Why Choose a Varian TrueBeam Linear Accelerator Over a Halcyon

Many clients ask us the differences between a TrueBeam linear accelerator and a Halcyon linear accelerator. Although both machines are highly effective in treating cancer, there are important differences that buyers should understand in choosing the best product for their facility.

Energies and Dose Rate

Two important considerations are the photon and electron energy levels for the machines.   The Halcyon has only one photon energy available (6MV), while the TrueBeam can have up to three photon energies and up to six electron energies.  Electron energies are particularly useful in treating skin lesions, which comprise over 50% of all types of cancer.

Dose rates are another important consideration, as a higher dose rate allows more radiation to be delivered to a tumor in a specified amount of time. The TrueBeam, with its “Flattening Free Filter” mode (FFF mode) can deliver a dose rate of up to 2,400 MU/minute.  The Halcyon, however, maxes out at 800MU/minute.

Patient Comfort

While energy levels affect the speed and ease of radiation dose delivery, a linac’s design is what shapes the patient’s experience while receiving treatment. The tube style (Halcyon) may be mildly claustrophobic for some patients, whereas TrueBeam linacs avoid this issue by having an open table configuration.

Treatment Capabilities

Facilities should also be aware that not all linacs are suitable for the same types of treatments. The Halcyon’s radiosurgery capabilities are more limited than TrueBeam’s, and it lacks the ability to perform the non-coplanar treatments critical to stereotactic (SRS) radiosurgery. A TrueBeam is able to perform total body treatments, and unlike a Halcyon, if offers non co-planar treatment support. This has many benefits, including a full range of radiosurgery treatments, such as single treatment of multiple brain metastases and SBRT.

Early Halcyon models (Halcyon 1.0) only are limited to MV-only imaging, and the more expensive Halcyon 2.0 models have KV imaging. On the other hand, a TrueBeam linear accelerator in all its configurations has both MV/KV radiographs synchronized with breathing, CBCT 4D, interactive CBCT, and automatic imaging.

Weaknesses and Maintenance

Even durable machines like linear accelerators require ongoing monitoring and maintenance, and facilities that use them for years may expect some repairs to arise in that time. That’s why it’s necessary to make sure the model purchased does not have more than its fair share of weaknesses. When thinking about long-term durability, one area to examine is the waveguide or “beam centerline.”  Varian’s low-energy predecessors to the Halcyon, the Unique and the 6EX models, had problems with these parts, meaning that these components had to be replaced every few years, especially those whose owners made heavy use of RapidArc.  As the Halcyon is still relatively new, it is not yet clear whether it will have the same pitfalls, but time will tell if it shares its predecessors’ weakness in this area.

The Halcyon is designed for speed and simplicity. So although it doesn’t allow for the more advanced treatments that are capable with a TrueBeam, it can make up for it with patient throughput in very busy environments.

The Ethos system, an upgrade to the Halcyon, allows for two other important features: Hypersight is used to produce CT Scanner-quality images, and can replace the need for a conventional CT Simulator. The Ethos is also capable of adaptive radiotherapy planning, meaning that a patients treatment plan can be updated and improved in the middle of the treatment cycle.

Backup Machines

For many centers, productivity requires having twin machines; patients can receive treatment on both without their providers having to replan. The fact that Halcyon is not a compatible backup with other machines means it ends up working alone.  That means Halcyons are unlikely to be good “backup machines” for other linacs, unless those linacs are also Halcyons.  Why?  Because it is unlikely anyone would want two Halcyons due to their various limitations, like lack of electron energies and limited SRS capabilities).

It is very difficult to find used and reconditioned Halcyons, whereas used and reconditioned TrueBeams, while not common, are available. This availability, paired with their treatment capabilities and more affordable maintenance, make TrueBeam linacs a better choice for most facilities.

Summary

Although the Halcyon is a wonderful linear accelerator that allows for IMRT/VMAT treatments, offers great patient throughput, and is easy to install, it does not stand up to its big brother, the TrueBeam (or its scaled down sibling, the VitalBeam).  TrueBeams simply have more features and capabilities, and a refurbished one is less expensive and cheaper to maintain than the Halcyon.  For smaller, independent centers that don’t have the luxury of multiple machines, we recommend the TrueBeam over the Halycon.