It is a versatile imaging tool

Date:14/02/2008 URL: http://www.thehindu.com/thehindu/seta/2008/02/14/stories/
2008021450031500.htm



It is a versatile imaging tool

Scanners that use combined positron emission tomography (PET) and computed tomography (CT) have been proving their potential as versatile medical imaging tools since 2000 when they became commercially available.

A PET scanner uses small amounts of radioactive pharmaceuticals targeted at specific organs, bone or tissues. Development of radiopharmaceuticals such as fluoro-deoxyglucose (FDG) which can act as a marker for sugar metabolism enhanced its potential u se. FDG contains Fl-18, a positron emitting radionuclide, whose presence will help to trace and locate the sites where the molecules get accumulated.
Special camera

A special camera that works with a computer provides pictures of the area of the body being imaged. Cancer cells often grow and multiply uncontrollably. They consume enormous amounts of energy. Basically, this energy comes from burning glucose.

Cancer cells metabolise sugar at higher rates than normal cells, and the radiopharmaceutical is drawn in higher amounts to cancerous areas (Society of Nuclear Medicine [SNM] Release, December 12, 2007)

PET scans produce three-dimensional images of the precise distribution of FDG in the body; FDG plays the role of a marker for the disease and its spread. CT scans on the other hand show the details of the anatomical structures.

Since 2000, when Beyer, Townsend and others introduced the concept of PET-CT imaging, state-of-the–art CT imaging technology has been combined with high-end PET systems (The Journal of Nuclear Medicine [JNM], January 2007).

Recently, researchers claimed that PET-CT imaging is superior to conventional imaging in detecting cancers in children (JNM, December 2007). The modality provides additional information, possibly sparing young patients from being overtreated.
Plaque inflammation

PET-CT offers a superior view of atherosclerosis plaque inflammation — a process in which deposits of fats, cholesterol, cellular waste products and other substances, collectively called plaque, builds up in the inner linings of the artery and limits the flow of blood through it (innovations-report.com, June 6, 2006).

PET-CT may be able to assess biologically active plaques; these are of concern as they may lead to “deadly consequences when they misbehave.”

Disease processes may obstruct blood vessels. Specialists insert prosthetic grafts to restore and ensure blood circulation.

According to Ora Israel, director of nuclear medicine and research operations at Rambam Health Care Campus, in Haifa, Israel, graft infection is a rare, but potentially severe complication occurring at a rate ranging between 0.5 and 5 per cent following prosthetic vascular reconstruction (ZAMP Bionews, June 5th, 2007).

Infection imaging

PET-CT imaging effectively diagnoses and differentiates infection, Israeli researchers noted at the 54th Annual Meeting of the SNM. Surgeons remove the infected blood vessel grafts in a complex surgical procedure.

“Sparing unnecessary high risk operations in patients…is of major significance” Dr Israel clarified. “PET-CT imaging can effectively diagnose graft involvement and differentiate it from infection that affects only soft tissue…in its vicinity,” she added (ZAMP Bionews, June 5th 2007)
Cancer screening

Can we justify using PET-CT for population screening for cancer? “Recommendations and decisions regarding cancer screening should be based on reliable data, not good intention, assumptions or speculation …”

“…We conclude from the available data that neither CT nor PET-CT cancer screening is currently warranted…The clinical and statistical relevance of occasionally detected cancers is likely too low to justify population wide screening efforts with these modalities” (The JNM, Supplement, January 2007).

The Journal of Nuclear Medicine, the scientific publication of the Society of Nuclear Medicine (SNM), U.S., published two supplements on PET-CT, one in 2005 and the second in January 2007. Both are available on the web.

As on January 2007, specialists are using more than 1700 PET and PET-CT units in the U.S. India has 15 PET scanners, nine of them are PET-CT; more will be installed in the near future.

Indian nuclear medicine specialists have been providing excellent service though the facilities available in India are too meagre.

Diagnostic nuclear medicine services are admittedly lucrative. Nuclear medicine physicians must collaborate and initiate well focused clinical research and development programmes to improve their professional competence and to create more specialists in the country.

K.S. PARTHASARATHY

Former Secretary, AERB
ksparth@yahoo.co.uk

© Copyright 2000 - 2008 The Hindu

MRI Images show damage caused by secondary smoking

January 3, 2008
MRI images show damage caused by secondary smoking
Bright images of minute structural damage in smokers’ lungs were obtained

• Prolonged exposure to cigarette smoke may
cause passageways in the lungs to break down
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• The scanner measured how far the helium atoms
Moved or diffused inside the lungs
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The health impact of second hand smoke has been very controversial (The Hindu, May 23, 2003). Physicians always suspected that second-hand smoke caused microscopic structural damage deep into the lungs. The damage was too tiny to be detected by any medical imaging tool.
Happy ending
Their suspicion had a happy ending, when Dr. Chengbo Wang, a magnetic resonance physicist and his radiologist colleagues in the Department of Radiology at the Children’s Hospital of Philadelphia teamed up with specialists at the University of Virginia School of Medicine to obtain bright medical images of the microscopic structural damage in the lungs of smokers by using a special type of magnetic resonance imaging.
They presented their findings on November 26 this year at the 93rd annual meeting of the Radiological Society of North America (RSNA) at Chicago. They studied 60 adults between ages 41 and 79; Forty five of them never smoked. They divided the non-smokers into groups with low and high exposure to second hand smoke.
The high exposure group smokers had lived with a smoker for at least 10 years, often during childhood (EurekAlert, November 26). The 15 current or former smokers formed the control group.
The research groups inhaled a mixture of nitrogen and He-3, a special type of helium made by polarizing it to make it more visible in the MRI. The researchers adjusted the MRI to take images showing this helium gas in the tissue.
The scanner measured how far the helium atoms moved or diffused inside the lungs during a time period-1.5 seconds-in the present study. The researchers could detect changes deep in the airways and sacs in the lungs.
Prolonged exposure to cigarette smoke may cause the passageways to break down; they may become enlarged; holes may develop. The helium atoms moved greater distance than in the lungs of normal subjects.
One-third of the non-smokers with high exposures to secondhand cigarette smoke had structural changes in their lungs similar to those found in smokers.
Paradoxical results
The researchers interpreted these changes as early signs of damage, representing very mild form of emphysema. Emphysema is a major cause of death in the US and is commonly found in heavy smokers (EurekAlert, Nov 26).
The researchers got some paradoxical results. Among two-thirds of the high exposure group of non-smokers, diffusion measurements were lower than those in the low exposure group.
Dr Wang argued that diffusion is lower in the group as their airways narrowed because of chronic bronchitis. Dr.Katarzyna Macura of John Hopkins School of Medicine, who moderated the RSNA session, noted that the results should be considered preliminary.
Study too small
She wanted animal studies to elucidate and confirm the apparent structural differences (medpage TODAY, Nov 27). She clarified that the study was too small to provide evidence of a cause and effect.
The detection of minute changes in lung is possible now because nearly 30 years ago scientists at Mainz University developed techniques to polarize nuclear spins of isotopes such as helium-3, an isotope which is extremely rare in nature. He-3 became available via the beta decay of tritium (CERN courier, Oct 2, 2001).
Scientists could use a laser beam to polarize helium gas; polarized helium-3 gas is more visible on MRI. Optical pumping of metastable helium-3 atoms can supply relatively large amounts of highly polarized gas.
The magnetic signals from these are a thousand times as large as those normally seen magnetic resonance imaging (CERN Courier, Oct 2, 2001).
Storage and transport of polarized gas from laboratory to hospital is a major challenge. The polarized helium atoms would lose their spin orientation when they collide with the walls of their containers.
Gas storage
Scientists found that they can store the gas at pressures of up to 10 bar for more than 100hours in glass vessels with their inner surfaces coated with a few mono layers of caesium.
Researchers at the Mainz University demonstrated the potential usefulness of He-3 techniques in human lung imaging in 1995. Dr. Wang and his colleagues applied the technique to study microscopic changes in the lungs of smokers.
Dr. Wang hoped that a conclusive study that demonstrates that breathing secondhand smoke can injure the lungs will push legislation prohibiting public exposure.
K.S.PARTHASARATHY
former Secretary, AERB
(ksparth@yahoo.co.uk)

Bhabha’s dream comes true

This article reminds the reader of the early years of atomic energy in India. Dr Bhabha wanted that the Government should use tyhe then available fairly inexpensive electric power to produce heavy water. He wanted the company producing heavy water should be under the Defence Ministry, The produce should be left to the Atomic Energy commission for its own use or sale. It took several years to fulfill Bhabha's dream.The Heavy Water Board, the agency producing heavy water lives up to the expectations of Dr.Bhabha.

K.S.Parthasarathy



SCIENCE&TECHNOLOGY
Friday,February 1,2008,Chandigarh,India
Bhabha’s dream comes true
K.S. Parthasarathy
Scientists and engineers in the Heavy Water Board (HWB), Department of Atomic Energy (DAE) have every reason to be proud. They fulfilled the dreams of Dr Homi Bhabha whose death anniversary was on January 24. The Board exported heavy water to South Korea seven times and once to China.
Last year, HWB supplied 4,400 kg of high quality, nuclear grade heavy water to Spectra Gases Inc. USA. HWB is emerging as a major exporter of this commercially important strategic material. A peep into history is in order.
In a note on the organisation of atomic energy research in India, sent to Jawaharlal Nehru on April 26, 1948, Dr Homi Bhabha wanted that the government “should explore immediately the possibility of utilising the cheap hydroelectric power in India for manufacturing heavy water on the one hand to our own requirements in a pile and on the other for sale to other countries”.
He desired that the government should come to an agreement with the Governments or atomic energy agencies of one or more countries such as Great Britain, France and Norway. “…that was the quickest and the most desirable way to develop atomic energy in India” he argued
Why did he bracket Norway with France and Great Britain? He knew that Norway had the knowhow to produce heavy water, an essential raw material to produce atomic energy. In 1942, Norway was producing 1.5 tons of heavy water annually at its Rjukan plant. (Smart Norwegian saboteurs damaged the plant in 1943;They did not want Germans to get any advantage. The old hydro power station and plant have been preserved as the monument of Norway’s heavy water industry.)
The “factory should be set up for the purpose under the Defence Ministry and put under the same security measures as the armaments factories of that Ministry”. Bhabha drove home the strategic importance of heavy water.
He wanted that “the heavy water produced should be at the disposal of the Atomic Energy Commission for use or sale”. Bhabha wanted to thwart a possible future turf war with the army!
At the second meeting of the Board of Research on Atomic Energy held in Bombay on 9th and 10th April 1948, Bhabha secured approval for three resolutions; one of which recommended that the government should investigate the feasibility of producing heavy water in India.
In the note enclosing the resolutions, Bhabha proposed to Nehru the setting up of a three Member Atomic Energy Commission directly under the Prime Minister as “the present Board……..cannot be entrusted with this work since it is an advisory body…….composed of 28 members including officials, scientists and industrialists”. “Secret matters cannot be dealt with under this organisation”, Bhabha asserted.
In 1954, Dr Bhabha convinced Nehru about setting up a fertiliser cum heavy water plant at Nangal. He argued that cheap electric power (1.35 paisa per kilowatt-hr, revised later to 6 paisa per kilowatt-hr!) will be available from the Bhakra-Nangal Hydel Project. Nangal plant produced the first drop of heavy water on August 9, 1962. Nangal plant was the largest plant of this type in the world.
Bhabha waited for over 14 years (from April 1948 to August 1962) to realise his dream to produce heavy water indigenously. The Heavy Water Board executed the first export order to South Korea in May 1998, just under 36 years later.
If Dr Bhabha were alive today, he would have congratulated the board for its achievements. He might have also expressed his dissatisfaction, as it took too long to fulfill his dream.
HWB faced many trials and tribulations (the difficulties in operating heavy water plants with fertiliser factories, power scarcity, export controls, poor national industrial infrastructure among others) in mastering a technology known only to a handful of advanced countries.
HWS has an impressive list of achievements, including energy conservation measures, maintenance of high capacity factors for the plants and product diversification among others.
The board kept the Nuclear Power Corporation of India Limited in good humour by supplying heavy water to the pressurised heavy water reactors in the country.
Overall, the board lives up to the expectations of Dr Bhabha,the architect of nuclear India.
Dr K.S.Parthasarathy is former Secretary, Atomic Energy Regulatory Board.

Missing footprints of A-bomb fallout in Himalayan ice fields

The article highlights the fact that nuclear fallout footprints were missing when a US-Chinese team examined the ice cores collected from a glacier in the Tibetan Plateau. The researchers observe that this may mean dwindling fresh water supplies for half the Indian population after a few decades
K.S.Parthasarathy




Missing footprints of A-bomb fallout in Himalayan ice fields
It means dwindling fresh water supply in future to half the Indian population
________________________________________
The total area of glaciers in the Tibetan plateau may shrink by 80 per cent by 2030
Glaciers worldwide are a barometer for global warming
________________________________________
Ice cores drilled from the peak of a Himalayan ice field in 2006 by researchers revealed a chilling reality. Unlike the cores retrieved worldwide, the ice cores from the Himalayan glaciers did not contain the footprints of fallout radioactivity from nuclear weapons testing.
Lonnie Thomson, distinguished professor of earth sciences at Ohio State University and a researcher from the Byrd Polar Research Centre, who led the team revealed the findings while addressing the American Geophysical Union at San Francisco on December 12, 2007.
The radioactive fallout from 520 atmospheric tests during the 1950s and early 1960s spread far and wide and deposited on various surfaces. The missing radioactivity originating as fallout from atmospheric tests during the 1950s and 1960s routinely provides researchers with a benchmark against which they can gauge how much new ice has accumulated on a glacier or ice field (EurekAlert, Dec 11, 2007). In 2006, the joint US-Chinese team drilled four cores from Naimona’nyi, a glacier 6050 metres high on the Tibetan Plateau. Missing nuclear fallout markers means that this Tibetan ice field has been shrinking at least since the atom bomb tests 50 years ago. Melting ice from the Himalayan glaciers is the source of fresh water for Ganges, Indus and Brahmaputra.
Thompson estimated that there are about 12,000 cubic metres of fresh water stored in the glaciers throughout the Himalayas.
Radioactivity signals
They release melt water each year and feed the rivers downstream. These ice fields are shrinking. If they are eventually lost, 500 million people who depend on glacier-fed streams will suffer critical shortage of water.
The radioactivity signals from strontium-90, caesium-136, tritium (H-3) and chlorine-36 were present in ice cores from Polar Regions and from tropical glaciers around the globe.
This means that the ice fields from these regions retained snow that fell during the last fifty years.
Ice cores
In 2000, Dr Thompson led a team of researchers and retrieved ice cores from Kilimanjaro’s northern ice fields. They found fallout footprints only 1.8 metres below the surface.
“By 2006, the surface of that ice field had lost more than 2.5 metres of solid ice (and hence recorded time) — including ice containing that signal.
Had we drilled those cores in 2006 rather than 2000, the radioactive horizon would be absent — like it is now on Naimona’nyi in the Himalayas” Dr Thompson said (EurekAlert, 2007). “If what is happening on Naimona’nyi is characteristic of the Himalayan glaciers, glacial melt water will eventually dwindle with substantial consequences for a tremendous number of people,” Dr Thompson warned. Researchers estimate that there are nearly 15,000 glaciers within the Himalayan mountain chain forming the main repository for fresh water in that part of the world. The total area of glaciers in the Tibetan plateau may shrink by 80 per cent by the year 2030 (EurekAlert, Dec 11).
D.P. Dobhal, a glaciologist with the Wadia Institute of Himalayan Geology, regularly measures the changes in the size and volume of the Chorabari glacier in the Himalayas (The NYT, July13, 2007).
Chorabari’s snout
Dhobhal estimated that the Chorabari’s snout (where glacier melt water empties out in to the river) retreated 29.5 ft every year for the last three years (The NYT, July 17,2007). According to the New York Times, the Indian Space Research Organization, using satellite imaging to gauge the changes to 466 glaciers has found more than a 20 per cent reduction in size from 1962 to 2001 with bigger glaciers breaking into smaller pieces each retreating faster than its parent.
Mean air temperature
Glaciers worldwide are a barometer for global warming (The NYT, July 17, 2007). The New York Times quoted a recent study which found that the mean air temperature in the northwestern Himalayan range had risen by 2.2 degrees Celsius in the last two decades, a rate considerably more than the rate of increase over the last 100 years.
The impact of global warming is getting attention worldwide. Professor Thompson based his findings on scientific observations. Other studies corroborated them.
Let us hope that Professor Thompson’s predictions may not come true; what is worrying is that it may remain so; just a hope!
K.S. PARTHASARATHY
Former Secretary, AERB
( ksparth@yahoo.co.uk)
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