目的：量測全身性放射照射（TBI）之射束特性與劑量參數。
材料與方法：本研究主要分為七部分來探討：射束輸出劑量比值（output ratio）、托盤與散射屏風因子（tray and spoiler factors）、百分深度劑量比（PDD）、組織與最大劑量比（TMR）、補償器因子（compensator factor）、射束剖面圖（beam profile）及劑量驗證等。所有射束特性及劑量參數之量測皆使用西門子 Primus 直線加速器六百萬伏特（MV）之光子射束。量測設置情況比照實際 TBI 治療時的情形：在 SSD 為 480 公分處放置假體，照野大小為 40 × 40 平方公分（此為 SAD 100 公分處之大小），準直儀及旋轉臂的角度各為 45 度及 270 度。此外，在假體前方還會放置一面 1 公分之散射屏風以提高表面劑量。本研究前五部分之劑量參數主要使用農夫型游離腔（Farmer type ion chamber）、電量計（electrometer）、平行板游離腔（parallel-plate ion chamber）及聚苯乙烯假體（polystyrene phantom）等設備來做量測；在射束剖面圖部分：分別將膠片（film）貼放在散射屏風上或將游離腔放在壓克力假體內做量測，進行兩者之比較；劑量驗證部分：在 TBI 治療病人的同時，將熱發光劑量計（TLD）貼放在病人 12 個不同的部位接收劑量，以評估病人實際接受到劑量的情形，是否與預期相符。
結果：射束輸出劑量比值為 0.0466，此值與一般標準校正情況下所得到之值，經平方反比及照野因子轉換後所得之值極為相近。拖盤因子、散射屏風因子及托盤與散射屏風因子分別為 0.949 、0.982 及 0.931。百分深度劑量比與組織與最大劑量比經轉換後之差異介於 2% 的範圍內。補償器因子在聚苯乙烯厚度低於 13 公分時的值為 0.045，而聚苯乙烯與鉛之厚度比值（thickness ratio）為 0.511。由膠片與游離腔所量得之射束剖面圖頗為一致。在劑量驗證部分，由熱發光劑量計所量得之劑量與處方劑量相比差異約為±5 % 。
結論：根據上述量測結果，所有誤差皆在 2 % 的範圍內（劑量驗證之熱發光劑量計的結果除外），故本研究量測射束特性及劑量參數之方法是可行的，且所有量測結果目前皆被實際使用
在臨床治療上面。
[ 放射治療與腫瘤學2010; 17(4): 293-301 ]

Materials and Methods : The set of measurements consists of seven items: output ratio, tray and spoiler factors, PDD, TMR, compensator factor, beam profile and dose verification. All measurements were performed on a 6 MV photon beam of Siemens Primus Linac. Experimental setup simulated TBI treatment conditions with SSD at 480 cm, field size at 40 × 40 cm2 at SAD 100 cm, and the collimator and gantry angles set to 45° and 270°, respectively. In addition, a 1 cm spoiler screen was placed in front
of the phantom to increase the surface dose. The first five items of dosimetry parameters were measured with a Farmer-type ion chamber, an electrometer, a parallelplate ion chamber and a polystyrene phantom. The beam profile was measured both with films placed on the spoiler screen and with ion chamber in a polystyrene phantom. For dose verification, TLDs were placed at twelve different sites on the patient skin during TBI treatment.
Results : The output ratio was 0.0466, very close to that obtained under calibration conditions after applying the inverse square correction and output factor correction for TBI treatment conditions. The tray factor, spoiler factor and the combined tray-andspoiler factor were 0.949, 0.982 and 0.931, respectively. The discrepancy between PDD and TMR was lower than 2 %. The compensator factor was 0.045 for polystyrene thickness up to 13 cm and the thickness ratio of polystyrene to lead was 0.511.
Beam profiles measured with films and ion chamber were almost the same. For dose verification, the discrepancies between TLD and prescribed dose were comparable to the intrinsic measurement uncertainty, ±5 %.
Conclusion : A comprehensive set of beam data and dosimetry parameters were measured and all ratio discrepancies seen during the study (except TLD part), consistent with those applied clinically, were within 2 % indicating the study viable.
[Therapeut Radiol Oncol 2010; 17(4): 293-301 ]