Iridium-192

Iridium-192 Definition

It is a radioactive isotope of Iridium with symbol 192Ir.

Source

It is a man-made radioactive element that is produced by nonradioactive Iridium metal in a nuclear reactor.

Color

It is a dense metal that is shiny and silvery-white in appearance.

Iridium-192 Properties

Know about some of the chemical as well as physical properties of this element.

• Its binding energy per nucleon is 7.938986 MeV (Megaelectronvolts).
• It has a melting point of 2,446°C.
• It has a boiling point of 4,428°C.
• Its specific gravity is 22.562 (at 20°C).
• It is a dense metal and has a relative density of 22.42.

Iridium-192 Fact Sheet

Know about some important facts associated with this substance.

• The mass number of this radioactive element is 192.
• The atomic number of this element is 77.
• Its neutron number is 115.
• The atomic mass of this radioactive substance is 191.962605012 u (unified atomic mass units).
• It has a mass excess of -34.833207 MeV(Megaelectronvolts).

Half Life

The half-life of this isotopic substance is 73.828 days.

Picture 1 – Iridium-192
Source – en.wikipedia.org

Iridium-192 Lifetime

The lifetime of this radioactive element is 106.51 days.

Iridium-192 Decay Modes

Its decay modes are Beta Particles and Gamma Radiation. It decays 95.13% of the time through negative beta emission to ¹⁹²Pt (daughter nuclide). For the remaining 4.87% of the time, it decays through electron capture to ¹⁹²Os. A gamma photon with an average energy of 0.38 MeV (max 1.06 MeV) is released in the process.

Iridium-192 Isotopes

As aforesaid, Iridium-192 is a radioactive iridium isotope. It is also the most common isotope used for high dose rate brachytherapy applications. Once World War II ended, new isotopes such as cobalt-60, caesium-137 and iridium-192 became available for Industrial Radiography. Consequently, the use of radon and radium decreased.

Specific Activity

Its specific activity differs depending on the concentration of ¹⁹²Ir in the source. For applications of high dose, its specific activity is 2.4×102 TeV/g.

Iridium-192 Production

For commercial use, ¹⁹²Ir is produced in a nuclear reactor by reaction of ¹⁹¹Ir with neutrons. This technique has numerous benefits. It ensures minimal generation of unwanted isotopes and large cross section of isotopes for interaction of neutrons. As a result, high concentration of ¹⁹²Ir is produced comparatively easily.

Iridium-192 Radiation Safety

Being a radioactive substance, necessary safeguards must be taken while using it. It should be kept safe in order to avoid accidental exposure or deliberate misuse and disposed following state guidelines. In case of an accidental exposure, victims should remove clothes and discard them permanently. It is important to take showers. Immediate medical help should be sought.

Iridium-192 Applicator

High-dose rate (HDR) Iridium-192 Brachytherapy is often facilitated with the aid of a flexible applicator. It is also used for medical treatment, such as for the cure of stomal recurrence after Tracheostomy is performed for subglottic carcinoma.

Iridium-192 Low Dose Supply

Iridium-192 suppliers render this radioactive element in low doses in wires of 100 – 140 mm in length and 0.3 mm in thickness that can still be cut into smaller pieces as needed. The wires are non-reactive and flexible.

For high dose rate, Platinum/Iridium alloy capsules that are 3.5 mm long and 0.6 mm diameter in size are used. These, used a high ¹⁹²Ir concentration, provides it with a high activity. The tablet comes coated in Platinum of thickness 1 mm, which weaken the consistency of any electrons produced during decay. The tablet is also welded to the end of a wire allowing it to be deployed using a HDR Remote Afterloading machine.

This radioactive element does not necessarily require sterilizing by end user when deployed for high dose rate (hdr) as it is rendered in a sealed sterilized package.

Iridium-192 Uses

Know about some of the main applications of this radioactive substance.

• It is a commonly used isotope in high dose rate Brachytherapy.
• It is also used for medical reasons in Brachytherapy for the treatment of various types of cancer.
• It also has applications in industrial radiography. It is used to capture x-ray images of heavy metal objects.
• Radioactive Ir-192 is principally applied for non-destructive testing (NDT). It is also used to a lesser extent as a radio- tracer in the oil industry.

Iridium-192 Implants

Ir-192 implants have medical uses in healthcare industry. These are used for curative reasons, primarily in the breast and the head. These implants are manufactured in wire form and are introduced into the target area through a catheter. The implant wire is removed after being left in place for the time required to deliver the desired dose. This procedure is very effective at providing localized radiation to the tumor site while minimizing the patient’s whole body dose.

Iridium-192 Benefits

There are numerous advantages of using this radioactive element which can be summarized as follows:

• Its application can be tailored to high or low dose rate, as per requirement.
• It is relatively easy to manufacture.
• It has a stable daughter product.
• It can be reused.

Iridium-192 Drawbacks

Some of the main disadvantages of this element are:

• Broad spectrum of photons is emitted during the emission process.
• It involves frequent recalibrations as a consequence of radioactive decay.
• It needs replacement after every three to four months.

Iridium-192 Cancer Treatment

192Ir is used as a source of gamma radiation for curing cancer with the application of Brachytherapy. Brachytherapy is a type of radiotherapy that involves the placement of a sealed radioactive source inside or adjacent to the region that requires treatment. Specific treatments involve procedures such as:

• High Dose Rate Prostate Brachytherapy
• Bilary Duct Brachytherapy
• Intracavitary Cervix Brachytherapy

Iridium-192 Toxicity

Very little is known regarding the toxicity of iridium compounds. This is due to the fact that they are used in extremely small amounts. However, the radioisotopes of iridium are known to be quite dangerous. The same can be said for 192Ir, which is a radioactive Iridium isotope. Accidental exposure to 192Ir radiation can lead to injuries. High-energy 192Ir gamma radiation can elevate the risk of cancer.

Iridium-192 Health Hazards

External exposure to this substance can lead to problems like

• Burns
• Radiation poisoning
• Acute radiation sickness
• Death

Internal Iridium-192 exposure can only happen if anyone swallows its tablet or other forms sold commercially. Ingestion of 192Ir can result in burning of the linings of the intestines and the stomach. Swallowed tablets are usually excreted in feces. Long-term effect would depend on how powerful the swallowed contents were and how much duration they stayed in the body. 192Ir as well as other isotopes of Iridium such as 192mIr and 194mIr tend to get deposited in the liver. This can result in health hazards from both gamma and beta radiation.

References
1. http://ozradonc.wikidot.com/iridium-192