Ernest Lawrence, a Berkeley inventor of the cyclotron, would love to hear this story. His invention has not only enriched uranium for The Bomb, but will now be used for clinical applications.
Varian Medical Systems out of Palo Alto, California just received the European CE Mark of approval for the company’s Proton Therapy System. Maybe the largest and most expensive medical device, the 250 mega-electron volt proton accelerator requires its own building. The advantage, of course, is the ability to precisely target tumors, as protons have a much shorter and predictable range of energy delivery than photons.
From Varian, here are the components you’ll be getting in the package:
Proton accelerator: 250 MeV Superconducting Cyclotron
The latest 250 MeV (Mega-electron-Volt) Superconducting Cyclotron is a key component of Varian proton therapy delivery. Stable beam current and beam intensity modulation allow precision spot scanning and three-dimensional proton dose distribution for unprecedented precision.
Improved manufacturing techniques mean that the lightweight, compact size helps reduce the total cost of ownership. In addition, superconducting magnet coils result in high extraction efficiency, low energy consumption, excellent reliability, and an overall reduction in operating costs and maintenance.
Unlike some other accelerators, the superconducting cyclotron, behaves in a very linear and predictable manner. This allows for complete automation and eliminates the need for routine operators.
Beam transport system
The proton accelerator is connected to one or multiple treatment rooms by the beam transport system (BTS). The BTS is segmented so that additional treatment rooms can be added to the system later, providing scalability to treat more patients as the clinic grows.
A key element of the BTS is the energy selection system (ESS). The ESS transforms the energy of the beam that the cyclotron produces from 250 MeV particles to the desired treatment energy between 250 MeV and 70 MeV. This translates to a possible range of range of 36.5–4.0 cm in water. Range shifters directly in front of the patient can be used to reduce the range to under 4.0 cm.
The ESS is used to set and verify the beam energy and spread to guarantee optimal treatment precision. The ESS is located close to the particle accelerator and outside the treatment rooms. This eliminates neutron production in the treatment room.
The BTS consists of a beam tube under vacuum and with a variety of magnets. Quadruple magnets are used to focus the proton beam and dipole magnets are used to deflect the beam to the selected treatment room. The magnets of the BTS system are tuned automatically by the control system to accommodate the selected treatment room, energy, and size of the beam.
Treatment Rooms
Varian’s proton therapy delivery system is modular and the number of treatment rooms scalable. It is possible to start with a single-room system that can be expanded to a multi-room facility later. Two types of treatment rooms are available, which can be combined in any desired ratio to match patient demand.
Gantry beam rooms are similar to the Varian® Clinac® and Trilogy™ gantries in which the beam can be fully rotated around the isocenter point. The proton gantry in combination with the treatment table offers the flexibility to select any desired beam angle for optimal beam delivery.
Fixed beam rooms offer a horizontal beam that can be optimized for eye, head, and neck treatments or be combined with a versatile treatment table for a variety of dedicated treatments.
Gantry
A gantry is a steel structure that houses the final section of the BTS and the delivery "nozzle." The gantry rotates around the patient, delivering the beam at the desired angle. The combination of a gantry and treatment table offers the flexibility to treat patients from all angles. The unique mechanical design of the Varian gantry—two large roller bearings for support, balanced with counterweights—provides exceptional mechanical rigidity. The operator can select an angular position with a precision of ± 0.1°.
The Varian proton gantry can be equipped with one of two types of beam delivery systems, also called "nozzles." The nozzle is equipped with motion sensors to help ensure patient safety. Alerts sound if these sensors detect if the gantry nozzle and patient come too close and the motion of the gantry and the table is slowed down. Additional contact sensors are hard-wired to emergency brakes.
Standard table
The treatment table support is located in front of the gantry as an integral part of the gantry enclosure. The treatment table, nozzle contour, and diagnostic equipment positioned close to the patient are optimized to achieve a 4-π treatment-angle range as far as possible. All patient tables are equipped with six numerically controlled axes, and bending due to patient weight will be automatically detected and corrected.
Press release: Varian Medical Systems Has Received CE Mark for Proton Therapy System
Product info page: Proton Therapy
