Effects of breathing variation on gating window internal target volume in respiratory gated radiation therapy

Jing Cai, Robert McLawhorn, Paul W. Read, James M. Larner, Fang Fang Yin, Stanley H Benedict, Ke Sheng

Research output: Contribution to journalArticle

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Abstract

Purpose: To investigate the effects of breathing variation on gating window internal target volume (ITVGW) in respiratory gated radiation therapy. Method and Materials: Two-dimensional dynamic MRI (dMRI) of lung motion was acquired in ten volunteers and eight lung cancer patients. Resorted dMRI using 4DCT acquisition method (RedCAM) was generated for selected subjects by simulating the image rebinning process. A dynamic software generated phantom (dSGP) was created by moving a solid circle (to mimic the "tumor") with dMRI-determined motion trajectories. The gating window internal target area (ITAGW, 2D counterpart of ITVGW) was determined from both RedCAM and dSGP/dMRI. Its area (A), major axis (L1), minor axis (L2), and similarity (S) were calculated and compared. Results: In the phantom study of 3 cm tumor, measurements of the ITAGW from dSGP (A=10.0±1.3 cm2, L 1=3.8±0.4 cm, and L2=3.3±0.1 cm) are significantly (p<0.001) greater than those from RedCAM (A=8.5±0.7 cm2, L 1=3.5±0.2 cm, and L 2=3.1±0.1 cm). Similarly, the differences are significantly greater (p<0.001) for the 1 cm tumor (A=1.9±0.5 cm2, L 1=1.9±0.4 cm, and L 2=1.3±0.1 cm in dSGP; A=1.3±0.1 cm2, L 1=1.5±0.2 cm, and L 2=1.1±0.1 cm in RedCAM). In patient studies, measurements of the ITA GW from dMRI (A=15.5±8.2 cm2, L 1=5.0±1.1 cm, and L 2=3.8±1.2 cm) are also significantly greater (p<0.05) than those from RedCAM (A=13.2±8.5 cm2, L 1=4.3±1.4 cm, and L 2=3.7±1.2 cm). Similarities were 0.9±0.1, 0.8±0.1, and 0.8±0.1 in the 3 cm tumor phantom, 1 cm tumor phantom, and patient studies, respectively. Conclusion: ITVGW can be underestimated by 4DCT due to breathing variations. An additional margin may be needed to account for this potential error in generating a PTVGW. Cautions need to be taken when generating ITVGW from 4DCT in respiratory gated radiation therapy, especially for small tumors (<3 cm) with a large motion range (>1 cm).

Original languageEnglish (US)
Pages (from-to)3927-3934
Number of pages8
JournalMedical Physics
Volume37
Issue number8
DOIs
StatePublished - Aug 2010
Externally publishedYes

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Respiration
Radiotherapy
Software
Volunteers
Lung Neoplasms
Neoplasms
Lung

Keywords

  • 4DCT
  • dynamic MRI
  • internal target volume
  • residual tumor motion
  • respiratory gated radiation therapy

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

Cite this

Effects of breathing variation on gating window internal target volume in respiratory gated radiation therapy. / Cai, Jing; McLawhorn, Robert; Read, Paul W.; Larner, James M.; Yin, Fang Fang; Benedict, Stanley H; Sheng, Ke.

In: Medical Physics, Vol. 37, No. 8, 08.2010, p. 3927-3934.

Research output: Contribution to journalArticle

Cai, Jing ; McLawhorn, Robert ; Read, Paul W. ; Larner, James M. ; Yin, Fang Fang ; Benedict, Stanley H ; Sheng, Ke. / Effects of breathing variation on gating window internal target volume in respiratory gated radiation therapy. In: Medical Physics. 2010 ; Vol. 37, No. 8. pp. 3927-3934.
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abstract = "Purpose: To investigate the effects of breathing variation on gating window internal target volume (ITVGW) in respiratory gated radiation therapy. Method and Materials: Two-dimensional dynamic MRI (dMRI) of lung motion was acquired in ten volunteers and eight lung cancer patients. Resorted dMRI using 4DCT acquisition method (RedCAM) was generated for selected subjects by simulating the image rebinning process. A dynamic software generated phantom (dSGP) was created by moving a solid circle (to mimic the {"}tumor{"}) with dMRI-determined motion trajectories. The gating window internal target area (ITAGW, 2D counterpart of ITVGW) was determined from both RedCAM and dSGP/dMRI. Its area (A), major axis (L1), minor axis (L2), and similarity (S) were calculated and compared. Results: In the phantom study of 3 cm tumor, measurements of the ITAGW from dSGP (A=10.0±1.3 cm2, L 1=3.8±0.4 cm, and L2=3.3±0.1 cm) are significantly (p<0.001) greater than those from RedCAM (A=8.5±0.7 cm2, L 1=3.5±0.2 cm, and L 2=3.1±0.1 cm). Similarly, the differences are significantly greater (p<0.001) for the 1 cm tumor (A=1.9±0.5 cm2, L 1=1.9±0.4 cm, and L 2=1.3±0.1 cm in dSGP; A=1.3±0.1 cm2, L 1=1.5±0.2 cm, and L 2=1.1±0.1 cm in RedCAM). In patient studies, measurements of the ITA GW from dMRI (A=15.5±8.2 cm2, L 1=5.0±1.1 cm, and L 2=3.8±1.2 cm) are also significantly greater (p<0.05) than those from RedCAM (A=13.2±8.5 cm2, L 1=4.3±1.4 cm, and L 2=3.7±1.2 cm). Similarities were 0.9±0.1, 0.8±0.1, and 0.8±0.1 in the 3 cm tumor phantom, 1 cm tumor phantom, and patient studies, respectively. Conclusion: ITVGW can be underestimated by 4DCT due to breathing variations. An additional margin may be needed to account for this potential error in generating a PTVGW. Cautions need to be taken when generating ITVGW from 4DCT in respiratory gated radiation therapy, especially for small tumors (<3 cm) with a large motion range (>1 cm).",
keywords = "4DCT, dynamic MRI, internal target volume, residual tumor motion, respiratory gated radiation therapy",
author = "Jing Cai and Robert McLawhorn and Read, {Paul W.} and Larner, {James M.} and Yin, {Fang Fang} and Benedict, {Stanley H} and Ke Sheng",
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T1 - Effects of breathing variation on gating window internal target volume in respiratory gated radiation therapy

AU - Cai, Jing

AU - McLawhorn, Robert

AU - Read, Paul W.

AU - Larner, James M.

AU - Yin, Fang Fang

AU - Benedict, Stanley H

AU - Sheng, Ke

PY - 2010/8

Y1 - 2010/8

N2 - Purpose: To investigate the effects of breathing variation on gating window internal target volume (ITVGW) in respiratory gated radiation therapy. Method and Materials: Two-dimensional dynamic MRI (dMRI) of lung motion was acquired in ten volunteers and eight lung cancer patients. Resorted dMRI using 4DCT acquisition method (RedCAM) was generated for selected subjects by simulating the image rebinning process. A dynamic software generated phantom (dSGP) was created by moving a solid circle (to mimic the "tumor") with dMRI-determined motion trajectories. The gating window internal target area (ITAGW, 2D counterpart of ITVGW) was determined from both RedCAM and dSGP/dMRI. Its area (A), major axis (L1), minor axis (L2), and similarity (S) were calculated and compared. Results: In the phantom study of 3 cm tumor, measurements of the ITAGW from dSGP (A=10.0±1.3 cm2, L 1=3.8±0.4 cm, and L2=3.3±0.1 cm) are significantly (p<0.001) greater than those from RedCAM (A=8.5±0.7 cm2, L 1=3.5±0.2 cm, and L 2=3.1±0.1 cm). Similarly, the differences are significantly greater (p<0.001) for the 1 cm tumor (A=1.9±0.5 cm2, L 1=1.9±0.4 cm, and L 2=1.3±0.1 cm in dSGP; A=1.3±0.1 cm2, L 1=1.5±0.2 cm, and L 2=1.1±0.1 cm in RedCAM). In patient studies, measurements of the ITA GW from dMRI (A=15.5±8.2 cm2, L 1=5.0±1.1 cm, and L 2=3.8±1.2 cm) are also significantly greater (p<0.05) than those from RedCAM (A=13.2±8.5 cm2, L 1=4.3±1.4 cm, and L 2=3.7±1.2 cm). Similarities were 0.9±0.1, 0.8±0.1, and 0.8±0.1 in the 3 cm tumor phantom, 1 cm tumor phantom, and patient studies, respectively. Conclusion: ITVGW can be underestimated by 4DCT due to breathing variations. An additional margin may be needed to account for this potential error in generating a PTVGW. Cautions need to be taken when generating ITVGW from 4DCT in respiratory gated radiation therapy, especially for small tumors (<3 cm) with a large motion range (>1 cm).

AB - Purpose: To investigate the effects of breathing variation on gating window internal target volume (ITVGW) in respiratory gated radiation therapy. Method and Materials: Two-dimensional dynamic MRI (dMRI) of lung motion was acquired in ten volunteers and eight lung cancer patients. Resorted dMRI using 4DCT acquisition method (RedCAM) was generated for selected subjects by simulating the image rebinning process. A dynamic software generated phantom (dSGP) was created by moving a solid circle (to mimic the "tumor") with dMRI-determined motion trajectories. The gating window internal target area (ITAGW, 2D counterpart of ITVGW) was determined from both RedCAM and dSGP/dMRI. Its area (A), major axis (L1), minor axis (L2), and similarity (S) were calculated and compared. Results: In the phantom study of 3 cm tumor, measurements of the ITAGW from dSGP (A=10.0±1.3 cm2, L 1=3.8±0.4 cm, and L2=3.3±0.1 cm) are significantly (p<0.001) greater than those from RedCAM (A=8.5±0.7 cm2, L 1=3.5±0.2 cm, and L 2=3.1±0.1 cm). Similarly, the differences are significantly greater (p<0.001) for the 1 cm tumor (A=1.9±0.5 cm2, L 1=1.9±0.4 cm, and L 2=1.3±0.1 cm in dSGP; A=1.3±0.1 cm2, L 1=1.5±0.2 cm, and L 2=1.1±0.1 cm in RedCAM). In patient studies, measurements of the ITA GW from dMRI (A=15.5±8.2 cm2, L 1=5.0±1.1 cm, and L 2=3.8±1.2 cm) are also significantly greater (p<0.05) than those from RedCAM (A=13.2±8.5 cm2, L 1=4.3±1.4 cm, and L 2=3.7±1.2 cm). Similarities were 0.9±0.1, 0.8±0.1, and 0.8±0.1 in the 3 cm tumor phantom, 1 cm tumor phantom, and patient studies, respectively. Conclusion: ITVGW can be underestimated by 4DCT due to breathing variations. An additional margin may be needed to account for this potential error in generating a PTVGW. Cautions need to be taken when generating ITVGW from 4DCT in respiratory gated radiation therapy, especially for small tumors (<3 cm) with a large motion range (>1 cm).

KW - 4DCT

KW - dynamic MRI

KW - internal target volume

KW - residual tumor motion

KW - respiratory gated radiation therapy

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