SBRT is delivered through devices called linear accelerators, which form beams of fast-moving subatomic particles. [msk-node-teaser: 26710] At Memorial Sloan Kettering, doctors who specialize in radiation therapy, called radiation oncologists, use a computerized system to shape the radiation beams to match a three-dimensional outline of the tumor. This outline is generated by an MRI scan, which you will have before your procedure. Your radiation oncologist will collaborate with medical physicists to design a treatment plan that allows the delivery of radiation that conforms to the dimensions of your tumor. SBRT is performed while you are lying on a table. Imaging technology on the linear accelerator helps ensure you are in the same position for every session and that the target area does not shift during treatment. You will be awake during the procedure, which usually takes between 30 minutes and an hour.