自從1895年侖琴博士(Dr. Wilhelm Conrad Roentgen)發現X光以來，如何將游離輻射(ionization radiation)有效應用於各項有益於人類和平的用途上，相關的各種研究至今未曾中斷過。1896年一月29號，人類首次利用游離輻射來治療惡性腫瘤(俗稱癌症)，所使用的方式是採直接照射患部的原始方法。到2001年的今天，放射治療(radiotherapy)的進展已隨著學理與科技的進步，達到可對輻射在人體內的劑量分布與空間分布，分別進行最佳化調控(modulation) 的技術境界。
目前臨床醫學治療癌症的方法與技術中，利用游離輻射來治療癌症的放射治療方法仍然佔有非常重要的地位。晚近用於臨床治療癌症的放射治療技術，依照其技術水準的區分，可略分為三大類主要的技術分野。若以這三種放射治療技術實際應用於臨床上的時間早晚來排列，則依序是：(a)傳統的二度空間放射治療技術(conventional 2D radiotherapy technique)。(b)三度空間順形放射治療技術(3D conformal radiotherapy)。(c)強度調控放射治療技術(intensity modulated radiotherapy; IMRT)。

在進行放射治療的程序之前，臨床的工作人員都會設計出一個內容包括照射區域的人體器官組織空間分布狀況、射束給予方法與輻射劑量分布等資訊的放射治療計畫(radiotherapy plan)。使用各種不同的放射治療技術治療病人時，對放射治療計畫的設計考量也不盡相同。為了能選擇出一個最合適於某種狀況下使用的治療計畫與方式，通常會以治療計畫或技術間的相互比較來作為選擇的依據。常用的比較工具與比較指標有等劑量曲線(isodose curve)、劑量-體積長方圖(dose-volume histogram)等。

本實驗的目的是建立不同放射治療計畫與技術間，取捨依據的客觀方法。研究方法是利用正常組織發生併發症機率模式(normal tissue complication probability model; NTCP model)與腫瘤控制機率模式(tumor control probability model; TCP model)為指標參數，來分析以不同的放射治療計畫與技術，應用於臨床實際治療中國人罹患率遠高於其他人種的鼻咽癌(nasopharyngeal cancer; NPC)時的治療計畫資料。

在取得由不同放射治療技術之治療計畫治療NPC時，所推算出的TCP值與包括視神經交叉(chiasm)、腦幹(brainstem)、脊髓(spinal cord)與腮腺(parotid gland)等正常組織器官的NTCP值之後，本實驗將以不同的評分方程式(score function)，來評定不同的放射治療技術實際運用於鼻咽癌的治療時的得分狀況，作為臨床選擇放射治療技術或放射治療計畫時的參考。

The comparison of Intensity Modulated Radiation Therapy (IMRT) with other conventional radiotherapy techniques has become an important research topic in recent years. The purpose of my study is to compare conventional 2 way, 3D CRT with IMRT techniques for external-beam treatment for nasopharyngeal carcinoma (NPC). Each patient’s contour data was planned using 2D, 3D CRT and IMRT separately. Data form radiation planning system was used to derive NTCP and TCP values from dose volume histogram (DVH). To calculate the NTCP, the effective volume DVH reduction scheme theory was used. Finally, three kinds of score function including K-value, TCP and NTCP are introduced to evaluate the impact of IMRT and conventional techniques on ranking of radiation treatment plans.

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