Wojciech Szubert

Numerical simulations of the blood flow in the patient-specific arterial cerebral circle region

The Cerebral Circle Region, also known as the Circle of Willis (CoW), is a loop of arteries that form arterial connections between supply arteries to distribute blood throughout the cerebral mass. Among the population, only 25% to 50% have a complete system of arteries forming the CoW. 3D time-varying simulations for three different patient-specific artery anatomies of CoW were performed in order to gain a better insight into the phenomena existing in the cerebral blood flow. The models reconstructed on the basis of computer tomography images start from the aorta and include the largest arteries that supply the CoW and the arteries of CoW. Velocity values measured during the ultrasound examination have been compared with the results of simulations. It is shown that the flow in the right anterior artery in some cases may be supplied from the left internal carotid artery via the anterior communicating artery. The investigations conducted show that the computational fluid dynamic tool, which provides high resolution in both time and space domains, can be used to support physicians in diagnosing patients of different ages and various anatomical arterial structures.

A 3D model of thrombus formation in a stent-graft after implantation in the abdominal aorta.

Here we present a 3D kinetic model of thrombus formation in an endovascular prosthesis after implantation in an abdominal aorta with an aneurysm. The computational fluid dynamic technique (CFD) was used to determine the process of thrombus formation and growth in the stent-graft on the basis of the medical data from computed tomography angiography and Doppler ultrasound examination of 10 patients. The Quemada model was used to describe rheological properties of blood. Results of the CFD simulations were validated based on actual data from patients with diagnosed thrombi in aortic implants. The results show that the elaborated CFD model correctly predicted thrombus formation, shape and deposition site in an endovascular prosthesis. The developed CFD model of thrombus growth can be applied to predict the risk of thrombus formation in stent-grafts and assist in selection of geometry of the endovascular prosthesis to reduce possible complications after stent-graft implantation using only basic medical data.

Endovascular treatment of pseudoaneurysms in pancreatitis.

Introduction Haemorrhagic complications are commonly reported in the course of acute pancreatitis (AP). The most dangerous are pseudoaneurysms secondary to wall erosion of the vessels crossing the inflammation area. Aim To evaluate the efficacy of different embolisation techniques of pseudoaneurysms secondary to AP. Material and methods The treatment outcomes in 10 AP patients were analysed in a follow-up period of 1 to 10 months (most frequently: splenic or gastroduodenal artery aneurysms). A total of 12 endovascular procedures were performed (thrombin embolisation, coil embolisation or combined). The efficacy of aneurysm sac exclusion and the patency of the treated vessel were compared. Results The follow-up examination on postprocedural day 7 revealed aneurysm refilling in 3 out of 11 cases. Three patients showed an occlusion of the aneurysm-parent vessel. One month after the procedures, involving 10 patients, a vessel occlusion was confirmed in 3 and aneurysm sac refilling in another 2 patients. Taking into consideration the type of the procedure performed, treatment failure in the form of sac refilling was observed in half of thrombin-based procedures, 25% of coil embolisations and 33% of sandwich technique procedures. Similar failure distribution was noted for vessel occlusion. Conclusions It seems that thrombin injection was least successful, whereas thrombin injection into the sac and implantation of coils into the aneurysm neck seems to be the optimal procedure, in respect to both the cost-effectiveness of the procedure and late outcomes.

The role of MRI in diagnostic algorithm of cervicofacial vascular anomalies in children.

Summary Background: Vascular anomalies are usually diagnosed through their clinical picture and history. The purpose of this study was to assess the role of MR imaging in initial assessment of cervicofacial vascular anomalies in children. Material/Methods: Twenty pediatric patients with vascular anomalies located in the cervicofacial region underwent MRI examination in our department. Images were evaluated for lesion detectability and its signal characteristics (on T1w, T2w images with fat suppression and contrast enhanced T1w sequences); the extent of the lesions and surrounding tissue involvement were also assessed. Results: In the studied group MR images revealed all anomalies and provided information of their anatomic extent and invasion of surrounding anatomic structures. Nine hemangiomas and six venous malformations were found among studied patients. Two children had multiloculated lesions corresponding to lymphatic malformations. One examination visualized a lesion consisting mainly of dilated vascular channels with an apparent feeding artery, which was consistent with arteriovenous malformation. Two remaining lesions were mixed malformations. Nine patients had lesions limited to subcutaneous tissue. Two masses infiltrated bone structures. There was muscle involvement found in nine cases. Conclusions: MR imaging is a well-established method for detection and monitoring of vascular anomalies in children. With ultrasound used mostly for initial diagnosis and additional flow assessment, angiography viewed as an invasive therapeutic method and computed tomography used only in specific situations due to its high irradiation dose, magnetic resonance is the best imaging method used in differential diagnosis and topographical characterization of vascular malformations and tumors of cervicofacial area in pediatric patients. Noninvasively and without irradiation, it enables evaluation of the extent and characteristics of lesions and planning proper therapeutic strategy.

Pancreatitis-Related Abdominal Aortic Pseudoaneurysms Treated With Stent-Grafts

Endovascular treatment of pseudoaneurysms that develop as a complication of pancreatitis is increasingly more common. A case of a pseudoaneurysm of the abdominal aorta initially treated by implantation of a straight aortic stent-graft is presented. In the 4 months after the procedure, chronic inflammation of the retroperitoneal space caused a further perforation on the posterior wall of the aorta in the area of the bifurcation, distal to the graft. Implantation of a bifurcated stent-graft was subsequently performed. The aneurysm was excluded, with the implant and peripheral arteries remaining patent.

3D Blood Vessels Reconstruction Based on Segmented CT Data for Further Simulations of Hemodynamic in Human Artery Branches

Abstract We aimed at the reconstruction of the branches of human aortic arch for blood perfusion analysis used later in the Computational Fluid Dynamic (CFD). The reconstruction was performed based on segmentation results obtained from CT data. Two segmentation algorithms, region growing and level set were implemented. Obtained binary segmentation results were next evaluated by the expert and corrected if needed. The final reconstruction was used for preparation of a numerical grid and for further calculation of blood hemodynamic. The collected data composed of blood velocity and blood flow rate in function of time were compared with USG-Doppler data. Results demonstrate that proposed algorithm may be useful for initial reconstruction of human cardiac system, however its accuracy needs to be improved as further manual corrections are still needed.

Evaluating an algorithm for 3D reconstruction of blood vessels for further simulations of hemodynamic in human artery branches

We aimed at verification of a novel algorithm for semiautomatic reconstruction of the branches of human aortic arch for blood perfusion analysis used later in the Computational Fluid Dynamic (CFD). The algorithm works on initially adjusted CT scans divided into segments. Obtained binary segmentation results were next checked manually and corrected if needed. The final reconstruction was used for preparation of a numerical grid and for further calculation of blood hemodynamic. The collected data composed of blood velocity and blood flow rate in function of time were compared with USG-Doppler data. Preliminary results demonstrate that proposed algorithm may be useful for initial reconstruction of human cardiac system, however its accuracy needs to be improved as further manual corrections are still needed.

Acute brain ischemia as a complication of the Ehlers-Danlos syndrome, the case series.

Vascular type of Ehlers–Danlos syndrome involves many severe complications leading not only to organ-specific symptoms but often ends in a sudden death. The aim of this paper was to present a diagnostic possibilities and its efficiency rate in patients with vascular complications of Ehlers–Danlos syndrome who suffered from artery dissection resulting in acute brain or limb ischemia. We analysed three patients with diagnosed Ehlers–Danlos syndrome who were referred to radiology department for diagnostic imaging of affected vascular beds, each experienced brain ischemia. The paper also aims at offering some general recommendations for patients suffering from possible complications of type IV Ehlers–Danlos syndrome basing on our own experience and available literature data.

Posterior Wall Capture and Femoral Artery Stenosis Following Use of StarClose Closing Device: Diagnosis and Therapy

A case of femoral artery obstruction following application of a StarClose type arterial puncture closing device (APCD) is presented. Ultrasonographic and angiographic imaging of this complication was obtained. The posterior wall of the vessel was accidentally caught in the anchoring element of the nitinol clip. This complication was successfully resolved by endovascular treatment and the implantation of a stent.

Arterio-biliary fistulas: What to choose as endovascular treatment?

Objectives Endovascular procedures are the treatment of choice in cases of intrahepatic fistulas. Arterio-biliary fistulas are the rarest and most difficult to treat, due to high risk of infection. Methods Eight cases of persistent hemobilia that developed as a result of arterio-biliary fistulas are presented. Five cases developed as a result of iatrogenic injury, two cases as a result of chronic infection, one case as a consequence of trauma. Results Patients were treated using endovascular embolization or combined endovascular and endoscopic biliary tract revision. The results were monitored after six to seven days and one month after embolization. The embolizations were considered effective in all cases. One patient had four asynchronous fistulas requiring separate treatments sessions. Four patients required a revision of their biliary ducts after embolization and restoration of patency. In one patient, a migration of the coil to biliary ducts occurred. Conclusion Endovascular treatment of arterio-biliary fistulas is safe and effective. The use of embolization with soft and biodegradable materials like histoacrylic glue or thrombin may be the optimal method of treatment in comparison with coils which have a risk of migration or chronic infection.