Angiography: CT not as effective as conventional
There is no conclusive evidence that CT angiography is life-saving
Every physician who advertises CT angiography points out that it is painless and takes less time
Risks from radiation exposure are significant when radiation is used for mass screening
Whole-body CT scanning technology fell by the wayside thanks to the uncompromising stand of professional associations and regulatory agencies which highlighted its dangers. But some specialists widely practise cardiac CT tests such as calcium scoring and CT angiography though independent assessments have not proved their effectiveness.
During conventional angiography, the physician threads a thin catheter through the groin artery into the heart, injects a contrast medium and takes x-ray pictures.
These pictures show whether narrowing or blockages in the artery impede the flow of blood. For those with severe blockage, the options are angioplasties possibly with insertion of stents or bypass surgeries.
Risk of bleeding
During cardiac catheterization, there is some risk of bleeding, and a tiny risk for major complications, such as heart attack, stroke, even death.
Every physician who advertises CT angiography points out that it is painless, takes less time and is an attractive option. According to the New York Times, more than 1,000 cardiologists and hospitals installed CT scanners in the U.S. There is undeniable financial incentive to order too many of these tests.
A comparison
The owners argue that the test is cheap, at about $600, paid for by insurers as against $ 4,000 for a cardiac catheterization done at their local hospital.
However, there is no conclusive evidence that CT angiography leads to treatment that saves lives (Health Affairs, Nov/Dec 2008). Conventional angiography remains the gold standard.
Risks from radiation exposure, though small to an individual, are significant when radiation is used for mass screening. There was broad consensus that radiation exposure from CT is of concern.
In India, certain private hospitals advertise CT angiography as very beneficial; none of them refers to radiation risks. Everyone praises the technology. A private hospital used a letter from a member of the faculty of a premier medical research centre to substantiate correlation between CT angiography and conventional angiography!
I sought his reaction to this crude anecdotal approach.
“I routinely write letters to people who have done investigation and what I have done was just to let them know what was the outcome.
“I did not think in my wildest dream that they will utilise it to advertise my letter. I was not aware of it. They are commercial organisations and medicine in a private hospital has become good money making art/business,” he responded to my e-mail.
Pro-screening physicians formed the Screening for Heart Attack Prevention and Education (SHAPE) task force. They want non-invasive imaging of all asymptomatic men (aged 45-75 years) and women (55-75years) except those at very low risk (Archives of Internal Medicine, May 26, 2008).
Evidence of the effectiveness of this recommendation is scanty. These specialists propose the existence of “vulnerable plaques.” The difficulty is that CT cannot identify them.
No clinical utility
“I do not think ‘vulnerable plaque’ has been shown to have any clinical utility,” Dr. Rita Redberg, Professor of Medicine at University of California, San Francisco, responded when I sought her views on promotion of CT by the Indian private hospitals and the SHAPE guidelines.
CT angiography is not as effective as conventional angiography. Those knowledgeable in the field must take the lead in exposing the tendency of hospitals to exploit the “worried well.”
K.S. PARTHASARATHY, FORMER SECRETARY, AERB
KSPARTH@YAHOO.CO.
© Copyright 2000 - 2008 The Hindu
Wednesday, December 24, 2008
Friday, December 12, 2008
Story of uranium
Story of uranium
K.S. Parthasarathy
AT the tender age of 15 years, Martin Klaproth dropped out of school. He could not pay his fees. He learnt chemistry from the work benches as an apprentice under an apothecary. He struggled for long hours "in the cramped and unhealthy conditions and the tedium of preparing the raw materials and maintaining the hardware for the crushing, grinding, mixing, boiling and distilling that made up his daily routine".
Later, Martin opened his own business. He could spend more time to do research in analytical chemistry. He analysed all types of materials from various countries. He extracted a new element from a piece of rock, some mine-owner gave him. He called it uranium. He announced the discovery at a meeting of the Royal Prussian Academy of Sciences, Berlin, on September 24, 1789.
Uranium remained virtually useless for several decades; small amounts of uranium added to glass before melting gave the glass a pale-yellowish green hue. Some glass specimens contained up to 25 per cent uranium! Geiger counters screamed when it faced the glass surface.
In 1896, Henri Becquerel discovered that uranium is radioactive .In 1934, Enrico Fermi and his coworkers demonstrated beta activity when they bombarded uranium with neutrons. In 1938, Otto Hahn and Leise Meitner discovered nuclear fission and release of fission neutrons.
On December 2, 1942, Fermi and his team achieved the first self-sustaining nuclear chain reaction in a pile of 400 tons of graphite, six tons of uranium metal and 58 tons of uranium oxide, at the University of Chicago. It produced 0.5 watt of thermal power!
Scientists realised the full potential of uranium when they could design, construct and operate nuclear power reactors 168 years after Klaproth discovered it.
India's tryst with uranium started in 1937 when an English man discovered its presence with copper mineral at Mosabani area. There was apparently no followup on this till late 40s.
Dr Homi Bhabha, the architect of nuclear India, knew the value of uranium. "It must be clearly understood that the possession of sufficient quantities of uranium is a sine qua non for the generation of atomic energy….. So far, no large and concentrated deposits of uranium-bearing minerals have been found in India,……It is essential, therefore, that our immediate programme should include an extensive and intense search for sources of uranium. These geological surveys would take at least two years if carried out in any careful and exhaustive way, and it is possible that their result may be negative. In that case India would either have to depend on an agreement with a foreign power for the purchase of her uranium or go in for the much more costly process of extracting uranium from monazite", Dr Bhabha wrote to Pandit Nehru on April 26, 1948.
Dr Bhabha informed Nehru that the Geological Survey of India under Dr. M.S.Krishnan was organizing surveys for thorium and uranium. He insisted that to ensure secrecy, these surveys should be organised directly under the Atomic Energy Commission and Dr. Krishnan "should be allocated full time to this work"
According to Dr K.S. Koppiker, formerly Head, Uranium and Rare Earth Division, BARC, Indian scientists set up in 1949, the first uranium laboratory in Pedder road, Mumbai, at the residence of Dr Bhabha, where Kenilworth building stands today.
Their neighbours complained that they could not suffer the unbearable releases of acid fumes from the laboratory. In July 1954, scientists shifted the lab to an abandoned godown owned by the Bombay Dyeing Company near Siddhi Vinayak Temple.
Uranium is present in trace quantities in soil, rock, water etc. Typical concentration in soil is about 3 ppm (milligramme per kilo gramme).
(K.S. Parthasarathy is Raja Ramanna Fellow, Department of Atomic Energy)
K.S. Parthasarathy
AT the tender age of 15 years, Martin Klaproth dropped out of school. He could not pay his fees. He learnt chemistry from the work benches as an apprentice under an apothecary. He struggled for long hours "in the cramped and unhealthy conditions and the tedium of preparing the raw materials and maintaining the hardware for the crushing, grinding, mixing, boiling and distilling that made up his daily routine".
Later, Martin opened his own business. He could spend more time to do research in analytical chemistry. He analysed all types of materials from various countries. He extracted a new element from a piece of rock, some mine-owner gave him. He called it uranium. He announced the discovery at a meeting of the Royal Prussian Academy of Sciences, Berlin, on September 24, 1789.
Uranium remained virtually useless for several decades; small amounts of uranium added to glass before melting gave the glass a pale-yellowish green hue. Some glass specimens contained up to 25 per cent uranium! Geiger counters screamed when it faced the glass surface.
In 1896, Henri Becquerel discovered that uranium is radioactive .In 1934, Enrico Fermi and his coworkers demonstrated beta activity when they bombarded uranium with neutrons. In 1938, Otto Hahn and Leise Meitner discovered nuclear fission and release of fission neutrons.
On December 2, 1942, Fermi and his team achieved the first self-sustaining nuclear chain reaction in a pile of 400 tons of graphite, six tons of uranium metal and 58 tons of uranium oxide, at the University of Chicago. It produced 0.5 watt of thermal power!
Scientists realised the full potential of uranium when they could design, construct and operate nuclear power reactors 168 years after Klaproth discovered it.
India's tryst with uranium started in 1937 when an English man discovered its presence with copper mineral at Mosabani area. There was apparently no followup on this till late 40s.
Dr Homi Bhabha, the architect of nuclear India, knew the value of uranium. "It must be clearly understood that the possession of sufficient quantities of uranium is a sine qua non for the generation of atomic energy….. So far, no large and concentrated deposits of uranium-bearing minerals have been found in India,……It is essential, therefore, that our immediate programme should include an extensive and intense search for sources of uranium. These geological surveys would take at least two years if carried out in any careful and exhaustive way, and it is possible that their result may be negative. In that case India would either have to depend on an agreement with a foreign power for the purchase of her uranium or go in for the much more costly process of extracting uranium from monazite", Dr Bhabha wrote to Pandit Nehru on April 26, 1948.
Dr Bhabha informed Nehru that the Geological Survey of India under Dr. M.S.Krishnan was organizing surveys for thorium and uranium. He insisted that to ensure secrecy, these surveys should be organised directly under the Atomic Energy Commission and Dr. Krishnan "should be allocated full time to this work"
According to Dr K.S. Koppiker, formerly Head, Uranium and Rare Earth Division, BARC, Indian scientists set up in 1949, the first uranium laboratory in Pedder road, Mumbai, at the residence of Dr Bhabha, where Kenilworth building stands today.
Their neighbours complained that they could not suffer the unbearable releases of acid fumes from the laboratory. In July 1954, scientists shifted the lab to an abandoned godown owned by the Bombay Dyeing Company near Siddhi Vinayak Temple.
Uranium is present in trace quantities in soil, rock, water etc. Typical concentration in soil is about 3 ppm (milligramme per kilo gramme).
(K.S. Parthasarathy is Raja Ramanna Fellow, Department of Atomic Energy)
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