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Quantifying the Sensitivity of Target Dose on Intrafraction Displacement in Intracranial Stereotactic Radiosurgery
Jannie Schasfoort1, Mark Ruschin2, Arjun Sahgal2
1Gamma Knife Center Tilburg, Department of Medical Physics, Elisabeth-TweeSteden Hospital, Tilburg, The Netherlands.
Practical Radiation Oncology
|December 20, 2021
Summary
Mask-immobilized stereotactic radiosurgery (SRS) requires understanding intracranial tumor motion tolerance. This study quantified dose sensitivity to motion, finding that target volume and location significantly impact accuracy, suggesting patient-specific thresholds for optimal treatment.
Area of Science:
- Medical Physics
- Radiation Oncology
- Neurosurgery
Background:
- Mask-immobilized stereotactic radiosurgery (SRS) with gating is an emerging technique.
- The acceptable level of intracranial tumor motion during SRS to maintain dosimetric goals is not well-defined.
Purpose of the Study:
- To quantify the sensitivity of stereotactic radiosurgery (SRS) target dose to intracranial tumor motion.
Main Methods:
- Simulated translational and rotational tumor movements using nose-marker displacements (±0.5-1.5 mm) in clinical SRS plans.
- Quantified effects on D99 (minimum dose to 99% of target) and target coverage using mixed-effect modeling, considering displacement, target volume, and location.
Main Results:
- Translational motion had a greater impact on dose metrics than rotational motion.
- Pitch rotations affected dose more than yaw rotations.
- For mean target volume, 1.5 mm translational displacement reduced D99 by 13.0% and coverage by 4.4%; 1.5 mm pitch rotation reduced D99 by 6.9% and coverage by 1.9%.
Conclusions:
- Tumor dose sensitivity to motion is dependent on target volume and location.
- Patient- and target-specific motion thresholds can optimize the balance between dosimetric accuracy and treatment time.
