BRACHYTHERAPY-Application of Pair Production

Brachytherapy

• The term brachyteraphy refers to radiation therapy in which the source of radiation is in direct contact with the tumor.
• External beam radiotherapy, on the other hand, uses a radiation source that is 80-100 cm away from the patient.
• Since the source is normally inside the tumor volume, brachytherapy dose distribution is almost entirely determined by the inverse square law.
• Because of this inverse square dependency, proper radiation source positioning is important

Isotopes

The primary isotope used in brachytherapy was radium.

Radium has recently been replaced with cesium due to its long half-life and high energy content.

Iridium, Cs, and gold (Au) (Ir). Because of their lower energies, these isotopes have longer half-lives than radium and can be shielded more easily.

How to perform brachytherapy

Temporary implants have longer half lives and higher energies than permanent implants.

These sources may come in a variety of shapes and sizes, including needles, seeds, and ribbons.

Treatment lasts between 1-3 days on average.