四维CT确定肝癌放疗内靶区的临床应用

Use of four-dimensional computed tomography scans to determine internal target volume for hepatic malignancies

目的:探讨四维CT(four-dimensional computed tomography,4DCT)扫描的勾画方法,以及其在快速确定肝脏肿瘤内靶区(internal target volume,ITV)中的作用。方法:2011年1月至2013年8月,便利抽样选择复旦大学附属肿瘤医院接受放疗的17例肝癌患者为研究对象,对其进行4DCT扫描。采用5种方法确定内靶区,即ITV_(AllPhase)、ITV_(2Phase)、ITV_(MIP)、ITV_(MinIP)和ITV_(2M)。将ITV_(AllPhase)作为参考标准计算靶区,其他4种方法生成的ITV与之比较,得出体积的百分比、适形指数(matching index,MI)、低估的体积百分比。同时评估了肿瘤大小/呼吸幅度比值对4种ITVs的影响。结果:肿瘤的呼吸运动幅度在上下方向最显著,为(8.4±3.5)mm。ITV_(2M)的体积大小最接近参考体积(ITV_(AllPhase)),其次是ITV_(2Phase),最差的是ITV_(MinIP)和ITV_(MIP)。ITV_(2M)的MI为(0.93±0.03);其次是ITV_(2Phase),为(0.89±0.05);最差的为ITV_(MinIP)和ITV_(MIP),分别为(0.81±0.10)和(0.82±0.10)。经过分析ITV_(2Phase)的MI和肿瘤大小与呼吸幅度的比例正相关,(r=0.524,P=0.031)。ITV_(2M)与参考体积(ITV_(AllPhase))低估的体积百分比最小,为(0.07±0.03);其次是ITV_(2Phase),为(0.12±0.06);最差的是ITV_(MinIP)和ITV_(MIP),分别为(0.18±0.10)和(0.18±0.12)。肿瘤大小与呼吸幅度的比例与ITV_(2M)的低估值无相关性(r=-0.34,P=0.18);但与ITV_(2Phase)的低估值负相关(r=-0.539,P=0.024)。结论:ITV_(2M)法可以可靠快速地确定肝癌内靶区,值得推广。

Objective：To explore the methods of the four-dimensional CT scanning,and its role in the rapid determination of liver tumor in the internal target volume.Methods：From January 2011 to August 2013,17 cases of patients with hepatocellular carcinoma who received radiotherapy in a tumor hospital were selected by convenience sampling,and the 4 DCT scan was performed.Five methods are used to determine the internal target volumes,namely ITV_（AllPhase）,ITV_（2 Phase）,ITV_（MIP）,ITV_（MinIP）,and ITV_（2 M）.ITV_（AllPhase）：contouring the GTV on each of the ten respiratory phases of the 4DCT data set and combining these GTVs.ITV_（2Phase）：contouring the GTV on the extreme respiratory phases（0% phase= peak inhalation,50%phase = peak exhalation）and combining these GTVs.ITV_（MIP）：contouring the GTV on the MIP of the 4DCT dataset.ITV_（MinIP）：contouring the GTV on the MinIP of the 4DCT dataset.ITV_（2 M） ：combining ITV_（MIP）and ITV_（MinIP）.Using ITV_（AllPhase）as the reference standard ITV,we compared the percentage of volumes, matching indices（MI）and the percentage of underestimated volumes of the respective ITVs generated from the other four approaches.At the same time,the effects of tumor size/respiration ratio on the four types of ITVs were also evaluated.Results：The respiratory motion amplitude was the most significant in the upper and lower direction：（8.4±3.5）mm.The volume size of ITV_（2 M）was closest to the reference volume（ITV_（AllPhase））,the second was ITV_（2 Phase）,and the worst were ITV_（MinIP）and ITV_（MIP）.The MI of ITV_（2 M） was（0.93±0.03）;the second was ITV_（2 Phase）,which was（0.89±0.05）;the worst were ITV_（MinIP）and ITV_（MIP）,which were（0.81±0.1）and（0.82±0.10）.After analysis we found that MI of ITV_（2 Phase）was positively correlated with the ratio of tumor size to respiratory amplitude（r=0.524,P=0.031）.Compared with the reference volume（ITV_（AllPhase））,ITV_（2 M） had the lowest percentage of underestimation;the second was ITV_（2Phase）：（0.12±0.06）;the worst were ITV_（MinIP）and ITV_（MIP）：（0.18±0.10）and（0.18±0.12）,respectively.The ratio of tumor size to respiratory rate was not correlated with the underestimated value of ITV_（2M）（r=-0.34,P=0.18）,but was negatively correlated with the underestimated value of ITV_（2Phase）（r=-0.539,P=0.024）.Conclusions：ITV_（2M） can reliably and quickly determine the target area of liver cancer,and it is worth popularizing.