AbstractID: 6912 Title: Potential Application of Transverse Magnetic Field in X-Ray
Therapy
Our preliminary Monte Carlo simulation results demonstrate that transverse magnetic
fields are capable of producing local dose peaks and valleys for radiation therapy photon
beams. These dose enhancement and reduction effects can potentially be used to increase
the dose delivered to target volumes and reduce the dose to adjacent normal tissues. A
prototype superconducting magnet (15T on winding at peak current) is used for computer
simulation. The magnitude of the dose effects depends on the magnetic field strength and
gradient, photon beam energy, size, and orientation relative to the magnet. For example,
over 40% dose enhancement and reduction are observed for a 24MV x-ray beam when
the beam axis is at 2cm away and parallel to the magnet surface. The dose enhancement
effect decreases as the angle between the beam axis and the magnet surface increases; it
practically disappears for angles more than 20 degrees. The dose reduction effect is
maintained however for all angles. We have also developed magnetic field visualization
tools to help identify the potential high dose effect regions during treatment planning. It
is found that the isomagnetic field strength plot of the field component perpendicular to
both the magnet surface and the beam direction is useful in locating the high dose
regions. However, the vector plot showing the direction of the magnetic field is useful to
identify the high dose regions in the orthogonal plane. This is especially important as the
high dose regions may occur outside the initial radiation field border on this plane.