PROBLEM TO BE SOLVED: To allow a dose distribution check before implementing radiotherapy to be simply carried out.SOLUTION: A plurally of radioactive-ray irradiation range detectors 1 are prepared that has a polymer gel sheet internally arranged, is formed of transparent resin, and is composed of a transparent holding member having a stacking mechanism part for arranging the radioactive-ray irradiation range detector with the radioactive-ray irradiation range detectors vertically stacked. Then, in a state where a plurality of radioactive-ray irradiation range detectors 1 is stacked by the stacking mechanism part, radioactive-ray is irradiated. In this case, the polymer gel sheet gets cloudy in responce to an irradiation state of the radioactive-ray. The radioactive-ray irradiation range detector 1 getting cloudy is checked by a visual observation, or the plurality of radioactive-ray irradiation range detectors 1 are read by a scanner with the radioactive-ray irradiation range detectors separated one by one, and from the cloudy state of each of the read polymer gel sheets, a detection of the radioactive-ray irradiation state is carried out.SELECTED DRAWING: Figure 6COPYRIGHT: (C)2016,JPO&INPIT【課題】放射線治療を行う前の線量分布確認が簡単に行えるようにする。【解決手段】ポリマーゲルシートが内部に配置され、透明樹脂より成形され、上下に重ねて配置するためのスタッキング用機構部を有する透明保持部材よりなる放射線照射範囲検出器1を複数個用意する。そして、複数個の放射線照射範囲検出器1をスタッキング用機構部で重ねた状態で、放射線を照射する。このとき、ポリマーゲルシートは、放射線の照射状態に対応して白濁する。この白濁した放射線照射範囲検出器1を目視で確認する。あるいは、複数の放射線照射範囲検出器1を、1個ごとに分離した状態でスキャナーで読み取り、読み取ったそれぞれのポリマーゲルシートの白濁状態から、放射線照射状態の検出を行う。【選択図】図6
