利用放射線治療頭頸部腫瘤時，常常因腫瘤長的位置比較靠近表面區域，使得治療計畫會試著以較強的光子通量去補足因皮膚免除效應而劑量不足的部分，這高強度的輻射劑量反而會造成較高的皮膚劑量，造成頭頸部癌症病患在治療後會有明顯的皮膚效應產生。本實驗利用兩種不同型號之金氧半場效電晶體(MOSFET) ，TN-502RD與TN-502RDM，測量MOSFET 的基本特性後，並在直線加速器與斷層治療機下使用擬人假體測量頭頸部表面劑量，所得實際測量值與治療計劃系統之計算值相比。實驗結果顯示，MOSFET 在劑量依存性、能量依存性、劑量重現性和劑量率依存性沒有明顯的依存性問題，但在角度依存性上，在空氣中測量最大差異值達36%，TN-502RD比TN-502RDM 更具有角度依存性上的問題。在頭頸部表面劑量測量中，斷層治療機之實際測量值與電腦治療計畫計算值差異較小為-0.9 %~5 %，在直線加速器之實際測量值與電腦治療計畫計算值差異為2.1 % ~ 46.1 %，顯示出斷層治療機之電腦治療計畫計算值較為接近實際測量值。

Many tumors of head and neck cancer patients are located near the surface area in radiation therapy. In order to compensate the underdose due to skin sparing effect, the treatment planning system will apply the higher fluence to satisfy the dose constrains of the target, and therefore cause the obvious skin reaction after radiation therapy. This work used two types of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), TN-502RD and TN-502RDM, measuring the dose linearity, energy dependence, angular dependence, reproducibility and dose rate dependence, then the skin dose in head and neck cancer patients using linac and tomotherapy. The comparisons of calculation dose versus measurement were also evaluated. The results showed the maximum variation of 36 % only in angular dependence for both types detector. There were not significant dependence on the other characteristic measurements of MOSFET. We found TN-502RD had more obvious angular dependence than TN-502RDM. In MOSFET measurements and treatment planning system calculation values comparison of skin dose for head and neck cancer clinical applications, the discrepancy were -0.9 % to 5 % and 2.1 % to 46.1 % for tomotherapy and linac, respectively.