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What is Technetium-99m?

Technetium-99m is a nuclear isomer of Technetium 99. It is a radioactive substance that radiates “Gamma Rays”.

Technetium 99m Symbol

It is symbolized as 99mTc. The metastable state of the nuclear isomer is indicated by the “m”. This state is created by exciting the nucleons (neutrons or protons) of an atomic nucleus.

Technetium-99m Radiation

This nuclear isomer is radioactive and it radiates “Gamma Rays” (γ).

Technetium-99m Half Life

When a radioactive substance is undergoing decay, the time it takes to decrease by half is indicated as its half-Life. Technetium 99m undergoes gamma radiation and it takes 6 hours to decrease by half. That means the half-life of this substance is 6 hours.

It has a considerably long half-life considering the fact that it emits gamma-ray. Usually, the half-life of radioisotopes undergoing gamma decay is too short.

Technetium-99m production

Technetium 99m is not a natural but an artificially produced substance. It is the product of Molybdenum 99 (99Mo) caused by radioactive decay (decay-product). To produce this nuclear isomer, Molybdenum 98(98Mo) is first bombarded with a neutron. This produces 99M that has a half-life of 66 hours. The 99M decays to produce metastable Technetium (Tc) or 99mTc. Producing Technetium 99m in this process is allowed only for medical purposes.

Technetium-99m Picture
Picture 1 – Technetium-99m
Source –

Technetium 99m Generator

Technetium 99m Generator is the name for the device used to produce metastable Technetium. With the help of this generator, 99mTc is extracted from decaying Molybdenum 99. 99Mo has a long half-life of 66 hours. So, the generator and the 99Mo can easily be carried away to the place where the decay product 99mTc is required.

Technetium-99m Properties

Here are some basic properties of this nuclear isomer:

Atomic Number

The atomic number of Technetium 99m is 43.

Atomic Weight

The atomic weight of this substance is 99.

Physical State

It is a radioactive metal which is silver-grey in color.


99mTc is soluble in Nitric Acid, Aqua Regia and concentrated Sulfuric Acid. It is insoluble in Hydrochloric Acid.

Technetium 99m in Nuclear Medicine

Radioactive isotopes are used in Nuclear Medicine. The radioactive decay of the isotopes is relied upon to diagnose and treat the patient. The function of this branch of medicine depends on the concept that the body reacts to substances differently when there is a disease present.

To diagnose the disease, the radioactive substance is bound to another chemical substance that can work inside the body without causing any harm. After that, both the chemicals are transported inside the body. As a result, the radioactive isotope can work as a medical tracer from inside the body. It can be detected by special medical equipments.

As 99mTc has a much longer half life than other gamma ray radiating isotopes, it is very useful in the field of nuclear medicine.

Technetium 99m in Bone Scan

It is widely used to scan fractures and other problems of bones. Ligand Methylene-Diphosphonate (MDP) is a substance that is easily taken up by the bones. So, Technetium 99m is chemically attached to it to be easily transported to the bones via hydroxyapatite for imaging. In this way, the diagnosis of the bones can be easily done.

Technetium 99m Albumin Aggregated (MAA)

It is the name of a radiopharmaceutical substance. It is used in nuclear medicine. The MAA is an injectable substance.

Technetium 99m Medicines

The names of the principal medicines of 99mTc are:

  • Technetium sestamibi or Cardiolite (trade name)
  • Technetium tetrofosmin or Myoview (trade name)

Technetium 99m Uses

It is used as a medical tracer in radioactive isotope medical tests. 99mTc is used in the treatment of the following diseases:

  • Brain
  • Myocardium
  • Thyroid
  • Lungs
  • Liver
  • Gallbladder
  • Kidney
  • Skeleton
  • Blood
  • Tumors

Technetium-99m Benefits

Some of the main benefits of using this radioactive substance are mentioned bellow:

  • The principal benefit of this radioactive substance is its long half life. 6 hours is long enough for various medical examinations to be done. Also, it is short enough for the99mTc to be eliminated from the system without causing any harm.
  • The radiation dose to the patient remains low because 99mTc emits gamma-ray.
  • 99mTc can be tagged or attached to a variety of chemicals so that it can be used for the treatment of various parts of the human body.
  • It emits the 140 keV gamma rays, which is readily detectable.

It is one of the most useful radioactive isomers and is widely used in nuclear medicine. It can only be produced artificially for medicinal purposes. Technetium 99m has great contribution in the advancement of nuclear medicine.



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