Poster — Thur Eve — 35: The impact of intensity and energymodulated photon radiotherapy (XMRT) optimization on a variety of organ geometries
Abstract
We previously reported on a novel, modulated in both energy and intensity; photon radiotherapy (XMRT) optimization technique. The purpose of this investigation was to test this XMRT optimization against conventional intensity modulated radiotherapy (IMRT) optimization on four different organ test geometries. All geometries mimicked clinically relevant scenarios. Both IMRT and XMRT were based on a linear programming approach where the objective function was the mean dose to healthy organs and organspecific linear dosepoint constraints were used. For IMRT, the beam energy was fixed to 6 MV while XMRT optimized in terms of both 6 and 18 MV beams. All plans consisted of a seven beam coplanar arrangement. All organ geometries were contoured on a 25cm diameter cylindrical water phantom in open source radiotherapy research software known as CERR. Solutions for both IMRT and XMRT were obtained for each geometry using a numerical solver Gurobi. Analyzing the quality of the solutions was done by comparing dose distributions and dose volume histograms calculated using CERR. For all four geometries, IMRT and XMRT solutions were comparable in terms of target coverage. For two of the geometries, IMRT provided an advantage in terms of reduced dose to the healthy structures. XMRT showed improved dosemore »
 Authors:
 Department of Physics and Astronomy, University of Calgary, Calgary, AB (Canada)
 (Canada)
 Department of Mathematics and Statistics, University of Calgary, Calgary, AB (Canada)
 Publication Date:
 OSTI Identifier:
 22407657
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Medical Physics; Journal Volume: 41; Journal Issue: 8; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 60 APPLIED LIFE SCIENCES; COMPARATIVE EVALUATIONS; CYLINDRICAL CONFIGURATION; LINEAR PROGRAMMING; OPTIMIZATION; ORGANS; PHANTOMS; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RADIOTHERAPY
Citation Formats
McGeachy, P., VillarrealBarajas, J. E., Khan, R., Department of Medical Physics, Tom Baker Cancer Center, Calgary, AB, and Zinchenko, Y. Poster — Thur Eve — 35: The impact of intensity and energymodulated photon radiotherapy (XMRT) optimization on a variety of organ geometries. United States: N. p., 2014.
Web. doi:10.1118/1.4894894.
McGeachy, P., VillarrealBarajas, J. E., Khan, R., Department of Medical Physics, Tom Baker Cancer Center, Calgary, AB, & Zinchenko, Y. Poster — Thur Eve — 35: The impact of intensity and energymodulated photon radiotherapy (XMRT) optimization on a variety of organ geometries. United States. doi:10.1118/1.4894894.
McGeachy, P., VillarrealBarajas, J. E., Khan, R., Department of Medical Physics, Tom Baker Cancer Center, Calgary, AB, and Zinchenko, Y. Fri .
"Poster — Thur Eve — 35: The impact of intensity and energymodulated photon radiotherapy (XMRT) optimization on a variety of organ geometries". United States.
doi:10.1118/1.4894894.
@article{osti_22407657,
title = {Poster — Thur Eve — 35: The impact of intensity and energymodulated photon radiotherapy (XMRT) optimization on a variety of organ geometries},
author = {McGeachy, P. and VillarrealBarajas, J. E. and Khan, R. and Department of Medical Physics, Tom Baker Cancer Center, Calgary, AB and Zinchenko, Y.},
abstractNote = {We previously reported on a novel, modulated in both energy and intensity; photon radiotherapy (XMRT) optimization technique. The purpose of this investigation was to test this XMRT optimization against conventional intensity modulated radiotherapy (IMRT) optimization on four different organ test geometries. All geometries mimicked clinically relevant scenarios. Both IMRT and XMRT were based on a linear programming approach where the objective function was the mean dose to healthy organs and organspecific linear dosepoint constraints were used. For IMRT, the beam energy was fixed to 6 MV while XMRT optimized in terms of both 6 and 18 MV beams. All plans consisted of a seven beam coplanar arrangement. All organ geometries were contoured on a 25cm diameter cylindrical water phantom in open source radiotherapy research software known as CERR. Solutions for both IMRT and XMRT were obtained for each geometry using a numerical solver Gurobi. Analyzing the quality of the solutions was done by comparing dose distributions and dose volume histograms calculated using CERR. For all four geometries, IMRT and XMRT solutions were comparable in terms of target coverage. For two of the geometries, IMRT provided an advantage in terms of reduced dose to the healthy structures. XMRT showed improved dose reduction to healthy organs for one geometry and a comparable dose distribution to IMRT for the remaining geometry. The inability to exploit the benefits of using multiple energies may be attributed to limited water phantom diameter and having the majority of the organs in close proximity to the transverse axis.},
doi = {10.1118/1.4894894},
journal = {Medical Physics},
number = 8,
volume = 41,
place = {United States},
year = {Fri Aug 15 00:00:00 EDT 2014},
month = {Fri Aug 15 00:00:00 EDT 2014}
}

Purpose: To develop a new radiotherapy plan optimization technique that, for a given organ geometry, will find the optimal photon beam energies and fluences to produce a desirable dose distribution. This new modulated (both in energy and fluence) photon radiotherapy (XMRT) was compared with intensity modulated radiotherapy (IMRT) for a simple organ geometry. Methods: The XMRT optimization was formulated using a linear programming approach where the objective function is the mean dose to the healthy organs and dosepoint constraints were assigned to each organ of interest. The organ geometry consisted of a target, two organs at risk (OARs), and normalmore »

Poster  52: Smoothing constraints in Modulated Photon Radiotherapy (XMRT) fluence map optimization
Purpose: Modulated Photon Radiotherapy (XMRT), which simultaneously optimizes photon beamlet energy (6 and 18 MV) and fluence, has recently shown dosimetric improvement in comparison to conventional IMRT. That said, the degree of smoothness of resulting fluence maps (FMs) has yet to be investigated and could impact the deliverability of XMRT. This study looks at investigating FM smoothness and imposing smoothing constraint in the fluence map optimization. Methods: Smoothing constraints were modeled in the XMRT algorithm with the sum of positive gradient (SPG) technique. XMRT solutions, with and without SPG constraints, were generated for a clinical prostate scan using standard dosimetricmore » 
Poster — Thur Eve — 48: Dosimetric dependence on bone backscatter in orthovoltage radiotherapy: A Monte Carlo photon fluence spectral study
This study investigated dosimetric impact due to the bone backscatter in orthovoltage radiotherapy. Monte Carlo simulations were used to calculate depth doses and photon fluence spectra using the EGSnrcbased code. Inhomogeneous bone phantom containing a thin water layer (1–3 mm) on top of a bone (1 cm) to mimic the treatment sites of forehead, chest wall and kneecap was irradiated by the 220 kVp photon beam produced by the Gulmay D3225 xray machine. Percentage depth doses and photon energy spectra were determined using Monte Carlo simulations. Results of percentage depth doses showed that the maximum bone dose was about 210–230%more » 
Poster — Thur Eve — 45: Comparison of different Monte Carlo methods of scoring linear energy transfer in modulated proton therapy beams
In this work, we demonstrate inconsistencies in commonly used Monte Carlo methods of scoring linear energy transfer (LET) in proton therapy beams. In particle therapy beams, the LET is an important parameter because the relative biological effectiveness (RBE) depends on it. LET is often determined using Monte Carlo techniques. We used a realistic Monte Carlo model of a proton therapy nozzle to score proton LET in spreadout Bragg peak (SOBP) depthdose distributions. We used three different scoring and calculation techniques to determine average LET at varying depths within a 140 MeV beam with a 4 cm SOBP and a 250more » 
SUET368: Evaluating Dosimetric Outcome of Modulated Photon Radiotherapy (XMRT) Optimization for Head and Neck Patients
Purpose: The dosimetric outcome of optimized treatment plans obtained by modulating the photon beamlet energy and fluence on a small cohort of four Head and Neck (H and N) patients was investigated. This novel optimization technique is denoted XMRT for modulated photon radiotherapy. The dosimetric plans from XMRT for H and N treatment were compared to conventional, 6 MV intensity modulated radiotherapy (IMRT) optimization plans. Methods: An arrangement of two noncoplanar and five coplanar beams was used for all four H and N patients. Both XMRT and IMRT were subject to the same optimization algorithm, with XMRT optimization allowing bothmore »