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CyberKnife® M6™: Peripheral dose evaluation for brain treatments.
Summary
Peripheral dose (PD) in brain stereotactic radiotherapy (SRT) is reduced with the Iris™ collimator. A new model accurately estimates PD without in vivo measurements, aiding treatment optimization.
Area of Science:
- Medical Physics
- Radiotherapy
- Radiation Oncology
Background:
- Stereotactic radiotherapy (SRT) for brain tumors requires precise dose delivery.
- Understanding peripheral dose (PD) to healthy tissues is crucial for minimizing side effects.
- CyberKnife M6™ Robotic Radiosurgery System is a common platform for SRT.
Purpose of the Study:
- To evaluate the peripheral dose (PD) in brain SRT using the CyberKnife M6™ system.
- To develop and validate a model for estimating PD before treatment.
- To compare the effectiveness of different collimator types on PD.
Main Methods:
- Peripheral dose was measured using thermoluminescent dosimeters on an anthropomorphic phantom.
- Measurements assessed the influence of distance, collimator type (fixed vs. Iris™), and aperture size.
- A predictive model for PD was developed by fitting functions to measurement data.
- In vivo measurements were conducted on 30 patients to validate the model.
Main Results:
- Peripheral dose was lower with the Iris™ collimator compared to the fixed collimator.
- In vivo measurements showed an average thyroid dose of 55mGy.
- The developed model demonstrated a low average relative difference (3.4%) compared to in vivo doses for various organs.
Conclusions:
- The Iris™ collimator significantly reduces thyroid PD in brain SRT compared to fixed collimators.
- The proposed model enables accurate estimation of PD without the need for in vivo measurements.
- This predictive method can aid in optimizing treatment planning to minimize radiation exposure to healthy tissues.
