Hypofractionated partial breast irradiation (
HPBI) involves treatment to the breast tumor using high doses per fraction. Recent advances in MRI‐Linac solutions have potential in being applied to HPBIdue to gains in the soft tissue contrast of MRI; however, there are potentially deleterious effects of the magnetic field on the dose distribution. The purpose of this work is to determine the effects of the magnetic field on the dose distribution for HPBItumors using a tangential beam arrangement ( TAN), 5‐beam intensity‐modulated radiation therapy ( IMRT), and volumetric modulated arc therapy ( VMAT). Methods
Five patients who have received
HPBIwere selected with two patients having bilateral disease resulting in a total of two tumors in this study. Six planning configurations were created using a treatment planning system capable of modeling magnetic field dose effects: TAN, IMRTand VMATbeam geometries, each of these optimized with and without a transverse magnetic field of 1.5 T. Results
The heart and lung doses were not statistically significant when comparing plan configurations. The magnetic field had a demonstrated effect on skin dose: for
VMATplans, the skin (defined to a depth of 3 mm) D1cc was elevated by +11% and the V30 by +146%; for IMRTplans, the skin D1cc was increased by +18% and the V30 by +149%. Increasing the number of beam angles (e.g., going from IMRTto VMAT) with the magnetic field on reduced the skin dose. Conclusion
The impact of a magnetic field on
HPBIdose distributions was analyzed. The heart and lung doses had clinically negligible effects caused by the magnetic field. The magnetic field increases the skin dose; however, this can be mitigated by increasing the number of beam angles.