肺癌是臨床常見惡性腫瘤之一。近年來，其發病率和死亡率呈上升的趨勢。放射治療已成為中晚期肺癌患者 的主要治療手段之一。本文研究採用共面和非共面射束的三維順形放射治療(3DCRT)、強度調控放射治療(IMRT) 與體積弧形調控技術(VMAT)治療方式的差異，討論六種技術的優劣，為臨床最適治療計劃提供參考。方法是選 擇九個立體定向放射治療(SBRT)肺部的患者的十個腫瘤部位用於本研究。對於每個計劃靶(PTV)建立六個治療技 術，1 個共平面和1 個非共面3DCRT、IMRT 和VMAT，使得98%的PTV 接受100%的處方劑量。比較每種技術 的劑量分佈及劑量體積分佈直方圖(Dose Volume Histogram, DVH)。結果顯示IMRT 和VMAT 技術的順形指數(CI) 相似，並且明顯優於3DCRT 技術；PTV 中的劑量均質性指標(HI)在共平面IMRT 技術中顯著高於相應的3DCRT 和VMAT 共平面技術；共平面VMAT 技術產生最大脊隨劑量，相較3DCRT 有明顯減少。結論為所有立體定向 放射治療技術中，VMAT 技術有較高的順形指數，IMRT 技術在目標劑量均勻性指數方面較其他技術好，但沒有 一種技術在所有劑量指數中顯著超越其他技術；觀察DVH 圖，VMAT 又有更好的正常組織免除效應。故在選 擇最佳的治療計劃，除了要考慮腫瘤的控制率，更要盡可能的降低正常組織併發症發生率。

Lung nodule detection by computerized tomography has developed into a low-dose scan because of new CT device. The purpose of this study is to reduce the radiation dose and at the same time, the computer tomography images can be clearly to detect early lung cancer of the non-calcified nodules. With the advancement of science and technology, newer multi-slice computer tomography (MSCT) technology has become the best weapon for early lung cancer screening. This study adopted a retrospective approach and total of 100 subjects were analyzed. The two groups of subjects were with similar BMI, the same setting of parameters, but using 64-slice and 128-slice dual source multi-slice CT (DSCT) examination, retrospectively. Comparing these two groups, the results show that the two DSCT for low-dose chest examination of small nodules can reveal minimum diameter of 1.4mm and 1.6mm. But in the radiation dose, the 128-slice DSCT had fewer CT dose index (CTDIvol), mean dose-length products, and mean effective dose (E) than 64-slice DSCT (p<0.0001). Using the newer CT scanner can not only maintain interpretable image quality but also reduce the radiation dose.