TrueBeam Linear Accelerator

How it works

The TrueBeam is the newest model of medical linear accelerator, the mechanism that transforms electrons into photons by shooting them at a metal target at nearly the speed of light. The energy from that impact is measured in millions of volts. When the photons, or X-rays, contact cancer cells, the result is meant to be so lethal that the cancer cells will lose their ability to reproduce and will then die.

An important part of the new machine's radiation delivery precision is its built-in imaging capabilities. TrueBeam's on-board imaging system captures CT scans and fluoroscopy, or movie-like X-ray images to help doctors ensure that the patient's tumor and normal organs are positioned with millimeter accuracy, and that motion is properly controlled.

The respiratory gating feature is especially good for tumors in the chest and belly because it adjusts for movements in tumors, which are nudged in various directions with each breath. With respiratory gating, the TrueBeam sends out radiation only when the tumor is within the beam's line of delivery. In combination with the TrueBeam's on-board imaging, the effect is a much higher degree of protection for healthy tissue adjacent to the cancer.

Types of treatments

TrueBeam is used for stereotactic ablative radiotherapy. SABR, also known as radiosurgery or stereotactic body radiation therapy (SBRT), is a type of cancer therapy in which very precisely focused beams of radiation target the tumor. The beams are as exact as a scalpel, but accomplish tumor destruction without any incisions. The TrueBeam requires almost the same amount of space as an operating room. It stands 9 feet tall and 15 feet long, and including all its components, weighs more than 9 tons. Its curvilinear arm, called a gantry, rotates in a complete circle to enable treatment from any direction. The level of control is remarkable considering the weight of the gantry.


The TrueBeam linear accelerator is capable of delivering radiation at a faster dose rate than most conventional linear accelerators. This advance translates into shorter treatment times for patients. The time for a typical radiation treatment could be cut in half with the TrueBeam. Other special features improve the accuracy of treatment so the overall duration of a course of treatment may also be shortened from several weeks to just a few days.

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