急性肠缺血的多排螺旋CT研究

【作者】 强金伟；

【导师】 冯晓源； 李克；

【作者基本信息】 复旦大学 ， 影像医学与核医学， 2008， 博士

【摘要】 第一部分肠系膜动脉栓塞致急性肠缺血的多排螺旋CT实验研究目的评估多排螺旋CT(MDCT)显示实验性、动脉堵塞性急性肠缺血(AMI)的早期征象及其动态演化规律,以期能早期诊断肠缺血。材料和方法12只巴马猪,随机分成四组,每组3只。应用Seldinger技术经股动脉穿刺,行肠系膜上动脉(SMA)造影后用明胶海绵和血凝块栓塞其部分空肠和回肠分支。于术前、术后3h、6h、9h、12h用MDCT进行平扫和增强后动脉、静脉和延迟三期扫描,并用容积再现(VR)、最大强度投影(MIP)和薄层最大强度投影(TSMIP)技术进行肠系膜血管重建。与DSA对比,观察CT血管造影(CTA)显示肠系膜血管正常解剖、SMA栓塞、肠系膜和肠道结构变化,比较栓塞后各时间点的动态变化。结果12只实验猪均显示急性肠缺血病理改变,随时间延长,缺血呈进行性加重。MDCT及CTA能清晰地显示正常猪的肠道和肠系膜血管解剖。CTA显示全部57支栓塞血管,34支未栓塞血管中,CTA显示29支通畅,5支中断,敏感性和特异性分别为100%和85.3%。TSMIP显示栓塞远端梳状分支血管和毛发状密集直血管消失,以此标准,TSMIP正确定性24个栓塞肠段中的23个和全部12个正常肠段,敏感性和特异性分别为95.8%和100%。早期、直接的肠缺血CT征象为:SMA血管中断,栓塞远端梳状或毛刷状密集直血管消失,以及肠段强化减弱,早期、间接的征象为肠腔扩张及积液。结论MDCT及CTA能清晰地显示正常猪的肠道和肠系膜血管解剖,很可靠地诊断模型猪的动脉堵塞性肠缺血,显示肠缺血的早期变化。第二部分肠系膜静脉结扎致急性肠缺血的多排螺旋CT实验研究目的评估多排螺旋CT显示实验性、静脉堵塞性急性肠缺血的早期征象及其动态演化规律。材料和方法12只巴马猪,随机分成三个实验组和一个对照组,每组3只。实验组9只猪经剖腹结扎SMV主干远端空肠、回肠和回结肠支,对照组3只猪仅剖腹分离暴露SMV。于术前、术后6h、12h、18h用MDCT进行平扫和增强后动脉、静脉和延迟期三期扫描,并进行肠系膜血管CTA重建。比较手术前后肠系膜血管、肠道、腹腔形态的动态变化,结果与病理对照。结果9只实验猪均显示急性肠缺血病理改变,随时间延长,缺血呈进行性加重。SMV结扎后6h,肠壁充血、水肿、静脉淤张,病变限于粘膜及粘膜下层;12h水肿加重,病变累及全层,肠壁增厚明显;18h出现粘膜弥漫性坏死、脱落、溃疡,肌纤维断裂、纤维素性渗出,肠腔扩张积液,肠壁变薄。MDCTA可准确显示SMV主干、大属支及其远端小分支直至肠壁边缘的直小静脉,显示SMV结扎点的位置。静脉堵塞性肠缺血的早期MDCT改变为肠壁增厚,系膜水肿,腹水,肠壁强化高于正常,SMA痉挛、充盈欠佳、显影延迟和延长,SMV显影淡、延迟;随时间推移,出现肠壁变薄,肠腔扩张、积液,系膜水肿、腹水加重,肠壁强化减弱。结论结扎猪SMV属支可成功地复制人类静脉堵塞性肠缺血。MDCT能清晰显示肠系膜血管解剖、堵塞的静脉、早期肠缺血改变及其动态演化规律,可靠地诊断静脉堵塞性肠缺血。第三部分多排螺旋CT肠系膜血管造影的技术优化及三维解剖学研究目的研究多排螺旋CT肠系膜血管造影(MDCTA)的技术优化方案,观测肠系膜血管的三维影像学解剖。方法140例患者根据扫描准直、重建层厚、对比剂浓度、注射速率和延迟时间分成7个研究组,行全腹部MDCT增强扫描,用VR、MIP和TSMIP技术进行肠系膜血管三维重建,对血管边缘的光滑度及分支级别进行评分,比较不同技术参数、重建方法显示血管的能力。观察和测量100例肠系膜血管的空间解剖特征。结果0.6mm准直时,1.0mm层厚重建的动脉CTA像评分最高,但差异无统计学意义;1.0mm和1.5mm层厚重建的静脉CTV像优于0.6mm层厚,差异有统计学意义,以1.0mm层厚最佳。0.6mm准直优于1.2mm准直,但差异无统计意义。370mgI/ml对比剂在显示肠系膜动脉和静脉方面均优于300mgI/ml,差异有统计意义。注射速率4.0ml/s和5.0ml/s显示动脉优于3.0ml/s,差异有统计意义;显示静脉差异无统计意义。静脉期延迟时间以动脉期延后25s最佳。100例肠系膜血管均清晰显示,VR及MIP像整体性好,可显示3～4级分支,前者空间立体感强,TSMIP可显示5～6级分支至肠壁周围血管网。MDCTA可清晰显示肠系膜血管的位置、起源、管径、走向、分布、吻合支及解剖变异。结论最优化方案为:0.6mm准直、1.0mm重建层厚、对比剂浓度370mgI/ml、4.0ml/s以上注射速率、团注测试法确定动脉期时间和静脉期延迟时间为动脉期延后25s。MDCTA能很好的显示肠系膜血管的三维解剖学特征,为临床诊断和治疗提供依据。第四部分多排螺旋CT肠系膜血管造影在急性肠缺血中的应用目的探讨多排螺旋CT肠系膜血管造影(MDCT angiography)在急性肠缺血(AMI)中的应用价值。材料和方法43例经临床或手术病理证实的AMI患者行全腹MDCT平扫、0.6mm准直的动脉期和门脉期扫描,采用VR、MIP和TSMIP血管重建技术进行肠系膜动脉和静脉成像,重点观察肠系膜血管的异常表现,并结合肠道和肠系膜异常征象。结果AMI的原因为:SMA栓塞4例、SMA血栓形成6例,SMV血栓形成13例,SMA夹层5例,绞窄性肠梗阻10例,血管炎5例。43例AMI中,17例手术治疗,其中6例见肠坏死作手术切除,其余11例为肠缺血。7例和19例分别经DSA介入和内科保守治疗,24例好转,1例恶化、1例死亡。MDCTA可清晰地显示AMI的血管异常,如血管堵塞、狭窄或夹层的部位、形态、程度和范围;显示血管走向的异常,如聚拢、推移、扭曲或扭转等;并显示侧枝血管。MDCTA可明确导致AMI的原因,如粥样硬化斑块、栓子、血栓形成、夹层、肿瘤血管侵犯、绞窄性肠梗阻和血管炎等。结论MDCT三维血管成像能很好地显示AMI的直接征象,即肠系膜血管的异常,如结合间接征象可在病变早期诊断AMI并明确病因。更多还原

【Abstract】 PARTⅠMDCT and CTA of Acute Mesenteric Ischemia Induced by Embolization of SMA in an Experimental Porcine ModelObjective To assess the usefulness of multidetector row CT (MDCT) and CT angiography (CTA) for detecting the early sign of acute mesenteric ischemia (AMI) in experimental porcine model. Materials and Methods 12 pigs were assigned to four groups with 3 pigs in each group. The digital subtraction angiography (DSA) of superior mesenteric artery (SMA) and the embolization of branches of SMA were performed using a percutaneous Seldinger technique, with gel foam and blood clot. MDCT pre- and postcontrast with arterial, venous and delay phase scans, and CTA with three-dimentional reconstrations were carried out at preoperation, 3 h, 6 h, 9 h, and 12 h after occlusion. The normal mesenteric vascular anatomy, arterial occlusion, mesentery and bowel changes, and dynamic evolution were evaluated. Results AMI changes were identified pathologically in all 12 experimental pigs, with the severity corresponding to the time of embolization. CTA showed all 57 embolized branches of SMA and 29 of 34 unoccluded arterial branches with 5 false-positive vessel occlusions. Its sensitivity and specificity were 100% and 85.3% respectively. Thin-slab maximum intensity projection (TSMIP) identified the disappearance of distal combed vessel branches and brush vasa recta, which were clearly delineated in normal bowel segment. Using this criterion, TSMIP correctly defined 23 of 24 ischemic bowel segments and all 12 normal bowel segments with 95.8% of sensitivity and 100% specificity. The early direct ischemic signs were occluded vessels, the disappearance of distal combed or brushy vasa recta, and poor bowel enhancement. The early indirect sign was bowel dilatation with fluid. Conclusion MDCT and CTA reliably define normal and occluded mesenteric vessels in the pig. It can easily detecte ischemic bowel segment by identified early changes of ischemia.PARTⅡMDCT Evaluation of Acute Mesenteric Ischemia Induced by Ligation of SMV in an Experimental Porcine ModelObjective To evaluate MDCT for detecting the early sign and dynamic evolution of AMI induced by occlusion of SMV in experimental porcine model. Materials and Methods 12 pigs were assigned randomly to three experimental groups and one control group with 3 pigs in each group. After performing laparotomy, SMV was separated and ligated in 9 pigs, and separated wothout ligation in 3 control pigs. MDCT pre- and postcontrast with arterial, venous and delay phase scans, and CTA reconstrations of mesenteric vessels were carried out at preoperation, 6 h, 12 h and 18h after ligation. The changes of mesenteric vessels, bowel, abdominal cavity pre-and post-operation, and dynamic evolution were evaluated. The results were compared with those of pathology. Results AMI changes were identified pathologically in all 9 experimental pigs. The congestion, edema and venular engorgement were found limiting to submucosa at 6h, and involving all layers with thicken wall, hemorrhage, and loss of some mucosa at 12h ligation of SMV. Diffuse necrosis, loss, ulcer and hemorrhage of mucosa, degeneration and fragmentation of muscular fibers, and fibrinous effusion, with bowel dilatation, fluid and thinness were seen at 18h. MDCTA clearly delineated main trunk of SMV, peripheral major and minor tributaries up to brushy vasa recta. It correctly identified the location and shape of ligation. The early ischemic findings were bowel wall thickness, mesenteric stranding, ascites and pronounced bowel enhancement. SMA and its major branches appeared spasm which displaying poor filling and delayed and prolonged visualization, and SMV and its tributaries appeared poor and delayed opacification. With time lapse, thinning bowel wall, dilatating bowel with fluid, aggravating edema of mesentery and acites and poor enhanced bowel were identified. Conclusion Human venous occlusive AMI can be duplicated successfully by the ligation of porcine SMV tributaries. MDCT can reliably define normal and occluded mesenteric vessels, detecte early changes mesenteric ischemia and evolution, and diagnosis venous occlusive AMI.PARTⅢThe Optimization of Parameters and Anatomical Evaluation of Mesenteric Vessels with MDCT AngiographyObjective To optimize the parameters of multidetector row CT (MDCT) angiography in demonstrating mesenteric vessels and investigate the imaging anatomy of mesenteric vessels. Materials and Method One hundred and forty patients with no abnormal alimentary tract were divided into seven groups with 20 cases each, according to the collimation, slice thickness, the concentration of contrast medium, injection rate and delay time. Enhanced MDCT of whole abdomen were performed, and CT angiograms of mesenteric vessels were reconstructed with volume rendering (VR), maximum intensity projection (MIP) and thin-slab maximum intensity projection (TSMIP). The margin and branches of vessels were scored. The parameters and reconstruction techniques were compared. Three-dimensional (3D) anatomical architectures of 100 cases of mesenteric vessels were analyzed. Results At 0.6mm collimation, CT angiography reconstructed with 1.0mm slice thickness had highest scores in demonstrating mesenteric arteries without statistically significant difference among different slice thickness. CT venography with1.0mm slice thickness was superior to 0.6mm and 1.5mm in demonstrating veins, with statistical difference in the former. CT angiography with 0.6mm collimation was better than that with 1.2mm, with no statistical difference. The 370mgI/ml contrast medium was better than 300mgI/ml in delineating mesenteric arteries as well as veins. The injection rate of 4.0ml/s and 5.0ml/s were superior to 3.0ml/s in demonstrating mesenteric arteries but veins. The optimal delay time of venous phase was 25s behind the arterial phase. Mesenteric vessels were well displayed in all 100 cases. The 3th to 4th -order branches of vessels could be identified in VR and MIP images with better whole view, and better 3D view in the former. In contrast, TSMIP could clearly show the 5th to 6th-order branches of vessels including the vasa recta at the margin of bowel. MDCT angiography clearly displayed the location, origin, diameter, direction, distribution, vascular anastomosis and variation of mesenteric vessels. Conclusion The optimal protocol of MDCT angiography for mesenteric vessels is 0.6mm collimation, 1.0mm slice thickness with 0.5mm increment, 370mgI/ml contrast medium at 4.0ml/s or 5.0ml/s injection rate, the delay time of arterial phase decided by test bolus, and venous phase being 25s behind arterial phase. MDCT with 3D reformatting can clearly visualize the anatomical features of mesenteric vessels; thus it is helpful for the early diagnosis and intervention of pancreatic cancer, ischemic or inflammatory bowel diseases. PARTⅣThe Application of MDCT Angiography of Mesenteric Vessels in Acute Mesenteric IschemiaObjective To evaluate mesenteeric MDCT angiography in the diagnosis of acute mesenteric ischemia (AMI). Materials and Method 43 cases of AMI proven by clinical criteria, or operation and pathology underwent whole abdomen MDCT precontrast, arterial phase and venous phase with 0.6mm collimation. The mesenteric arteries and veins were reconstructed by using VR, MIP, and TSMIP techniques, and abnormal CT angiography findings as well as abnormal bowel and mesentery were analyzed. Results 43 patients with AMI were resulted from SMA embolism (n=4), SMA thrombosis (n=6), mesenteric and portal venous thrombosis (n=13), SMA dissection (n=5), strangulated bowel obstruction (n=10) and vasculitis (n=5). Among 43 patients with AMI, 17 cases were managed by surgery, with 6 infarctions and 11 ischemias identified. 7 and 19 patients were managed by DSA guided interventional and internal conservative therapy respectively, with improvement in 24 cases, deterioration and death in one case respectively. MDCT angiography showed clearly the position, shape, severity and extent of the vascular occlusion, narrow and dissection. It could also demonstrate the abnormal course and direction of the vessels including vascular gather together, shift, tortuosity, retortion, and twist. Furthermore, the pathogenesis of various conditions leading to AMI including atherosclerotic plaque, emboli, thrombosis, dissection, tumorous invasion, strangulated bowel obstruction and vasculitis could identified by MDCT angiography. Conclusion MDCT angiography can clearly demonstrate the abnormal mesenteric vessels which is the direct sign leading to AMI, and identify AMI and its etiology at early stage, with the combination with its indirect findings.更多还原