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SU-E-J-59: Dual Imaging Guided Localization System for Spine Radiosurgery.
Medical Physics
|May 19, 2017
Summary
This study compared ExacTrac and cone beam computed tomography (CBCT) for spine radiosurgery localization. Both systems showed systematic differences, leading to established tolerance levels for accurate patient positioning.
Area of Science:
- Medical Physics
- Radiation Oncology
- Radiosurgery Imaging
Background:
- Accurate patient localization is critical for effective spine radiosurgery.
- ExacTrac and cone beam computed tomography (CBCT) are commonly used imaging systems for treatment verification.
Purpose of the Study:
- To compare the localization accuracy of ExacTrac and CBCT systems in single fraction spine radiosurgery.
- To evaluate the inherent systematic deviations of both ExacTrac and CBCT for spine radiosurgery.
Main Methods:
- ExacTrac and CBCT systems were evaluated using the linac isocenter as a reference.
- A phantom study and a patient study (51 patients) were conducted to quantify displacement discrepancies.
- Discrepancies were measured in four dimensions (3 translations, 1 rotation) and analyzed using a Student's t-test.
Main Results:
- Phantom and patient studies showed systematic differences of approximately 1 mm in the anterior/posterior and superior/inferior directions between ExacTrac and CBCT.
- Statistical significance was found for discrepancies in the A/P and S/I directions (p < 0.000).
- Angular differences were minimal, and a procedure was developed to mitigate systematic discrepancies.
Conclusions:
- The observed systematic differences between ExacTrac and CBCT justify established patient localization tolerance levels.
- A 2 mm translation and 1-degree rotation tolerance is appropriate for single fraction spine stereotactic radiosurgery (SRS) treatment.
