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Title: TH-CD-209-08: Quantification of the Interplay Effect in Proton Pencil Beam Scanning Treatment of Lung

Abstract

Purpose: To quantify the dose degradation caused by the interplay effect based on a beam specific motion analysis in proton pencil beam scanning (PBS) treatment of lung tumors Methods: PBS plans were optimized on average CT using a beam-specific PTV method for 10 consecutive patients with locally advanced non-small-cell-lung-cancer (NSCLC) treated with proton therapy to 6660/180 cGy. End inhalation (CT0) and end exhalation (CT50) were selected as the two extreme scenarios to acquire the relative stopping power ratio difference (Δrsp) for a respiration cycle. The water equivalent difference (ΔWET) per radiological path was calculated from the surface of patient to the iCTV by integrating the Δrsp of each voxel. The motion magnitude of each voxel within the target follows a quasi-Gaussian distribution. A motion index (MI (>5mm WET)), defined as the percentage of target voxels with an absolute integral ΔWET larger than 5 mm, was adopted as a metric to characterize interplay. To simulate the treatment process, 4D dose was calculated by accumulating the spot dose on the corresponding respiration phase to the reference phase CT50 by deformable image registration based on spot timing and patient breathing phase. Results: The study indicated that the magnitude of target underdose in amore » single fraction plan is proportional to the MI (p<0.001), with larger motion equating to greater dose degradation and standard deviations. The target homogeneity, minimum, maximum and mean dose in the 4D dose accumulations of 37 fractions varied as a function of MI. Conclusion: The MI quantification metric can predict the level of dose degradation in PBS lung cancer treatment, which potentially serves as a clinical decision tool to assess whether patients are suitable to receive PBS treatment.« less

Authors:
; ; ; ; ; ;  [1]; ;  [2]
  1. University of Pennsylvania, Philadelphia, PA (United States)
  2. Walter Reed Military Hospital, Bethesda, MD (United States)
Publication Date:
OSTI Identifier:
22679335
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; LUNGS; PATIENTS; PROTON BEAMS; RADIATION DOSES; RADIOTHERAPY; RESPIRATION; STOPPING POWER

Citation Formats

Kang, M, Huang, S, Solberg, T, Teo, B, McDonough, J, Simone, C, Lin, L, Mayer, R, and Thomas, A. TH-CD-209-08: Quantification of the Interplay Effect in Proton Pencil Beam Scanning Treatment of Lung. United States: N. p., 2016. Web. doi:10.1118/1.4958202.
Kang, M, Huang, S, Solberg, T, Teo, B, McDonough, J, Simone, C, Lin, L, Mayer, R, & Thomas, A. TH-CD-209-08: Quantification of the Interplay Effect in Proton Pencil Beam Scanning Treatment of Lung. United States. doi:10.1118/1.4958202.
Kang, M, Huang, S, Solberg, T, Teo, B, McDonough, J, Simone, C, Lin, L, Mayer, R, and Thomas, A. Wed . "TH-CD-209-08: Quantification of the Interplay Effect in Proton Pencil Beam Scanning Treatment of Lung". United States. doi:10.1118/1.4958202.
@article{osti_22679335,
title = {TH-CD-209-08: Quantification of the Interplay Effect in Proton Pencil Beam Scanning Treatment of Lung},
author = {Kang, M and Huang, S and Solberg, T and Teo, B and McDonough, J and Simone, C and Lin, L and Mayer, R and Thomas, A},
abstractNote = {Purpose: To quantify the dose degradation caused by the interplay effect based on a beam specific motion analysis in proton pencil beam scanning (PBS) treatment of lung tumors Methods: PBS plans were optimized on average CT using a beam-specific PTV method for 10 consecutive patients with locally advanced non-small-cell-lung-cancer (NSCLC) treated with proton therapy to 6660/180 cGy. End inhalation (CT0) and end exhalation (CT50) were selected as the two extreme scenarios to acquire the relative stopping power ratio difference (Δrsp) for a respiration cycle. The water equivalent difference (ΔWET) per radiological path was calculated from the surface of patient to the iCTV by integrating the Δrsp of each voxel. The motion magnitude of each voxel within the target follows a quasi-Gaussian distribution. A motion index (MI (>5mm WET)), defined as the percentage of target voxels with an absolute integral ΔWET larger than 5 mm, was adopted as a metric to characterize interplay. To simulate the treatment process, 4D dose was calculated by accumulating the spot dose on the corresponding respiration phase to the reference phase CT50 by deformable image registration based on spot timing and patient breathing phase. Results: The study indicated that the magnitude of target underdose in a single fraction plan is proportional to the MI (p<0.001), with larger motion equating to greater dose degradation and standard deviations. The target homogeneity, minimum, maximum and mean dose in the 4D dose accumulations of 37 fractions varied as a function of MI. Conclusion: The MI quantification metric can predict the level of dose degradation in PBS lung cancer treatment, which potentially serves as a clinical decision tool to assess whether patients are suitable to receive PBS treatment.},
doi = {10.1118/1.4958202},
journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 43,
place = {United States},
year = {2016},
month = {6}
}