Proton Therapy | Treatment Solutions

Varian has designed proton therapy delivery to be highly adaptive and scalable to help clinics improve efficiency and treat more patients.

Proton therapy facility layout with accelerator, beam transport system, and five treatment rooms of which four are equipped with rotating gantries.

Not only is Varian proton therapy delivery designed to accommodate advanced imaging techniques and treatment planning technologies, but improved manufacturing techniques mean that Varian can offer clinics the option of starting with a single-room center and expanding to a multi-room facility. Since hardware is modular, even large centers can expand and upgrade as required.

Under normal circumstances, proton therapy delivery requires a dedicated building to house the therapy equipment. The accelerator and beam transport system are placed in a concrete vault to shield radiation. The treatment rooms can either be equipped with rotating gantries or fixed beam rooms. Up to about five or six treatments rooms—gantries and/or fixed beam rooms—can be connected to a single accelerator with comfortable waiting times.

Various methods to reach optimum dose conformation are known in proton therapy and grouped in two classes: passive or 'scattering' methods and active or 'scanning methods'.

Beam delivery

In passive or 'scattering' methods, the energy of the beam transported to the nozzle is set for each treatment at a fixed value that corresponds to the deepest point of the target volume to be irradiated. The energy or 'depth' of the beam is changed with a rotating wheel or 'path modulator' of variable thickness. The rotating wheel, in combination with a 'path compensator' or 'bolus' and a specific collimator, makes it possible to generate a dose distribution that conforms to the distal part of the target volume.

Active or pencil beam scanning

The active treatment method referred to as 'pencil beam scanning' was developed to enable optimum dose conformation both at the distal and proximal areas of the target volume. Pencil beam scanning also minimizes neutron dose to the patient. Longitudinal beam delivery is achieved by changing the energy with the energy selection system. As the energy selection system (ESS) is located directly after the accelerator, the neutron flux near the patient is virtually reduced to zero. Two scanning magnets make it possible to move the beam in the X and Y direction in the beam's plane. With this kind of focused 'pencil beam,' numerous small volumes, also called 'voxels', can be irradiated and the whole tumor area is treated in three dimensions. Varian's pencil beam scanning nozzle offers optimal dose conformity in combination with the lowest possible neutron flux and a maximum flexibility with a field area of 30 x 40 cm².

Disclaimer

The proton therapy device technology described here has not been cleared by the US Food and Drug Administration (“FDA”) for clinical use and is in development. The FDA has a unique set of standards for proton therapy devices because the entire proton therapy facility must be built for the specific device. For these types of devices, the FDA allows proton therapy sponsors to discuss projects with potential customers and to engage in contracts/orders to build proton therapy facilities and /or to purchase proton therapy equipment. However, contracts or other engagements specific to clinical practice are strictly prohibited; that is, no engagements or agreements for patient scheduling or physician group practice to use proton therapy equipment are permitted in advance of FDA clearance.