日本放射線技術学会 = Japanese Society of Radiological Technology
抄録
目的: 高精度放射線治療に用いられる6軸寝台の平行移動･回転における3次元的位置精度評価法を提案し,精度を測定する. 方法:レーザで示される座標軸上に2台の高精解像度デジタルカメラを設置し,6軸寝台に固定したピン先端を2方向から撮影することで3次元的な位置座標を測定する. 6軸寝台を各軸平行移動･回転させたときのピン先端座標と設定した寝台移動量 /角度によって理論的に計算されるピン先端座標との差を誤差とした. 結果: Z軸方向平行移動のZ軸座標値の標準偏差が±0.24 mmと6軸寝台の表示最小単位の0.1 mmを超えたが,その他の誤差の平均値および標準偏差は0.1 mm以下であった. X軸回転では回転原点の変位が確認された. 結語:ピン設置の不確かさ,カメラの設置誤差,マニュアル測定によるばらつき,これらによる測定結果への影響は0.1 mmを超えず, 6軸寝台による平行移動･回転時の 3次元的位置精度の評価が出来た. In this study, we proposed and evaluated a positional accuracy assessment method with two high-resolution digital cameras for add-on six-degrees-of-freedom radiotherapy (6D) couches. Two high resolution digital cameras (D5000, Nikon Co.) were used in this accuracy assessment method. These cameras were placed on two orthogonal axes of a linear accelerator (LINAC) coordinate system and focused on the isocenter of the LINAC. Pictures of a needle that was fixed on the 6D couch were taken by the cameras during couch motions of translation and rotation of each axis. The coordinates of the needle in the pictures were obtained using manual measurement, and the coordinate error of the needle was calculated. The accuracy of a HexaPOD evo (Elekta AB, Sweden) was evaluated using this method. All of the mean values of the X, Y, and Z coordinate errors in the translation tests were within ﾂｱ0.1 mm. However, the standard deviation of the Z coordinate errors in the Z translation test was 0.24 mm, which is higher than the others. In the X rotation test, we found that the X coordinate of the rotational origin of the 6D couch was shifted. We proposed an accuracy assessment method for a 6D couch. The method was able to evaluate the accuracy of the motion of only the 6D couch and revealed the deviation of the origin of the couch rotation. This accuracy assessment method is effective for evaluating add-on 6D couch positioning.
高解像度デジタルカメラを用いた高精度放射線治療用6軸寝台の位置精度測定法の検討
ME-PR-TAKEMURA-A-67_1174.pdf
(1.08MB)
