Evaluation of U-Net Based Architectures for Automatic Aortic Dissection Segmentation

Segmentation and reconstruction of arteries is important for a variety of medical and engineering fields, such as surgical planning and physiological modeling. However, manual methods can be laborious and subject to a high degree of human variability. In this work, we developed various convolutional neural network ( CNN ) architectures to segment Stanford type B aortic dissections ( TBADs ), characterized by a tear in the descending aortic wall creating a normal channel of blood flow called a true lumen and a pathologic channel within the wall called a false lumen. We introduced several variations to the two-dimensional ( 2D ) and three-dimensional (3 D ) U-Net, where small stacks of slices were inputted into the networks instead of individual slices or whole geometries. We compared these variations with a variety of CNN segmentation architectures and found that stacking the input data slices in the upward direction with 2D U-Net improved segmentation accuracy, as measured by the Dice similarity coefficient ( DC ) and point-by-point average distance ( AVD ), by more than 15\% . Our optimal architecture produced DC scores of 0.94, 0.88, and 0.90 and AVD values of 0.074, 0.22, and 0.11 in the whole aorta, true lumen, and false lumen, respectively. Altogether, the predicted reconstructions closely matched manual reconstructions.

Spot Stenting Combined With False Lumen Endovascular Occlusive Repair for Post-dissection Abdominal Aortic Aneurysm

Purpose: To introduce a new spot stenting, combined with a false lumen endovascular occlusive repair (SS-FLEVOR) technique for treating post-dissection abdominal aortic aneurysms. Technique: This technique is demonstrated in a 74-year-old man who received an initial thoracic endovascular aortic repair 7 years ago and suffered from distal aortic expansion during the follow-up session. All the tears located more than 15 mm away from the orifice of visceral arteries were excluded by spot stenting in the aortic true lumen. Then, a compliant stent-graft was implanted in the false lumen to seal the tears near the visceral arteries orifice from the outside. In addition, coils were deployed to block the potential backflow from the intercostal arteries and to induce false lumen thrombosis. Moreover, visceral arteries originated from false lumen were repaired by covered-stents implanted from the true lumen. The distal iliac arteries were sealed either with iliac extensions or cover-stents. This new technique has been applied in 5 patients, resulting in 100% technical success and encouraging intermediate outcomes. Conclusion: SS-FLEVOR is a feasible and safe technique to promote false lumen thrombosis in selected cases.

Direct true lumen cannulation for type A aortic dissection (Samurai technique) in emergency scenarios

Choosing the optimal arterial cannulation site in type A aortic dissection may be challenging. Aortic dissection is a dynamic condition that can change at any time. Thus all the alternatives available should be known by surgeons in order to adapt to the possible problems that may arise. In this video tutorial, we present a patient with acute type A aortic dissection who, after cardiopulmonary bypass with axillary arterial cannulation, developed a major complication: intraoperative malperfusion due to pressurization of the false lumen. The patient developed occlusion of the right coronary artery with electrocardiogram changes, inferior akinesia, and ventricular arrhythmias. Cerebral saturation was also significantly decreased. This scenario of acute malperfusion calls for immediate action. We proceeded to switch the cardiopulmonary bypass configuration from axillary to direct true lumen cannulation. This technique, also known as the Samurai technique, is feasible in most cases and advantageous in this emergency situation, allowing prompt reestablishment of adequate perfusion of the true lumen . Some authors even advocate more widespread use of this technique because it may ensure antegrade perfusion while avoiding progression of the dissection flap and reduce the rate of the most common complications of other cannulation sites such as plexus injury during axillary cannulation or cerebral embolization through mobilization of thrombi or calcification from femoral retrograde perfusion. This technique is useful in cases of circumferential dissection and in patients with relative contraindications for peripheral cannulation such as morbid obesity or peripheral arterial occlusion by atherosclerosis or by the dissection itself.

The short-term safety and effectiveness of a new distal perforating stent graft in Type B aortic dissection: a retrospective study

Background Spinal artery ischemia (SCI) events can result from over coverage of the descending thoracic aorta with a coated stent during Thoracic Endovascular Aortic Repair (TEVAR). The aim of this study was to determine whether a new distal perforating stent could reduce the incidence of spinal cord ischemia while remodeling the true lumen. Methods TBAD patients treated with Talos stent in the vascular surgery Department of Yan 'an Hospital affiliated to Kunming Medical University between December 2017 and October 2019 were retrospectively analyzed to investigate the short-term safety and effectiveness of Talos stent. Results A total of the 20 patients, including 14 males and 6 females, with an average age of 52.65 ± 8.98 years (range 37–68 years), were included in the analysis. Stent-grafts were successfully implanted in all patients under local anesthesia, with a technical success rate of 100%. The average operation time was 50.75 ± 13.01 min. A total of 2 cases (10%) presented chest pain associated with intercostal artery ischemia that was relieved on the 3rd and 5th postoperative day, respectively. Postoperative mean follow-up was 16.15 ± 3.99 months. No paraplegia or other complications occurred. And stenting did not induce new tears. No migration, deformation, or fracture of the stents occurred. There was a significant difference in the remolding of the true lumen preoperatively and at 12 months postoperatively (P < 0.05). Conclusions Talos stent has achieved satisfactory clinical treatment results in short term.

Describing The Use of Two Hybrid Prostheses in The Staged Surgical Repair of Aortic Dissection

Background-Reconstruction of the thoracoabdominal aorta after dissection (Stanford Type A with extension into descending aorta) has limited surgical options. Described here is a novel technique for the staged surgical repair of the thoracoabdominal aorta after reconstruction of the ascending aorta with aortic arch using a hybrid prosthesis. Case presentation- The thoracoabdominal aorta is accessed via a lateral thoracotomy. After a left-left bypass to perfuse the descending aorta, the proximal end of the prosthesis is anastomosed to the proximal aorta and distal end of the new prosthesis is then inserted into the true lumen of the descending aorta and the stent is deployed. Conclusion-Using this technique, operative time is reduced with accurate reconstructions of the anatomy.

Aortic remodelling and false lumen changes after the frozen elephant trunk technique using the thoraflex hybrid stented graft for aortic dissection

Background Despite the marked improvement in the aortic dissection repair techniques, residual dissected aorta with a patent false lumen remains an issue. So, the aim of our study is to observe the effect of inserting the Thoraflex Hybrid Graft on the aortic diameters in patients with type A aortic dissection involving the arch and descending aorta. Patients with type I aortic dissection who had aortic dissection repair using the Thoraflex Hybrid Graft in University Hospitals Birmingham were studied. Radiological assessment with computed tomography of the aorta was done at the level of the diaphragm to measure the true lumen, false lumen and total aortic diameters. Significance of change of diameters at early post-operative as compared to the pre-operative period was analysed. Results Eight cases were done in the acute setting, while 14 cases were done in the chronic setting. The ratio of true lumen to the total aortic diameter has significantly increased in the follow-up period as compared to the pre-operative period (P = 0.031). Whereas false lumen to total aortic diameter ratio has significantly decreased (P = 0.024). Subgroup analysis revealed that these changes were not significantly altered by whether the dissection was acute or chronic. Conclusions The Thoraflex Hybrid Graft will induce positive aortic remodelling with expansion of true lumen and will diminish the false lumen. But we could not find a significant difference between acute or chronic cases due to small sample size.

Aortic Geometric Alteration Associated With Acute Type B Aortic Dissection: Angulation, Tortuosity, and Arch Type

Background: Acute type B aortic dissection is a highly serious aortic pathology. Aortic geometric parameters may be useful variables related to the occurrence of acute type B aortic dissection (aTBAD). The aim of the study is to delineate the alteration in aortic geometric parameters and analyze the specific geometric factors associated with aTBAD.Methods: The propensity score matching method was applied to control confounding factors. The aortic diameter, length, angulation, tortuosity, and type of aortic arch of the aTBAD and control group were retrospectively analyzed via three-dimensional computed tomography imaging created by the 3mensio software (version 10.0, Maastricht, The Netherlands). The geometric variables of true lumen and false lumen in the descending aorta were measured to estimate the severity of aortic dissection. Multivariable logistic regression models were used to investigate the significant and specific factors associated with aTBAD occurrence. The area under the receiver operating characteristic curve (AUC) was used to estimate the performance of the model.Results: After propensity score matching, 168 matched pairs of patients were selected. The ascending aorta and aortic arch diameters were dilated, and the ascending aorta and total aorta lengths were elongated in aTBAD group significantly (P &lt; 0.001). The ascending aorta and aortic arch angulations in the aTBAD group were sharper than those of the controls (P = 0.01, P &lt; 0.001, respectively). The aortic arch and total aorta tortuosities were significantly higher in the aTBAD group (P = 0.001, P &lt; 0.001, respectively). There were more type III arch patients in the aTBAD group than the controls (67.9 vs. 22.6%). The true lumen angulation was sharper than that in the false lumen (P &lt; 0.01). The true lumen tortuosity was significantly lower than that in the false lumen (P &lt; 0.001). The multivariable models identified that aortic arch angulation, tortuosity, and type III arch were independent and specific geometric factors associated with aTBAD occurrence. The AUC of the multivariable models 1, 2, 3 were 0.945, 0.953, and 0.96, respectively.Conclusions: The sharper angulation and higher tortuosity of aortic arch and type III arch were the geometric factors associated with aTBAD in addition to the ascending aorta elongation and aortic arch dilation. The angulation and tortuosity of the true and false lumens may carry significant clinical implications for the treatment and prognosis of aTBAD.