(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: Deep Inspiration Breath Hold(DIBH) during radiotherapy is an effective approach to reduce the irradiated heart volume for left-breast cancer patients.The range of motion during breath hold(BH) has been investigated in our previous study.Here,we report its dosimetrical impact calculated in the treatment planning system(TPS) according to the motion detected using a surface guided radiotherapy(SGRT) solution during DIBH manipulated by Active Breath Control device.
Methods: Five patients received 3D conformal treatments were randomly selected.Our previous study using CatalystHD(C-RAD,Uppsala,Sweden)has showed the motion range(2.5mm-13.1mm) of the chest wall.To evaluate the dosimetrical impact,new isocenters for four patients were created quantitatively in A-P direction compared with the original plan,and recalculated in Pinnacle TPS using collapsed cone convolution algorithm.The fifth patient’s plan was recalculated using shifted isocenters beam by beam according to the average motion of every BH measured in a real fraction.The mean and maximum dose of target and OAR were statistically analyzed.
Results: All patients received tangential radiation to the left breast/chest wall(typical doses 180cGyx28 or 266cGyx16).Compared with the original plan, the average percentage differences of mean dose(APDMD) to target are -1.03%,-1.74%, -2.17% and -2.37% for the motion of 3mm, 6mm, 9mm, and 12mm,respectively.The APDMD to heart and left-lung are 5.97%, 13.91%, 22.16%, 32.12%, and 7.19%, 15.29%, 22.43%, 28.98% for the motion of 3mm, 6mm, 9mm,and 12mm,respectively.Linear regression functions of motion have been established for mean and maximum heart dose.The fifth patient’s plan calculated with the real motion shows an increase of 16.14% and 40.65% in mean heart dose and maximum heart dose,respectively.
Conclusion: The dosimetrical impact of mm-level motion during DIBH on heart is not negligible.It should be monitored carefully to further prevent the development of late cardiac complications.In addition,the surface mapping system can be used as a sound solution to monitor the motion during DIBH for left-breast cancer patients.
Keywords
Breast, Surface Matching, Dosimetry
Taxonomy
Not Applicable / None Entered.
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