Application and set-up error of deep inspiration breath-hold (DIBH) technique for whole breast irradiation in left breast cancer
2018
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 DIBH.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 (Σ) and random setup error (σ) in the left-right (x), superior-inferior (y) and anterior-posterior (z) direction were Σx 1.9 mm, Σy 2.1 mm, Σz 2.0 mm, σx1.3 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.
Key words:
Breast neoplasm; Radiotherapy dosage; Deep inspiration breath-hold technique; Setup error
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