The purpose of this study is to investigate the effects of the dose distributions caused by a low-strength magnetic
field transverse to the incident photon beams in inhomogeneous medium of the body such as the lung. A
simple water-air-water phantom was used to evaluate the magnetic field induced dose effect by the field size of
the beam and the beam energy. The Gafchromic BET3 self-developing dosimetry film was utilized for all measurements.
Our results indicated that a localized magnetic field within the air region offers the capability of
producing dose enhancement and dose reduction regions between the proximal and distal interfaces. It was
demonstrated that the magnitude of the dose perturbation depends not only on the beam energy, but also on
the field size of the beam. It is expected that this magnet technology could be further developed to provide
higher dose to the tumor and lower dose to the normal tissue in radiation therapy for lung cancer.