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The Analysis of Positioning Accuracy for Frameless Noncoplanar Stereotactic Radiosurgery Treatment Using Optical Surface Monitoring System

S Wang1*, X Qian2 , Y Ma3 , (1) Department of Radiation Oncology, Saint Alphonsus Cancer Care Center, Boise, ID, (2) Department of Radiation Oncology, Stony Brook University Hospital, Stony Brook, NY, (3) Department of Radiation Oncology and Oncology Area of the CHU de Quebec Research Center, Hotel-Dieu de Quebec, Quebec, Canada


(Sunday, 7/14/2019) 4:30 PM - 5:00 PM

Room: Exhibit Hall | Forum 6

Purpose: Stereotactic radiosurgery (SRS) has evolved from frame-based approaches to frameless, and noncoplanar field is commonly used for linear accelerator based SRS to achieve a good dose conformity. The aim of this study is to assess the patient positioning accuracy for frameless noncoplanar SRS treatment by using optical surface monitoring system (OSMS).

Methods: A frameless SRS mask was fabricated for each patient immobilization. The OSMS is used to detect and reconstruct the skin surface before and during the treatment. The positioning accuracy with OSMS for frameless noncoplanar SRS treatment for 20 patients was analyzed. Patient position was compared and validated using cone beam computed tomography (CBCT) which has often been considered as the "gold standard" in a rigid transformation with 6 degrees of freedom of lateral, longitudinal, vertical, rotation, roll, and pitch.

Results: Patient positioning analysis showed that the average accuracy with OSMS was 0.215, 0.375 and 0.25 mm in respective vertical, longitudinal and lateral direction, and 0.19, 0.13 and 0.23° in respective rotation, roll, and pitch, which achieves agreement of <1 mm and 0.5° for SRS tolerance.

Conclusion: The assessment demonstrated that the OSMS can ensure accurate and precise positioning during frameless noncoplanar SRS treatment. Compared to other x-ray based image guided radiotherapy systems, the OSMS does not produce any additional ionizing radiation.


Patient Positioning, Optical Imaging, Stereotactic Radiosurgery


TH- External beam- photons: Motion management (intrafraction)

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