Motion-robust intensity-modulated proton therapy for distal esophageal cancer

Jen Yu; Xiaodong Zhang; Li Liao; Heng Li; Ronald Zhu; Peter Chul Park; Narayan Sahoo; Michael Gillin; Yupeng Li; Joe Y. Chang; Ritsuko Komaki; Steven H. Lin

doi:10.1118/1.4940789

Motion-robust intensity-modulated proton therapy for distal esophageal cancer

Jen Yu, Xiaodong Zhang, Li Liao, Heng Li, Ronald Zhu, Peter Chul Park, Narayan Sahoo, Michael Gillin, Yupeng Li, Joe Y. Chang, Ritsuko Komaki, Steven H. Lin

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60 Scopus citations

Abstract

Purpose: To develop methods for evaluation and mitigation of dosimetric impact due to respiratory and diaphragmatic motion during free breathing in treatment of distal esophageal cancers using intensity-modulated proton therapy (IMPT). Methods: This was a retrospective study on 11 patients with distal esophageal cancer. For each patient, four-dimensional computed tomography (4D CT) data were acquired, and a nominal dose was calculated on the average phase of the 4D CT. The changes of water equivalent thickness (ΔWET) to cover the treatment volume from the peak of inspiration to the valley of expiration were calculated for a full range of beam angle rotation. Two IMPT plans were calculated: one at beam angles corresponding to small ΔWET and one at beam angles corresponding to large ΔWET. Four patients were selected for the calculation of 4D-robustness-optimized IMPT plans due to large motion-induced dose errors generated in conventional IMPT. To quantitatively evaluate motion-induced dose deviation, the authors calculated the lowest dose received by 95% (D95) of the internal clinical target volume for the nominal dose, the D95 calculated on the maximum inhale and exhale phases of 4D CT (D_CT₀ and D_CT)₅₀, the 4D composite dose, and the 4D dynamic dose for a single fraction. Results: The dose deviation increased with the average ΔWET of the implemented beams, ΔWET_ave. When ΔWETave was less than 5 mm, the dose error was less than 1 cobalt gray equivalent based on D_CT₀ and D_CT₅₀. The dose deviation determined on the basis of D_CT₀ and D_CT₅₀ was proportionally larger than that determined on the basis of the 4D composite dose. The 4D-robustness-optimized IMPT plans notably reduced the overall dose deviation of multiple fractions and the dose deviation caused by the interplay effect in a single fraction. Conclusions: In IMPT for distal esophageal cancer, ΔWET analysis can be used to select the beam angles that are least affected by respiratory and diaphragmatic motion. To further reduce dose deviation, the 4D-robustness optimization can be implemented for IMPT planning. Calculation of D_CT₀ and D_CT₅₀ is a conservative method to estimate the motion-induced dose errors.

Original language	English (US)
Pages (from-to)	1111-1118
Number of pages	8
Journal	Medical physics
Volume	43
Issue number	3
DOIs	https://doi.org/10.1118/1.4940789
State	Published - Mar 1 2016

Keywords

4D-robustness optimization
IMPT
WET
distal esophageal cancer

ASJC Scopus subject areas

Biophysics
Radiology Nuclear Medicine and imaging

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10.1118/1.4940789

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title = "Motion-robust intensity-modulated proton therapy for distal esophageal cancer",

abstract = "Purpose: To develop methods for evaluation and mitigation of dosimetric impact due to respiratory and diaphragmatic motion during free breathing in treatment of distal esophageal cancers using intensity-modulated proton therapy (IMPT). Methods: This was a retrospective study on 11 patients with distal esophageal cancer. For each patient, four-dimensional computed tomography (4D CT) data were acquired, and a nominal dose was calculated on the average phase of the 4D CT. The changes of water equivalent thickness (ΔWET) to cover the treatment volume from the peak of inspiration to the valley of expiration were calculated for a full range of beam angle rotation. Two IMPT plans were calculated: one at beam angles corresponding to small ΔWET and one at beam angles corresponding to large ΔWET. Four patients were selected for the calculation of 4D-robustness-optimized IMPT plans due to large motion-induced dose errors generated in conventional IMPT. To quantitatively evaluate motion-induced dose deviation, the authors calculated the lowest dose received by 95% (D95) of the internal clinical target volume for the nominal dose, the D95 calculated on the maximum inhale and exhale phases of 4D CT (DCT0 and DCT)50, the 4D composite dose, and the 4D dynamic dose for a single fraction. Results: The dose deviation increased with the average ΔWET of the implemented beams, ΔWETave. When ΔWETave was less than 5 mm, the dose error was less than 1 cobalt gray equivalent based on DCT0 and DCT50. The dose deviation determined on the basis of DCT0 and DCT50 was proportionally larger than that determined on the basis of the 4D composite dose. The 4D-robustness-optimized IMPT plans notably reduced the overall dose deviation of multiple fractions and the dose deviation caused by the interplay effect in a single fraction. Conclusions: In IMPT for distal esophageal cancer, ΔWET analysis can be used to select the beam angles that are least affected by respiratory and diaphragmatic motion. To further reduce dose deviation, the 4D-robustness optimization can be implemented for IMPT planning. Calculation of DCT0 and DCT50 is a conservative method to estimate the motion-induced dose errors.",

keywords = "4D-robustness optimization, IMPT, WET, distal esophageal cancer",

author = "Jen Yu and Xiaodong Zhang and Li Liao and Heng Li and Ronald Zhu and Park, {Peter Chul} and Narayan Sahoo and Michael Gillin and Yupeng Li and Chang, {Joe Y.} and Ritsuko Komaki and Lin, {Steven H.}",

note = "Publisher Copyright: {\textcopyright} 2016 American Association of Physicists in Medicine.",

year = "2016",

month = mar,

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doi = "10.1118/1.4940789",

language = "English (US)",

volume = "43",

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T1 - Motion-robust intensity-modulated proton therapy for distal esophageal cancer

AU - Yu, Jen

AU - Zhang, Xiaodong

AU - Liao, Li

AU - Li, Heng

AU - Zhu, Ronald

AU - Park, Peter Chul

AU - Sahoo, Narayan

AU - Gillin, Michael

AU - Li, Yupeng

AU - Chang, Joe Y.

AU - Komaki, Ritsuko

AU - Lin, Steven H.

PY - 2016/3/1

Y1 - 2016/3/1

N2 - Purpose: To develop methods for evaluation and mitigation of dosimetric impact due to respiratory and diaphragmatic motion during free breathing in treatment of distal esophageal cancers using intensity-modulated proton therapy (IMPT). Methods: This was a retrospective study on 11 patients with distal esophageal cancer. For each patient, four-dimensional computed tomography (4D CT) data were acquired, and a nominal dose was calculated on the average phase of the 4D CT. The changes of water equivalent thickness (ΔWET) to cover the treatment volume from the peak of inspiration to the valley of expiration were calculated for a full range of beam angle rotation. Two IMPT plans were calculated: one at beam angles corresponding to small ΔWET and one at beam angles corresponding to large ΔWET. Four patients were selected for the calculation of 4D-robustness-optimized IMPT plans due to large motion-induced dose errors generated in conventional IMPT. To quantitatively evaluate motion-induced dose deviation, the authors calculated the lowest dose received by 95% (D95) of the internal clinical target volume for the nominal dose, the D95 calculated on the maximum inhale and exhale phases of 4D CT (DCT0 and DCT)50, the 4D composite dose, and the 4D dynamic dose for a single fraction. Results: The dose deviation increased with the average ΔWET of the implemented beams, ΔWETave. When ΔWETave was less than 5 mm, the dose error was less than 1 cobalt gray equivalent based on DCT0 and DCT50. The dose deviation determined on the basis of DCT0 and DCT50 was proportionally larger than that determined on the basis of the 4D composite dose. The 4D-robustness-optimized IMPT plans notably reduced the overall dose deviation of multiple fractions and the dose deviation caused by the interplay effect in a single fraction. Conclusions: In IMPT for distal esophageal cancer, ΔWET analysis can be used to select the beam angles that are least affected by respiratory and diaphragmatic motion. To further reduce dose deviation, the 4D-robustness optimization can be implemented for IMPT planning. Calculation of DCT0 and DCT50 is a conservative method to estimate the motion-induced dose errors.

AB - Purpose: To develop methods for evaluation and mitigation of dosimetric impact due to respiratory and diaphragmatic motion during free breathing in treatment of distal esophageal cancers using intensity-modulated proton therapy (IMPT). Methods: This was a retrospective study on 11 patients with distal esophageal cancer. For each patient, four-dimensional computed tomography (4D CT) data were acquired, and a nominal dose was calculated on the average phase of the 4D CT. The changes of water equivalent thickness (ΔWET) to cover the treatment volume from the peak of inspiration to the valley of expiration were calculated for a full range of beam angle rotation. Two IMPT plans were calculated: one at beam angles corresponding to small ΔWET and one at beam angles corresponding to large ΔWET. Four patients were selected for the calculation of 4D-robustness-optimized IMPT plans due to large motion-induced dose errors generated in conventional IMPT. To quantitatively evaluate motion-induced dose deviation, the authors calculated the lowest dose received by 95% (D95) of the internal clinical target volume for the nominal dose, the D95 calculated on the maximum inhale and exhale phases of 4D CT (DCT0 and DCT)50, the 4D composite dose, and the 4D dynamic dose for a single fraction. Results: The dose deviation increased with the average ΔWET of the implemented beams, ΔWETave. When ΔWETave was less than 5 mm, the dose error was less than 1 cobalt gray equivalent based on DCT0 and DCT50. The dose deviation determined on the basis of DCT0 and DCT50 was proportionally larger than that determined on the basis of the 4D composite dose. The 4D-robustness-optimized IMPT plans notably reduced the overall dose deviation of multiple fractions and the dose deviation caused by the interplay effect in a single fraction. Conclusions: In IMPT for distal esophageal cancer, ΔWET analysis can be used to select the beam angles that are least affected by respiratory and diaphragmatic motion. To further reduce dose deviation, the 4D-robustness optimization can be implemented for IMPT planning. Calculation of DCT0 and DCT50 is a conservative method to estimate the motion-induced dose errors.

KW - 4D-robustness optimization

KW - IMPT

KW - WET

KW - distal esophageal cancer

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Motion-robust intensity-modulated proton therapy for distal esophageal cancer

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