目的：本研究運用四維電腦斷層（four dimensional computed tomography, 4D CT）擷取病人在 不同呼吸相位的斷層影像，並收集病人腹圍和身體質量指數（body mass index, BMI）資訊，分 析呼吸對於腫瘤位移程度的影響因子。 材料與方法：選擇10 位原發性肺癌或肺轉移，8 位肝癌或肝臟轉移病人，收集病人的BMI 及腹 圍資料。每位病患取得一組正常呼吸的CT 影像，接著掃描另一組4D CT 並重組出最大密度投 影影像（Maximum Intensity Projection, MIP），以此兩組影像分別界定出腫瘤範圍（CTVNB 和 CTVMIP），計算出兩者之間的體積差異百分比（Vdiff），以Vdiff 做為因呼吸造成的腫瘤移動範圍指 標，之後使用SPSS 軟體進行線性迴歸分析。 結果：對肺臟腫瘤病人來說，Vdiff 和BMI 與腹圍之間無相關性。肝臟腫瘤病人群組則發現Vdiff 和 BMI 呈顯著相關性而腹圍則無，表示BMI 是呼吸對於肝臟腫瘤位移程度的影響因子。 結論：得知BMI 與腹圍對肺部腫瘤的病人的腫瘤位移無相關性，但在肝臟腫瘤的病人則顯示出相 關性；肝臟腫瘤的病人在正常呼吸的情況下，BMI 和Vdiff 之間呈現反向的關係，BMI 越高則Vdiff 越低。推測此關係是因為肝臟腫瘤位於腹部橫隔附近，橫膈膜移動幅度會受到病人的胖瘦影響， 胖的人其橫隔膜移動幅度較小。在臨床上可根據病人體型來選擇適當的呼吸控制及治療方式。

Purpose : To analyze the correlation between body mass index (BMI) and respiration-induced tumor motion, and waist circumference and respiration-induced tumor motion by using different respiratory phases from four dimensional computed tomography (4D-CT) Materials and Methods : Ten patients with primary lung cancer or metastatic lung lesion, and eight patients with primary hepatic cancer or metastatic hepatic lesion who received radiotherapy (RT) during Dec. 2014 to Nov. 2015 were included in this study. Data of BMI and waist circumference for each patient were collected. Images from free breathing CT scans and MIP images from 4D-CT scans were obtained for each patient and used for delineating CTVNB and CTVMIP, respectively. We calculated the percentage of volume difference (Vdiff) between CTVNB and CTVMIP. Linear regression analysis between Vdiff and BMI, and Vdiff and waist circumference were performed by using Statistical Package for Social Sciences (SPSS) 19 (SPSS Inc., Chicago, IL) . Results : For patients with pulmonary tumor, there was no correlation between Vdiff and BMI, and between Vdiff and waist circumference. For patients with hepatic tumor, our study showed a significant correlation between Vdiff and BMI, but no correlation between Vdiff and waist circumference. According to the correlation analysis in our study, BMI was a factor influencing the magnitude of respiration-induced hepatic tumor motion. Conclusion : Our study showed that there was a significant correlation between Vdiff and BMI for patients with hepatic tumor. We speculate that the small Vdiff for patients with hepatic tumor and high BMI was caused by the tumor location which near the diaphragm, and the magnitude of diaphragm motion was easily influenced by the BMI. Therefore, we could design appropriate treatment techniques for breathing control according to the BMI of the patient.