The radiation sources used for brachytherapy are placed directly in, or next to the tumor. Therefore, the irradiation effect is confined only to the target tumor being treated. In contrast, the radiation used in external beam radiotherapy (EBRT) must travel from outside the body through healthy tissue. Thus, compared to EBRT, radiation exposure to healthy tissues is much reduced with brachytherapy.
The radiation sources used for brachytherapy have a ‘steep dose gradient’ – at a short distance away from the radiation source, the level of radiation quickly reduces to very low levels. In physics, this is known as the ‘inverse square law’, which states that around a source of radiation, the dose ‘falls off’ at the square of the distance.
Therefore, brachytherapy enables the radiation dose and distribution of the radiation to be exactly matched to the size and shape of the tumor. Furthermore, tissues around the tumor receive a much lower dose than anticipated by other radiation methods.
The combination of precision delivery and ‘steep dose gradient’, only found in brachytherapy, means that surrounding healthy tissues are not exposed to harmful levels of irradiation. As a result, there is less toxicity and the risk of side effects is much reduced.1-3
Brachytherapy is only minimally invasive and therefore avoids many of the risks associated with extensive surgery.
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