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目的利用不同匹配区域对锥形束CT(CBCT)与定位CT(FBCT)分别配准,测量出鼻咽癌放射治疗中颈部的变形误差。方法分析2007年4月2008年12月收治鼻咽癌患者23例,调整治疗床前198次CBCT扫描。将鼻咽部扫描CBCT图像匹配区域分为上下两个区域进行对比分析。其中上匹配区域为:上界为蝶窦上缘,下界为颈4下缘,侧界包括下颌骨外轮廓,前界为上颌窦1/2,后界为平棘突后缘;下匹配区域为:上界约颈4下缘,下界约胸2-3下缘,侧界包括椎体外轮廓,前界包括皮肤,后界平棘突后缘。匹配方式选择骨,比较匹配结果差异。结果选择上与下匹配区域结果除Y(头脚)方向旋转误差无统计学差异外,余均有统计学差异(P<0.05)。差值在X(左右)、Z(前后)、Y(头脚)方向平移分别为(1.14±2.80)、(0.47±1.41)、(0.58±3.88)mm,旋转误差X、Y、Z方向分别为(0.90±1.98)、(0.80±2.03)、(0.68±1.90)°。结论鼻咽癌放射治疗中颈部区域存在一定变形误差,通过CBCT引导发现变形误差并进行正确纠正是必须的,结合临床实际及靶区与危及器官的变化为重新计划提供依据。
Objective To measure the neck deformation of radiotherapy for nasopharyngeal carcinoma (NPC) by using different matching regions to register CBCT and FBCT respectively. METHODS: Twenty-three patients with nasopharyngeal carcinoma were treated in April 2007 and December 2008, and 198 CBCT scans were performed before treatment. The nasopharynx scan CBCT image matching area is divided into upper and lower regions for comparative analysis. The upper matching area is: the upper bound is the upper edge of the sphenoid sinus, the lower bound is the lower edge of the neck 4, the lateral border includes the outer contour of the mandible, the anterior boundary is the maxillary sinus 1/2 and the posterior bound is the trailing edge of the flat spinous process; As follows: the upper edge of the lower edge of the neck 4, the lower edge of about 2-3 lower edge of the chest, lateral boundaries, including the outer contour of the vertebral body, the anterior boundary including the skin, the posterior boundary of the spinous process margin. Bone matching method, compare the difference between the matching results. Results There was no statistically significant difference between the results of upper and lower matching regions except Y (head and foot) rotation error (P <0.05). The translations were (1.14 ± 2.80), (0.47 ± 1.41) and (0.58 ± 3.88) mm in X (left), Z (front) and Y (head) (0.90 ± 1.98), (0.80 ± 2.03), (0.68 ± 1.90) °. Conclusions There is a certain deformation error in the neck region during radiotherapy of nasopharyngeal carcinoma. It is necessary to find out the deformation error and correct it by CBCT. Combining with the clinical practice and the change of the target area and the organ at risk, it provides a basis for re-planning.