Radiotherapy otherwise known as radiation therapy is a common part of cancer treatment. Advances in both imaging technology and radiation delivery provide more a more specific attack on the cancer with less damage to surrounding tissue in the organs at risk. There are two types of radiotherapy: external and internal.
Depending on the type of cancer the following techniques may be used:
IMRT: intensity modulated radiotherapy
A treatment for head and neck cancers and for prostate cancer. When used for head and neck cancers, it minimizes damage to the salivary glands, upper aero-digestive tract mucosa, optic nerves, inner ear, swallowing muscles, brain stem, and spinal cord.
IGRT: image guided radiotherapy
With highly “focused” radiation, it is critical to know the tumour's location, size, and shape accurately. Imaging techniques include computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET).
3D-CRT: three-dimensional conformal radiotherapy
This technique fits the shape of the radiation dose to the shape of the tumour.
Several linear accelerator systems are used for treating metastatic tumours in the head, and some cancers of the lung, kidneys, liver, spine, and prostate.
Charged particles, such as protons from an accelerator, deposit most of their energy in a small area called the Bragg peak at the end of their penetration range. This method is the closest to a “magic bullet” that can be aimed at just the cancer.
There are two forms of internal radiotherapy:
- Brachytherapy - putting solid radioactive material (the source) close to or inside the tumour for a limited period of time
- Radioisotope treatment - by using a radioactive liquid, which is given either as a drink or as an injection into a vein