Investigation of dosimetric effect of beam current fluctuations in synchrotron-based proton PBS continuous scanning.

In proton pencil beam scanning (PBS) continuous delivery, the beam is continuously delivered without interruptions between spots. For synchrotron-based systems, the extracted beam current exhibits a spill structure, and recent publications on beam current measurements have demonstrated significant fluctuations around the nominal values. These fluctuations potentially lead to dose deviations from those calculated assuming a stable beam current.

Deep learning based linear energy transfer calculation for proton therapy.

This study aims to address the limitations of traditional methods for calculating linear energy transfer (LET), a critical component in assessing relative biological effectiveness (RBE). Currently, Monte Carlo (MC) simulation, the gold-standard for accuracy, is resource-intensive and slow for dose optimization, while the speedier analytical approximation has compromised accuracy. Our objective was to prototype a deep-learning-based model for calculating dose-averaged LET (LET) using patient anatomy and dose-to-water (D) data, facilitating real-time biological dose evaluation and LET optimization within proton treatment planning systems.

A fast GPU-accelerated Monte Carlo engine for calculation of MLC-collimated electron fields.

Background: Although intensity-modulated radiation therapy and volumetric arc therapy have revolutionized photon external beam therapies, the technological advances associated with electron beam therapy have fallen behind. Modern linear accelerators contain technologies that would allow for more advanced forms of electron treatments, such as beam collimation, using the conventional photon multi-leaf collimator (MLC); however, no commercial solutions exist that calculate dose from such beam delivery modes. Additionally, for clinical adoption to occur, dose calculation times would need to be on par with that of modern dose calculation algorithms.

Physical characterization of therapeutic proton delivery through common dental materials.

Purpose: Dental fixtures are commonplace in an aging, radiation treatment population. The current, local standard of practice in particle therapy is to employ treatment geometries to avoid delivery through implanted dental fixtures. The present study aims to observe the physical effect of delivering therapeutic proton beams through common dental fixture materials as prelude to an eventual goal of assessing the feasibility of using treatment geometries not specified for avoidance of oral implants.

Initial Results of a Phase 2 Trial of F-DOPA PET-Guided Dose-Escalated Radiation Therapy for Glioblastoma.

Purpose: Our previous work demonstrated that 3,4-dihydroxy-6-[18F]-fluoro-L-phenylalanine (F-DOPA) positron emission tomography (PET) is sensitive and specific for identifying regions of high density and biologically aggressive glioblastoma. The purpose of this prospective phase 2 study was to determine the safety and efficacy of biologic-guided, dose-escalated radiation therapy (DERT) using F-DOPA PET in patients with glioblastoma.

Methods And Materials: Patients with newly diagnosed, histologically confirmed glioblastoma aged ≥18 years without contraindications to F-DOPA were eligible.

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.

Incorporation of Biologic Response Variance Modeling Into the Clinic: Limiting Risk of Brachial Plexopathy and Other Late Effects of Breast Cancer Proton Beam Therapy.

Purpose: The relative biologic effectiveness (RBE) rises with increasing linear energy transfer toward the end of proton tracks. Presently, there is no consensus on how RBE heterogeneity should be accounted for in breast cancer proton therapy treatment planning. Our purpose was to determine the dosimetric consequences of incorporating a brachial plexus (BP) biologic dose constraint and to describe other clinical implications of biologic planning.

Biologic Dose and Imaging Changes in Pediatric Brain Tumor Patients Receiving Spot Scanning Proton Therapy.

Purpose: To evaluate the incidence of imaging changes in our pediatric brain tumor population treated with spot-scanning proton therapy and analyze the spatial correlation of imaging changes with a novel biologic dose model.

Methods And Materials: All pediatric patients treated during the first year of our institution's experience who received a minimum treatment planning dose (TPD) of 5040 cGyE with available follow-up magnetic resonance imaging scans were selected for analysis. Posttreatment magnetic resonance imaging scans were fused with the treatment planning computed tomography.

Highly efficient and sensitive patient-specific quality assurance for spot-scanned proton therapy.

The purpose of this work was to develop an end-to-end patient-specific quality assurance (QA) technique for spot-scanned proton therapy that is more sensitive and efficient than traditional approaches. The patient-specific methodology relies on independently verifying the accuracy of the delivered proton fluence and the dose calculation in the heterogeneous patient volume. A Monte Carlo dose calculation engine, which was developed in-house, recalculates a planned dose distribution on the patient CT data set to verify the dose distribution represented by the treatment planning system.

A linear relationship for the LET-dependence of Gafchromic EBT3 film in spot-scanning proton therapy.

Radiochromic film (RCF) is a valuable dosimetric tool, primarily due to its sub-millimeter spatial resolution. For accurate proton dosimetry, the dependence of film response on linear energy transfer (LET) must be characterized and calibrated. In this work, we characterized film under-response, or 'quenching', as a function of dose-weighted linear energy transfer (LET) in several proton fields and established a simple, linear relationship with LET.

A Monte-Carlo-based and GPU-accelerated 4D-dose calculator for a pencil beam scanning proton therapy system.

Purpose: The presence of respiratory motion during radiation treatment leads to degradation of the expected dose distribution, both for target coverage and healthy tissue sparing, particularly for techniques like pencil beam scanning proton therapy which have dynamic delivery systems. While tools exist to estimate this degraded four-dimensional (4D) dose, they typically have one or more deficiencies such as not including the particular effects from a dynamic delivery, using analytical dose calculations, and/or using nonphysical dose-accumulation methods. This work presents a clinically useful 4D-dose calculator that addresses each of these shortcomings.

Investigating Dependencies of Relative Biological Effectiveness for Proton Therapy in Cancer Cells.

Purpose: Relative biological effectiveness (RBE) accounts for the differences in biological effect from different radiation types. The RBE for proton therapy remains uncertain, as it has been shown to vary from the clinically used value of 1.1.

A robust intensity modulated proton therapy optimizer based on Monte Carlo dose calculation.

Purpose: Accuracy of dose calculation models and robustness under various uncertainties are key factors influencing the quality of intensity modulated proton therapy (IMPT) plans. To mitigate the effects of uncertainties and to improve the dose calculation accuracy, an all-scenario robust IMPT optimization based on accurate Monte Carlo (MC) dose calculation was developed.

Methods: In the all-scenario robust IMPT optimization, dose volume histograms (DVHs) were computed for the nominal case and for each uncertainty scenario.

Clinically Applicable Monte Carlo-based Biological Dose Optimization for the Treatment of Head and Neck Cancers With Spot-Scanning Proton Therapy.

Purpose: Our aim is to demonstrate the feasibility of fast Monte Carlo (MC)-based inverse biological planning for the treatment of head and neck tumors in spot-scanning proton therapy.

Methods And Materials: Recently, a fast and accurate graphics processor unit (GPU)-based MC simulation of proton transport was developed and used as the dose-calculation engine in a GPU-accelerated intensity modulated proton therapy (IMPT) optimizer. Besides dose, the MC can simultaneously score the dose-averaged linear energy transfer (LETd), which makes biological dose (BD) optimization possible.

A fast GPU-based Monte Carlo simulation of proton transport with detailed modeling of nonelastic interactions.

Purpose: Very fast Monte Carlo (MC) simulations of proton transport have been implemented recently on graphics processing units (GPUs). However, these MCs usually use simplified models for nonelastic proton-nucleus interactions. Our primary goal is to build a GPU-based proton transport MC with detailed modeling of elastic and nonelastic proton-nucleus collisions.