05 April 2011
Scans Such As X–Rays Are The Diagnostic Answer To Many Diseases, But Are They Also Guilty Of Putting Us At Health Risks?
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% 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 underwent—have 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–99M 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