The smaller size (and weight) of the equipment reduces manufacturing, transportation, installation, rigging, and facility costs. The accelerator vault interior requires only 20’ x 30’ of space for the 16’ diameter synchrotron. The Lunder Building at MGH features a Radiance 330 gantry-based proton therapy suite inside the space of two former linac vaults. The reduced scale and adaptable equipment configurations* will enable many hospitals to add proton therapy as an extension of the existing cancer center, obviating the need to purchase more land for a separate facility.
The custom-designed Radiance 330 isocentric gantry is smaller than commercial predecessors. Protons have less entrance dose than X-rays, therefore it is not necessary to spread it out over as many different beam angles as has been the case, for example, with IMRT. That’s why one only needs a half-gantry to enter the patient’s body from any beam incidence angle; previous generations used 360 degree gantries.
* Including vertical beamlines between accelerator and treatment room
The compact and advanced design of the Radiance 330 synchrotron accelerator supports single and multiple treatment room facilities. The beam transport system is a beam-line and beam-switchyard behind-the-scenes that guides the proton beam from the synchrotron to the treatment room, and is extensible to as many as three treatment rooms. An affordable facility can be designed with future expansion in mind for those who prefer to add an additional treatment room at a later time.
Our project inside the Lunder Building at MGH/Boston features a Radiance 330 gantry-based proton therapy suite inside the space of two former linac vaults. The system is embedded within the existing and operational Radiation Oncology Department, retrofit into the hospital without interrupting daily operations.
The Radiance 330 synchrotron supports both isocentric gantries and fixed-beam treatment rooms with one or more ports. The reduced scale and adaptable equipment configurations will enable many hospitals to add proton therapy as an extension of the existing cancer center, obviating the need to purchase more land for a separate facility.
The compact and advanced design of the Radiance 330 synchrotron accelerator makes it much lighter weight than alternative choices. At only 16 tons, a two-level configuration using a vertical beam line can be adapted to fit the constraints and limitations of the available space.
Upon completion of acceptance testing at the assembly and test facility, the system is disassembled and crated, then installed using forklifts and pallet jacks, freight elevators and staff corridors, and reassembled inside the vault.
In the photo, riggers maneuver part of the gantry frame through hospital corridors toward the basement level treatment room vault inside the Lunder Building at MGH/Boston.
The synchrotron raises the energy of the particle a small amount every time it cycles around the system’s ring. The more times it cycles the more energy the particles have. This is a very clean process. The particles are well controlled, have very narrow energy spread and only interact with materials by design. This leads to a very low neutron production, and very low radioactivation of components. This results in a particle beam of higher purity and quality (shape, angular distribution, and energy spread) – all the way through the system from the source through the nozzle and into the patient.
Radiance 330 utilizes a treatment delivery technique known as Fidelity Beam Scanning. The 3mm-6mm proton beam is magnetically deflected to scan the target in iso-energy layers. The scanning proton beams generated by this synchrotron are transported all the way to the patient under vacuum, until the last possible moment, arriving with virtually no contamination of the beam and a narrow beam shape. Fidelity between planned and delivered dose is a major objective of treatment delivery; proton imaging* using the synchrotron’s higher energies will help remove uncertainties in range prediction – addressing another important aspect of this pursuit. Treatment delivery with Radiance 330 results in a sharper Bragg peak and the lowest possible radiation dose to the patient outside the target volume.
*Proton radiography/tomography with Radiance 330 has not been cleared by the FDA for clinical use.