目的:評估利用照野中之照野(field-in-field, FIF)技術治療接受乳房保留手術(breast conservation therapy, BCT)之乳癌病患腫瘤位置之劑量均勻性及治療所需時間。
材料與方法:使用Focus治療計劃系統做BCT乳癌病人之治療計劃，並使用傳統之相切照野但不使用楔型濾片，在此兩個相切照野中各自再加上兩個衍生出來之較小照野。此治療計劃傳送至Siemens直線加速器治療病人，此六個照野可排成一個治療序列，放射師在擺設病人後，可讓機器依序列地一次完成治療。另外我們使用二維陣列Matrixx測量系統，驗證此治療計劃之準確性，做法如同一般做IMRT時之驗證方式，把治療計劃套用到個體假體上，完成一個在5.36公分度處之平面劑量，Matrixx測量系統亦擺設在相同深度做測量，就可驗證治療計劃之準確性。
結果:採用以此方式治療之前10個病人，比較此方法和傳統加楔型濾片之結果，整體最大劑量值(Global maximum dose)平均降低5%，大於105%之體積平均減少28%，大於110%之體積平均減少70%，全部MU(治療監測單位)平均減少48%，每個病人每次之治療時間約節省2分鐘。這兩種方法之前述各個特性，我們做統計比較，p值皆小於0.05。Matrixx量系統和治療計劃比較之結果，在治療區域內皆小於1.6%。此技術現已例行用於BCT乳癌病人治療。
結論:使用照野中之照野之技術治療BCT乳癌病患，可讓病人得到較均勻之劑量分佈，也可減少治療時間及放射師之工作負荷。

Purpose:To develop a Field-in-Field technique for breast treatment, to produce a uniform dose distribution in the treatment volume, and to efficiently implement this technique in the clinic.
Material and Methods:Using the Focus planning system, we first employ two tangent fields as in conventional breast treatment technique, but without using the wedge. Based on the dose distribution resulting from these open tangent fields, we create two smaller fields inside each tangent field, to achieve a more uniform dose in the breast volume. The treatment plan including the final six fields are then sent to the treatment database. In the actual treatment, these six fields are properly arranged so that they can be automatically delivered in one sequence without having to enter the treatment room. In addition, to verify the accuracy of this technique, we used a 2D detector system to measure the delivered dose distribution in a phantom and compare it with the planned results.
Results:We compared the treatment plans of the first ten patients using this field-in-field technique with those using the conventional technique. The gloobal maximum dose was reduced by about 5%, the volumes receiving at least 105% and 110% doses were reduced by 28% and 70%, respectively. The total MU was also reduced by about 48%. The in-room time of each patient was reduced by 2 minutes. The p-values of these comparisons were all less than 0.05. The difference between the measured and the planned doses were less than 1.6% inside the treatment fields.
Conclusion:The Field-in-field technique can produce more uniform dose distribution inside the treatment volume for breast treatment. It also reduces the treatment time and lessens the work load for the therapist. This method has been implemented for routine clinical use.