WARF: P07282US

Quadrupole Magnetic Fan Beam Former for Ion Radiation Therapy Systems


Thomas (Rock) Mackie, David Westerly

The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing a radiation treatment system that uses magnetic deflection to convert a pencil beam into a fan beam made up of individually controllable beamlets.
OVERVIEWExternal beam radiation therapy is a tumor treatment technique that directs one or more high-energy radiation beams to the tumor. Advanced external beam radiation systems treat tumors with multiple x-ray fan beams that can be rotated around the patient. Each beam consists of individual "beamlets" whose intensity can be controlled to allow for the treatment of complex tumor shapes. However, x-ray energy still is deposited to all tissue along the entire path of the beam up to the exit point.

The dose intensity from protons is not uniform along the beam path and rises to a “Bragg peak” near a point where the proton beam stops completely.  Controlling the placement of the Bragg peak so it is located on the tumor reduces the amount of radiation delivered to the patient’s healthy tissue.  Unlike x-ray radiation therapy, ions allow for separate control of the total dose of radiation (intensity) and distance the Bragg peak occurs (range).

Existing proton therapy techniques utilize one of two methods.  The spread out Bragg peak (SOBP) approach spreads the ion beam out into an “area beam” using scattering foils and brass collimators to cover the entire tumor in one exposure.  This method is fast, but is less precise and requires a special compensator to adjust for the tumor shape.  The magnetic spot scanning (MSS) approach uses the original ion “pencil beam” and steers it around the tumor with successive exposures.  Due to the multiple exposures the process is slow.  The potential for high accuracy is negated due to patient movement, which risks missing tumor areas.
THE INVENTIONUW-Madison researchers have developed a radiation treatment system that uses magnetic deflection to convert a pencil beam into a fan beam made up of individually controllable beamlets.  Both intensity and range can be controlled separately for each beamlet.  This system combines benefits of treating different portions of the tumor at once (SOBP) with the precise control of each individual beamlet (MSS).  The magnetic deflection technique also reduces neutron contamination to the patient compared to other conventional techniques used to form a fan-shaped beam.

The magnet system incorporates one or more quadrupole magnets, which consist of two pairs of magnets that oppose each other on separate magnet axes.  These axes are perpendicular to each other and also perpendicular to the incoming beam axis.  One set has opposed north poles and the other has opposed south poles.  Once the beam is in fan form, its intensity and range of individual sections may be modulated to provide the ability to treat wide areas while maintaining high resolution in the direction normal to the fan beam.
  • External ion beam radiation therapy for the treatment of tumors
  • Combines the benefits of SOBP and MSS
  • Reduces neutron contamination of patient
  • Increases efficiency of beam delivery
For More Information About the Inventors
Contact Information
For current licensing status, please contact Jeanine Burmania at or 608-960-9846.
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