Nontoxic electron collimators.

Purpose: The goal of this work was to develop and test nontoxic electron collimation technologies for clinical use.

Methods: Two novel technologies were investigated: tungsten-silicone composite and 3D printed electron cutouts. Transmission, dose uniformity, and profiles were measured for the tungsten-silicone.

Multicellular Spheroids as In Vitro Models of Oxygen Depletion During FLASH Irradiation.

Purpose: The differential response of normal and tumor tissues to ultrahigh-dose-rate radiation (FLASH) has raised new hope for treating solid tumors but, to date, the mechanism remains elusive. One leading hypothesis is that FLASH radiochemically depletes oxygen from irradiated tissues faster than it is replenished through diffusion. The purpose of this study was to investigate these effects within hypoxic multicellular tumor spheroids through simulations and experiments.

External beam radiation therapy with kilovoltage x-rays.

Kilovoltage (kV) x-rays are most commonly used for diagnostic imaging due to their sensitivity to tissue composition. In radiation therapy (RT), due to their fast attenuation, kV x-rays are typically only used for superficial irradiation of skin cancer and for intra-operative RT (IORT). Recently, however, a number of kV RT techniques have emerged.

Precision radiotherapy using monochromatic inverse Compton x-ray sources.

Purpose: The dosimetric properties of inverse Compton (IC) x-ray sources were investigated to determine their utility for stereotactic radiation therapy.

Methods: Monte Carlo simulations were performed using the egs brachy user code of EGSnrc. Nominal IC source x-ray energies of 80 and 150 keV were considered in this work.

Initial Steps Towards a Clinical FLASH Radiotherapy System: Pediatric Whole Brain Irradiation with 40 MeV Electrons at FLASH Dose Rates.

In this work, we investigated the delivery of a clinically acceptable pediatric whole brain radiotherapy plan at FLASH dose rates using two lateral opposing 40-MeV electron beams produced by a practically realizable linear accelerator system. The EGSnrc Monte Carlo software modules, BEAMnrc and DOSXYZnrc, were used to generate whole brain radiotherapy plans for a pediatric patient using two lateral opposing 40-MeV electron beams. Electron beam phase space files were simulated using a model of a diverging beam with a diameter of 10 cm at 50 cm SAD (defined at brain midline).

Monte Carlo calculated kilovoltage x-ray arc therapy plans for three lung cancer patients.

: The intent of this work was to evaluate the ability of our 200 kV kilovoltage arc therapy (KVAT) system to treat realistic lung tumors without exceeding dose constraints to organs-at-risk (OAR).: Monte Carlo (MC) methods and the McO optimization framework generated and inversely optimized KVAT treatment plans for 3 SABR lung cancer patients. The KVAT system was designed to treat deep-seated lesions with kilovoltage photons.

A 3D printed modular phantom for quality assurance of image-guided small animal irradiators: Design, imaging experiments, and Monte Carlo simulations.

Purpose: The goal of this work was to develop and test a cylindrical tissue-equivalent quality assurance (QA) phantom for micro computed tomography (microCT) image-guided small animal irradiators that overcomes deficiencies of existing phantoms due to its mouse-like dimensions and composition.

Methods: The 8.6-cm-long and 2.

Inverse optimization of low-cost kilovoltage x-ray arc therapy plans.

Purpose: The objective of this work was to investigate the benefits of using inverse optimization treatment planning for kilovoltage arc therapy (KVAT) and to assess the dosimetric limitations of KVAT.

Methods: Monte Carlo (MC) calculated, inversely optimized KVAT plans of spherical, idealized breast, lung, and prostate lesions were calculated using the EGSnrc/BEAMnrc and DOSXYZnrc MC codes. The dose delivered with the KVAT system, which generates 200-225 kV photon beamlets, was calculated and inversely optimized using an optimization framework developed at McGill University.

Monte Carlo simulations of a kilovoltage external beam radiotherapy system on phantoms and breast patients.

Purpose: To determine the most suitable lesion size and depth for radiotherapy treatments with a prototype kilovoltage x-ray arc therapy (KVAT) system through Monte Carlo simulations of the dose delivered to lesion, dose homogeneity, and lesion-to-skin ratio.

Methods: Monte Carlo simulations were used to calculate dose distributions generated by a novel low-energy kilovoltage x-ray system to a variety of clinically relevant lesion sizes and depths in phantoms and for hypothetical partial breast irradiations of patients in supine and prone positions. The treatments by 200 kV KVAT system were modeled for four sizes of tumor (1-4 cm diameter) at three depths (superficial, middle, and deep) in two sizes of cylindrical water phantoms (16.

Feasibility of external beam radiation therapy to deep-seated targets with kilovoltage x-rays.

Purpose: Radiation therapy to deep-seated targets is typically delivered with megavoltage x-ray beams generated by medical linear accelerators or Co sources. Here, we used computer simulations to design and optimize a lower energy kilovoltage x-ray source generating acceptable dose distributions to a deep-seated target.

Methods: The kilovoltage arc therapy (KVAT) x-ray source was designed to treat a 4-cm diameter target located at a 10-cm depth in a 40-cm diameter homogeneous cylindrical phantom.

Effect of J coupling on 1.3-ppm lipid methylene signal acquired with localised proton MRS at 3 T.

The purpose of this work was to investigate the effect of J-coupling interactions on the quantification and T2 determination of 1.3-ppm lipid methylene protons at 3 T. The response of the 1.