Technical Note: Enhancing the surface dose using a weak longitudinal magnetic field

• Published in: Medical physics (Lancaster) Vol. 43; no. 6; pp. 2927 - 2932
• Main Authors: Carlone, Marco, Tadic, Tony, Keller, Harald, Rezaee, Mohammad, Jaffray, David
• Format: Journal Article
• Language: English
• Published: United States American Association of Physicists in Medicine 01.06.2016
• Subjects: 07 ISOTOPES AND RADIATION SOURCES; 60 APPLIED LIFE SCIENCES; charged particle focusing; cobalt; COBALT 60; depth dose; DEPTH DOSE DISTRIBUTIONS; Dose‐volume analysis; dosimetry; Electron beams; Electron scattering; magnetic field; Magnetic field measurements; MAGNETIC FIELDS; Magnets; PEAKS; PHYSICAL PROPERTIES; radiation therapy; Scintigraphy; surface dose; Surface scattering; Therapeutic applications, including brachytherapy; X‐ray scattering; magnetic field; surface dose; depth dose; charged particle focusing
• ISSN: 0094-2405; 2473-4209; 2473-4209
• DOI: 10.1118/1.4949001

Purpose: The surface dose in radiotherapy is subject to the physical properties of the radiation beam and collimator. The purpose of this work is to investigate the manipulation of surface dose using magnetic fields produced with a resistive magnet. Better understanding of the feasibility and mechanisms of altered surface dose could have important clinical applications where the surface dose must be increased for therapeutic goals, or reduced to enhance the therapeutic benefit. Methods: A resistive magnet capable of generating a peak magnetic field up to 0.24 T was integrated with a cobalt treatment unit. The magnetic fringe field of the magnet was small due to the self-shielding built within the magnet. The magnetic field at the beam collimation jaws of the cobalt irradiator was less than 10 G. The surface dose and depth dose were measured for varying magnetic field strengths. Results: The resistive magnet was able to alter the dose in the buildup region of the 60Co depth dose significantly, and the magnitude of dose enhancement was directly related to the strength of the longitudinal magnetic field. Peak magnetic fields as low as 0.08 T were able to affect the surface dose. At a peak field of 0.24 T, the authors measured a surface dose enhancement of 2.8-fold. Conclusions: Surface dose enhancement using resistive magnets is feasible. Further experimental study is needed to understand the origin of the scattered electrons that contribute to the increase in surface dose.