Xing Jun, Li Jian-Bin, Zhang Ying-Jie, Li Feng-Xiang, Fan Ting-Yong, Xu Min, Shang Dong-Ping, Han Jian-Jun
Department of Radiation Oncology, Shandong Tumor Hospital, Jinan 250117, China.
Zhonghua Zhong Liu Za Zhi. 2012 Feb;34(2):122-8. doi: 10.3760/cma.j.issn.0253-3766.2012.02.009.
To compare the position and magnitude of internal target gross volume (IGTV) of primary hepatocarcinoma delineated by three methods based on four-dimensional computed tomography (4D-CT) and to investigate the relevant factors affecting the position and magnitude.
Twenty patients with primary hepatocarcinoma after transcatheter arterial chemoembolization (TACE) underwent big bore 4D-CT simulation scan of the thorax and abdomen using a real-time position management (RPM) system for simultaneous record of the respiratory signals. The CT images with respiratory signal data were reconstructed and sorted into 10 phase groups in a respiratory cycle, with 0% phase corresponding to end-inhale and 50% corresponding to end-exhale. The maximum intensity projection (MIP) image was generated. IGTVs of the tumor were delineated using the following three methods: (1) The gross tumor volume (GTV) on each of the ten respiratory phases of the 4D-CT image set was delineated and fused ten GTV to produce IGTV10; (2) The GTVs delineated separately based on 0% and 50% phase were fused to produce IGTV(IN+EX); (3) The visible tumor on the MIP image was delineated to produce IGTV(MIP). Twenty patients were divided into groups A and B based on the location of the target center,and were divided into groups C and D based on the tumor maximum diameter. The patients were divided into groups E and F based on the three-dimensional (3D) motion vector of the target center. The position of the target center, the volume of target, the degree of inclusion (DI) and the matching index (MI) were compared reciprocally between IGTV10, IGTV(IN+EX) and IGTV(MIP), and the influence of the tumor position and 3D motion vector on the related parameters were compared based on the grouping.
The average differences between the position of the center of IGTVs on direction of X, Y and Z axes were less than 1.5 mm, and the difference was statistically not significant. The volume of IGTV10 was larger than that of IGTV(IN+EX), but the difference was not significant (t = 0.354, P = 0.725). The volume of IGTV10 was larger than that of IGTV(MIP) but the difference was not significant (t = -0.392, P = 0.697). The ratio of IGTV(IN+EX) to IGTV10 was 0.75 +/- 0.15 and the ratio of IGTV(MIP) to IGTV10 was 0.78 +/- 0.14. The DI of IGTV(IN+EX) in IGTV10 was (74.85 +/- 15.09)% and that of IGTV(MIP) in IGTV10 was (68.87 +/- 13.69)%. The MI between IGTV10 and IGTV(IN+EX), IGTV10 and IGTV(MIP) were 0.75 +/- 0.15 and 0.67 +/- 0.13, respectively. The median of ratio of IGTV(IN+EX)/ IGTV10 was 0.57 in group A versus 0.87 in group B, statistically with a significant difference between the groups A and B (Z = -3.300,P = 0.001). The median of ratio of IGTV(MIP)/IGTV10 was 0.51 in the group A and 0.72 in group B, with a significant difference between the groups A and B (Z = -3.413, P = 0.001). The median of ratio of IGTV(IN+EX)/IGTV10 was 0.79 in group C versus 0.74 in group D, with a difference not significant (Z = -0.920, P = 0.358). The median of ratio of IGTV(MIP)/IGTV10 was 0.85 in group C versus 0.80 in group D, with a non-significant difference (Z = -0.568, P = 0.570). The median of ratio of IGTV(IN+EX)/IGTV10 was 0.87 in group E versus 0.68 in group F, with a significant difference between the two groups (Z = -2.897, P = 0.004). The median of ratio of IGTV(MIP)/IGTV10 was 0.85 in the group E versus 0.81 in the group F, with a non-significant difference (Z = -0.568, P = 0.570).
The center displacement of the IGTVs delineated separately by the three techniques based on 4D-CT images is not obvious. IGTV(IN+EX) and IGTV(MIP) can not replace IGTV10, however, IGTV(IN+EX) is more close to IGTV10 comparing with IGTV(MIP). The ratio of IGTV10 and IGTV(MIP) is correlated to the 3D motion vector of the tumor. When the tumor is situated in the upper part of the liver and with a 3D motion vector less than 9 mm, IGTV10 should be the best IGTV.
比较基于四维计算机断层扫描（4D-CT）的三种方法所勾画的原发性肝癌内部靶区大体积（IGTV）的位置和大小，并探讨影响其位置和大小的相关因素。
20例行经动脉化疗栓塞术（TACE）后的原发性肝癌患者，使用实时位置管理（RPM）系统对胸部和腹部进行大孔径4D-CT模拟扫描，同时记录呼吸信号。重建带有呼吸信号数据的CT图像，并在一个呼吸周期内将其分为10个时相组，0%时相对应吸气末，50%时相对应呼气末。生成最大密度投影（MIP）图像。采用以下三种方法勾画肿瘤的IGTV：（1）勾画4D-CT图像集10个呼吸时相上的每个时相的肿瘤大体积（GTV），并将10个GTV融合生成IGTV10；（2）分别基于0%和50%时相勾画的GTV进行融合，生成IGTV(IN+EX)；（3）勾画MIP图像上可见的肿瘤，生成IGTV(MIP)。根据靶区中心位置将20例患者分为A组和B组，根据肿瘤最大直径分为C组和D组。根据靶区中心的三维（3D）运动向量将患者分为E组和F组。相互比较IGTV10、IGTV(IN+EX)和IGTV(MIP)之间靶区中心位置、靶区体积、包容度（DI）和匹配指数（MI），并根据分组比较肿瘤位置和3D运动向量对相关参数的影响。
IGTV中心在X、Y和Z轴方向上的平均差异小于1.5 mm，差异无统计学意义。IGTV10的体积大于IGTV(IN+EX)，但差异无统计学意义（t = 0.354，P = 0.725）。IGTV10的体积大于IGTV(MIP)，但差异无统计学意义（t = -0.392，P = 0.697）。IGTV(IN+EX)与IGTV10的比值为0.75±0.15，IGTV(MIP)与IGTV10的比值为0.78±0.14。IGTV(IN+EX)在IGTV10中的DI为(74.85±15.09)%，IGTV(MIP)在IGTV10中的DI为(68.87±13.69)%。IGTV10与IGTV(IN+EX)、IGTV10与IGTV(MIP)之间的MI分别为0.75±0.15和0.67±0.13。IGTV(IN+EX)/IGTV10比值的中位数在A组为0.57，在B组为0.87，A组和B组之间差异有统计学意义（Z = -3.300，P = 0.001）。IGTV(MIP)/IGTV10比值的中位数在A组为0.51，在B组为0.72，A组和B组之间差异有统计学意义（Z = -3.413，P = 0.001）。IGTV(IN+EX)/IGTV10比值的中位数在C组为0.79，在D组为0.74，差异无统计学意义（Z = -0.920，P = 0.358）。IGTV(MIP)/IGTV10比值的中位数在C组为0.85，在D组为0.80，差异无统计学意义（Z = -0.568，P = 0.570）。IGTV(IN+EX)/IGTV10比值的中位数在E组为0.87，在F组为0.68，两组之间差异有统计学意义（Z = -2.897，P = 0.004）。IGTV(MIP)/IGTV10比值的中位数在E组为0.85，在F组为0.81，差异无统计学意义（Z = -0.568，P = 0.570）。
基于4D-CT图像的三种技术分别勾画的IGTV中心位移不明显。IGTV(IN+EX)和IGTV(MIP)不能替代IGTV10，然而，与IGTV(MIP)相比，IGTV(IN+EX)更接近IGTV10。IGTV10与IGTV(MIP)的比值与肿瘤的3D运动向量相关。当肿瘤位于肝脏上部且3D运动向量小于9 mm时，IGTV10应为最佳的IGTV。
