APPLICATIONS OF TECHNOLOGY:
- Proton beam therapy
- Particle accelerators using superconducting magnets
ADVANTAGES:
- High energy acceptance
- Fixed magnetic field
- Reduces gantry weight and size
- Lowers cost
- Opens up gantry space for diagnostic instruments
ABSTRACT:
Berkeley Lab physicists Weishi Wan and David Robin have designed a smaller and lighter-weight proton beam gantry that could substantially reduce the high cost of ion beam therapy for the treatment of solid tumors. Using this design, gantries for proton beam therapy can be half the size and 20 percent of the weight of today’s systems, saving capital, construction, and operating costs. The system uses superconducting magnets in the rotatable gantry to direct a proton beam to a tumor site.
Superconducting magnets triple the field strength of conventional resistive magnets, and because of their smaller size and great strength, they can be housed in gantries much smaller than those of current proton beam systems, significantly reducing their costs. However, use of superconducting magnets has been limited given their tendency to heat up when the magnetic field is changed to accommodate the change of energy of the ion beams to increase or decrease beam penetration into a targeted tumor. This heating is not unique to superconducting magnet systems but much more problematic because cryogenic temperatures, approaching absolute zero, are required to maintain superconductivity.
The Berkeley Lab technology includes a design scheme that allows the system to change energy levels without changing the strength of the magnetic field. The design uses a strategy of “strong focusing” to maintain tight control of the beam through a series of three 90 degree bends. Unlike early “fixed field” designs that employ a long chain of superconducting magnets, the Berkeley Lab system uses three clusters of seven magnets, and includes sextapole and octopole magnets in the center of each cluster.
The result is a gantry with high energy acceptance — it allows the beam to pass through with an energy shift of ±21%, or between 150 MeV and 230 MeV. Other superconducting magnet gantry designs with weaker focusing power only allow the beam to pass through with ±2% energy shift. As a result, the magnetic field has to be changed to keep up with the change in beam energy. The multipole components minimize the impact of focus distorting lens aberrations, preserving the quality of the beam as it reaches the patient. The high energy acceptance will increase the speed of energy scanning, thus decreasing treatment time.
Gantries equipped with conventional resistive magnets weigh more than 100 tons and require extra shielding. Consequently the cost of the gantry alone may exceed $15 million, opening the door to a compact design, such as that developed by Berkeley Lab.
DEVELOPMENT STAGE: Proven principle.
STATUS: Patent pending. Available for licensing or collaborative research.
FOR MORE INFORMATION:
SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:
Compact Toroidal Magnet for Carbon Ion Beam Therapy, IB-3054
REFERENCE NUMBER: IB-3267
