Nuclear medicine Dr S. S. Verma In the early decades of the nuclear era it became apparent that high levels of nuclear radiation can be harmful, even fatal but it was also realised that there are a number of ways in which controlled use of radiation could be medically beneficial to humans. In the 1990s, nuclear medicine had quietly established itself as a true life saving discipline.

 

Trends How ants find  their way Ever wondered how ants find their way straight to the uncovered food in your kitchen? Now scientists have discovered how the humble wood ant navigates over proportionally huge distances, using just very poor eyesight and confusing and changing natural landmarks. On the first trip ants store images of the route as they travel and on later trips to the food site will navigate using a combination of landmarks and memories of the whole landscape. Trained ants with paint markers. (Image courtesy Biotechnology and Biological Sciences Research Council)

Prof Yash Pal

Nuclear medicine
Dr S. S. Verma

In the early decades of the nuclear era it became apparent that high levels of nuclear radiation can be harmful, even fatal but it was also realised that there are a number of ways in which controlled use of radiation could be medically beneficial to humans.

In the 1990s, nuclear medicine had quietly established itself as a true life saving discipline. Nuclear medicine relies heavily on the knowledge that has been amassed in the field of nuclear physics. For example gamma-emitting radioisotopes are preferred for diagnostic procedures that require placing the material inside the body. Since gamma rays interact less with matter than some other forms of radiation, they do less damage to tissue and are more likely to make it out of the body where they can be detected. The half-life of an implanted radioisotope is a critical parameter for determining dosages, since it indicates over what period of time the irradiation will be appreciable.

Use of radioactive isotopes offers an important technique for diagnostic procedures and treatments for thyroid, liver, blood, brain and arthritis etc. disorders and for cancer treatments. Treatment can be carried out in two ways i.e., internally and externally.

Internal treatment

i) The radioisotopes are added to molecules and these molecules can then be used as tracers. Many body functions can be studied by monitoring the location and activity of the tracer molecules, as they are absorbed during the body processes.

For example, the activity of the thyroid gland in hormone production can be determined by monitoring its iodine uptake with radioactive iodine-123. This isotope emits gamma rays and has a half-life of 13.3 hrs. The body requires iodine and when ingested it collects in the thyroid gland near the throat.

Similarly, the liver quickly absorbs radioactive solutions of iodine and gold. The uptake of radioactive iodine and gold can be monitored to see if there is an abnormality in thyroid gland or liver functioning.

One of the most commonly used diagnostic tracers is technetium-99 (99Tc), its half-life is 6hrs and it combines with a large variety of compounds.

ii) Seed implants: a procedure predominantly used to treat prostate cancers. Radioactive seeds are implanted and placed directly on the cancer mass. The seeds are about the size of a grain of rice. Usually 70-150 seeds are implanted. They work by delivering high doses of radiation directly to the tumor without affecting nearby healthy tissues.

Prior to implantation, ultrasound may be used to map out the tissue. The results help determine where and how many seeds will be implanted.

iii) Brach therapy: a local treatment for early stage carcinomas in which sealed radioactive sources are used to deliver radiation to the tumor from a short distance. May be combined with external beam radiation, depending upon the type and severity of the cancer.

The two radioactive sources used are 103Pd and 125I. This treatment has been used to treat eye plaques and cancers of the prostate, lungs, brain, and female reproductive organs (uterus, ovaries, cervix).

External treatment

Beam Radiation Therapy: large machines are used to produce high and low energy X-ray beams.

The amount of radiation required is dependent upon the type of cancer. For example, the level of radiation necessary to destroy a skin carcinoma is less than the amount needed to treat a cancer that is located deep within the body. This treatment is offered for a large variety of cancers, and may be used alone or in conjunction with other cancer treatments. 

Trends
How ants find their way

Ever wondered how ants find their way straight to the uncovered food in your kitchen? Now scientists have discovered how the humble wood ant navigates over proportionally huge distances, using just very poor eyesight and confusing and changing natural landmarks.

On the first trip ants store images of the route as they travel and on later trips to the food site will navigate using a combination of landmarks and memories of the whole landscape.

The scientists found the ants even used different sets of landmark memories depending on whether they were on their way to food, or whether they were full and heading back to the nest.

No ice on moon

Alas, the moon is not for winter sports. Never mind the difficulty of a triple axel in a bulky spacesuit (though the diminished gravity might help) — ice, it turns out, is hard to come by up there.

That’s the latest word from astronomers at Cornell and the Smithsonian Institution, who used high-resolution radar-mapping techniques to look for ice deposits at the lunar poles.

Robotic whiskers

Many mammals use their whiskers to explore their environment and to construct a three-dimensional image of their world. Rodents, for example, use their whiskers to determine the size, shape and texture of objects, and seals use their whiskers to track the fluid wakes of their prey. Two Northwestern University engineers have been studying the whisker system of rats to better understand how mechanical information from the whiskers gets transmitted to the brain and to develop artificial whisker arrays for engineering applications. 

THIS UNIVERSE 
PROF YASH PAL

My 11-year-old ward asked me: “Naniji, a snake has poison in his body; when he bites someone he dies. Why doesn’t the poison in its body kill the snake itself?”  Please explain.

What I have found out in this regard can be summarised in the following way. The stuff that snake venom is made of cannot even be called a poison. It is a complex cocktail devised by each snake species consisting of proteins and enzymes — indeed mostly the latter. It would be relatively harmless if ingested. It would be digested like food. But when injected into the blood stream it can become lethal, quickly affecting the heart and/or the brain.

The enzymes and proteins can eat up cells, muscle, blood and what not in a short period of time. And yet the snakes are immune to their own venom. In fact, there are snakes that are immune to the venom of several others. This immunity is built into their system.

If we release water vapour in vacuum around the earth, will the water change into ice? If it does what will absorb the energy released?

This is a common-place happening in the upper reaches of the atmosphere. Water vapour convected up first turns into water and then into little ice crystals. In the process heat is released and goes to heat up the residual atmosphere. If the atmosphere were too thin, in other words if you were in the vacuum of outer space the heat would be radiated away into space.

I might mention that quite a bit of our rain starts out as tiny crystals of ice, floating in the upper atmosphere.