Assessment of Tracking Jaws Based on MLC Aperture to Reduce Normal Tissue Irradiation in VMAT

Abstract

assigned into the balloon. For each irradiation case, dose profiles with and without the pacemaker were computed. It was normalized such that the prescribed dose is 34 Gy on the surface of 1cm from the balloon surface. Results: The attenuation by the pacemaker located at 5 cm distance from the balloon surface was determined to be 21.0% by ion chamber measurements vs. 23.6% by simulations. At 10 cm distance, the attenuation was 15.7% and 17.9%, respectively. In MC simulations, significant dose enhancement over the battery could be at least a factor of 3 at any iodine based contrasts of 0%, 10%, and 25%. A titanium capsule component absorbed more doses by up to 150% but it didn’t cause significant dose perturbations on complementary metal oxide semiconductor (CMOS) on substrate that is known to be radiation-sensitive. Conclusions: The results from measurements and MC calculations indicate that the actual dose involving a pacemaker is different from one calculated in a homogeneous water condition of treatment planning system. Therefore, the dose perturbation should be considered for pacemaker dependent patients in HDR balloon brachytherapy when evaluating a safe clinical distance from the balloon. Author Disclosure: W. Sung: None. J. Lee: None. J. Kim: None. C. Choi: None. Y. Shin: None. J. Jung: None. S. Kim: None. S. Ye: None.