Robust radiobiological optimization of ion beam therapy utilizing Monte Carlo and microdosimetric kinetic model.

To develop a Monte Carlo (MC)-based and robust ion beam therapy optimization system that separates the optimization algorithm from the relative biological effectiveness (RBE) modeling. Robustly optimized dose distributions were calculated and compared across three ion therapy beams (proton, helium, carbon). The effect of different averaging techniques in calculating RBE in mixed beams was also investigated.

Evaluation of the Efficacy of Rotational Corrections for Standard-Fractionation Head and Neck Image-Guided Radiotherapy.

Purpose: Modern linear accelerators are equipped with cone beam computed tomography and robotic couches that can correct for errors in the translational (X, Y, Z) and rotational (α, β, γ) axes prior to treatment delivery. Here, we compared the positional accuracy of 2 cone beam registration approaches: (1) employing translational shifts only in 3 degrees of freedom (X, Y, Z), versus; (2) using translational-rotational shifts in 6 degrees of freedom (X, Y, Z, α, β, γ).

Methods: This retrospective study examined 140 interfraction cone beam images from 20 patients with head and neck cancer treated with standard intensity-modulated radiation therapy.

Positioning reproducibility with and without rotational corrections for 2 head and neck immobilization systems.

Purpose: The purpose of this study was to evaluate the impact of offline rotational corrections and assess intrafraction motion for head and neck (H&N) cancer patients immobilized with and without a custom neck cushion.

Methods And Materials: Fifty H&N cancer patients were immobilized and imaged with pretreatment and posttreatment cone beam computed tomography (CBCT) for each treatment fraction. Of these patients, 25 had a custom neck cushion added to their immobilization.

Experimental and theoretical dosimetry of the RIC-100 phosphorus-32 brachytherapy source for implant geometries encountered in the intraoperative setting.

Purpose: Experimental and theoretical dosimetry of the RIC-100 phosphorus-32 brachytherapy source is presented for implant geometries that may occur in an intraoperative setting during treatment of localized spinal tumors with temporary superficial radiation. Dose variation, due to source shape and size, is evaluated, and nonideal implant conditions are simulated.

Methods And Materials: Calibration, depth dose, and dose profiles were evaluated for several implant geometries and source sizes.

Optimizing mini-ridge filter thickness to reduce proton treatment times in a spot-scanning synchrotron system.

Purpose: Study the contributors to treatment time as a function of Mini-Ridge Filter (MRF) thickness to determine the optimal choice for breath-hold treatment of lung tumors in a synchrotron-based spot-scanning proton machine.

Methods: Five different spot-scanning nozzles were simulated in TOPAS: four with MRFs of varying maximal thicknesses (6.15-24.