ABSTRACT
Objective To analyze the correlation between treatment time and radiotherapy plan of deep inspiration breath-hold (DIBH) technique for the whole breast irradiation (WBI) in the left breast cancer after breast-conserving surgery,verify the inter-fractional reproducibility of radiotherapy,observe the heart location and dosimetric changes and calculate the effect of DIBH upon the WBI setup error after the surgery.Methods We prospectively enrolled 15 patients with left breast cancer undergoing WBI after breast-conserving surgery,who met the requirement of D1BH.Treatment time was recorded,its correlation with the number of field and monitor unit was analyzed.Inter-fractional setup errors and PTV delineation were calculated using cone beam CT (CBCT).The accuracy of the position and dose of the heart during radiotherapy was verified by the imaging fusion of CBCT and CT images.The variables among groups were analyzed by non-parametric Firedman test.Results The average treatment time of DIBH radiotherapy was 4.6 minutes.The treatment time was correlated with the maximal and total number of sub-fields and total monitor units.During DIBH treatment,the mean cardiac displacement volume was 19.1 cm3(3.8％).The mean cardiac dose difference between CBCT and planning CT was 5.1 cGy,and there was no significant difference in the heart V5-V30.The mean inter-fractional system setup error (∑) and random setup error (σ) in the left-right (x),superior-inferior (y) and anterior-posterior (z) direction were ∑x 1.9 mm,∑y 2.1 mm,∑z 2.0 mm,σx 1.3 mm,σy 1.3 mm,σz 1.4 mm,respectively.The corresponding minimal margins for setup error were 5.7 mm,6.2 mm and 6.0 mm,respectively.Conclusion DIBH for WBI after breast-conserving surgery does not significantly prolong the treatment time.Treatment time is related to treatment plan.DIBH yields high inter-fractional reproducibility and protects the heart.
ABSTRACT
Objective To study the effect of deep inspiration breath-hold(DIBH)technique on the heart dose in whole breast irradiation(WBI)for left breast cancer after breast-conserving surgery, and to investigate the anatomical factors for heart dose. Methods Fifteen patients with left breast cancer who received WBI after breast-conserving surgery and met breathing control requirements were prospectively enrolled as subjects. Simulated CT scans were performed during free breathing(FB)and DIBH. The WBI plans were optimized based on DIBH images.The position,volume,and radiation doses to the heart and lung were compared between the status of FB and DIBH. Correlation of heart dose with various anatomical factors was analyzed in FB status. Between-group comparison of categorical data was made by nonparametric Wilcoxon rank test.A two-variable correlation analysis was made by the Pearson method.Results There was no significant difference in heart volume between the status of FB and DIBH(P=0.773).The volume of both lungs was significantly larger in DIBH status than in FB status(P=0.001). The mean and maximum doses and V5-V40for the heart,left anterior descending coronary artery,left ventricle,right ventricle,and left lung were significantly lower in DIBH status than in FB status(all P<0.05). The greater DIBH increased the lung volume,the greater the mean heart dose decreased. In FB status,the left breast volume,heart-to-lung volume ratio,distance between the inferior margins of breast and heart,and maximum heart margin distance showed a linear correlation with heart dose. Particularly, the heart-to-lung volume ratio and maximum heart margin distance were independently correlated with heart dose. Conclusions DIBH technique in WBI for left breast cancer after breast-conserving surgery significantly reduces heart and lung doses compared with FB. Changes in lung volume are the basis for improving the relative anatomical location of the heart. The heart-to-lung volume ratio and maximum heart margin distance may provide a reference for DIBH technique.
ABSTRACT
Objective Objective To evaluate the effect of deep inspiration breath-hold technique (DIBH) on the dosimetry of target volume and organs at risk (OARs) in mediastinal lymphoma irradiation.Methods This was a prospectively study and five patients with stage Ⅰ and Ⅱ mediastinal lymphomas were included continuously.The absolute target volume,the absolute OAR doses,and the relative doses to volume were compared between DIBH and free-breathing (FB) scans,based on the principles of the affected site irradiation and the butterfly field.The differences were analyzed using paired t test.Results The median age of these five patients was 30 years.Compared with FB scan,DIBH scan led to significant decreases in the gross tumor volume (GTV)(Δ=29.4 cm3,P=0.006) and the planning target volume (PTV)(Δ=322 cm3,P=0.005) before chemotherapy,while no significant difference in clinical target volume (CTV) was found.Meanwhile,the lung volume of DIBH scan was significantly increased (mean Δ=1456 cm3,P=0.001),while the heart width of DIBH scan was significantly reduced (Δ=1.3 cm,P=0.012),as compared with those of FB scan.The mean doses to the lung and heart were significantly lower in DIBH scan than in FB scan (heart:8.5±4.7 Gy vs.11.6±4.7 Gy,P=0.022;lung:7.6±1.1 Gy vs.11.6±1.4 Gy,P=0.000).The absolute target volume of the heart was significantly reduced at V15 and above in DIBH scan than in FB scan (all P<0.05).Relative doses to volume of the lung and heart were significantly reduced at each dose level (from V5 to V35) in DIBH scan than in FB scan (all P<0.05).Conclusions DIBH technique can significantly reduce PTV,enlarge lung volume,and reduce the mean dose and relative doses to volume of the lung and heart at each level (from V5 to V35) compared with FB scan in mediastinal lymphoma radiation.