Monday, February 18, 2019

Heavy use of CT raises concerns about radiation exposure: Keep your radiation account

The use of radiation-based imaging is rising, especially in critically ill patients, who are often subject to CT scans and x-rays. In many ICUs, 100 millisieverts (mSv), the limit which otherwise should not exceed in five years, is exceeded within a week of admission. Children undergo between 5 million and 9 million CT scans annually.

Abdominal CTs are one of the highest radiation risk tests, which should not be repeated unless called for. It contains 10 mSv of radiation, the rough equivalent of 200 chest X-rays or 1,500 dental X-rays.

Incidentalomas, which include benign lung and thyroid nodules etc. are detected unexpectedly and can lead to unnecessary and expensive workup of the patient.

X-rays, PET scans and CT scans use ionizing radiation, while MRI scans and ultrasound do not use radiation. Ionizing radiations can damage the DNA and are potentially carcinogenic The National Cancer Institute (NCI) estimates that the additional risk of developing a fatal cancer from a scan is 1 in 2,000, while the lifetime risk of dying from cancer is 1 in 5.

Studies published in 2007 and 2009 by teams from Columbia University and the NCI predicted that up to 2% of future cancers might be caused by CT scans.

A 2011 report by the Institute of Medicine found that the two environmental factors most strongly associated with breast cancer were radiation exposure and the use of post-menopausal hormones.

A 2009 study by researchers at Brigham and Women’s Hospital in Boston found that among 31,000 patients, who had a diagnostic CT scan in 2007, 33% had more than five scans during their lifetime, 5% received 22 or more, and 1% underwent more than 38 scans.

Some doctors perform double scans, one with a contrast agent and a second without it. While some doctors refuse to accept or are unable to access radiology studies done elsewhere and therefore send patients for duplicate tests. Doctors who have a financial interest in radiology clinics or who own scanners are use imaging substantially more often than those who do not. And increasingly, specialists are requiring that patients get a scan before they first see a patient.

The effective doses from diagnostic CTs are “not much less than the lowest doses of 5 to 20 mSv received by some of the Japanese survivors of the atomic bombs” dropped over Hiroshima and Nagasaki in 1945.

Radiation exposure is cumulative; children are much more vulnerable to its effects.

Keep your radiation account...

Dr KK Aggarwal
Padma Shri Awardee
President Elect Confederation of Medical Associations in Asia and Oceania   (CMAAO)
Group Editor-in-Chief IJCP Publications
President Heart Care Foundation of India
Past National President IMA

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