</h3>
Why radiations are used to treat cancer despite of the fact that they cause cancer?
How do we know about blood circulation in our body?
How tumors can be detected and treated?
How do we investigate the proper amount of fertilizer consumed by a plant? </h3>
Prior to study the <b>nuclear physics</b> these and some other question arose in my mind. If you have the same questions in your mind you are at the right place, this post will help you to understand these questions. Lets move into it:
>Isotopes are the atoms in an element that have the same atomic number but a different atomic mass; that is, the same number of protons and thus identical chemical properties, but different numbers of neutrons and consequently different physical properties. Isotopes can be stable or unstable or radioisotopes. In the latter, their nuclei have a special property: they emit energy in the form of ionizing radiation while searching for a more stable configuration.
<sub>[source](http://www.foronuclear.org/en/ask-the-expert/120059-what-are-radioisotopes)</sub>
Radioisotopes of many elements can be made easily by bombardment with neutrons and other particles. As such isotopes have become available and are inexpensive, their use in medicine,agriculture,scientific research and industries has expanded tremendously. The application of radioactivity and radiations to human beings and other biological organisms is a vastly growing field.
Radioisotopes are used to find out what happens in many complex chemical reactions and how they proceed. Similarly in biology, they have helped in investigating into chemical reactions that take place in plants and animals. By mixing a samll amount of radioactive isotopes with fertilizer, we can easily measure how much fertilizer is taken up by a plant using radiation detector.
<sub>[source](https://pixabay.com/en/agriculture-bio-farm-power-2382176)</sub>
From such measurments, farmers know the proper amount of fertilizer to use. Through the use of radiation-induces mutations, improved varieties of certain crops such as rice, chickpea, wheat and cotton have been developed. They have improved plant structure. The plants have shown more resistance to diseases and pest. This results in better yield and grain quality. Radiations tracers and imaging devices have helped in understanding and diagnosis of many diseases.
<h1>Tracer Techniques:</h1>
A radioactive isotope behaves in just the same way as the normal isotope inside a living organism. But the location and concentration of a radioactive isotope can be determined easily by measuring the radiation it emits. Thus, a radioactive isotope acts as an indicator or tracer that make it possible to follow the course of chemical or biological process. The technique is to substitute radioactive atoms for stable atoms of the same kind in a substance and then to follow the "tagged" atoms with the help of radiation detector in the process.
In this way the details can be traced of how food molecules are digested; to what parts of the body of an organism they are diverted and how certain essential componds are synthesized by the organism. Isotopes which are gamma rays emitters are the best for this application.
Some chemicals such as hydrogen and sodium present in water and food are distributed uniformly throughout the body. Certain other chemicals are selectively absorbed by certain organs.Tracers studies reveal that if a small quantity of radioactive iodine <sub>53</sub>I<sup>131</sup>is taken in the food, most of it deposit in the thyroid glands of man and animals. If radioactive calcium <sub>20</sub>Ca<sup>45</sup>, is taken by man or animals orally or by injection, nearly 90% of it deposit in the bones of the young ones while only 40% in the old individuals. Phosphorous absorbed mostly by bones and cobalt by liver. They can serve as tracers.Small quantity of low activity radioisotope mixed with stable isotope is administered by injection or otherwise to a patient and its location is diseased tissue can be ascertained by means of radiation detector. For example, radioactive iodine can be used to check that a person's thyroid gland is working properly. A diseased or hyperactive gland absorbs more than twice the amount of iodine as compared to normal thyroid gland. Sodium being an important constitutent of the body fluids. The rate of flow of the blood etc in the body can be traced by giving radioisotpe of sodium <sub>11</sub> Na<sup>24</sup>
Tracers are widely used in medicine to detect malignant tumors and in agriculture to study the uptake of a fertilizer by a plant. For example, if a plant is given radioactive carbon-14, it will use it in exactly the same way as it always uses stable carbon-12. But the carbon-14 releases beta radiations and thus by measuring radioactivity in different parts of the plants, the path taken by the carbon-14 atoms can be known. This technique has helped to understand more elaborately the complex process of photosynthesis.
<h1> Radiation Therapy and Diagnostics:</h1>
The usefulness of x-rays in medical diagnostics is very well known. The rays can easily pass through less dense tissues of the flesh and the cracks or fractures of bones. However, they are stopped by denser parts like bones and to a less degree by tumors, etc. They can, therefore, give a shadow graph of any internal part of the body on a photographic film from which diagnosis of a crack or fracture in a bone or a tumor in the fleshy part can be made. The diagnostic usefulness of x-ray out-weighs the small radiations hazard involved with the exposure. However, unnecessary frequent exposures must always be avoided.
<h3>Treatment of Cancer:</h3>
No doubt that radiation can cause cancer, it can also be used to treat it as it can destroy rapidly growing cancer cells. Some of the normal cells surrounding a cancerous tumor are inevitably killed causing side effects characteristic of radiation sickness.
In treating a localized cancerous tumor a narrow beam of gamma rays from cobalt-60 or energetic x-rays is often used. The beam is directed at the tumor and the source is continously rotated such that while the beam impinges on the tumor all the time, its surrounding region recieves as low a dose as possible. The cancerous cells on the tumor can thus be destroyed to the relief of the patient without causing appreciable damage to the surrounding tissues. This is so-called external therapy.
<sub>[source](https://www.canceractive.com/images/MYPICS/Varian3.jpg)</sub>
The other mode of tratment is called internal therapy, in some cases of internal therapy a tiny gamma ray source of very short half life may be inserted directly inside the a tumor by surgical operation. It will kill majority of the cancer cells. This techniquebis sometimes used to treat cancer of the thyroid glands with radioisotope iodine <sub>53</sub>I<sup>131</sup>.
Alternatively the radioisotope is injected in to the blood. As iodine has special affinity to the thyroid glands, it concentrate there, particularly in the cancerous region. The intense radiation from the radioisotope kills most of the defective cells. Similarly, cancerous affections in other parts of the organisms may be treated by using the radioisotope of an element having special affinity to them.
<sub>[source](http://zniup3zx6m0ydqfpv9y6sgtf.wpengine.netdna-cdn.com/wp-content/uploads/2017/10/171024-Radioactive-liquid-and-thyroid-cancer_blog.png)</sub>
The radiation treatment may increase the life span of a cancer patient but it may not be completely effective. All the cancer cells may not be destroyed. Hence, there is always a likelihood of the recurrence of the disease.
References;
http://biology.homeomagnet.com/tracer-techniques/
https://www.cancer.gov/about-cancer/treatment/types/radiation-therapy/radiation-fact-sheet
http://www.world-nuclear.org/information-library/non-power-nuclear-applications/radioisotopes-research/radioisotopes-in-medicine.aspx