Objective: To compare and evaluate the diagnostic performance of visual evaluation and CT maximal density relative enhancement value in the diagnosis of intestinal ischemia complication in patients with closed loop obstruction and to explore the feasibility of CT maximal density relative enhancement value in quantifying the degrees of intestinal ischemia. Methods: The clinical and CT imaging data of 82 patients, 46 males and 36 females, aged from 19 to 78(52±18) years, with closed loop obstruction were retrospectively analyzed in the First Affiliated Hospital of Zhengzhou University from July 2017 to July 2019. All patients were classified into three groups: necrosis group (28 cases), ischemia group (22 cases), non-ischemia group(32 cases) using clinicopathologic results as reference standard. CT visual evaluation was performed by two experienced radiologists. The sensitivity, specificity, positive and negative predictive values and accuracy of the two observers were calculated respectively. The inter-observer agreement was analyzed by kappa analysis. Maximal density relative enhancement value was defined as the difference CT value of an ROI at dilated obstructed loops between contrast-enhanced and unenhanced CT images. The differences among groups were compared by one-way analysis of variance. Diagnostic performances were evaluated by receiver operating characteristic (ROC) curve analysis. Results: The sensitivity, specificity, positive and negative predictive values and accuracy of observer1 were 62.0%, 87.5%, 88.6%, 59.6%, 72.0%, and 58.0%, 93.8%, 93.5%, 58.8%, 72.0%for observer2, respectively. The kappa value of inter-observer agreement was 0.747. The unenhanced CT value of necrosis group, ischemia group and non-ischemia group was (53.7±9.7), (45.7±7.2) and (44.7±7.0) HU, enhanced CT value was (60.5±10.1), (65.0±11.6) and (87.0±15.8) HU, relative enhancement value was(6.8±8.4), (19.2±12.4) and(44.7±16.2)HU, respectively. All had a statistical difference among three groups (all P<0.05). The unenhanced CT value of necrosis group was higher than that of ischemia group and un-ischemia group (both P<0.05). The enhanced CT value of non-ischemia group was higher than that of ischemia group and necrosis (both P<0.05). The relative enhancement value all had a significant difference between groups (all P<0.05). Taking maximal density relative enhancement value below 19.5 HU as diagnosis threshold, the sensitivity, specificity and area under curve(AUC) were 96.9%, 74.0% and 0.947, respectively. Taking enhanced CT value below 66.5 HU as diagnosis threshold, the sensitivity, specificity and AUC were 93.8%, 60.0% and 0.903, respectively; the sensitivity was higher than that of objective visual evaluation. Conclusion: Maximal density relative enhancement value can quantize the bowel wall enhancement, and is a more reliable way in the diagnosis of intestinal ischemia than visual evaluation.
目的： 对比评估CT主观视觉评价法和客观测量肠壁最大密度相对强化值对闭袢性肠梗阻患者肠缺血并发症的诊断效能，探讨肠壁最大密度相对强化值测量法量化评估肠壁缺血的可行性。 方法： 回顾性收集2017年7月至2019年7月于郑州大学第一附属医院收治的82例闭袢性肠梗阻患者的临床影像学资料，男46例，女36例，年龄19~78（52±18）岁。根据手术及病理结果，分为肠缺血组（50例）和无缺血组（32例），其中肠缺血组又分为缺血坏死组（28例）和单纯缺血组（22例）。由两名放射科医师对其CT图像进行主观视觉评估，判断有无合并肠缺血；以手术病理结果为金标准判断两名医师对肠缺血诊断的灵敏度、特异度、阳性预测值、阴性预测值，以及观察者间的一致性。客观测量平扫、静脉期肠壁CT值最大值，并计算相对强化值；采用单因素方差分析比较缺血坏死组、单纯缺血组和无缺血组肠壁各期CT最大密度值及相对强化值差异性。利用受试者工作特征（ROC）曲线评估最大密度相对强化值对肠壁缺血诊断的灵敏度、特异度和曲线下面积（AUC）。 结果： 观察者1和观察者2对肠缺血诊断的灵敏度、特异度、阳性和阴性预测值及准确度分别为62.0%、87.5%、88.6%、59.6%、72.0%和58.0%、93.8%、93.5%、58.8%、72.0%。观察者间的一致性kappa值为0.747。肠缺血坏死组、单纯缺血组、无缺血组的平扫CT值分别为（53.7±9.7）、（45.7±7.2）和（44.7±7.0）HU，增强CT值分别为（60.5±10.1）、（65.0±11.6）和（87.0±15.8）HU，相对强化值分别为（6.8±8.4）、（19.2±12.4）和（44.7±16.2）HU，三组间比较差异均有统计学意义（均P<0.05）。组内两两比较，平扫CT值在肠缺血坏死组高于单纯缺血组和无缺血组，增强CT值无缺血组高于肠缺血坏死组和单纯缺血组，相对强化值两两比较差异有统计学意义（均P<0.05）；平扫CT值在单纯缺血组与无缺血组间、增强CT值在缺血坏死组与单纯缺血组间差异无统计学意义（均P>0.05）。以最大密度相对强化值<19.5 HU为界，诊断的灵敏度为96.9%，特异度为74.0%，AUC为0.947；以增强CT值<66.5 HU为界，诊断的灵敏度为93.8%，特异度为60.0%，AUC为 0.903。肠壁最大密度相对强化值对肠缺血的诊断灵敏度（96.9%）高于主观视觉评价法（62.0%、58.0%）（P<0.001）。 结论： CT肠壁最大密度相对强化值可量化评估小肠缺血状态，临床诊断闭袢性肠梗阻患者有无合并肠缺血较主观视觉评价法更敏感。.