目的：測量與比較照野交接技術(field junction)在頭頸部腫瘤併巨大頸部淋巴結的應用。材料和方法：取假體(Alderson Rando phanton)作模擬攝影訂定出照野的中心和範圍，並作電腦斷層攝影取得假體影像。本實驗所要探討的是單一中心照野技術(monoisocentric technique)和交接移動技術(moving junction technique)，並配合上兩種不同的頸部特製填充物(bolus)。一號填充物只用來調整前後徑差別，而二號填充物是用來調整前後徑及兩側徑差別的特製填充物。用單一中心照野技術或交接移動技術再配合上有無填充物，所以共有六種的不同的組合。首先用電腦治療計劃系統(ADAC computer treatment planning system)，模擬各種不同治療方式，去計算出各種治療方式的劑量分佈曲線，以作為評估擺放熱發光劑量計(TLD)的考量。然後，實地模擬各種實際治療情況去照射內含熱發光劑量計的實驗假體各三次，以獲得較接近實際治療所得到的吸收劑量的平均值。結果：經過校正，所有熱發光計量劑的誤差皆在3%以內。不論是單一中心照野技術或交接移動投術，只要配合上頸部特製填充物都可獲得均勻的劑量分佈。但是如果沒有配合頸部特製填充物的話，較薄的頸部會產生不可接受的高劑量區。然而不可避免的，還是有少數區域會有劑量分佈不均的現象，如高劑量區落在前頸淺處及側頸部，低劑量區落在後頸部。不過似乎還是以單一中心照野技術'配合上二號特製填充物，能產生最理想的劑量分佈。回頭比較用TLD實際測量出來和電腦所預測出來的值，發現大部份的誤差不會超過的，然而在某些地方，尤其在照野範周邊緣(-19~-22%)，照野交接處(±9%)及表淺處(-5~-7%)。結論：單一中心照野技術或交接移動技術，配合上良好的頸部特製填充物，可應用於臨床實際治療頭頸部腫瘤併巨大頸部淋巴結的病人，既簡單方便，又有均句的劑量分佈。至於最適合的然而，要配合上良好的頸部特製填充物，才能使劑量分布更為均勻。

Purpose: To probe into junction fields techniques of radiotherapy in head and neck cancer patients who need radical radiotherapy to whole pharyngeal wall and whole neck lymphatics. Material and Methods : We get a simulation film and CT scan image of an Alderson Rando phantom for defining field size and lsocenter, and for computer planning system In this study, we showed dose distribution data of monoisocentric technique and moving junction technique with or without bolus. Two different bolus were used: bolus 1 emphasized only AP depth, bolus 2 emphasized both AP and bilateral depth. So there were six various combinations by either monoisocentric or moving junction with or without bolus. First, isodose distribution by computer planning system was generated to decide where to place TLDs. The average radiation dose in different techniques were obtained by irradiating the phantom packed with TLDs. Results: Both monoisocentric techniques and moving junction techniques with adequate bolus could generate homogenous dose distributions. But if there were no bolus, there was hot area over neck. However there were still uneven dose distribution areas, such as hot areas in anterior superficial neck and lateral neck; cold areas in posterior lower neck. In comparison, monoisocentric technique with bolus 2 tended to create better dose distribution. After comparing data from TLDs and computer planning system, we found most differences were within 4%. However, inconsistency still existed in some locations such as field margins (underestimate 19-22%); junction areas (over/underestimate 9%); superficial areas (underestimate 5-7%). Conclusion: Both monoisocentric techniques and moving junction techniques combined with well-designed bolus can be satisfactorily applied in treating head and neck cancer patients with huge neck lymphadenopathy. There are not only good reproducibili﹒ ty but also good homogeneity. How to choose the optimal technique depends on patients' clinical status and individual hospital equipments. We suggest that the monoisocentric technique is a more convenient technique in junction fields. However, an well designed bolus is also very important to get a good dose distribution.