How Radiotherapy Treats Cancer using a LINAC

Added: 2026-05-06

[00:00:06][Music] over 50% of cancer patients will receive radiotherapy as part of their treatment and here at the Christie we are one of the largest departments in the UK we're housing up to 10 Linx like the one behind me the linear accelerator has four main parts one of them being the Gantry this rotates around the patient one of them being the mlc this one shapes the beam to the same as the target tumor and two Imaging systems these make sure the position of the patient is correct for the treatment typically the radiographers will put the patient in the same position every day while the Gantry rotates around them we deliver high energy radiation beams that destroy the cancer cells but spare the healthy tissue Linx are some of the most complex single machines you can find in medicine and as such they need round the-clock care and consistent servicing to make sure they can give effective treatment faults occur frequently and engineers and physicists work together to keep the Linx running safely Linux can deliver up to 18 million volts of radiation energy that's 200 times what you'd receive in a hand x-ray for treatments that are on or around the skin we can deliver up to 15 million electron volts but with this in mind there's still so much more going on behind the scenes right at the back of the linac sits an electron gun like this one in the center of the electron gun is a wire filament it emits electrons through a process known as thermionic emission just like in the back of an old TV when a high current is passed through the filament it begins to heat up and glow as the temperature of the filament increases the electrons gain more kinetic energy eventually gaining enough energy to be emitted from the filament surface the electrons are accelerated towards an anode on the wave guide but enter the wave guide through a slit the wave guide uses radio waves to accelerate the electrons to 99% speed of light nearly 300 million m/s think of this like the electrons are surfing the radio waves and get faster as they travel down the wave guide once accelerated the electrons pass through several coils and bending magnets to focus the beam which is steered towards the target the electrons hit the target with explosive energy causing it to emit x-rays the x-rays are then shaped to the Target by column before they reach the patient the x-rays pass through an ionization chamber as the beam is delivered the ionization chamber in the head measures how much radiation is emitted the chamber has two channels that measure the dose independently if the first dose Channel fails the second will act as a backup once all the radiation has been delivered for that treatment The Beam stops and the radiotherapy treatment is finished Engineers are responsible for inspecting and maintaining all these components as well as fixing or replacing them if things go wrong unlike with other machines used in medicine we can't see the radiation coming out of the Lin and the patient can't feel it so how do we know it's doing the right thing this is where the physics department come in it's our job to test the machine and make sure it's working correctly before we give it back for treatment we do this by measuring the beam in various ways like are the photons the right energy is the beam flat or Tilted is it the right size and do the Imaging systems line up with the linac correctly once we're happy that the machine is safe to treat on we can give it back to the radiographers and they can start treating patient again both physicists and Engineers go through this process at regular intervals like how you service your car with some tests run daily before treatment and some only once a year this makes sure that we catch any problems before they get worse and start preventing treatments radi therapy is a key part of cancer treatment and working with clinicians and radiographers engineers and physicists enable us to treat with submeter Precision using radiation we can't see or feel