Radiation can damage healthy cells. The radiation must be targeted to the cancer.
An advanced type of three-dimensional (3-D) conformal radiation, called strength modulated radiation therapy, or IMRT, more specifically conforms the dose to the tumours, allowing safer delivery of higher doses of radiation.
Certain techniques that allow ultra-precise doses of radiation to tumours include stereotactic radiosurgery, which uses 3-D imaging to define the exact location of a tumour. The intensely concentrated gamma rays or x-rays then concentrate on the tumour to treat it. The Gamma Knife is a treatment method that uses radioactive cobalt sources to concentrate several beams of radiation on a small region. Linear accelerators can also be used to administer stereotactic Radiation therapy to the brain. Many areas of the body may be treated with stereotactic body Radiation therapy (SBRT). Emerging areas for using SBRT include lung, liver and bone cancer.
Image-guided Radiation therapy (IGRT) is also used in combination with IMRT to ensure the radiation is transmitted to the targeted location. IGRT involves performing a CT scan at the time of radiation treatment to ensure the target is aligned in the correct location. IGRT may allow for changes during treatment in areas of the body that are sensitive to movement, such as the lungs, and tumours located close to vital organs and tissues.
Radiation can be used to cut off blood flow to a tumour in vascular organs such as the liver. For instance, radio embolisation uses microspheres filled with radioactive isotopes to block a tumour’s blood supply and starve it.