Prognostic implications of descending thoracic aorta dilation after surgery for aortic dissection

Background

The present study assessed whether descending thoracic aorta growth can be measured reliably by volumetric analysis using multi-detector row computed tomography (MDCT) and whether growth influences the need for future aortic interventions in survivors of acute type A aortic dissection.

MR imaging of complications of aortic surgery

Sixteen patients with a variety of complications of aortic surgery were evaluated with magnetic resonance (MR) imaging. More than one complication occurred in seven patients, resulting in the following types of abnormalities: graft occlusions, two; graft infections; five; pseudoaneurysms or aneurysmal dilatation of graft anastomoses, 10; perigraft hemorrhages, four; and aortoenteric fistulas, two. The MR findings were verified by surgery in 10, by CT in four, and by angiography in 11 patients. The size and extent of pseudoaneurysm or anastomotic dilatation, the presence of thrombus and vessel occlusion, the extent of abscesses, and the effect of pseudoaneurysms and abscesses on adjacent structures were readily demonstrated by MR. The size of the residual lumen in the case of thrombosis could be assessed. Abscesses were identified by their characteristic signal increase with long repetition rates and long echo delays. Magnetic resonance was also able to exclude suspected complications such as perigraft infection, hemorrhage, and graft occlusion in four patients.     

MR imaging after surgery for vertebrobasilar aneurysm

We examined the safety and utility of high-field MR in patients who had surgery for cerebral aneurysms of the vertebrobasilar system. Eighteen posterior (and three coincidental anterior) circulation aneurysms were treated. Twenty-one MR scans were obtained at a mean postoperative interval of 7.2 days. The mean size of the preoperative vertebrobasilar aneurysm was 2.2 cm; six were giant (greater than 2.5 cm) and eight were large (greater than 1.5, less than or equal to 2.5 cm). In 17 patients, Sugita nonmagnetic clips were used. In one other, a Drake tourniquet was used. No ill effects occurred from scanning with a high-field imaging unit at 1.5 T. The MR clip artifact was much less obtrusive than that on CT. In 11 cases, the aneurysm could be partially imaged postoperatively, mainly in very large aneurysms or in those treated by clipping the parent vessel. Of these, two revealed residual lumina on MR and nine looked completely thrombosed. Postoperative angiography showed that in four of the thrombosed-appearing aneurysms a residual lumen with a mean diameter of 1.0 cm had been missed. In the patient imaged after application of a Drake tourniquet, no artifact was seen, and a good assessment of progressive partial thrombosis was obtained. Evolution of the signal intensity of new aneurysm thrombus, in those minimally or not obscured by artifact, coincides with patterns previously described for hemoglobin in intracerebral hematomas. The earliest hyperintensity could be seen in either the periphery or the center of the new thrombus. All 15 patients examined with new postoperative deficits showed appropriate lesions, mainly small brainstem ischemic foci. Postoperative CT (performed in all but four of these patients) missed over 80% of these lesions, mainly owing to artifact from clip or bone. We conclude that MR is better than CT in the postoperative assessment of aneurysm patients, particularly in demonstrating small zones of ischemia. High-field MR scanning is safe if nonmagnetic surgical clips are used. MR is not accurate in assessing residual lumina.     

MR imaging after surgery for musculoskeletal neoplasm

Magnetic resonance (MR) imaging is the current radiologic method of choice for both detecting recurrent musculoskeletal neoplasm after surgical resection and defining its anatomic extent within soft tissue and bone. Various factors (such as the presence of surgical hardware and postsurgical seromas, hematomas, edema, scarring, and anatomic distortion) complicate the interpretation of postoperative MR imaging in these patients. By optimizing the MR imaging protocol, integrating relevant clinical and pathologic information (such as the date and extent of the most recent surgery and the histologic type and grade of the original tumor) during interpretation of the images, and being familiar with the typical manifestations of postsurgical changes and recurrent musculoskeletal tumors, the radiologist can maximize his ability to help guide patient management effectively.     

Thoracic aortic dissection: pitfalls and artifacts in MR imaging

Results of 53 thoracic magnetic resonance (MR) imaging examinations were reviewed to determine the prevalence and severity of artifacts and pitfalls that may occur in the evaluation of acute aortic dissection. Grade 1 artifacts and pitfalls were mimics of aortic dissection on individual images but could be demonstrated not to represent a dissection when other images from the same sequence were evaluated. Grade 2 artifacts and pitfalls required the use of images from other planes or sequences to distinguish them from a dissection. Grade 3 artifacts and pitfalls could not be distinguished from a dissection without the use of other imaging modalities. Of the 53 cases examined, 34 (64%) had artifacts or pitfalls of grade 1 or higher, 10 (19%) had artifacts or pitfalls of grade 2 or higher, and one case (2%) had grade 3 artifacts or pitfalls. Sixteen cases had more than one artifact or pitfall. Pitfalls and artifacts that mimic aortic dissection occur in a significant percentage of thoracic MR imaging examinations. An awareness of their existence, knowledge of normal anatomy, the use of axial images in all cases with the addition of images in other planes as needed, rotation of phase and frequency gradients as needed, and clinical correlation may avert misinterpretation in nearly all cases.     

MR imaging of the shoulder after surgery

This review article describes postoperative MR findings relating to surgery in shoulder impingement syndrome, including rotator cuff lesions, shoulder instability, and arthroplasty. Potentially misleading postoperative findings are emphasized. Because standard MR imaging may not always be the method of choice for post operative imaging, alternative imaging techniques have been included (MR arthrography, CT arthrography, and sonography).     

MR imaging of the aorta

Recent advances in noninvasive imaging methods, such as CT and MR imaging, have replaced most of invasive angiographic procedures in the diagnosis of acquired aortic disease, decreasing the cost and morbidity of diagnosis. This article reviews and illustrates present MR imaging methods for evaluation of the aorta. Common diseases of the aorta also are discussed with a focus on their unique morphologic and functional features and characteristic MR imaging findings. Knowledge of pathologic conditions of common aortic diseases and proper MR imaging techniques enables accurate and time-efficient aortic evaluation.     

Morphology and hemodynamics in dissection of the descending aorta. Assessment with MR imaging

Purpose: To obtain morphologic and functional information in patients with dissection of the descending aorta using contrast-enhanced MR angiography (MRA) and MR blood flow quantification of the true and false lumina.Material and Methods: Fourteen patients were studied prospectively using a 1.5 T unit. MRA was performed with a 3D FISP sequence (TR/TE/flip angle 4.7/1.9 ms/30°) after injection of 0.2 mmol Gd-DTPA per kg b.w. Flow quantification with phase velocity mapping was done at the level of the diaphragm using a 2D FLASH technique (TR/TE/flip angle 28/6.5 ms/30°) with an average temporal resolution of 23 frames per cardiac cycle (34 ms). A spectral broadening index was applied to quantify the amount of flow irregularity within both channels of the aorta. Extension of the dissection and involvement of the major branch vessels were analyzed.Results: The mean flow volume per minute was 1982 ml (SD 1083 ml) in the true and 1052 ml (SD 763 ml) in the false lumen. Average peak-velocities were 98 cm/s (SD 33 cm/s) in the true channel and 47 cm/s (SD 26 cm/s) in the false channel. Ten patients had bidirectional flow in the false lumen with a reflux volume ranging between 6.8% and 98%. Only 1 patient presented with bidirectional flow in the true lumen (reflux volume 15%). A significantly higher degree of flow irregularity was found in the false lumen compared with the true channel.Conclusion: Different hemodynamic patterns were found in aortic dissection. Their prognostic value and the impact on therapy, specifically percutaneous interventional procedures, have to be further studied.     

Follow-up of aortic dissection: Contribution of MR angiography for evaluation of the abdominal aorta and its branches

Spin-echo MR is an established method to evaluate thoracic aortic dissections, but is not well suited to study the abdominal aorta. In this study we evaluated whether MR angiography could provide a complete examination of the abdominal aorta. In 28 patients (40 MR studies) with suspected (n=6) or known (n=34) aortic dissection, MR studies were performed. Thoracic aorta was evaluated with spinecho and gradient-recalled-echo MR imaging. Axial two-dimensional time-of-flight MR angiography with thin overlapping slices was used to study the abdominal aorta. Intermediate and high signal intensity on MR angiography was interpreted as patent flow, and low signal was interpreted as thrombus. The presence of an intima flap and the re-entry site could be depicted in all MR studies. Thrombus in the false channel was seen in 8 studies. The origin of the abdominal visceral branches and their relation to the false-true channel could be depicted, except in 4 of 80 renal arteries studied. Extension of the dissection into the coeliac trunk was seen in 2 and in the superior mesenteric artery in 10 studies. Dilatation of the suprarenal abdominal aorta was seen in 20 studies, and of the infrarenal aorta in 9 studies. MR angiography provides valuable information about the abdominal aorta and its branches in patients with aortic dissection. This makes MR imaging appealing as the preferred imaging modality for the diagnosis and follow-up of aortic dissection.     

MR evaluation of chronic aortic dissection

Thirty patients with suspected or known chronic aortic dissection were imaged with magnetic resonance (MR), CT, and angiography. Five of these patients had previously undergone surgical repair of the ascending aorta for a type A dissection. Magnetic resonance demonstrated an intimal flap and a double lumen in 25 cases. In four cases with a thrombosed false lumen, proved angiographically, an intimal flap and double channel were not seen. In two of four aortic dissections with a thrombosed false lumen, CT made the diagnosis by showing displaced intimal calcifications not visualized on MR. In one case the aortic dissection was made on CT and angiography but was not supported by MR which showed an aortic aneurysm, subsequently confirmed at surgery. Magnetic resonance, CT, and aortography differentiated between type A (nine patients) or B (20 patients) dissection in all cases and demonstrated extension into the abdominal aorta. Extension into the iliac arteries was seen on MR in three patients but missed in nine patients. Magnetic resonance differentiated the true and false lumen in all but one case. Thrombosis of the false channel was identified in four cases by a decrease in signal intensity on the second echo image. Cardiac gating and longitudinal contiguous sections seemed to be more suitable for appreciation of the relationships with arch vessels. Transverse contiguous slices allowed determination of the origin of celiac, mesenteric, and renal arteries from either the true or the false lumen. This study confirms that MR is an accurate and noninvasive method for the evaluation and follow-up of chronic aortic dissection, obviating the need for iodinated contrast media.     

Coarctation of the aorta: MR imaging

Thirteen patients, aged 3-31 years, with coarctation of the thoracic aorta were examined by magnetic resonance (MR) imaging (total of 14 studies). Eight studies were performed preoperatively and six postoperatively. Catheterization data were available on 12 patients for verification of MR imaging findings. Electrocardiographically gated sagittal and left anterior oblique images best depicted the coarctations; however, involvement of arch vessels was best evaluated on transaxial images. MR imaging readily identified all coarctations but one, their site and extent, and involvement of the arch vessels. In addition, MR images depicted poststenotic dilatation and dilated collateral vessels. In patients studied postoperatively, restenosis could be evaluated, and complications such as postoperative aneurysm and perianastomotic hematoma were identified. MR imaging provides excellent anatomic detail of coarctation of the aorta, potentially obviating the need for angiography.     

MR imaging of blood pool signal variation with cardiac phase in aortic dissection

Electrocardiographic gated magnetic resonance imaging of the thoracic aorta was performed on a patient with aortic dissection. Magnetic resonance demonstrated the intimal flaps and double lumina, allowing correct classification of the dissection as proven surgically. The blood pool signal in the false lumen was low during diastole and higher during systole, which has not been previously described. This signal pattern allows definition of false luminal patency using a single spin-echo pulse sequence.     

MR imaging of aortic coarctation

Aortic coarctation accounts for 5%–10% of all congenital heart diseases and represents 7% of critically ill infants with heart disease. Magnetic resonance (MR) imaging allows the study of this disease with several advantages in comparison with conventional angiography, transesophageal echocardiography, and computed tomography. The MR protocol applied at our institution for both diagnosis and follow-up after surgical or endovascular treatment consists of four steps: morphologic study, cine MR study, flow analysis, and MR angiography (MRA). The first three sequences are acquired during breath-hold and with electrocardiographic gating. Anatomy is well depicted with dark-blood half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences. Cine true-fast imaging with steady-state precession (true-FISP) sequences show not only morphologic features but also blood-flow changes inside the aorta. Gradient-echo sequences for phase-velocity mapping allow flow analysis. Application of Bernoulli’s equation — here briefly presented and discussed — allows for calculation of the pressure gradient caused by the coarctation. MRA, acquired with a breath-hold three-dimensional T1-weighted gradient-echo sequence and intravenous administration of paramagnetic contrast material, allows for optimal depiction of the aortic lumen, with a panoramic view of the whole aorta, its main branches and possible collateral circulation.     

急性期Stanford B型主动脉夹层患者腔内修复术后主动脉重塑

【摘要】 目的 探讨急性期Stanford B型主动脉夹层（TBAD）胸主动脉腔内修复（TEVAR）术后主动脉重塑及其演变过程。方法 回顾性分析2013年6月至2018年6月单中心诊断为急性期TBAD并行TEVAR治疗的217例患者临床和影像学资料。通过RadiAnt Dicom Viewer工作站进行图像后处理,测量主动脉峡部、肺动脉分叉、膈肌、腹腔干、左肾动脉开口及腹主动脉分叉平面的真腔、假腔直径和总直径,记录假腔血栓化程度。 结果 主动脉峡部、肺动脉分叉平面真腔增大、假腔缩小,差异均有统计学意义（P＜0.05）,假腔血栓化率高;膈肌、腹腔干、左肾动脉开口平面真腔增大、假腔缩小,真腔增大差异均有统计学意义（P＜0.05）,假腔缩小差异均无统计学意义（P＞0.05）,假腔血栓化率较高;腹主动脉分叉平面真腔增大、假腔增大,差异均无统计学意义（P＞0.05）,假腔血栓化率低。各平面术后总直径较术前无明显变化,差异均无统计学意义（P＞0.05）。 结论 TEVAR术后胸降主动脉段重塑良好,真腔明显扩张,假腔明显缩小、血栓化率高。腹主动脉段重塑不良,可能与远端破口旷置有关。远端假腔直径和总直径变化不显著提示夹层可能稳定,远端破口暂无需手术处理,但严密影像学随访远端破口尚未处理患者十分重要。     

螺旋采集和黑血技术在主动脉夹层扫描中的应用

目的 :探讨快速稳态横向扰相梯度回波螺旋采集 (SpiralSPGR)结合双翻转恢复脉冲快速自旋回波 (Double IRFSE)序列在主动脉夹层病变成像中的应用。方法 :3 0例主动脉夹层运用自旋回波 (SE)、Double IRFSE、梯度回波(GRE)及SpiralSPGR序列进行扫描 ,将各种方法扫描的显示效果及图像质量进行对比分析。 结果 :Double IRFSE与spiralSPGR相结合对主动脉夹层的破口位置 ,累及范围 ,内膜片及附壁血栓的显示均优于传统的SE与GRE序列 ,且图像质量亦得到明显改善 ,而在真假腔的显示上两者相近。结论 :对于主动脉夹层病变的显示 ,Double IRFSE结合SpiralSPGR序列对主动脉夹层病变的显示更直观和可靠 ,不失为一种较好的主动脉成像辅助或替代方法     

MR imaging of double aortic arch

Magnetic resonance was used to demonstrate a double aortic arch in a patient initially noted to have a right aortic arch on chest radiography.