The principal goal of stereotactic radiosurgery (SRS) is to provide a method for focal irradiation of target tissue to high doses without increasing normal tissue complication. The results demonstrated the dosimetric merit of the 2.5 mm leaf width MLC system over the 5 mm leaf width system, albeit small, for the investigated range of intracranial SRS targets.Ĭonclusion: The clinical significance of these results warrants further investigation to determine whether the observed dosimetric advantages translate into outcome improvements. The use of collimation optimisation resulted in a decrease in differences between the MLC systems. Dose fall-off was steeper for the 2.5 mm MLC system with an overall median absolute difference ranging from 0.4 to 1.2 mm. The median reduction of normal tissue exposed to ≥100%, ≥50% and ≥25% of the prescription dose ranged from 13.4% to 29.7%, favouring the 2.5 mm MLC system. Results: The median conformity index difference between the MLC systems ranged between 0.8% and 14.2% the 2.5 mm MLC exhibited better dose conformation. Plan evaluation was based on target coverage and normal tissue avoidance criteria. Plan normalisation was such that 100% of the prescription dose covered 95% of the planning target volume. Dose computation was based on the pencil beam algorithm with allowance for tissue heterogeneity. Two collimation strategies, with collimation fixed at 0° or 90° and optimised per arc or beam, were also assessed. Comparative plans, with identical planning parameters, were based on a 5 mm leaf width MLC system.
2.5 mm leaf width plans served as reference. Methods: 68 lesions formed the basis of this study. Objectives: The impact of two multileaf collimator (MLC) systems for linear accelerator-based intracranial stereotactic radiosurgery (SRS) was assessed.
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