(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To know the actual dose delivered to the Target and Normal structures in Stereotactic body radiotherapy lung cancer patients.
Methods: Fifteen Lung cancer patients were taken for this study;All patients received a dose of 50 Gy from Unflattend photon beam of 6 MV in 5 fractions of SBRT. Initially, after Treatment plan, patient was setup with lasers in treatment room to match the external fiducial markers on the body of the patient. Cone Beam Computed Tomography (CBCT) performed on all patients before treatment for each fraction and patient position corrected as per shift obtained due to inter-fraction variations.These CBCT images were fused with the planned CT images in TPS and applied the same shifts to the fused CBCT images. PTV and Other Organs at risk (OAR) were edited as per the fused CBCT images in CT for contour in TPS for each fraction. Calculations were performed individually for each fraction on edited CT for contour images in TPS. The mean, maximum and minimum doses received by the planning target volume and mean doses of oesophagus, trachea and maximum dose of spinal cord were evaluated.
Results: Over the whole treatment, most patients experienced Significant deviations in dose and displacement for Spinal cord , trachea and Oesophagus. Compared with the planning values, the mean dose for PTV was -5% % to -0.2 %, for trachea was -20 % vs +20 % and for Esophagus was 2% to >20 %. The dose maximum in spinal cord changes from 0.2 % to 10%. For PTV, deviations in maximum dose and minimum dose were observed; whereas mean dose variations observed less than 3%.
Conclusion: This study shown the actual dose delivered to the PTV and normal structures while localization was performed to optimize the target coverage in daily IGRT corrections.
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