The Use of Radioactive Isotope in Medicine

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After the discovery of isotopy by Frederic Soddy and Kasimir Fajans, it was found that elements considered to be non-active may possess radioactive isotopes having almost identical chemical properties [1]. Radioisotopes are atoms with a nucleus that is seeking a more stable configuration by emitting radiation. Scientists have learned that more radioisotopes could be created by subjecting certain elements to radiation inside a nuclear reactor or bombarding them using a particle accelerator [2].

Nuclear medicine uses very small amounts of radioactive isotopes, or tracers, to diagnose and treat disease. A tracer having sufficiently long life span, or half life, should be selected to make it compatible with the duration of the operations and measurements to be performed, and also one whose radiation intensity is sufficient to execute the measurements, but without affecting the chemical state of the system. This is of particular importance in biological investigations, where the materials used are usually sensitive to radiation [1]. For instance, iodine-131 has a half life of 8 days which is long enough for it to concentrate in the thyroid gland, allowing doctors long enough to monitor its function, but not so long as to cause damage.

Iodine-131 is one of the most widely used isotopes. It is supplied in capsules or liquid of a specific activity designed to be swallowed by patients. Iodine is a naturally occurring element known as Iodide. It has many uses in nuclear medicine, where it is used as a tracer to diagnose and treat certain diseases, such as an overactive or cancerous thyroid gland.

There are only two naturally occurring isotopes of iodine that are I - 127 (stable) and I - 129 (radioactive). Other radioactive iodine isotopes (e.g., I - 131) do not occur in nature [3,4]. The radioactive isotope I - 123 is considered the agent of choice for brain, thyroid, and renal imaging and uptake measurements. I - 125 is used as a...
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