Dose optimization for intensity modulated radiotherapy (IMRT) using small field elements (beamlets) requires the computation of a large number very small, often only virtual fields typically few mm to 1 cm in size. The primary requirements suitable dose algorithm are (1) speed and (2) proper consideration penumbra which composed these beamlets. Here, finite size pencil beam (fsPB) is proposed was specifically designed purpose beamlet-based IMRT. employs an analytical function cross-profiles...

To study the dose-response of stage I non-small-cell lung cancer (NSCLC) in terms long-term local tumor control (LC) after conventional and hypofractionated photon radiotherapy, modeled with linear-quadratic (LQ) linear-quadratic-linear (LQ-L) approaches to estimate clinical α/β ratio within LQ frame. We identified studies curative radiotherapy as single treatment through MedLine search reporting 3-year LC primary outcome interest. Logistic models coupled biologically effective dose (BED) at...

For beamlet-based IMRT optimization, fast and less accurate dose computation algorithms are frequently used, while more needed to recompute the final for verification. In order speed up optimization process ensure close proximity between in verification, proper consideration of gradients tissue inhomogeneity effects should be ensured at every stage optimization. Due their speed, pencil beam often used precalculation beamlet distributions treatment planning systems. However, accounting...

Scanned ion beam delivery enables the highest degree of target dose conformation attainable in external radiotherapy. Nominal pencil widths (spot sizes) are recorded during treatment planning system commissioning. Due to changes beam-line optics, actual spot sizes may differ from these commissioning values, leading differences between planned and delivered dose. The purpose this study was analyse dosimetric consequences size variations particle therapy plans. For 12 patients with skull base...

Targeting at the development of an accurate and efficient dose calculation engine for online adaptive radiotherapy, we have implemented a finite-size pencil beam (FSPB) algorithm with 3D-density correction method on graphics processing unit (GPU). This new GPU-based is built our previously published ultrafast FSPB computational framework (Gu et al 2009 Phys. Med. Biol. 54 6287–97). Dosimetric evaluations against Monte Carlo calculations are conducted ten IMRT treatment plans (five...

This work describes the first imaging studies on a 1.0 Tesla inline MRI-Linac using dedicated transmit/receive RF body coil that has been designed to be completely radio transparent and provide optimum performance over large patient opening. A series of experiments was performed investigate characteristics new volumetric coil: (1) numerical electromagnetic simulations were used measure transmit efficiency in two positions; (2) image quality metrics signal-to-noise ratio (SNR), ghosting...

4D radiation dosimetry using a highly radiation-sensitive polymer gel dosimeter with real-time quantitative magnetic resonance imaging (MRI) readout is presented as technique to acquire the accumulated dose distribution during image-guided radiotherapy on an MRI-Linac. Optimized T 2-weighted Turbo-Spin-Echo (TSE) scans are converted into ΔR 2 maps and subsequently maps. The concept of temporal uncertainty introduced metric effective resolution. A mathematical framework optimize echo time TSE...

The magnetic resonance linear accelerator (MRL) offers improved soft tissue visualization to guide daily adaptive radiotherapy treatment. This manuscript aims report initial experience using a 1.5 T MRL in the first 6 months of operation, including training, workflows, timings and dosimetric accuracy.All staff received training MRI safety workflows. Initial sites chosen for treatment were stereotactic hypofractionated prostate, thoraco-abdomino-pelvic metastasis, prostate bed bladder. Adapt...

MRI-LINACs combine MRI and LINAC technologies with the potential for image guided radiation therapy optimal soft-tissue contrast. In this work, we present advantages limitations of plastic scintillation dosimeters (PSDs) relative dosimetry MRI-LINACs. PSDs possess many desirable qualities, including magnetic field insensitivity irradiation angle independence, which are expected to make them suitable An in-house PSD was used measure size output factors as well a percent depth dose...

Purpose The fringe field of the Australian MRI‐linac causes contaminant electrons to be focused along central axis resulting in a high surface dose. This work aims characterize this effect using Gafchromic film and high‐resolution detectors, MO Skin TM microDiamond. secondary aim is investigate influence inline magnetic on relative dose response these detectors. Methods has unique feature that linac mounted rails allowing for measurements performed at different strengths while maintaining...

Purpose: Unique characteristics of MRI-linac systems and mutual interactions between their components pose specific challenges for commissioning quality assurance. The Australian is a prototype system which explores the inline orientation, with radiation beam parallel to main magnetic field. aim this work was commission radiation-related aspects its application in clinical treatments. Methods: Physical alignment field fine-tuned shielding head designed achieve optimal characteristics. These...

This work describes the first live imaging and radiation delivery performed on a prototype 1.0 T inline MRI-Linac system in rat brain tumor model, which was conducted 29 January 2019.A human scale adapted to be suitable for animal studies via specially constructed open 6-channel receiver radiofrequency (RF) coil. A Fischer injected with 9L glioma cells right hemisphere imaged irradiated at day 11 post surgery as part of larger cohort survival study. The anesthetized positioned iscocenter...

Abstract The pursuit of real-time image-guided radiotherapy has prompted the development hybrid devices coupling MRI scanners with treatment units, usually linear accelerators (linacs). One challenges in MRI-linac technology is magnetic field impact on dose deposition. Dose deposition effects have to be considered radiation therapy chain as they alter distribution patients and influence response many commonly used detectors. In this presentation specific issues dosimetry for MRI-linacs will...

Abstract Consistency and clear guidelines on dosimetry are essential for accurate precise dosimetry, to ensure the best patient outcomes allow direct dose comparison across different centres. Magnetic Resonance Imaging Linac (MRI-linac) systems have recently been introduced Australasian clinics. This report provides recommendations reference measurements MRI-linacs behalf of Australiasian College Physical Scientists Engineers in Medicine (ACPSEM) MRI-linac working group. There two...

In carbon ion beams, biological effects vary along the track; hence, to quantify them, specific radiobiological models are needed. One of local effect model (LEM), in particular version I (LEM I), is implemented treatment planning systems (TPS) clinically used European particle therapy centers. From physical properties radiation, LEM calculates survival probabilities cell or tissue type under study, provided that some determinant input parameters initially defined. Mathematical can be...

Objective. This study aimed to investigate the dosimetric impact of using population-based relative electron density (RED) overrides in lieu simulation computerized tomography (CT) a magnetic resonance linear accelerator (MRL) workflow for male pelvis patients. Additionally, feasibility prostate specific membrane antigen positron emission tomography/CT (PSMA-PET/CT) scans assess patients' eligibility this proposed was examined.Approach. In study, 74 patients treated on an Elekta Unity 1.5 T...

In combined proton-carbon fixed-nozzle treatment facilities with raster scanning delivery, the scattering of proton pencil beams caused by nozzle elements and relatively large nozzle-to-isocenter distance cause a beam broadening. This may pose limitations to achievable dose conformity. One way counteract this effect is delivering in position closer than room isocenter. Purpose study was assess potential dosimetric benefit such solution, terms conformity normal tissue sparing,...

The aim of this study is to investigate off-axis irradiation on the Australian MRI-Linac using experiments and Monte Carlo simulations. Simulations are used verify experimental measurements determine minimum offset distance required separate electron contamination from photon field.Dosimetric were performed a microDiamond detector, Gafchromic® EBT3 film, MOSkinTM . Three field sizes investigated including 1.9 × 1.9, 5.8 5.8, 9.7 9.6 cm2 Each was maximum distance, approximately 10 cm, central...

The introduction of magnetic resonance (MR) linear accelerators (MR-Linac) marks the beginning a new era in radiotherapy. MR-Linac systems are currently being operated by teams radiation therapists (RTs), oncology medical physicists (ROMPs) and oncologists (ROs) due to diverse complex tasks required deliver treatment. This is resource-intensive logistically challenging. RT-led service delivery at treatment console paramount simplify process make best use this technology for suitable patients...