PROBLEM TO BE SOLVED: To provide a multileaf collimator for employing both broad irradiation and high resolution irradiation.SOLUTION: The multileaf collimator includes: pairs of leaves 2 configured to arrange, in the direction of thickness tL, a plurality of a pairs of leaves 1 whose end faces 1Le and 1Re are disposed so as to oppose to each other a drive mechanism 4 for driving each leaf plate of the pairs of the leaves 2 in the direction close to or away from each opposing leaf plate and a drive mechanism 5 for driving the pairs of the leaves 2 in the direction of the thickness tL. In at least a pair of leaves 1(w) of the pairs of the leaves 1, the opposing end face of each leaf plate is formed stepwise when viewed from the direction of the thickness tL so that a distal end of the each leaf plate overlaps to each other, viewed from an irradiation direction of particle beams, when driving the leaf plates in a direction close to each other. In at least one leaf plate, a cutout portion is also formed on the end face at the most distal end toward the other leaf plate of the stepwise end faces.COPYRIGHT: (C)2012,JPO&INPIT【課題】ブロード照射と高分解能の照射を両立するためのマルチリーフコリメータを得ることを目的とする。【解決手段】端面1Le、1Reが互いに対向するように配置したリーフ対1を厚みtL方向に複数並べたリーフ対群2と、リーフ対群2のリーフ板のそれぞれを、対向するリーフ板に対して接近または離反方向に駆動させるリーフ板駆動機構4と、リーフ対群2を厚みtL方向に駆動するリーフ対群駆動機構5と、を備え、複数のリーフ対1のうち少なくとも1つのリーフ対1(w)では、リーフ板どうしを接近方向に駆動させたときに、粒子ビームの照射方向から見てそれぞれのリーフ板の先端が相互に重なるように、それぞれのリーフ板の対向する端面が厚みtL方向から見て段差状をなし、かつ、少なくとも一方のリーフ板には、段差状をなす端面のうち、他方のリーフ板に向かって最先端となる端面に切欠き部が形成されている。【選択図】図1
