Original Article
Complicated respiratory motion analysis and new CT-based instruction model to enhance deep inspiration breath hold technique
Abstract
Background: Adjuvant radiotherapy reduces local recurrence and improves overall survival of breast cancer. But adjuvant radiotherapy also leads to excess mortality caused by heart and lung disease. Deep inspiration breath hold (DIBH) technique has been proven to reduce radiation exposure to heart and lung. However, effectiveness of DIBH variates from each patient. This study collected one institutional data and further analyzed associated physical factors.
Methods: Left breast cancer patients received left partial mastectomy followed by adjuvant radiotherapy with DIBH technique between Sep 1, 2013 and Sep 1, 2014 were included. Treatment plans based on both free breathing (FB) and DIBH computed tomography scan image for each patient were constructed. Physical factors including chest wall expansion at different levels were measured. Dose of ipsilateral, contralateral, and total lung, and heart were compared between FB and DIBH. Correlation between normal organ irradiated dose and physical factors change were calculated by Pearson correlation test.
Results: Anterior-to-posterior diameter (APd) increase of lung at half upper chest wall level, upper heart border level, and half lower chest wall level, and extra lung length of DIBH had positive correlation with the reduction of irradiated lung dose. The increase of APd of lung at upper heart border level, half lower chest wall level, and right-to-left diameter (RLd) at diaphragm level also had positive correlation with the reduction of Dmax of heart (Pearson correlation r=0.795, 0.835, 0.655; P=0.006, 0.003, and 0.04, respectively) and Dmax of left anterior descending artery (LAD) (r=0.788, 0.795, 0.673; P=0.007, 0.006, and 0.033, respectively). Increase of free-contour heart height had negative correlation with V30, Dmax of heart, and Dmax of LAD.
Conclusions: DIBH can reduce dose to critical organs. One-point chest wall motion monitored by Realtime Position ManagementTM (RPM) system can only represent the change of APd at diaphragm level and part of the change of half of lower chest wall level. Respiration is a complicated motion and multiple level monitoring system was suggested. Patient education to explain the idealist chest wall expansion condition with DIBH is important. Our CT-based instruction model provides a clearer instruction. This study suggested a new direction to evaluate and enhance DIBH performance.
Methods: Left breast cancer patients received left partial mastectomy followed by adjuvant radiotherapy with DIBH technique between Sep 1, 2013 and Sep 1, 2014 were included. Treatment plans based on both free breathing (FB) and DIBH computed tomography scan image for each patient were constructed. Physical factors including chest wall expansion at different levels were measured. Dose of ipsilateral, contralateral, and total lung, and heart were compared between FB and DIBH. Correlation between normal organ irradiated dose and physical factors change were calculated by Pearson correlation test.
Results: Anterior-to-posterior diameter (APd) increase of lung at half upper chest wall level, upper heart border level, and half lower chest wall level, and extra lung length of DIBH had positive correlation with the reduction of irradiated lung dose. The increase of APd of lung at upper heart border level, half lower chest wall level, and right-to-left diameter (RLd) at diaphragm level also had positive correlation with the reduction of Dmax of heart (Pearson correlation r=0.795, 0.835, 0.655; P=0.006, 0.003, and 0.04, respectively) and Dmax of left anterior descending artery (LAD) (r=0.788, 0.795, 0.673; P=0.007, 0.006, and 0.033, respectively). Increase of free-contour heart height had negative correlation with V30, Dmax of heart, and Dmax of LAD.
Conclusions: DIBH can reduce dose to critical organs. One-point chest wall motion monitored by Realtime Position ManagementTM (RPM) system can only represent the change of APd at diaphragm level and part of the change of half of lower chest wall level. Respiration is a complicated motion and multiple level monitoring system was suggested. Patient education to explain the idealist chest wall expansion condition with DIBH is important. Our CT-based instruction model provides a clearer instruction. This study suggested a new direction to evaluate and enhance DIBH performance.
