四维CT中MIP融合图像的肺癌内靶体积确定

Internal Target Volumes Determined with Maximum Intensity Projection(MIP) Fused Images of Four-Dimensional CT(4D-CT) in Lung Cancer

[目的]验证在最大密度投影(MIP)软件自动生成融合图像上勾画大体肿瘤体积(GTV)的可靠性。[方法]20例经病理确证为肺癌的患者,根据病灶邻近组织特点,分为A组(病灶周围环绕正常低密度肺泡组织)和B组(病灶周围与等密度或高密度组织紧邻)。同一个医师分别在四维CT(4D-CT)的10个时相、3个时相、2个时相、MIP融合图像上勾画GTV(GTV10、GTV3、GTV2、GTVMIP)。观察GTV体积变化和中心位移情况,比较四种方法之间的差异。[结果]A组GTV10与GTV3、GTV2和GTVMIP的比值分别为1.07±0.03、1.10±0.03和1.08±0.07;四者中心点在X、Y、Z轴上的差异小于1mm且无统计学意义(P>0.05)。B组GTV10与GTV3、GTV2、GTVMIP的比值分别为1.10±0.07、1.16±0.09、1.27±0.26;四者中心点在X、Y、Z轴上的差异小于1mm且无统计学意义(P>0.05)。[结论]对于周围环绕正常肺泡组织的肺内病灶,在四维CT中MIP图像上勾画GTV是可靠的,但病灶紧邻等密度或高密度组织时不够精确,建议代之以3个时相的融合图像,个别特殊情况代之以10个时相的融合图像。

[Purpose ] To verify the reliability on usage of maximum intensity projection（MIP） protocols for rapid generation of gross tumor volume（GTV）. [Methods] Twenty cases with lung cancer proved by pathology were divided into two groups including group A, lesions around normal hypo-density alveolus; and group B, lesions around the iso-or hyper-density tissues according to the difference tissues adjacent the lung lesions. GTVs were generated from fused images of four-dimensional CT（4D-CT） at the 10, 3, 2 respiratory phases and MIP by the same doctor. The volume change and center coordinate displacement of the GTVs were observed, and the four methods of drawing GTVs were analyzed. [Results ] The ratios of GTV10 to GTV3, GTV2,and GTVMIP were 1.07±0.03, 1.10±0.03, 1.08±0.07,respectively in group A, and 1.10±0.07,1.16±0.09,1.27±0.26,respectively in group B, while center coordinate displacement on X, Y, Z axes among those was less than lmm both group A and B with no significant statistic difference （P〉 0.05）. [Conclusions ] MIP protocol of 4D-CT is reliable for generating GTVs in the lesions around normal hypo-density alveolus. However, it is not accurate for the lesions around the iso-or hyper-density tissues, so the GTV3 derived from 10 or 3 respiratory phases are recommended.