HT治疗多发转移瘤的MVCT引导方案探讨

目的 探讨应用HT治疗多发转移瘤时合适的MVCT引导方案。方法 将48例采用HT的多发转移瘤患者按靶区分布情况分为头胸组(15例)、头盆组(15例)和胸盆组(18例)。于治疗分次内对各靶区分别行MVCT扫描,将所得图像与定位CT图像进行配准并记录摆位误差值。计算各CTV到PTV的外扩边界。配对t检验差异。结果 头胸组、头盆组、胸盆组患者摆位误差的两两比较显示,x轴分别为-0.15±1.25∶-0.21±2.34(P=0.71)、-0.16±1.31∶-1.29±3.72(P=0.00)、0.25±2.90∶-0.22±3.65(P=0.06),y轴分别为0.73±1.22∶1.56±2.54(P=0.00)、0.81±1.34∶3.20±3.90(P=0.00)、0.35±3.60∶0.38±3.78(P=0.87),z轴分别为0.93±1.44∶2.65±1.88(P=0.00)、1.24±1.75∶5.49±2.80(P=0.00)、1.95±2.81∶3.35±3.05(P=0.00)。3个组经过各自上段靶区修正后,各自下段靶区的外扩边界在三维方向上均有所减小,但均以y轴缩小最显著,分别为5.13∶4.01、9.17∶8.30、8.52∶7.13。结论 对于分离靶区的多发转移瘤的HT,不应单独使用任一部位的摆位误差值修正整体摆位误差,建议采用分次内不同部位进行引导的图像引导方案。

Megavoltage computed tomography image-guided helical tomotherapy for multiple metastases

Objective To investigate an appropriate megavoltage computed tomography (MVCT) protocol to guide helical tomotherapy (HT) for multiple metastases. Methods According to the location of target volume, 48 patients with multiple metastases undergoing HT were divided into head/chest group (n=15), head/pelvis group (n=15), and chest/pelvis group (n=18). Each target volume received MVCT scans during the treatment. The obtained MVCT images were registered to CT images and the setup errors were recorded. The CTV-PTV margins were calculated. Comparison was made by paired t test. Results In the head/chest group, there was no significant difference in the setup error in x-axis between the head and chest (-0.15±1.25 vs. -0.21±2.34, P=0.71), while the head had significantly smaller setup errors in y-and z-axis than the chest (0.73±1.22 vs. 1.56±2.54, P=0.00;0.93±1.44 vs. 2.65±1.88, P=0.00). In the head/pelvis group, the head had significantly smaller setup errors in x-, y-, and z-axis than the pelvis (-0.16±1.31 vs. -1.29±3.72, P=0.00;0.81±1.34 vs. 3.20±3.90, P=0.00;1.24±1.75 vs. 5.49±2.80, P=0.00). In the chest/pelvis group, there were no significant differences in setup errors in x-or y-axis between the chest and pelvis (-0.25±2.90 vs. -0.22±3.65, P=0.06;0.35±3.60 vs. 0.38±3.78, P=0.87), while the chest had a significantly smaller setup error in z-axis than the pelvis (1.95±2.81 vs. 3.35±3.05, P=0.00). In the three groups, the CTV-PTV margins of lower target volume were reduced in three dimensions after the correction of upper target volume, in which y-axis showed the largest reduction of CTV-PTV margins (5.13 vs. 4.01;9.17 vs. 8.30;8.52 vs. 7.13). Conclusions The setup error of individual target volume should not be used for correction of the overall setup error in HT for multiple metastases with isolated target volume. An MVCT protocol that provides image-based guidance for multiple target volumes is recommended.