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Title: SU-E-T-639: Proton Dose Calculation for Irregular Motion Using a Sliding Interface

Abstract

Purpose: While many techniques exist to evaluate dose to regularly moving lung targets, there are few available to calculate dose at tumor positions not present in the 4DCT. We have previously developed a method that extrapolates an existing dose to a new tumor location. In this abstract, we present a novel technique that accounts for relative anatomical shifts at the chest wall interface. We also utilize this procedure to simulate breathing motion functions on a cohort of eleven patients. Amplitudes exceeding the original range of motion were used to evaluate coverage using several aperture and smearing beam settings. Methods: The water-equivalent depth (WED) technique requires an initial dose and CT image at the corresponding tumor position. Each dose volume was converted from its Cartesian geometry into a beam-specific radiological depth space. The sliding chest wall interface was determined by converting the lung contour into this same space. Any dose proximal to the initial boundary of the warped lung contour was held fixed, while the remaining distal dose was moved in the direction of motion along the interface. Results: V95 coverage was computed for each patient using the updated algorithm. Incorporation of the sliding motion yielded large dose differences, with gammamore » pass rates as low as 69.7% (3mm, 3%) and V95 coverage differences up to 2.0%. Clinical coverage was maintained for most patients with 5 mm excess simulated breathing motion, and up to 10 mm of excess motion was tolerated for a subset of patients and beam settings. Conclusion: We have established a method to determine the maximum allowable excess breathing motion for a given plan on a patient-by-patient basis. By integrating a sliding chest wall interface into our dose calculation technique, we have analyzed the robustness of breathing patterns that differ during treatment from at the time of 4DCT acquisition.« less

Authors:
; ; ; ;  [1]
  1. Massachusetts General Hospital, Boston, MA (United States)
Publication Date:
OSTI Identifier:
22538148
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; 61 RADIATION PROTECTION AND DOSIMETRY; CHEST; COMPUTERIZED TOMOGRAPHY; INTERFACES; LUNGS; NEOPLASMS; PATIENTS; RADIATION DOSES; RESPIRATION

Citation Formats

Phillips, J, Gueorguiev, G, Grassberger, C, Paganetti, H, and Sharp, G. SU-E-T-639: Proton Dose Calculation for Irregular Motion Using a Sliding Interface. United States: N. p., 2015. Web. doi:10.1118/1.4925002.
Phillips, J, Gueorguiev, G, Grassberger, C, Paganetti, H, & Sharp, G. SU-E-T-639: Proton Dose Calculation for Irregular Motion Using a Sliding Interface. United States. doi:10.1118/1.4925002.
Phillips, J, Gueorguiev, G, Grassberger, C, Paganetti, H, and Sharp, G. Mon . "SU-E-T-639: Proton Dose Calculation for Irregular Motion Using a Sliding Interface". United States. doi:10.1118/1.4925002.
@article{osti_22538148,
title = {SU-E-T-639: Proton Dose Calculation for Irregular Motion Using a Sliding Interface},
author = {Phillips, J and Gueorguiev, G and Grassberger, C and Paganetti, H and Sharp, G},
abstractNote = {Purpose: While many techniques exist to evaluate dose to regularly moving lung targets, there are few available to calculate dose at tumor positions not present in the 4DCT. We have previously developed a method that extrapolates an existing dose to a new tumor location. In this abstract, we present a novel technique that accounts for relative anatomical shifts at the chest wall interface. We also utilize this procedure to simulate breathing motion functions on a cohort of eleven patients. Amplitudes exceeding the original range of motion were used to evaluate coverage using several aperture and smearing beam settings. Methods: The water-equivalent depth (WED) technique requires an initial dose and CT image at the corresponding tumor position. Each dose volume was converted from its Cartesian geometry into a beam-specific radiological depth space. The sliding chest wall interface was determined by converting the lung contour into this same space. Any dose proximal to the initial boundary of the warped lung contour was held fixed, while the remaining distal dose was moved in the direction of motion along the interface. Results: V95 coverage was computed for each patient using the updated algorithm. Incorporation of the sliding motion yielded large dose differences, with gamma pass rates as low as 69.7% (3mm, 3%) and V95 coverage differences up to 2.0%. Clinical coverage was maintained for most patients with 5 mm excess simulated breathing motion, and up to 10 mm of excess motion was tolerated for a subset of patients and beam settings. Conclusion: We have established a method to determine the maximum allowable excess breathing motion for a given plan on a patient-by-patient basis. By integrating a sliding chest wall interface into our dose calculation technique, we have analyzed the robustness of breathing patterns that differ during treatment from at the time of 4DCT acquisition.},
doi = {10.1118/1.4925002},
journal = {Medical Physics},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}