Quality Assurance Procedure for Synchrony Respiratory Tracking System of CyberKnife System

本品保驗證程序之目的，爲當腫瘤器官因呼吸而造成一規律移動下，驗證電腦刀呼吸同步追蹤系統(Synchrony respiratory tracking system)之治療準確度，並評估電腦刀呼吸同步追蹤系統於臨床治療上之貢獻。電腦刀立體定位放射手術系統(CyberKnife stereotactic radiosurgery system)，乃由一部6MV直線加速器裝載於一個具6維自由度之機械手臂上，一組影像導引系統(TLS)，一個擁有6維校正功能之治療床，與一組紅外線呼吸同步追蹤系統所組成。原廠之移動假體(Motion phantom)可模擬病患的呼吸運動，同時執行胸腹部表面運動與內部器官移動兩種不同的運動模式。原廠驗證片(Gafchromic dosimetry film-media type MD-55)與原廠球型立方體(Ball-cube)，供例行性品保驗證程序使用。紅外線同步感應器(IR-synchrony camera array)與紅外線追蹤標記(IR-tracking markers)；可偵測患者因呼吸造成之胸腹部體表處之運動。以移動假體(Motion phantom)模擬病患的呼吸運動，並執行電腦刀呼吸同步追蹤系統，將治療計畫以全系統測試(End-to-End test)實際執行於移動假體電腦刀呼吸同步追蹤系統例行之品保程序，在執行電腦刀呼吸同步追蹤系統時，其準確度誤差(total targeting error)皆小於1.5 mm。依據先前品保測試數據，甚至皆小於1 mm。三次品保驗證程序所得之整體準確度誤差，相較於原廠訂定之品保容許限值(<1.5 mm)，以t-test統計分析結果，p值小於0.005(P=0.0016)，顯見品保驗證結果，明顯小於原廠訂定之品保容許限值。在臨床治療上與執行呼吸同步追蹤系統品保驗證程序時，影響整體準確度誤差的因素，分別爲機械因素與人爲因素。例行之品保驗證程序顯示，電腦刀之呼吸同步追蹤系統可降低呼吸運動的影響至理想程度，確實可有效地補償腫瘤因呼吸運動而造成的位移誤差。
The purpose of this quality assurance procedure is to the treatment accuracy for Synchrony Respiratory Tracking System of CyberKnife system, This procedure can give us dose delivery accuracy estimation in organ moving in the clinical treatment. The CyberKnife system includes a 6MV medical linear accelerator mounted on a robotic arm, a target locating system, a 6D automatic motion couch, and an infrared Synchrony Respiratory Tracking System Motion phantom can simulate patients' breathing cycle which includes two kinds of movements, abdomen surface motion and inside organ motion, Film (Gafchromic dosimetry film-media type MD-55) and ball-cube are used for the routine procedure of quality assurance, IR-synchrony camera array and IR-tracking markers can monitor patient's chest and abdomen surface motion during respiratory cycle. The results of End to End test could give us the error estimation of this system. The accuracy error (total targeting error) of quality assurance procedure for Synchrony Respiratory Tracking System of CyberKnife system must be smaller than 1.5 mm. The data of our quality assurance procedure is smaller than 1 mm. The total targeting error of the system with this QA procedure is obviously smaller then the standard value (p value of the t-test is smaller then 0.005 with P=0.0016). Mechanical error and personal technique may affect the accuracy of the Synchrony Respiratory Tracking System. The routine procedure of quality assurance shows, the Synchrony Respiratory Tracking System of CyberKnife system can reduce the inf1uence of breath to ideal and can compensate the displacement error causing by breathing motion efficiently.