TY - JOUR
T1 - Evaluation of internal lung motion for respiratory-gated radiotherapy using MRI
T2 - Part II - Margin reduction of internal target volume
AU - Liu, H. Helen
AU - Koch, Nicholas
AU - Starkschall, George
AU - Jacobson, Marc
AU - Forster, Kenneth
AU - Liao, Zhongxing
AU - Komaki, Ritsuko
AU - Stevens, Craig W.
N1 - Funding Information:
Supported in part by a sponsored research agreement with Varian Oncology Systems and an internal research grant from M. D. Anderson Cancer Center.
PY - 2004/12/1
Y1 - 2004/12/1
N2 - Purpose To analyze the relationship between lung motion and skin surface motion during respiration, determine the uncertainties and variability of such a relationship, and assess the potential of reducing internal target margin for gated radiotherapy. Methods and materials Three healthy volunteers and four lung cancer patients were recruited in a prospective imaging study using MRI to track the internal lung and external skin motion during breathing. The relationship between the lung and skin motion was modeled using linear regression analysis. The slope of the linear fit and its confidence interval were analyzed for different lung locations, skin surface locations, and breathing patterns from separate imaging sessions. The margins of the internal target volume were calculated based on the residual lung motion during gating and its uncertainties from multiple treatment fractions for the gated treatment. Results The slope and confidence interval of the linear regression from the motion analysis were uniquely defined by the locations of the lung, skin surface, and breathing patterns. Statistically significant differences were observed among individuals and between different times of measurement. The normal free-breathing motion averaged from all volunteer and patient data was 13.4 ± 7.4 mm along the superior-inferior (SI) direction and 6.9 ± 2.6 mm along the anterior-posterior (AP) direction. With simulated respiratory gating, the average margin reduction was 5.5 ± 4.8 mm and 1.6 ± 1.0 mm, respectively, along the SI and AP directions (or 36% ± 15% and 25% ± 14%, respectively, relative to free-breathing motion). Conclusion Because respiratory movement is rather complex, the relationship between the lung and skin surface motion is affected by many anatomic and physiologic factors. The reduction of internal target margin and efficacy of the free-breathing gating technique should be assessed for individual cases.
AB - Purpose To analyze the relationship between lung motion and skin surface motion during respiration, determine the uncertainties and variability of such a relationship, and assess the potential of reducing internal target margin for gated radiotherapy. Methods and materials Three healthy volunteers and four lung cancer patients were recruited in a prospective imaging study using MRI to track the internal lung and external skin motion during breathing. The relationship between the lung and skin motion was modeled using linear regression analysis. The slope of the linear fit and its confidence interval were analyzed for different lung locations, skin surface locations, and breathing patterns from separate imaging sessions. The margins of the internal target volume were calculated based on the residual lung motion during gating and its uncertainties from multiple treatment fractions for the gated treatment. Results The slope and confidence interval of the linear regression from the motion analysis were uniquely defined by the locations of the lung, skin surface, and breathing patterns. Statistically significant differences were observed among individuals and between different times of measurement. The normal free-breathing motion averaged from all volunteer and patient data was 13.4 ± 7.4 mm along the superior-inferior (SI) direction and 6.9 ± 2.6 mm along the anterior-posterior (AP) direction. With simulated respiratory gating, the average margin reduction was 5.5 ± 4.8 mm and 1.6 ± 1.0 mm, respectively, along the SI and AP directions (or 36% ± 15% and 25% ± 14%, respectively, relative to free-breathing motion). Conclusion Because respiratory movement is rather complex, the relationship between the lung and skin surface motion is affected by many anatomic and physiologic factors. The reduction of internal target margin and efficacy of the free-breathing gating technique should be assessed for individual cases.
KW - Internal target volume
KW - Lung motion
KW - MRI
KW - Margin reduction
KW - Respiratory gating
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U2 - 10.1016/j.ijrobp.2004.05.054
DO - 10.1016/j.ijrobp.2004.05.054
M3 - Article
C2 - 15590178
AN - SCOPUS:10044243676
SN - 0360-3016
VL - 60
SP - 1473
EP - 1483
JO - International Journal of Radiation Oncology Biology Physics
JF - International Journal of Radiation Oncology Biology Physics
IS - 5
ER -