Linear accelerators are the machines that deliver external radiation therapy. They use a wave-guided device that accelerates electrons to high velocity, so that they collide with a heavy metal target to release x-rays.
The Middlesex Health Cancer Center is home to two of the most cutting-edge linear accelerators: the Novalis TX  and the Elekta. You can click on the Intensity Modulated Radiation Therapy (IMRT) link above to learn more.