如何使用模擬攝影機之擋影托盤(shadow tray)确認擋塊位置

How to Use the Shadow Tray of the Simulator to Verify Block Position

何聖佑(Sheng-Yow Ho) ； 鄭秀成(Shiu-Chen Jeng) ； 雷德(Louis T. Lui)

《放射治療與腫瘤學》 2卷3期 (1995/09) Pp. 261-266

https://doi.org/10.6316/TRO/199502(3)261

摘要

在放射治療技術上，一般皆以照野片(portal film)而來確認治療位置及驗證製作的遮擋鉛塊對重要器官和腫瘤外正常組織的保護情形。但照野片的品質，常不能滿足精確的要求。
本科現擁有Theratron 780c鈷六十遠隔治療機及Toshiba LX-40A 模擬攝影機。但Toshiba LX-40A原廠所附之擋影托盤與治療機STD(source-axis-distance)及擋塊托盤(block tray)大小不符。故設計訂製符合需要的擋影托盤，幷測量其準確性，發現STD與原設計短少0.4cm。故於等中心軸SAD(source-axis-distance)80cm 處，造成底片上擋塊陰影較實際約放大0.8%。
將製作好的擋塊，直接置於模擬攝影機的擋影托盤下確認，有以下優點：(l)擋塊位置易確認。即使有微小誤差，皆清晰可辨。(2)患者可减少因擋塊製作錯誤，而重覆照野片的輻射暴露。(3)確保治療品質。(4)操作方便。

關鍵字

放射治療技術 ； 模凝攝影機 ； 品質保證

並列摘要

The primary purpose of portal film is to verify the treatment volume and shielding block position under the actual condition of treatment. However, the quality of portal film is rarely satisfactory.
We have a Theratron 780c Co-60 teletherapy machine and a Toshiba LX-40A simulator in our department. However, the orginal specification of the size and STD (source-tray-distance) of the shadow tray in the simulator are totally different from those of the Co-60 unit. There fore we have to modify the shadow tray to make it suitable to our daily practice. The STD of the modified shadow tray is only 0.4cm shorter than our original design. This result in about 0.8% magnifying imaging of block shadow on films in the position of SAD=80cm. With the use of the modified shadow tray, we can verify the shielding block in the simulator directly with the following advantages: (1) clear anatomical field boundaries to prevent geographic marginal miss. (2) the avoidance of the repeat portal films due to wrong position of shielding block.(3) therapeutic quality assurance. (4) user-friendly.

並列關鍵字

Radiotherapeutic technique ； Simulator ； Quality assurance