The medical linear accelerator (linac) is a crucial piece of technology for the radiation oncology industry and is one of the most used machines in the field. The underlying principle of a linac is straightforward, but producing a consistent, stable beam of radiation and precise, sophisticated design for careful operation is essential.

A linear accelerator works by heating a filament that boils off a cloud of electrons; these electrons are then accelerated by an electric field applied between the filament (cathode) and a thin metal window (anode). The electrons then hit a target (where they produce Bremsstrahlung X-rays) or a scattering foil (to distribute an electron beam evenly.) 

Afterward, the beam can be shaped in the treatment head – a part of the LINAC machine. Below, we discuss the external and internal components of a Linear Accelerator.

External Components of a Linear Accelerator: 

Couch (Patient Positioning System) The couch supports and positions the patient during treatment. Modern LINAC couches allow for precise patient positioning for proper beam exposure, which can move on the x, y, and z-axis. More advanced couches may include the ability to allow a patient to be positioned to roll, pitch, and yaw.

Electronic Portal Imaging Device (EPID) The electronic portal imaging device forms an image using the MV treatment beam. EPIDs are valuable in tools for monitoring patient setup and quality assurance.

Gantry The linac is mounted on a rotating gantry that offers treatment from multiple angles.

kV Imaging System The kilovoltage imaging system consists of a kV X-ray generator and an electronic imaging device. Lower energies of the imaging system improve contrast, particularly when used to produce a cone-beam CT.

Stand Connected to the gantry, the stand contains electrons and other systems required for linac operation.

Read more on the internal components of Linear Accelerators such as the bending magnet, accelerating waveguide, circulator, and more.

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