PROBLEM TO BE SOLVED: To provide a multileaf collimator observation device and a radiotherapy apparatus which are easily and higly precisely observing the shape of a leaf opening of a multileaf collimator (MLC).SOLUTION: The observation device which has a plurality of movable leaves 31, is rotatably held around an axis of a treatment beam BM to observe the MLC 3 and specifies an irradiation field of radiation from a radiation source, is provided with: an imaging part 4 which is provided on the radiation source side of the MLC 3 to pick up the leaf opening shape of the MLC 3 a rotational angle detection part 5 to detect a rotational angle around an irradiation axis of the MLC 3 and a data processing part DP to store, calculate, and display data. The data processing part DP includes: a coordinate transformation means 6 for performing coordinate transformation of the leaf opening shape of treatment plan data preliminarily stored based on the rotational angle detected by the rotational angle detection part 5 a visual collation means 7 for displaying the reference leaf opening shape to which the coordinate transformation is performed and the actual leaf opening shape picked up by the imaging part for visual collation and an image processing collation means 8 for collating the reference leaf opening shape and the actual leaf opening shape by image processing.COPYRIGHT: (C)2011,JPO&INPIT【課題】マルチリーフコリメータ(MLC)のリーフ開口形状を容易に精度良く確認できるマルチリーフコリメータ観察装置および放射線治療装置を提供する。【解決手段】本発明は、複数の可動リーフ31を有し、治療ビームBMの軸周りに回転自在に保持され、線源からの放射線の照射野を規定するMLC3を観察するための観察装置であって、MLC3の線源側に設けられ、MLC3のリーフ開口形状を撮像するための撮像部4と、MLC3の照射軸周りの回転角を検出するための回転角検出部5と、データの保存、演算および表示を行うためのデータ処理部DPとを備える。データ処理部DPは、回転角検出部5で検出された回転角に基づいて予め保存された治療計画データのリーフ開口形状を座標変換する座標変換手段6と、座標変換された参照リーフ開口形状および撮像部で撮像された実リーフ開口形状を目視照合のために表示する目視照合手段7と、参照リーフ開口形状および実リーフ開口形状を画像処理により照合する画像処理照合手段8とを含む。【選択図】図1
