Abstract
The optimal leaf-margin of micro-multileaf collimators in stereotactically-guided conformal treatment was investigated. The margin size of 0-, 1-, 2-, and 3 mm were evaluated for the non-coplanar static conformal beam plan with 6 fields (SCB) and the dynamic arc plan with 5 arcs (DA) about 4 intracranial tumors with various shapes and volume. Non-targeted normal tissue volume irradiated 90% or more, 80% or more, 60% or more, and 40% or more of prescription doses increased straightforwardly as increasing the margin size. The doses cover 95% of the volume of the planning target volume (PTV)(D95) of 0-, 1-, 2-, and 3-mm margin plans were 87-91%, 91-93%, 92-94%, and 92-95% of prescription doses, respectively. Conformity indices of 0-, 1-, 2-, and 3-mm margin plans were 1.1-1.5, 1.2-1.5, 1.2-1.7, 1.4-1.9, respectively. Homogeneity indices of 0-, 1-, 2-, and 3-mm margin plans were 1.2-1.5, 1.2-1.3, 1.1-1.2, 1.1-1.3, respectively. There were no significant differences of planning results between SCB and DA. From the results, a leaf-margin of 1 mm is optimal, regardless of PTV shapes. A leaf-margin of 0-mm is also acceptable, and it is useful for lesions adjacent to organs at risk.
