目的:在18F-FDG PET/MR对进展期宫颈癌放疗靶区的勾画中,FDG PET自动勾画的肿瘤体积随着最大标准摄取值(SUVmax)不同百分比的阈值而改变,为了减少这种因素对PET和MR图像融合的干扰,我们试图找到一个使PET上宫颈癌肿瘤体积与MR上融合最好的SUVmax的百分阈值.方法:病理活检证实为宫颈癌(ⅡB或以上)的患者被纳入研究,在治疗前进行18F-FD)GPET/MRI扫描.由两名有经验的放射科医生来勾画肿瘤的边界.在MR上宫颈癌的体积是通过绘制T2WI MR矢状图像上每一层肿块的轮廓,通过计算每一层的面积乘以层厚得到的.在PET图像上,我们选取20％～60％的SUVmax(间隔5％),软件自动生成肿瘤的体积.记录FDG-PET上不同百分比SUVmax上肿瘤的平均体积和中位体积.采用SPSS 17.0软件用Pearson相关系数分析不同百分比的阈值上自动生成的PET的体积和MR上肿瘤体积的相关性.计算不同百分比SUVmax上PET体积和MR上肿瘤体积的平均差,采用Student's t检验比较不同百分比SUVmax上PET体积和MR上肿瘤体积的差别.结果:在这项研究中有20名患者符合纳入标准.在MR上原发肿瘤的平均体积为(40.5±28.0) cm3.35％ SUVmax值上PET的体积与MRI上肿瘤的平均体积的相关性最高,Pearson相关系数和绝对系数分别为0.888和0.789.而且在35％ SUVmax时二者平均体积差异最小,根据Student's t检验,在35％ SUVmax上得到的PET体积与MR体积差值没有统计学意义(P＞0.05).结论:我们研究的结果表明,在进展期宫颈癌的靶区勾画中,在35％ SUVmax时PET上自动勾画的肿块体积与MRI体积有显著的相关性,35％ SUVmax PET体积与MR体积无明显统计学差异.%Objective:In advanced cervical cancer radiotherapy target delineation,tumor volumes auto contoured by FDG PET scan change at different percentages of maximum standardized uptake value (SUVmax).To reduce such effect which interferes from PET and MR image fusion,we attempted to get a cutoff SUVmax at which the tumor volume correlates best with MRI volume on the primary tumors of cervical carcinoma.Methods:Patients with biopsy-proven cervical carcinomas (stages ⅡB and above) were included in this study and underwent pretreatment 18F-FDG PET/MRI.The dimensions were measured by two competent radiologists.Counters of the diseases were drawn in each slice on sagittal T2WI MR images,and volumes of the cervical carcinoma were calculated by tumor area multiplying slice profile.Volumes of the FDG PET scan at 20％～60％(with an interval of 5％) of SUVmax were auto calculated.Mean and median volumes of different SUVmax cutoff percentages on FDG-PET scan were recorded.Pearson correlation was used to analyze the correlation of MR and PET volumes at different thresholds with SPSS 17.0.The mean difference values between PET volumes at different thresholds and MR volumes were calculated,the difference between different SUVmax percentage PET volume and MR volume were analyzed by Student's t test.Results:Data of 20 patients were available for the study.The mean MRI volume of the primary tumor was (40.5±28.0) cm3.The mean MRI volume correlates significantly(P＜0.001) with 35％ SUVmax PET volume with good correlation according to the Pearson bivariate correlation (r=0.888,r2=0.789).The mean difference between MRI and PET volumes was the least at 35％ SUVmax.There was no significant difference in the MRI and FDG-PET volumes obtained with SUVmax cutoff values of 35％ SUVmax (P＞0.05) according to the Student's t test.Conclusions:18F-FDG PET-MR SUV-based primary tumor volume estimation at 35％ SUVmax value correlates significantly with the criterion standard MR T2WI volumes for primary cervical tumor in our population.The difference of 35％ SUVmax PET volume with MR T2WI volume is no statistical significance.
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