April 06--As the world watches Japan after it announced that contaminated water from its
crippled nuclear plants would be released into the sea, experts are talking
about a touchy topic: Is radiation from medical devices harmful?
Medical scans have emerged as the final diagnostic answer for many
diseases such as cancer. Nuclear medicine scans and treatment are considered
as the most underutilized but maximum potential fields. But what about
excessive prescriptions? More so for the common man who in this
technology-driven age begins his morning with radiation-whether benign or
not-from mobile phones and continues through the day as he walks through metal
detectors and hunches over the computer.
A Canadian study published last month found that patients who underwent
low-radiation heart scans had an increased risk of cancer. The study looked at
82,861 patients who had a heart attack in Quebec between April 1996 and March
2006: 77 percent had at least one cardiac procedure with lowdose ionizing
radiation within a year of the attack. It found 12,020 cancer cases affecting
the abdomen or pelvis and chest areas.
Cancer specialist M Basade quoted a New England Journal of Medicine's
article stating: "There is documented evidence associating an accumulated dose
of 90 mSv (millisievert) from two or three CT scans with an increased risk of
cancer.'' The American FDA states that undergoing certain nuclear scans would
involve radiation doses of that equal to about 2,000 chest X-rays .
Not all agree with this view. Many experts point out that Earth's natural
radiation would result in people getting exposed to 2-3 mSv a year.
Radiologist Dr Bhavin Jhankaria said, "Most of these theories are based on
extrapolations drawn up after studying the survivors of Hiroshima and
Nagasaki. They are mere statistical assumptions and not conclusive studies.''
Jhankaria added that in countries such as Sweden and Finland-whose
healthcare systems recorded every scan that a citizen underwenthave never
showed any adverse cancer-medical scan graph. "Every medical follow-up of each
patient is recorded in these countries. Surely if radiation is so dangerous,
then it would have shown up in these countries .''
He felt that such studies should be undertaken so that the benefits of
medical scans can be better highlighted.
Many medical reviews have studied the risk-benefit graph of medical
scans. A study by the University of California San Francisco (UCSF) said "The
amount of radiation during a typical body CT scan (10 mSV) is equivalent to
two years of radiation from background sources. The risk of getting fatal
cancer from this amount of radiation is about 1 in 2,000.''
Dr K S Parthasarathy, former secretary of AERB, said: "Safe dose of
radiation depends on the context. So when 400 mSv is safe for a cardiac
patient undergoing angioplasty (it saves his life), it may not be safe for a
normal person."
The US authorities recently released a study on the health impact of
airport scanners , which give out very small amounts of low-dose radiation. Dr
Rebecca Smith-Bindman , a radiology professor at UCSF, whose study appears in
the Archives of Internal Medicine, said: "You need to go through an airport
scanner 200,000 times to be equivalent to the dose of one CT scan. I'd rather
focus on getting rid of some of those CTs."
THE COST OF TREATMENT
ABDOMEN X-RAY
Dose (mSv) | 0.5-0 .7 Background radiation for 62-88 days
LUMBAR SPINE X-RAYS
Dose (mSv) | 1.8 Background radiation for 7 months
HEAD CT
Dose (mSv) | 2.0 Background radiation for 8 months
CHEST CT
Dose (mSv) | 8.0 Background radiation for 3 years
ABDOMEN AND PELVIS CT
Dose (mSv) | 10.0 Background radiation for 3 years
VIRTUAL COLONOSCOPY
Dose (mSv) | 10.2 Background radiation for 3 years
WHOLE BODY PET/LOW DOSE NON-CONTRAST CT
Dose (mSv) | 8.5-10 .3 Background radiation for 3 years
PROSPECTIVE ECG-GATED CORONARY CT ANGIOGRAM
Dose (mSv) | 4.0 Background radiation for 1 year
RETROSPECTIVE ECG-GATED CORONARY CT ANGIOGRAM
Dose (mSv) | 18.0 Background radiation for 5 years
TC-99 M SESTAMIBI 1 DAY CARDIAC REST-STRESS TEST
Dose (mSv) | 12 Background radiation for 3.5 years
CORONARY ANGIOGRAPHY (DIAGNOSTIC)
Dose (mSv) | 4.6-15 .8 Background radiation for 2-5 years
CORONARY ANGIOGRAPHY (WITH INTERVENTION)
Dose (mSv) | 7.5-57 .0 Background radiation for 2-19 years
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