by Cancer is one of the leading causes of death globally. Radiation therapy or radiotherapy has been an effective treatment option for cancers for decades. However, the technology used for radiation therapy has advanced significantly over the years. One such major advancement is the development of linear accelerators which are now widely used for radiation treatment. In this article, we will discuss linear accelerators in detail and how they are revolutionizing cancer treatment.
What are Linear Accelerators?
A linear accelerator, also known as a linac, is a device that uses high frequency radio waves to accelerate charged particles to high energies in a linear path inside a tube called the waveguide. The most common type of linear accelerator used in radiation therapy is the medical linear accelerator or medical linac for short. As the name suggests, medical linacs are designed specifically for clinical applications in radiation oncology.
Medical linacs produce high-energy X-ray or electron beams that are used to destroy cancer cells. The particle beam is aimed at the specific tumor location using image-guidance technology and delivers a targeted radiation dose to cancel out the cancer cells while minimizing damage to surrounding healthy tissues. This allows clinicians to deliver higher and more effective radiation doses compared to conventional radiation sources like cobalt-60 machines.
Advantages of Linacs over Older Radiation Technologies
Older forms of external beam radiation like cobalt-60 teletherapy units produced lower energy gamma rays that required multiple treatments over several weeks to achieve a therapeutic dose. Medical linacs, on the other hand, have several advantages:
– Higher energies: Linear Accelerators for Radiation photon beams with energies ranging from 4 MV to 25 MV which allow deeper penetration into the body. This makes linacs suitable for treating tumors located deeper inside the body.
– Varied beam types: In addition to photons, linacs can also generate electron beams. This offers flexibility of different treatment options based on the tumor location and size.
– Image-guidance: Advanced linacs incorporate onboard imaging technologies like CBCT and kV imaging for precise tumor targeting and positioning verification before each treatment session. This improves accuracy and precision.
– Faster treatment: With higher doses per fraction, linacs can deliver the entire prescribed radiation dose over a shorter period usually 1-2 months compared to 6-8 weeks with older machines. This is more convenient for patients.
– Less shielding requirements: As linacs produce beams in short pulses with micropauses unlike continuous beams, they require less space and shielding infrastructure. This makes them more economical to install and operate.
Main Components and Working of a Medical Linac
All medical linacs have the basic components of an electron gun, waveguide structure and target. Let us examine how these components work together to generate the therapeutic radiation beam:
– Electron gun: Contains a cathode that emits electrons which are accelerated by a high voltage into the waveguide structure.
– Waveguide: Long cylindrical channel made of conductors that carry microwave frequency electromagnetic waves to accelerate the electrons.
– Target: Usually made of tungsten, where the high-energy electron beam strikes and produces bremsstrahlung or braking radiation in the form of photon beams.
– Beam shaping and collimation: Magnets and collimators shape and restrict the radiation beam to the desired field size before it exits the treatment head.
– Gantry: Rotating circular structure that houses the linac and treatment head allowing it to rotate 360 degrees around the patient for different beam angles.
– Control system: Consists of computers and interfaces that operate all linac components, deliver accurate doses, monitor radiation safety systems.
This process of electron acceleration and photon production enables medical linacs to generate beams of 4-25 MV that can precisely target tumors for effective radiotherapy.
Advanced Technologies on Modern Linacs
Constant innovations are enhancing linac capabilities for improved personalized care:
– Flattening filter free (FFF) mode: Removes flattening filter to deliver higher instantaneous dose rates up to 2400 MU/min shortening treatment times. Useful for treating moving organs.
– Volumetric arc therapy (VMAT): Sophisticated software and beam control allows delivery of intensity modulated arcs resulting in faster, safer plans with higher conformality.
– Integrated MRI-linac systems: Enables real-time soft tissue visualization during treatment for highly precise dose painting directly on tumor.
– Proton beam therapy: Some linacs act as synchrotrons accelerating protons to even higher energies for non-invasive treatment of deep-seated tumors near critical organs.
– Artificial intelligence (AI): AI and machine learning algorithms are improving automatic treatment planning, helping detect errors and ensuring consistent high quality.
To summarize, linear accelerators are revolutionizing cancer radiotherapy by delivering higher precision radiation with greater convenience and safety compared to older technologies. Continued advancement in linac hardware and software is helping maximize tumor control while reducing side effects. Equipped with the latest technologies like MRI integration and proton capabilities, medical linacs signify the future of external beam radiation therapy for years to come.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it.
