Radioisotopes are widely used for a number of purposes following are some major applications of radioisotope.

Biochemical analysis

Biochemical assays are used to detect the presence and absence of radioisotopes. Therefore radioactive isotopes are used to label biological molecules. Such assays estimate the concentration of different constituents of plasma, body fluids, urine, blood etc. This technique is called radioimmuno-assays. An example is iodine bioassay which uses gamma emitters’ radionuclides of Iodine-125 and Iodine-131 that accrues inside thyroid. Therefore gamma detector can be used to quantify the iodine content (uptake and intake) of the person’s thyroid. The amount of measured radioiodine in the thyroid is compared with the Annual Limit on Intake (ALI) [1].

Urinalysis

Radioisotopes are eliminated from the body in body fluids. By determining the active contents in urine one can analyse the uptake and intake of a specific radionuclide [1].

Tracer studies

Radioisotope is used for biological labelling of cells or entities for identification or tracing specific molecules in an organism. S 35 P 32 and I 125 are widely used radioisotopes used for labelling [2].

Carbon dating

Radioactive carbon-14 decay could be used to estimate the age of organic materials. For example carbon dating revealed that the burial cloth of Jesus Christ originated during the medieval times between A.D. 1260-1390. Similarly mummified remains found frozen in the Italian Alps were at least 5000 years old [3].

Potassium dating

Radio potassium-40 decays to stable 40Ar. Thus, by measuring relative ratio of 40K and 40Ar in rocks enable us to determine the age of rocks since its formation [4].

Clinical diagnostic

Positron Emission Tomography (PET) and PETCT make use of radionuclides emitting positron particle that is injected in to the target cell or tissue. Radionuclide decay release positron particles which interact with the nearby negatively charged particle resulting in the emission of gamma rays which is detected by a PET or gamma camera to give an exact image of the target [5].

Radionuclide Therapy (RNT)

This therapy makes use of radioisotopes that emits radiations upon their decay. These emitted radiations are used to target specific cancerous cells, tumours etc. to control their abnormal growth or completely eradicate it. For example cobalt-60 is use as a source of gamma radiation for radionuclide therapy, gamma knife radiosurgery and brachytherapy. Similarly targeted alpha therapy uses alpha-emitting radionuclide such as Bi-213, Lead-212, and Boron-10 to for treating pancreatic, ovarian and melanoma cancers [6].

Sterilizing

Sterilization of surgical instruments such as syringes, gloves, clothing and instruments using gamma mitting radionuclides including Cobalt-60, Cs-137 etc. [7].

Radiopharmaceuticals

Incorporation of radioisotopes to biologically active substances is introduced into body in order to observe the functioning of an organ functioning or a metabolic path way etc. For example Yttrium-90 and Iodine-131 is used as radiopharmaceuticals for the treatment of non-Hodgkin’s lymphoma and hyperthyroidism respectively (Table 1) [8].

Table 1: Lists of radionuclides and their biomedical applications [9-48].

Radioisotopes are used for numerous medical purposes which marks it potential in the field of medical science.

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