Stereotactic radiosurgery requires certain key tools and technologies, such as specialized treatment planning software, a source of high-energy radiation (medical linear accelerator), devices to shape the radiation beams, and quality assurance tools, such as an X-ray imager, which is used to check your position relative to the radiation beam before treatment begins.
Sophisticated computer software and three-dimensional images of your lesion and surrounding anatomy indicate the optimal way of treating your condition. The resulting treatment plan—unique to you—specifies the number of radiation beams as well as the angles required to precisely deliver the radiation dose prescribed by your doctor without harming surrounding healthy tissue.
Medical Linear Accelerator
A specially equipped linear accelerator is used to generate the radiation beams for your treatment. It is optimized to deliver high radiation doses to very small targets with extreme precision. It generates a radiation beam shaped to limit the dose to the region of abnormality. To do this it employs one of two devices.
One device—for addressing relatively small tumors or abnormalities—is a cylindrical metal block called a cone. Cones have holes of various sizes down the middle. The size and shape of your abnormality determines the correct hole size. A second device—for addressing larger tumors or abnormalities—is called a multileaf collimator, or MLC. The MLC has 120 computer-controlled tungsten metal fingers, or leaves, that can be individually adjusted to create an aperture of almost any shape. The radiation beam is passed through this aperture, and shaped by it. This ability to change the beam shape over time gives the doctors very fine control over how, and where, the radiation dose is administered.
With the radiation beam shaped so exactly, care must be taken to ensure that it is aimed at the targeted area with great precision. A special X-ray imager, mounted on the linear accelerator, is used to check your position relative to the radiation beam before treatment begins. Adjustments can be made to the position of the treatment couch, if required, so that you are positioned for treatment with submillimeter accuracy.