目的：本研究針對局部晩期頭頸癌患者，透過比較使用強度調控弧形治療與強度調控放射治療在劑量學上與效率的差異，進而探討使用強度調控弧形治療於頭頸癌患者每日治療之適行性。材料與方法:本研究篩選九位接受放射線治療之局部晩期頭頸癌患者。我們採用每位患者實際接受的治療計劃（強度調控弧形治療或強度調控放射治療）當作基準，使用與實際治療計劃相左的計劃方式產生新的治療計劃，以用來比較此兩種計劃方式在劑量學上的差異。每位患者的放射治療皆採用適應性（adaptive)放射治療搭配同時整合加強治療（SIB)技術，皆含ー初始治療計劃及一縮小範圍計劃，兩治療計劃之電腦斷層模擬定位影像取得時間約間隔四週。我們採用SmartArc運算程式來執行計算所有本研究之治療計劃。劑量學比較的項目包含靶區的劑量分佈包覆性、劑量順形度及均勻度、以及危及器官的閃避程度，同時分析兩種治療技術所使用 的機器監測輸出單位與花費之治療時間。
結果:強度調控弧形治療平均每個計劃使用2.07個弧形照野，強度調控放射治療平均每個計劃使用6.5個照野。此二種計劃方式所得之PTV劑量包覆性皆達預設標準且並無統計上之顯著差異。不論在劑量順形度或均勻度方面，兩者結果皆無統計上之顯著差異。在各個危及器官的保護方面，各項DVH的比較參數，兩種治療計劃所得之數據結果皆相似，對於腮腺的保護方面，兩者亦無明顯差異。相較於強度調控放射治療，強度調控弧形治療顯著地減少機器監測輸出單位達 16.1% (757.0 vs 635.4 MUs,p= 0.011 )，同時縮短平均治療時間達 4.2 分鐘（48.3%, 8.7 vs 4.5 minutes, p < 0.001 )。
結論:本研究顯示針對頭頸癌患者而言，強度調控弧形治療與強度調控放射治療皆能達到臨床所接受的劑量分怖。強度調控弧形治療能縮短治療時間及減少機器監測輸出單位。因強度調控弧形治療能提高治療效率，同時不降低計劃品質，因此使用此治療計劃於頭頸癌患者是可行的。

Purpose : The aim of this study was to investigate the feasibility of applying VMAT for HNC patients in daily practice by comparing volumetric-modulated arc therapy (VMAT) with intensity-modulated radiation therapy (IMRT) for patients with locally advanced head-and-neck cancer (HNC) with regard to the dosimetric parameters and efficiency of delivery.
Material & Method : Nine locally advanced HNC patients on either an IMRT or VMAT treatment plan were selected for this study. Another corresponding plan using an alternative technique was generated for comparison. We applied an adaptive strategy with a simultaneous integrated boost (SI巳）technique in all radiation therapy protocols, including an initial plan and a reduced plan with acquisition of CT images about 4 weeks later. The Philips Pinnacle3® Planning System v. 9.0 was adopted for designing all treatment plans. Dosimetric parameters compared between VMAT and IMRT plans included target coverage, dose conformity, dose homogeneity, organs at risk (OAR) sparing, monitor units (MUs) and treatment delivery time.
Result: The average number of arc used in the VMAT plan was 2.07 and the number of fields per IMRT plan was 6.5. The VMAT and IMRT plans had similar PTV coverage (Vioo% > 98% and > 96%, respectively). There was no significant difference between VMAT and IMRT in conformity (CI= 1.73 and 1.63, respectively, p= 0.546), homogeneity of PTV-H (HI= 1.08 and 1.07, respectively, p= 0.387), PTV-M (HI = 1.10 and 1.10, respectively, p= 0.891) and PTV-L (HI = 1.13 and 1.12, respectively, p= 0.369). There were similar dose-volume histogram distributions between these two techniques for most of OARs. No significant difference existed in performance of parotid sparing by using these two techniques. Compared to IMRT, VMAT technique significantly reduced the MUs by 16.1% (757.0 versus 635.4 MUs, p= 0.011) and the average treatment time by 4.2 minutes (8.7 versus 4.5 minutes, p < 0.001).
Conclusion : This study demonstrated that equally clinical acceptable dose distributions can be achieved in both VMAT and IMRT techniques for HNC. In addition, VMAT provided faster delivery time and lower executed monitor units. Therefore, it is feasible to apply VMAT for HNC for improving the efficiency without compromising the quality of planning dosimetry.