Applied Radiation Biology and Radiotherapy

Brachytherapy

Brachytherapy is the administration of radiation therapy by placing radioactive sources adjacent to or into tumours or body cavities.

With this mode of therapy, a high radiation dose can be delivered locally to the tumour with rapid dose fall-off in the surrounding normal tissues. In the past, brachytherapy was carried out mostly with Radium or Radon sources. Currently, use of artificially produced radionuclides such as ¹³⁷Cs, ¹⁹²Ir, ¹⁹⁸Au, ¹²⁵I, and ¹⁰³Pd is rapidly increasing.

According to the technique of implant loading, brachytherapy can be:

Manual loading
Manual after-loading
Remote-controlled afterloading

According to the location of the implant, brachytherapy can be:

Mould (sources places in contact with the skin or skin tumour)
Intracavitary (sources placed in natural body cavities e.g: esophagus, uterine cavity)
Interstitial (sources placed into tissues or tumours, e.g: prostate)

According to the removal of the radioactive sources, brachytherapy implants can be:

Temporary (sources are inserted and later removed)
Permanent (sources are inserted and left in place for the remainder of their active life)

According to the dose rate of the sources used, brachytherapy can be:

Low Dose-Rate (LDR): 0.4 to 2.0 Gy per hour
Medium Dose-Rate (MDR): 2.0 to 12.0 Gy per hour
High Dose-Rate (HDR): > 12.0 Gy per hour

By ICRU definition, HDR is > 12.0 Gy/h, although the usual dose rate employed in current HDR brachytherapy units is about 100-300 Gy per hour.