leukaemia and 135 of 176,587 were diagnosed with brain cancer. The authors say that, of every 10,000 people between the ages of 0-20 years receiving 10 mGy from a CT scan, there would be about one expected excess leukemia case, whereas there were would be one excess case of brain cancer for every 30,000 people.

Applying the dose estimates for one head CT scan before the age of 10 years, this would translate into approximately one excess case of leukaemia and one excess brain tumour per 10,000 patients in the decade after the first exposure.

Lead author Dr Mark Pearce Pearce says, in the UK, the Ionising Radiation (Medical Exposure) Regulations mean that a CT scan should only be done when clinically justified. This might explain the relatively low levels of CT use in the UK compared with other countries. "The immediate benefits of CT outweigh the potential long term risks in many settings and because of CT’s diagnostic accuracy and speed of scanning, notably removing the need for anesthesia and sedation in young patients, it will, and should, remain in widespread practice for the foreseeable future. "

Reacting to the study eminent radiologist Dr Harsh Mahajan said, "I agree with the findings of the study. Unnecessary radiation exposure has been found to cause cancer. However, such high radiation doses were more common in CT machines used a decade ago. The present ones expose patients to lower radiation levels. "

A study published in the Lancet on Wednesday has upheld the risks from radiation overexposure after studying around 180,000 patients between 1985 and 2002