目的：探討四種不同直線加速器放射治療設備用於肺癌病人合併瀰漫性肋膜轉移姑息性治療時 的劑量分佈及可行性。 材料與方法：以6 MV 的X 光及適當的最佳化條件，分別針對同一位肋膜轉移的病患產出三 維順形放射治療、強度調控放射治療、強度調控弧形治療及螺旋放射治療等四種不同的治療 計畫。給予計畫靶區（PTV）的總劑量為50 Gy ，共分20 次照射，並使用劑量- 體積直方圖 （DVH）、順形指數（CI）、均勻度指數（HI）等工具來評估計畫靶區及危急器官的劑量分佈。 結果：整體而言，強度調控放射治療、強度調控弧形治療及螺旋放射治療可達成的計畫靶區劑 量分佈相當。四種技術能包覆98% 計畫靶區體積的劑量均超過48.5 Gy 。螺旋放射治療具有最 高的順形指數和最低的均勻度指數，而三維順形放射治療的最大劑量（58 Gy）和包覆2% 計畫 靶區體積的劑量（56.82 Gy）最高。螺旋放射治療同側肺接受45 Gy 的體積最小（45%），同側 肺部的平均劑量（45 Gy）也最低。三維順形放射治療的對側肺接受18 Gy 的體積（0%）和對 側肺部的平均劑量（1.14 Gy）最低。全肺部的累積劑量（integral dose）的大小順序為強度調控 弧形治療 > 螺旋放射治療 > 強度調控放射治療 > 三維順形放射治療。螺旋放射治療給予的監測 單位（Monitor Unit）量最多，總治療時間也最長。 結論：強度調控放射治療、強度調控弧形治療和螺旋放射治療均可達到95% 以上的計畫靶區包 覆率，和三維順形放射治療相比，對危急器官的保護較佳，然而，有些正常組織接受到中低劑 量的體積會較大，而使得強度調控放射治療、強度調控弧形治療和螺旋放射治療具有較高的累 積劑量。要判斷那一種技術較佳仍需要臨床上的關聯。

Purpose : To investigate the performance and feasibilities of four different linac-based radiation therapy devices in palliating a lung adenocarcinoma patient presenting with diffuse pleural seeding and intractable pain. Patients and Methods : Treatment plans were generated for three dimensional conformal radiotherapy (3D-CRT), Intensity-modulated radiation therapy (IMRT), Volumetric- modulated arc therapy (VMAT) and Helical Tomotherapy (HT) using 6 MV photon beam with adequate optimization criteria. The total prescribed dose to planning target volume (PTV) was 50 Gy in 20 fractions. Dose distributions to PTV and organs at risk (OAR) were compared using dose-volume histograms (DVHs), conformity indexes (CIs), and homogeneity indexes (HIs). Results : In general, IMRT, VMAT and HT all resulted in comparable PTV coverage. The D98 of all four techniques were all greater than 48.5 Gy. HT had the highest CI (0.982) and the lowest HI (0.035), whereas 3D-CRT had the highest D2% (56.82 Gy) and Dmax (58 Gy). HT had the lowest ipsilateral lung V45 (55%) and ipsilateral mean lung dose (45 Gy). 3D-CRT had the lowest contralateral lung V18 (0%) and contralateral mean lung dose (1.14 Gy). The integral dose (L.Gy) for total lung tissue was VMAT > HT > IMRT > 3D-CRT. HT delivered the most monitor units (MUs) and needed the longest treatment time. Conclusion : IMRT, VMAT and HT all could attain over 95% PTV coverage and had superior OAR sparing compared to 3D-CRT. However, larger volumes of some healthy tissues (especially contralateral lung) received low-to-intermediate doses, which contributed to a higher integral dose in VMAT, HT and IMRT. The superiority of one technique over another needed further clinical correlation.