Dosimetric effects of rotational offsets in stereotactic body radiation therapy (SBRT) for lung cancer.
To quantitatively evaluate dosimetric effects of rotational offsets in stereotactic body radiation therapy (SBRT) for lung cancer. Overall, 11 lung SBRT patients (8 female and 3 male; mean age: 75.0 years) with medially located tumors were included. Treatment plans with simulated rotational offsets of 1°, 3°, and 5° in roll, yaw, and pitch were generated and compared with the original plans. Both clockwise and counterclockwise rotations were investigated. The following dosimetric metrics were quantitatively evaluated: planning target volume coverage (PTV V100%), max PTV dose (PTV Dmax), percentage prescription dose to 0.35cc of cord (cord D0.35cc), percentage prescription dose to 0.35cc and 5cc of esophagus (esophagus D0.35cc and D5cc), and volume of the lungs receiving at least 20Gy (lung V20). Statistical significance was tested using Wilcoxon signed rank test at the significance level of 0.05. Overall, small differences were found in all dosimetric matrices at all rotational offsets: 95.6% of differences were < 1% or < 1Gy. Of all rotational offsets, largest change in PTV V100%, PTV Dmax, cord D0.35cc, esophagus D0.35cc, esophagus D5cc, and lung V20 was - 8.36%, - 6.06%, 11.96%, 8.66%, 6.02%, and - 0.69%, respectively. No significant correlation was found between any dosimetric change and tumor-to-cord/esophagus distances (R(2) range: 0 to 0.44). Larger dosimetric changes and intersubject variations were observed at larger rotational offsets. Small dosimetric differences were found owing to rotational offsets up to 5° in lung SBRT for medially located tumors. Larger intersubject variations were observed at larger rotational offsets.
['Yang|Yun|Y|', 'Catalano|Suzanne|S|', 'Kelsey|Chris R|CR|', 'Yoo|David S|DS|', 'Yin|Fang-Fang|FF|', 'Cai|Jing|J|']
D000368:Aged D000369:Aged, 80 and over D016477:Artifacts D006801:Humans D008175:Lung Neoplasms D008875:Middle Aged D056888:Patient Positioning D016634:Radiosurgery D011879:Radiotherapy Dosage D011880:Radiotherapy Planning, Computer-Assisted D015203:Reproducibility of Results D012399:Rotation D012680:Sensitivity and Specificity D016896:Treatment Outcome
Rotation Lung SBRT 6D correction IGRT