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Hazards from MRI scanners
This Universe Trends
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Hazards
from MRI scanners
Magnetic Resonance Imaging (MRI) scanner is a unique diagnostic tool. Recently, specialists and regulatory agencies have highlighted some of the dangers from this irreplaceable, life-saving equipment. MRI scanners use powerful magnets. These exert tremendous force on any magnetic substance coming closer to it. “Missile effects” due to the magnetic attraction caused the most notable accidents. Dr Moriel NessAiver, a physicist has published 14 telling photos of hair-raising incidents in a Four of them depict chairs stuck in the gantry; in other instances the objects which flew into gantry were a welding tank, an oxygen tank and a steel stand used to hang glass bottles for intravenous drips. In one instance, the hospital has to engage four men to pull a gurney (a cot mounted on wheels) with a patient on it off a scanner! In July 2001, Michael Colombini, a six-year-old child died under tragic circumstances. Surgeons at the Westchester Medical Centre, New York, successfully removed a benign tumour from his brain. Shortly, while undergoing an MRI scan, his oxygen supply failed. An anesthesiologist brought in an oxygen tank from outside. The steel tank shot out of his hand due to the tremendous magnetic force of the scanner and smashed Michael’s head. He died two days later. Non-magnetic oxygen tanks are available for use near MRI. On May 10, 2005, the US Food and Drug Administration (FDA) issued a public health notification titled “MRI caused injuries in patients with implanted neurological stimulators”. The FDA has received many reports of serious injury, including coma and neurological impairment, in patients with implanted neurological stimulators who underwent MRI scans. The heating of electrodes at the end of lead wires from implanted devices may cause injury to the surrounding tissues. Tattoos or eyeliners containing iron oxide may heat causing minor burns during MRI procedures. The FDA cautioned that any type of implanted neurological stimulators for spinal cord, peripheral nerve and neuromuscular system can cause injury, though the reports received by the FDA so far involved deep brain stimulators and vagus nerve stimulators. When exposed to intense electromagnetic fields used by the MRI scanners, the operational or functional aspects of the implant, material or device may change. Dr Frtank G. Shellock at the University of Southern California made 11 recommendations to avoid hazards related to “missiles” and metallic objects. His articles contain specific recommendations to protect patients. His web site called www.MRIsafety.com contains useful test reports of various devices. Dr Shellock cautioned that the presence of aneurism clips in an individual or patient who has to enter an MR environment requires utmost care. Certain types of clips are absolutely contraindicated. Dr R.P. Klucznic and coworkers from Welford Hall Medical Centre reported the death of a patient due to acute intracranial hemorrhage caused by the movement of an aneurism clip during an MRI scan. Autopsy revealed a torn middle cerebral artery. Dr E. Kanal and coworkers from the University of Pittsburgh Medical centre showed that 63 out of 1791 reportedly non-ferromagnetic aneurism clips moved in the magnetic resonance field. This unexpected result confirms the need for testing the ferromagnetic properties of implantable metallic devices, researchers cautioned. In a review article on MRI safety published in the Radiology (2004) Journal, Dr Shellock and Dr John V. Crues state: “Most reported cases of MR related injuries and a few fatalities that have occurred have apparently been the result of failure to follow safety guidelines or of use of inappropriate or outdated information related to the safety aspects of biomedical implants and devices.” Patients, physicians and MR technologists, must be fully aware of MRI hazards; they must make every effort to maintain a safe MR environment to reap the benefits from this unique diagnostic tool. |
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This Universe
The other day, while imbibing a drink of water, I started to casually rub the rim of the glass with my wet finger; after a while, a humming sound emanated as a result.
Why did this happen? That was a nice observation. If you had done that using a wine glass with a long stem, the sound would have been purer in pitch and louder. In some circles this is a game people play at parties. I would like you to do some experimentation. Put different amounts of water in the glass and try to observe if the pitch of the sound changes. You will find that it does. The glass has a natural frequency of vibration, depending on the length of the air column, besides its structure. Strike the glass with a spoon and listen to the pitch of the sound. Then you do your moving-a-wet-finger-over-the-rim experiment. You should find that the dominant pitch is the same. This shows that the finger is not doing any special magic. It is continuously exciting vibrations in the glass because of the friction between the slightly wet finger and the rim of the glass. It is because of the continuous stimulation by the finger that you get a continuing sound. (You will find that very wet finger is not very efficient in this regard because the friction is reduced or eliminated). In fact, this is rather similar to the way a bow excites vibrations in a violin string. The sound is almost continuous but at the same frequency that you would hear if you
plucked that string. All things are, in principle, musical instruments, some better than the others. In many of them, cavities of air, their shape and length, are crucial. Remember that instrument called the Jaltarang? If a bow could be drawn over the rims of the cups used in the Jaltarang, we would have an entirely different musical instrument! If you play the violin or have an access to a bow, you might find that the bow could perhaps replace
your wet finger. When a few drops of water are sprinkled over hot oil, what makes
it crackle and fizz? Hot oil is very much hotter than the boiling point of water. When you put drops of water in hot oil, they sink in a little (water being heavier than oil) and then convert into steam that escapes with explosive force. That is the reason for the noise. Of course nothing like this happens if you pour a little oil on boiling water, for the obvious reason that oil stays near the surface and cannot be vaporised suddenly because the boiling water is just not
hot enough. How do fish get the oxygen they need from water? Some oxygen is always dissolved in water. Fish extract it out using their gills. You must have noticed that in a home aquarium, a motor keeps blowing air into the fish tank; you can see the bubbles rising up. This is to oxygenate the water and keep it “breathable” — that is for creatures with gills. |
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Trends Researchers in Germany have discovered a way to fight cancer by using parts of a virus found in tree shrews and small Southeast Asian
mammals. The researchers, at the Mayo Clinic in Germany, used a virus to create a disguise for an engineered measles virus that enables it to sneak past the immune system. It kills cancer cells without harming healthy cells. The finding was a key step forward in the science of redirecting or retargeting a virus through genetic engineering, a report in the Journal of Virology said.
— PTI Hardy
bacteria
Scientists have discovered bacteria in an unlikely location — at the bottom of the near-freezing waters of Antarctica! It was in March this year that researchers accidentally discovered a vast community of bacteria and clams on the ocean floor while exploring Antarctic waters that opened up after the vast Larsen B Ice Shelf collapsed in 2002. “The area had been isolated under the ice for at least 10,000 years, and the discovery means that the chance of life happening in other places that are even more restricted is increased,” said Eugene Domack, a Professor of Geosciences at the Hamilton College in New York, who led the international team
to Antarctica earlier this year. Bacteria presence at a depth of 2,800 feet, in an environment Domack called the “coldest of the cold,” may be the reason life has been possible under a 600-foot layer of ice. Similar communities have been found around the world, but “never in such an extreme region,” said Jim Barry, a deep-sea ecologist at Monterey Bay Aquarium Research Institute. —
PTI Ice-free
Arctic?
The current warming trends in the Arctic may shove the Arctic system into a seasonally ice-free state not seen for more than one million years, according to a new report. The melting is accelerating, and a team of researchers were unable to identify any natural processes that might slow the de-icing of the Arctic. Such substantial additional melting of Arctic glaciers and ice sheets will raise sea level worldwide, flooding the coastal areas where many of the world’s people live. Melting sea ice has already resulted in dramatic impacts for the indigenous people and animals in the Arctic, which includes parts of Alaska, Canada, Russia, Siberia, Scandinavia and Greenland. Missing pulsar found
Ending a long astronomical search, a team of Indian and British scientists has finally found a celestial body called pulsar, which has long been missing, from remnants of a star that exploded hundreds of years ago. The discovery of this pulsar has been made by scientists from the Tata Institute of Fundamental Research, Pune, and Mullard Astronomy Observatory, Cambridge, along with a student from the National Institute of Technology, Durgapur. “The discovery has been made in India using an Indian telescope called Giant Metrewave Radio Telescope (GMRT),” Dr Y Gupta from TIFR told PTI. The GMRT is located at Khodad, about 80 kms
from Pune. — PTI |
