Abstract
This study details a validation process for linear accelerator‐based treatment of trigeminal neuralgia using HD‐MLC field collimation. Nine trigeminal neuralgia treatment plans utilizing HD‐MLC were selected for absolute dose measurement at isocenter using a commercial scintillating detector in an anthropomorphic phantom. Four plans were chosen for film dosimetry measurements in each of the three principal planes to assess spatial dose distribution agreement with the treatment planning system. Additionally, trajectory log analysis for each treatment field in the nine cases was performed to assess mechanical positioning accuracy of the MLC system during delivery. Scintillator and film measurements both revealed mean dose agreement at isocenter of better than 3% while FWHM of the 2D dose distribution in each plane showed agreement between plan and measurement within 0.2 mm. Analysis of log files revealed a maximum MLC leaf positioning error of 0.04 mm across 178 treatment fields. In conjunction with a quality‐controlled treatment delivery methodology, an appropriately commissioned treatment planning system can be used for accurate and clinically appropriate design of trigeminal neuralgia treatment plans utilizing HD‐MLC.
Highlights
After more than five decades of development, stereotactic radiosurgery (SRS) is a widely available treatment technique for intracranial tumors using both dedicated units like Gamma Knife and CyberKnife, as well as linear accelerators.[1]
In this paper we report results for: (a) verification of multi-leaf collimating (MLC) beam shapes, (b) total dose delivered to representative treatment volume, and (c) the shape of the cumulative dose distribution
Nine clinical trigeminal neuralgia treatment plans were selected for verification testing
Summary
After more than five decades of development, stereotactic radiosurgery (SRS) is a widely available treatment technique for intracranial tumors using both dedicated units like Gamma Knife and CyberKnife, as well as linear accelerators (linacs).[1] SRS uses finely collimated beams to deliver ablative doses in a single or few fractions to treat benign and malignant tumors in the brain. SRS delivery on linacs became possible only after refinements in mechanical precision of the delivery system. Investigators of linacs as a radiosurgery tool constructed special hardware that attached to the accelerator and allowed a higher degree of precision to be achieved than was possible with standard linac treatments.[2] The use of a tertiary collimating system with circular apertures closer to the patient on a linac reduces both the beam penumbra and the susceptibility to positioning error.[3] Modern linacs for SRS delivery from vendors come with both circular collimator attachments and a computer-controlled multi-leaf collimating (MLC) system which is integrated in the head of the machine to shape the beam. The user has the option of using either beam shaping device depending on the application
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