Sarah Dowdell

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The purpose of this study was to assess the possibility of introducing site-specific range margins to replace current generic margins in proton therapy. Further, the goal was to study the potential of reducing margins with current analytical dose calculations methods. For this purpose we investigate the impact of complex patient geometries on the capability(More)
PURPOSE Evaluate the sensitivity of intensity-modulated proton therapy (IMPT) lung treatments to systematic and random setup uncertainties combined with motion effects. METHODS Treatment plans with single-field homogeneity restricted to ±20% (IMPT-20%) were compared to plans with no restriction (IMPT-full). 4D Monte Carlo simulations were performed for 10(More)
PURPOSE Validate clinical pencil beam (PB) and Monte Carlo (MC) based dose calculations using a heterogeneous lung phantom and assess the clinical significance of these findings in lung patients. METHODS A modified IMRT lung phantom and a matrix-array of ionization chambers was used to measure the distal fall-off of the proton beam. The treatment was(More)
Relative motion between a tumor and a scanning proton beam results in a degradation of the dose distribution (interplay effect). This study investigates the relationship between beam scanning parameters and the interplay effect, with the goal of finding parameters that minimize interplay. 4D Monte Carlo simulations of pencil beam scanning proton therapy(More)
PURPOSE To report on the efforts funded by the AAPM seed funding grant to develop the basis for fluorescent nuclear track detector (FNTD) based radiobiological experiments in combination with dedicated Monte Carlo simulations (MCS) on the nanometer scale. METHODS Two confocal microscopes were utilized in this study. Two FNTD samples were used to find the(More)
Light-activated gene expression systems hold promise as new tools for studying spatial and temporal gene patterning in multicellular systems. Photo-caged forms of nuclear receptor agonists have recently been shown to mediate photo-dependent transcription in mammalian cells, however, because intracellularly released agonists can rapidly diffuse out of cells,(More)
PURPOSE Patient specific apertures are commonly employed in passive double scattering (DS) proton therapy (PT). This study was aimed at identifying the potential benefits of using such an aperture in pencil beam scanning (PBS). METHODS An accurate Geant4 Monte Carlo model of the PBS PT treatment head at Massachusetts General Hospital (MGH) was developed(More)
PURPOSE To determine differences in motion interplay effects between single-field uniform dose (SFUD) and intensity modulated proton therapy (IMPT) treatments for lung patients. METHODS SFUD and IMPT treatment plans were generated for 10 lung cancer patients. The spot spacing was set to 0.7σ for all treatment plans and all plans used 2 fields delivered to(More)
PURPOSE For proton radiation therapy, Monte Carlo simulation (MCS) methods are recognized as the gold-standard dose calculation approach. Although previously unrealistic due to limitations in available computing power, GPU-based applications allow MCS of proton treatment fields to be performed in routine clinical use, on time scales comparable to that of(More)
PURPOSE To investigate the impact of complex patient geometries on the capability of analytical dose calculation algorithms to accurately predict dose distributions and to verify currently used uncertainty margins in proton therapy. METHODS Dose distributions predicted by an analytical pencilbeam algorithm were compared with Monte Carlo simulations (MCS)(More)