Modern diagnostic concepts in dissection and aortic occlusion

For the diagnostic work-up of the aorta, non-invasive cross-sectional imaging techniques have almost replaced invasive catheter angiography. CT- and MR-angiography are supplemented by sonography which is used predominantly for the assessment of abdominal aortic aneurysm and dissections of the thoracic aorta. This review deals with the diagnostic approach to two disease entities involving the aorta: aortic dissection and aortic occlusion. Transoesophageal echocardiography (TEE), CT- and MR-angiography (MRA) are used in the assessment of aortic dissection. Published sensitivity and specificity values regarding the detection and classification of dissections into Stanford A and Stanford B range between 96-100% for all three modalities. Results for multislice CTA have not yet been reported, but can be expected to be at least as good. The ability to delineate additional information regarding the precise morphology of true and false lumen, entry and reentry-sites, the development of thrombus or paraaortic hematomas, as well as the assessment of aortic regurgitation or involvement of coronary arteries depend on the chosen technique. Reflecting the ability to collect functional imaging data, both TEE and MRA are superior to CTA in the assessment of aortic valve involvement, while TEE is the modality of choice for evaluation of coronary arteries. Sonography is of limited use in the assessment of abdominal dissections. For the evaluation of patients with suspected aortic occlusion both CTA and MRA represent the imaging modalities of choice. Both provide for a comprehensive and precise depiction of the underlying aortic morphology, the extent of collateral flow as well as delineation of distal run-off vessels. MRA should be employed in patients with impaired renal function as paramagnetic contrast agents are not nephrotoxic.     

Reconstruction methods in postprocessing of CT- and MR-angiography of the aorta

The aim of the study was to investigate the use of 2D and 3D reconstructions in examinations of the aorta with CT and MRI. Postprocessing of 5 data sets including 2D MPR reconstructions, 3D MIP reconstructions and 3D volume rendering reconstructions acquired with contrast enhanced CTA and 5 data sets acquired with contrast enhanced MRA were performed. The luminal diameter, the length of the aneurysm and the detection of dissection was assessed for the reconstructions and the source images. Aneurysms and dissections of the aorta were correctly identified on source images. 2D MPR reconstructions and source images allow for a clear and easy image analysis including cases with high signal intensity or density of surrounding tissue and complex anatomical structures. The diameter and length of pathological findings can be determined correctly wit 2D MPR reconstructions, even when the vessel orientation is not exactly inplane or throughplane in relation to the source images. MIP reconstructions are suitable for contrast enhanced MRA data sets with high C/N ratio and volume rendering reconstructions are suitable for contrast enhanced CTA data sets, where calcifications and bone have also high density. For 3D visualization of large volumes MIP reconstructions are the method of choice for MRA and volume rendering reconstructions for CTA, respectively. In addition, 2D MPR can be necessary to determine the diameter and length of pathological findings.     

二维平扫与三维增强法MRA在急性下肢动脉闭塞中的应用

目的 比较两种方法在急性下肢动脉闭塞中的应用价值。旨在临床急诊提供快速、准确的检查方法。方法 采用二维平扫ＴＯＦ法及三维增强法对１０例急性下肢动脉闭塞患进行检查。９例进行急诊手术,以手术结果为金标准进行效果评定。结果 二维平扫与三维增强诊断下肢动脉闭塞敏感性分别为７０％、１００％。三维增强对病变长度的估计准确性大于二维平扫。结论 三维增强法快速准确,是急性下肢动脉闭塞首选的检查方法《二维平扫法有价值,如定位明确,在大腿段病变可用二维平扫。     

人巨细胞病毒相关性缺血性脑血管病患者头MRA检查分析

目的　探讨人巨细胞病毒（human　cytomegalovirus，HCMV）活动性感染相关性缺血性脑血管病患者头MRA特点。方法　采用病例-对照研究的方法，应用免疫荧光方法检测外周血白细胞HCMV　pp65作为HCMV活动性感染指标，将研究对象分为两组：HCMV活动性感染组（HCMV　pp65检测阳性）和非HCMV活动性感染组（HCMV　pp65检测阴性）。观察37例HCMV活动性感染相关的缺血性脑血管病患者和104例非HCMV活动性感染相关的缺血性脑血管病患者MRA检查结果，同时比较两组间年龄，性别，高血压，高脂血症，糖尿病等缺血性脑血管病相关因素。结果　HCMV活动性感染组和非HCMV活动性感染组间年龄，性别，高血压，高脂血症，糖尿病等构成均无统计学差异。比较两组头MRA检查异常的发生率，两组狭窄，动脉硬化及同时含两种以上病变的发生率，P值均大于0．05，亦无统计学意义。HCMV活动性感染组无血管闭塞的发生，HCMV非活动性感染组有5例发生血管闭塞。比较两组颈内动脉系统，椎基底动脉系统及两者皆受累的发生率无统计学意义。比较两组头MRA检查颈内动脉，大脑前动脉A1段，大脑中动脉M1段，大脑後动脉P1段狭窄或／和闭塞的发生率均无统计学意义。结论　HCMV活动性感染相关性缺血性脑血管病患者与非活动性感染相关性缺血性脑血管病患者头MRA检查比较无显着性差异，但本文病例数较少，有待扩大样本量進一步研究证实。     

3D-TOF-MRA诊断偏侧面肌痉挛、三叉神经痛的病因

目的　研究增强三维体积扫描时间飞跃法磁共振血管成像 (3D -TOF -MRA)对偏侧面肌痉挛 (HFS)、三叉神经痛 (TN)病因诊断的临床价值。方法　常规颅脑MRI及增强 3D -TOF -MRA脑干薄层扫描 48例HFS患者和 46名对照、42例TN患者和 40名对照 ,盲法诊断面神经、三叉神经根部解剖改变 ,患者组与各自对照组作对照分析。结果　 (1)HFS、TN患者症状侧面神经根部、三叉神经根部受压迫 45侧 (93 .8% )和 3 6侧 (85 .7% ) ,其中血管压迫 44侧 (91.7% )和 3 2侧 (76.2 % ) ,肿瘤压迫 1侧 (2 .1% )和 4侧(8.9% ) ;无症状侧受血管压迫 8侧 (16.7% )和 4侧 (9.5 % ) ;对照组双侧受压迫 4侧 (4 .4% )和 5侧 (6.3 % )。 (2 )常见压迫面神经的血管为小脑前下动脉 (AICA) 17侧 (3 8.6% ) ,小脑后下动脉 (PICA) 12侧 (2 7.3 % ) ,椎动脉 (VA) 6侧 (13 .6% ) ;压迫三叉神经的血管为小脑上动脉 (SCA) 18侧 (5 6.3 % ) ,小脑前下动脉 (AICA) 5侧 (15 .6% ) ,起源不清的血管 (DIV) 4侧 (12 .5 % )。 (3 )面神经根部、三叉神经根部血管压迫发生HFS、TN的相对危险度估计值为 2 6.6和 9.84。 (4 )手术证实面肌痉挛组 3例、三叉神经痛组 6例神经血管压迫 ,面肌痉挛组 1例、三叉神经痛组 4例肿瘤压迫神经。结论　MRI加增强 3D -TOF -MRA     

烟雾病的临床和影像学特点分析

目的分析烟雾病的临床和影像学特点。方法总结45例烟雾病患者临床和影像学特点,其中17例经磁共振成像血管造影（MRA）确诊,26例经数字减影血管造影（DSA）确诊,2例经CT血管造影（CTA）确诊。结果本组患者中年龄最小6岁,最大58岁,≤15岁年龄组发病8例,〉15岁年龄组发病37例。发病年龄高峰在40岁左右。本组中19例为脑梗死,均是多发性脑梗死,26例为出血性脑卒中,表现为脑室出血10例,基底节区出血9例,脑叶出血5例,SAH2例。结论烟雾病在成年发病多于儿童和青少年。出血性脑卒中以脑室和基底节区出血多见,脑梗死常表现为多发性脑梗死。MRA、DSA和CTA均能明确脑血管病变的部位和性质,CT和MRI可见脑卒中病变部位呈多发性特点。     

静脉注射Gd－DTPA在三维TOF法磁共振脑血管成像中的应用价值

为了降低饱和作用, 提高单体积三维TOF法静脉血管及动脉小分支的显示能力, 我们采用了静脉注射造影剂(Gd-DTPA)的方法缩短血液的T1值, 减少饱和作用影响。结果表明, 增强MRA不但动脉小分支显示能力提高, 而且扫描层面内的重要脑内静脉血管结构显示很清楚, 血管的CNR提高。增强MRA短时间内同时显示高分辨率的动静脉血管结构将明显提高MRA的临床应用价值, 减少对静脉血管疾病的遗漏。     

弥散加权磁共振与磁共振血管成像在急性脑梗死诊断中的临床应用

目的　评价弥散加权磁共振成像 (Diffusion -weightedimaging ,DWI)及磁共振血管成像 (MagneticReso nanceAngiography ,MRA)在脑梗死早期的临床应用价值。 方法　对 3 0例急性脑梗死患者行DWI和MRA检查 ,并与CT、常规MRI的结果进行分析比较。结果　在超早期及早期急性脑梗死中DWI可显示CT及T2 WI不能显示的病灶 ,对于T2 WI能显示的病灶DWI能更清楚、更全面的显示该病灶 ,MRA能快速发现血管病变的部位和程度。结论　DWI与MRA对急性脑梗死的早期诊断十分敏感 ,联合检查可同时显示脑实质和脑血管情况 ,为早期溶栓治疗提供了切实可行的影像学资料     

Contrast circulation in adult fontan patients using MR Time Resolved Angiography: Application for CT pulmonary angiography

BackgroundWhen patients with Fontan circulation require a computed tomographic pulmonary angiogram (CTPA), there are significant challenges in achieving adequate contrast opacification due to the altered anatomical connections. This study used Time Resolved Angiography with Interleaved Stochastic Trajectories (TWIST) Magnetic Resonance Angiography (MRA) to examine contrast circulation in a cohort of patients with Fontan circulation who were having routine MRI follow up to inform the contrast timing of any subsequent CT.MethodsThis is a single centre, cross-sectional, observational, retrospective study. The time to peak (TTP) signal intensity from the MRA was recorded using regions of interest on the aorta, pulmonary arteries, cavae and Fontan conduit. Patients were grouped by ejection fraction, global longitudinal strain, indexed stroke volume and cardiac index to examine if these cardiac performance parameters affected the mean TTP. Statistical analysis was performed to find the mean TTP for each of the vessels, which was consequently compared between the different cardiac performance parameters.Results35 patients were included in the study. Mean TTP contrast enhancement was 31s in the thoracic aorta, 46s in the right pulmonary artery, 41s in the left pulmonary artery and 55s in the Fontan conduit. Cardiac performance shows no statistically significant relationship to the peak contrast enhancement whether measured by ejection fraction, global longitudinal strain, stroke volume index or cardiac index.ConclusionThe mean optimal timing for a single-phase examination of the Fontan circulation, following an upper limb injection, was 55 s following start of contrast injection irrespective of cardiac performance. In TWIST MRA, the IV bolus is 4–5 s duration. A longer bolus is required for CTA, around 20s, suggesting an additional delay will be required. We propose that an optimal single phase CTPA to be protocolled at 70 s following the start of contrast injection, assuming adequate iodinated contrast dose.     

Two-dimensional coronary MRA: limitations and artifacts

Our purpose was to assess image quality and interpretation problems of two-dimensional (2D) coronary MR angiograms. The coronary arteries of 27 subjects (12 normal volunteers and 15 patients) were evaluated with 2D coronary MR angiography (MRA). Coronary MRA was performed with a fat-suppressed electrocardiographically gated breath-hold gradient-echo sequence with k-space segmentation using a 1.5-T imager. Image quality throughout the study was occasionally degraded by: image ghosting (22%), ringing (19%), and/or blurring (22%) and incomplete fat-suppression (19%). Intermittent difficulties with breathholding were encountered in 44% of subjects. When limiting the analysis to those images with optimal image quality, interpretative difficulties were sometimes found: misregistration due to inconsistent breathholding (37%); difficulty in distinguishing veins from arteries (37%); obscured anatomy due to overlapping structures (26%); and poor visualization of portions of the left main coronary artery (59%). Two-dimensional coronary MRA studies have image quality and interpretive problems which need to be understood and addressed before routine clinical scanning is initiated.Correspondence to: A. J. Duerinckx