Experimental validation of coarse ridge filters for FLASH proton therapy.

Background: To maximize the potential benefit of the FLASH sparing effect during treatment, normal tissue regions would ideally be irradiated only briefly, typically for a couple of hundred milliseconds. Achieving such fast proton irradiation involves a mono-energetic beam at the highest cyclotron energy and the use of 3D-printed conformal energy modulators (CEM). In ConformalFLASH, a dedicated snout is mounted on the nozzle, containing the CEM, a range shifter, and an aperture.

Verification of dose and dose rate for quality assurance of spread-out-Bragg-peak proton FLASH radiotherapy using machine log files.

Background: Ultra-high dose rate radiotherapy elicits a biological effect (FLASH), which has been shown to reduce toxicity while maintaining tumor control in preclinical radiobiology experiments. FLASH depends on the dose rate, with evidence that higher dose rates drive increased normal tissue sparing. The pattern of dose delivery also has significance for conformal proton FLASH delivered via pencil beam scanning (PBS) given its unique spatio-temporal distribution of dose deposition.

Toward MR-integrated proton therapy: modeling the potential benefits for liver tumors.

Magnetic resonance imaging (MRI)-integrated proton therapy (MRiPT) is envisioned to improve treatment quality for many cancer patients. However, given the availability of alternative image-guided strategies, its clinical need is yet to be justified. This study aims to compare the expected clinical outcomes of MRiPT with standard of practice cone-beam CT (CBCT)-guided PT, and other MR-guided methods, i.

Model studies of the role of oxygen in the FLASH effect.

Current radiotherapy facilities are standardized to deliver dose rates around 0.1-0.4 Gy/s in 2 Gy daily fractions, designed to deliver total accumulated doses to reach the tolerance limit of normal tissues undergoing irradiation.

Thermoacoustic range verification during pencil beam delivery of a clinical plan to an abdominal imaging phantom.

Purpose: The purpose of this phantom study is to demonstrate that thermoacoustic range verification could be performed clinically. Thermoacoustic emissions generated in an anatomical multimodality imaging phantom during delivery of a clinical plan are compared to simulated emissions to estimate range shifts compared to the treatment plan.

Methods: A single-field 12-layerproton pencil beam scanning (PBS)treatment plancreated in Pinnacle prescribing6 Gy/fractionwas delivered by a superconducting synchrocyclotron to a triple modality (CT, MRI, and US) abdominal imaging phantom.

A physicochemical model of reaction kinetics supports peroxyl radical recombination as the main determinant of the FLASH effect.

Background And Purpose: FLASH radiotherapy, a technique based on delivering large doses in a single fraction at the micro/millisecond timescale, spares normal tissues from late radiation-induced toxicity, in an oxygen-dependent process, whilst keeping full anti-tumor efficiency. We present a theoretical model taking into account the kinetics of formation and decay of reactive oxygen species, in particular of organic peroxyl radicals ROO formed by addition of O to primary carbon-centred radicals R and known to play a major role at the origin radio-induced complications.

Materials And Methods: The model focuses on the time-dependent evolution of radiolytic products in living matter exposed to continuous irradiation at dose-rates in the range 10-10Gy·s.

Estimation of respiratory phases during proton radiotherapy from a 4D-CT and Prompt gamma detection profiles.

Proton radiotherapy has a potential to provide an effective cancer treatment while sparing greater volume of healthy tissue than the conventional X-ray based radiotherapy. However, in lungs this potential is hindered by motion due to breathing. An important quantity in treatment verification is the correlation between the respiratory phases (RP) and the timing of pencil beam scanning (PBS).

Reassessment of stopping power ratio uncertainties caused by mean excitation energies using a water-based formalism.

Purpose: In proton therapy planning, the accuracy of the Stopping Power Ratios (SPR) calculated in the stoichiometric CT calibration is affected by, among others, uncertainties on the mean excitation energies (I-values) of human tissues and water. Traditionally, the contribution of these uncertainties on the SPR has been conservatively estimated of the order of 1% or more for a reference tissue of known composition. This study provides a methodology that enables a finer estimation of this uncertainty, eventually showing that the traditional estimates of the uncertainty are too conservative.

Estimating patient specific uncertainty parameters for adaptive treatment re-planning in proton therapy using in vivo range measurements and Bayesian inference: application to setup and stopping power errors.

In proton therapy, quantification of the proton range uncertainty is important to achieve dose distribution compliance. The promising accuracy of prompt gamma imaging (PGI) suggests the development of a mathematical framework using the range measurements to convert population based estimates of uncertainties into patient specific estimates with the purpose of plan adaptation. We present here such framework using Bayesian inference.