目的:運用重複電腦斷層（computed tomography, CT)掃描和重新設計電腦治療計劃，觀察鼻咽癌患者在強度調控放射治療（intensity modulated radiotherapy, IMRT)過程中腫瘤及正常腿腺 器官的體積及體表輪廓的變化。
材料與方法:對38例初次治療鼻咽癌患者進行強度調控放射治療，鼻咽、頸部、鎖骨上均淋巴區均使用IMRT技術，並得到計劃1 (dose-volume histogram, DVH1 );在患者放射治療22 (44 Gy)次後按照原固定體位和參考坐標重新作CT掃描，由同一位主治醫師勾畫治療靶區及周圍正常組織器官並對第二次CT掃描影像重新製作電腦治療計劃得到計劃2 (DVH2)，同一病患之前後計劃均用同樣的物理目標函數和約束條件進行優化。應用CT掃描影像和DVH資料對放射治療前和治療22次後之GTV、GTV-LN、腮腺、下頷腺體積的變化，以及前後次定位CT圖像中鼻咽部和頸部水平同一層面的左右輪廓橫徑變化來和腫瘤大小及淋巴轉移狀態進行比較分析。
結果：放射治療過程中體重，腫瘤及腮腺體積存在著明顯的變化，體重平均下降2.97% (2.33 kg. 1.5~3.7 kg)，與計劃1相比較，計劃2的腮腺體積明顯平均縮小15.67% (10.83 cc, 95% CI: 7.45~14.21 cc)，GTV 縮小 15.49% (3.83 cc, 95% CI: 2.36~5.30 cc)、GTV-LN 縮小 41.81% (15.12 cc, 95% CI: 8.66~21.57 cc)，下頜腺縮小 15.83% (3.39 cc, 95% CI: 2.14~4.65 cc)。 影像橫切面左右輪廓橫徑平均減少0.32~0.89 cm (1.93%~6.04%)，其中又以中央橫切面向上 3公分的輪廓橫徑減少最多（0.89 cm, 6.04%)，（ Pく 0.05)。從腫瘤的期別來看，T1-3和T4的GTV體積平均縮小分別是2.23 cc，6.91 cc(P= 0.0013) ; N1-2與N3的GTV-LN體積平均縮小各別是8.59 cc、38.93 cc ( P< 0.0001 )都具有統計學上的意義。在輪廓橫徑變化上則與淋巴轉移狀態（N-stage)及體重減少有關（Pく 0.05)。
結論：鼻咽癌使用IMRT治療過程中病人體重下降、輪廓減少、腫瘤和腮腺體積會發生一些變化，特別是腮腺、下頷腺和GTV-LN變化較明顯，建議放射治療中，後期有必要重新掃瞄CT，重新製作電腦治療計劃，以減少正常器官的劑量和副作用。

Objective : To investigate the changes of the tumor and salivary gland volumes in intensity modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) through 2nd phase of computed tomography (CT) treatment planning.
Materials and Methods : Thirty-eight patients with nasopharyngeal carcinoma were enrolled in this study, the primary tumor and neck lymph nodes were treated by IMRT; and formed the plan1 (DVH1), re-planning CT with same position after twenty-two radiation treatments formed the plan2 (DVH2). All target volumes and organs at risk were outlined by the same physician. The physical objective and dose constraints were optimized with same criteria. The data obtained from CT treatment planning and DVH were analyzed. The volumes,weights, and outline changes in the transverse diameter of CT images varied between before and after treatments.
Results : Patient weight, volumes of tumors and salivary glands decreased remarkably during radiotherapy. The average weight decreased by 2.97% (2.33 kg, range 1.5~3.7 kg). Compared Plan 1 with Plan 2, the parotid glands was significantly reduced by 15.67% (10.83 cc, 95% CI: range 7.45〜14.21 cc), submandibular glands 15.83% (3.39 cc, 95% CI: range 2.14〜4.65 cc), GTV decreased 15.49% (3.83 cc, 95% CI: range 2.36〜5.30 cc), and GTV-LN decreased 41.81% (15.12 cc, 95% CI: range 8.66〜21.57 cc) . The transverse diameter of head and neck CT images reduced by average of 0.32 〜0.89 cm (1.93%~6.04%), especially at the transverse diameter in the level of 3 cm above the set-up center (0.89 cm). The GTV volume on average shrank 2.23 cc and 6.91 cc as comparing T1-3 with T4 disease (p = 0.0013); The GTV-LN volume shrank on average 8.59 cc, 38.93 cc (P< 0.0001) as comparing N1-2 with N3 disease. The transverse diameter changes of head and neck contours were correlated significantly with N stage and body weight loss.
Conclusion : For NPC patients treated with IMRT, weight loss, volume reduction of salivary gland, and body contour change are common. The salivary glands on average reduced volume by 15% and GTV-LN by 40% after one-month treatment. The transverse diameter of head and neck regions could decrease up to 0.89cm. We recommend repeat simulation after one-month of radiotherapy in order to reduce the dose to the normal organs and avoid missing treatment targets.