| Abstract: | 癌症病患因呼吸時引起的器官和腫瘤位移對放射治療準確性的影響，是治療成敗的重要因素之一。即時位置管理呼吸同步追蹤調控系統簡稱為呼吸調控瞄準器(Real-Time Position Management Respiratory Gating System, RPM)是一種能控制因呼吸動作所引起的位移變數的新方法。這系統能減少治療的範圍和對正常組織的傷害。去年本科引進目前台灣第一部即時位置管理呼吸同步追蹤調控系統。本文主要目的是要評估本系統的可靠性及準確度。初步探討點是評估本系統紅外線雷射(Infra-red laser system)及CCD攝影機的追蹤能力及準確性。研究結果發現本系統追蹤能力很好。僅次我們使用本系統與31位罹患不同部位腫瘤的病患,實施呼吸運動資料的收集，並利用呼吸運動方程式做呼吸模擬。結果顯示，在肺部正面側面移動平均為8.73毫米(mm.)，肺部上下為8.67 mm.；在上腹部正面側面移動平均為10.72 mm.，上腹部上下為13.83 mm。經過50%的呼吸調控範圍後，上、中肺部之側面移動減少約五分之二的移動範圍，比起上下移動為二分之一，下肺部和上腹部之側面移動減少約二分之一的運動範圍而上下移動減少少於50%。患者的平均呼吸頻率為 胸部為3.13秒而在腹部為3.20秒。在呼吸模擬運動方程式中移亦可發現所用方程式非常符合呼吸運動方程式。 因此，呼吸運動所造成的器官和腫瘤位移在立體三度空間的環境中是不可被忽視的，並有可能影響腫瘤是否得全愈。呼吸調控瞄準器確實可減少治療範圍，對腫瘤能提高治療劑量，增加腫瘤控制率(tumor control probability, TCP)，而對正常組織能減少傷害，減少正常組織併發正率(normal tissue complication probability, NTCP)
Organ motion in the body is one of the major factors that can affect the success or failure of a radiation therapy regimen in most cancer patient. Respiratory gating system is a relatively new and revolutionary technique used to control motion uncertainty brought about by the natural movement of the body parts especially in area immediately above and below the diaphragm. The technique was originally developed for use in radiotherapy of tumors that are located in region with constant motion in conjunction with the respiratory cycle, but later it can also be use to control motion artifacts in diagnostic imaging to make CT scan and MRI more accurate in delineating the actual size and location of the tumors. In our radiation oncology department, we have commissioned a new Real-Time Position Management Respiratory Gating System (RPM) last year. In this study, I would like to assess the accuracy and efficacy of the system in minimizing the motion variable brought about by the respiratory cycle. We planned and use the system in 31 consecutive patient scheduled for treatment of tumor in the supra- and infra- diaphragmatic region. Results shows that the anterior-posterior movement of the chest wall has an average value of 8.73 mm., while in the superior-inferior direction it was 8.67 mm.; on the abdominal side the anterior-posterior movement has an average value of 10.72 mm, while in the superior-inferior direction it was 13.83 mm. With a duty cycle of 50%, the movement in the upper and middle part of the chest wall was decreased by 2/5 the original displacement in the anterior-inferior direction, while in the superior-inferior direction, the decrease was roughly 1/2, while in the lower chest wall and upper abdomen, it was around 50% of the original displacement of the planning target volume (PTV) in the anterior-posterior direction and less than 50% in the superior-inferior direction. The average breathing cycle last around 3.13 seconds in the upper chest region and 3.20 seconds in the abdominal region. The motion data in the superior-inferior direction correlated quite well with that for the anterior-posterior direction, in the upper chest wall region, while in the lower abdominal region, there was no good correlation, thus we would be cautious in doing extrapolative work in the abdominal region specially in relation to data obtain in the anterior-posterior direction as compare to the superior-inferior direction. In the study we can see that the motion displacement for normal and tumor region in a cancer patient, is a very significant factor to consider in treatment planning, which may determine the success or failure of the treatment. The system was able to decrease the margin around the tumor, which translate into a better conformality of the treatment plan which would allow us to do more dose escalation to improve the tumor control probability (TCP) and decrease the normal tissue within the planning target volume (PTV), which translates into less normal tissue complication probability (NTCP). |
