双能CT低能级虚拟单能图像对下咽鳞状细胞癌病灶显示及T分期的评估价值

Value of low-energy virtual monochromatic images of dual-energy CT in the evaluation of tumor visibility and T staging in hypopharyngeal squamous cell carcinoma

目的探讨双能CT 45 keV低能级虚拟单能图像(VMI)对下咽鳞状细胞癌病灶显示及T分期的评估价值。方法回顾性分析2018年4月至2020年1月在复旦大学附属眼耳鼻喉科医院治疗前行双能CT检查的58例下咽鳞状细胞癌患者的临床及影像资料。采用增强静脉期图像, 经双能后处理软件获得2组图像, 分别为45 keV VMI和标准混合图像(30% 80 kV+70% 140 kV)。由1名高年资和1名低年资放射科医师分别以5分Likert法独立评估2组图像对下咽鳞状细胞癌病灶的总体显示评分。高年资医师进一步对各解剖亚区(梨状窝、咽后壁、环后区)下咽癌病灶的显示以及判断深部侵犯(食管入口、带状肌、椎前肌)进行评分, 并以盲法分别利用这2组图像对所有病灶进行T分期。以病理T分期(手术病例)或临床T分期(非手术病例)为金标准, 计算2组图像T分期的准确度。采用Wilcoxon符号秩检验比较2组图像评分的差异, 采用McNemar-Bowker检验比较2组图像T分期准确度的差异。结果高年资医师对45 keV VMI及标准混合图像总体显示评分为3.5(3, 4)分和3(2, 3)分, 差异有统计学意义(Z=-7.03, P<0.001);低年资医师的评分为3(3, 4)分和2(2, 3)分, 差异有统计学意义(Z=-6.93, P<0.001)。45 keV VMI对梨状窝、咽后壁及环后区病灶显示评分和侵犯带状肌的评分均高于标准混合图像, 差异有统计学意义(P<0.05);2组图像对侵犯食管入口和椎前肌的评分差异无统计学意义(P>0.05)。采用45 keV VMI和标准混合图像对下咽癌T分期的准确度分别为87.9%(51/58)和81.0%(47/58), 差异无统计学意义(χ^(2)=3.33, P=0.189)。结论 45 keV VMI对下咽鳞状细胞癌的病灶显示和评价侵犯带状肌优于标准混合图像, 对T分期的准确度有限提高, 但差异无统计学意义, 对于判断食管入口和椎前肌是否受侵犯无明显优势。

Objective To investigate the value of low-energy virtual monoenergetic image(VMI)at 45 keV in visualizing the primary tumor and T staging of hypopharyngeal squamous cell carcinoma.Methods The clinical and imaging data of 58 patients with hypopharyngeal squamous cell carcinoma from April 2018 to January 2020 at Eye&ENT Hospital,Fudan University were analyzed retrospectively.All the patients underwent a venous phase contrast-enhanced dual-source dual-energy CT scan before treatment.The VMI at 45 keV and standard linearly blended image(30%80 kV+70%140 kV)were acquired from dual-energy post-processing software.One senior radiologist and one junior radiologist independently assessed the visibility of the tumor on the 45 keV VMI and standard linearly blended image using a 5-point Likert rating scale.Furthermore,the senior radiologist assessed the visibility of the tumor at each subsite(piriform fossa,posterior pharyngeal wall,postcricoid region)and determined the invasion depth of the tumor(extension to esophagus,invasion to strip muscles and prevertebral muscles)and performed the T staging of the primary tumor using the two sets of images blindly.The accuracy of T staging was calculated,using pathological T staging(surgical cases)or clinical T staging(non-surgical cases)as the gold standard.The image scores of the two sets of images were compared using Wilcoxon rank sum test.McNemar-Bowker test was used to compare the accuracy of T staging using the two sets of images.Results The overall image scores of the 45 keV VMI and standard linearly blended image from the senior radiologist were 3.5(3,4)and 3(2,3)respectively(Z=-7.03,P<0.001),and the scores from the junior radiologist were 3(3,4)and 2(2,3)(Z=-6.93,P<0.001).The scores of the 45 keV VMI were significantly higher than those of the standard linearly blended image in visualizing tumors in the piriform fossa,posterior pharyngeal wall,and postcricoid region,as well as in detecting invasion to the strip muscles(P<0.05).There was no significant difference in the scores of the two sets of images in determining whether the tumor extended to esophagus or invaded prevertebral muscles(P>0.05).Referring to pathological and clinical T stage,the accuracy of T staging determined by the 45 keV VMI and standard linearly blended image was 87.9%(51/58)and 81.0%(47/58)respectively,and the difference was not significant(χ^(2)=3.33,P=0.189).Conclusions The 45 keV VMI is superior to the standard linearly blended image in visualizing tumors and detecting invasion to the strip muscles of hypopharynx squamous cell carcinoma.However,the accuracy of determining T staging using 45 keV VMI is slightly improved than that of standard linearly blended image,and the difference is not statistically significant.In determining whether the tumor extends to esophagus or invades prevertebral muscles,45 keV VMI shows no significant advantage over standard linearly blended image.