Alignment Accuracy RS Patients Treated On True Beam STx: Assessment of Online and Offline 6D Couch Shifts
N Mail*, F Li, M diMayorca, D Clump, R Lalonde, M Huq, UPMC Shadyside Hospital, Pittsburgh, PA
Presentations
PO-GePV-M-166 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
ePoster Forums
Purpose: To evaluate the geometric alignment accuracy for Brain SRS patients by direct comparison of the 6D couch shifts from online and offline CBCT-CT image fusions. The mean 6D couch shift differences and the percentage of patients aligned within the safe allowable 6D couch shift are reported.
Methods: 264 intracranial stereotactic radiosurgery (SRS) cases were randomly selected for the assessment of alignment accuracy through the 6D couch shift applied during online and offline CBCT-CT fusion. Online registration was performed at treatment by therapists and approved by a physician and a physicist. Offline registration was performed by physicists and thoroughly reviewed. The mean 6D shift difference between online and offline fusion was assessed. Also, the percentage of the patient population aligned online within one-millimeter translational range and one degree rotation of the offline registration is reported.
Results: The mean difference between online and offline 6D couch shift was 0.20±0.31, 0.20±0.35, and 0.22±0.39 mm along the X, Y, and Z directions, respectively. Similarly, the mean shift couch angle was 0.24±0.31, 0.21±0.35, and 0.22±0.39 degrees for Pitch, Yaw, and roll, respectively. The percentage of patients aligned in the range of 0-1 mm was 97.1, 97.3, and 97.7% along X, Y and Z directions, respectively. Similarly, 97.3, 97.4 and 98% of the patient population were aligned in 0–1-degree range along the pitch, Yaw, and roll directions.
Conclusion: Online and offline 6D couch shifts were less than 1 mm and 1 degree for approximately 97% of the patient population. The range of the setup uncertainties in this study was reasonably low because of the consistency followed in online and offline CBCT-CT auto registration using rigid skull only. Stereotactic radiosurgery (SRS) can be planned and delivered on a True Beam within sub millimeter and sub degree alignment accuracy.Keywords: Online-fusion, offline-fusion, Brain-SRS, True-Beam, 6D-couch-shif
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