Dynamic motion analysis of aorta : image processing methods for MDCT and Cine-MR image

Dept. of Biomedical Engineering/박사This dissertation was to study on image processing method for dynamic motion analysis of aorta using sequential images. The visualization of blood vessel motion and imaging protocols for cross-sectional aorta images are proposed.To accomplish assess the aorta motion, muti-steps image processing strategy was applied. First, the image pre-processing was applied to image enlargement and segmentation of aorta. Second, the intensity profile of aorta was used for wall boundary extraction. Third, semi-automatic extraction of target aorta boundary tracing over first frame is then automatically tracked throughout the image frames. The visualization of aorta motion in the sequential images provides a quantitative source of their motion in space. In order to visualize the blood vessel wall motion, velocity vector mapping was applied to the sequential images. It provided the information of aorta wall movement velocity and aortic displacement.To evaluate the proposed methods, clinical validation have been designed using MDCT and Cine-MR images.The aortic wall movement property, the movement profiles on aorta calcification, aortic displacement, and relations between wall movement and age were assessed using MDCT images. The number of subjects (14 men, 16 women; mean age, 55.9 ± 14.99 years; range, 31-80 years) were 30 and have valvular heart disease. The correlation between wall movement at three different position of thoracic aorta and entire study population group was -0.63 (p < 0.001), -0.51 (p < 0.05) and -0.45 (p < 0.05) respectively. The profiles of wall variation in aorta calcification indicate dyssynchoronous aorta expansion. The clusters which are include the calcification point showed low variation throughout the image samples.The aortic wall movement of Turner syndrome group were also assessed using Cine-MR images. The number of subjects (17 women; mean age, 21.6 ± 6.6 years; range, 11-38 years) were 17. The wall movement data of total subjects were presented as mean ± standard deviation. The movement of descending aorta at three different position were 0.79 ± 0.25, 0.59 ± 0.15 and 0.53 ± 0.15 respectively.There was a significant decrease of the aortic wall motion at all thoracic levels throughout the ages. Although specific assessment of vascular aging was not available for the diseased subjects, a potential distinction on the aorta aging at the different ages was possible.In contrast to the ascending aorta, the descending segments presented a significantly lesser magnitude of displacement and appear rather fixed at their thoracic position.The results of this dissertation provide the fundamental characteristics of blood vessel motion and could be used not only clinical researches also clinical applications, such as vascular aging, assessment of vascular disease, and early detection of vascular abnormalityope

Компьютерно-томографические критерии оценки истинного и ложного просветов при расслоении аорты

The aim of study Based on computed tomography data, to determine the most characteristic criteria for true lumen (TL) and false lumen (FL) in aortic dissection. To identify the relationship of the studied features with the stage of aortic dissection.Materials of the study Computed tomography (CT) data of 115 patients diagnosed with aortic dissection (AD) who were treated at the N.V. Sklifosovsky Research Institute for Emergency Medicine were analyzed. The average age of the patients was 54.5 years (median — 56 years), men predominated in the studied group. AD types according to the De Bakey classification were distributed as follows: Type I — in 47% of patients, Type II — in 16.5%, Type III — in 36.5%. Dissection in the acute stage occurred in 62% of the patient, in the subacute — in 16%, in the chronic — 22%.Results In the studied group, FL in all cases prevailed over the TL by size, regardless of the stage and type of AD. Analysis of lumen ratio showed that in 63.55% of patients, FL occupied 75% or more of the aortic cross-sectional area. Location of FL: at the level of the ascending aorta, along the right and anterior walls of the aorta — 94.5%; in the descending thoracic aorta, along the posterior and left walls — 84%; in the abdominal aorta, along the posterior and left walls — 70%. Calcifications of the non- dissected part of the aortic wall, as a sign of a true lumen, were found in 59.1%. There was no correlation between calcification and the AD stage. Partial thrombosis of one of the lumens was detected in 59% (in FL — 85%, in TL — 13%, thrombosis of both lumens — 2%). The beak signs occurred in 85% of patients with AD, however, it was significantly more often detected in patients with acute and subacute AD stages than in the chronic stage (p&lt;0.001). The cobweb sign was found in one third of patients with AD, however, it was statistically significantly more often determined in patients in acute and subacute stages (p&lt;0.05).Conclusion CT is reasonably considered a highly informative method of diagnosing AD. The signs of true and false lumen presented in the work, as well as their combination, make it possible to perform a quick and error-free marking of the aortic lumen with a high degree of probability. A number of the described CT signs correlate with the stage of AD.Цель исследования По данным компьютерной томографии выявить наиболее характерные критерии для истинного и ложного просветов аорты при ее расслоении. Определить связь изучаемых признаков со стадией расслоения.Материал исследования Проанализированы данные компьютерной томографии (КТ) 115 пациентов с диагнозом «Расслоение аорты» (РА), находившихся на лечении в НИИ СП им. Н.В. Склифосовского. Средний возраст больных составил 54,5±12 года (медиана — 56 лет), в изученной группе преобладали мужчины. Типы РА по классификации De Bakey среди больных распределялись следующим образом: I тип — у 47% больных, II тип — у 16,5%, III тип — у 36,5%. Расслоение в острой стадии имело место у 62% больных, в подострой — у 16%, в хронической — 22%.Результаты В исследованной группе ложный просвет (ЛП) по размерам во всех случаях преобладал над истинным просветом (ИП) независимо от стадии и типа РА. Анализ соотношения просветов показал, что у 63,55% больных ЛП занимал 75 и более процентов площади поперечного сечения аорты. ЛП на уровне восходящей аорты располагался по правой и передней стенкам аорты — в 94,5% наблюдений; в нисходящей грудной — по задней и левой стенкам — в 84%; в брюшной — по задней и левой стенкам аорты — в 70%. Кальцинаты нерасслоенного участка аортальной стенки, как признак истинного просвета, были обнаружены в 59,1% случаев. Какой-либо корреляции между кальцинозом и стадией РА не было выявлено. Частичный тромбоз одного из просветов определялся у 59% пациентов (в ЛП — 85%, в ИП — в 13%, тромбоз обеих просветов — 2%). Признаки «клюва» обнаружены у 85% больных с РА, однако значительно чаще они определялись у больных в острой и подострой стадиях РА, чем в хронической (p&lt;0,001). Признак «паутины» встречался у трети больных с РА, однако статистически значимо чаще — у больных в острой и подострой стадии (р&lt;0,05).Заключение Компьютерная томография обоснованно считается высокоинформативным методом диагностики расслоения аорты. Представленные в работе признаки истинного и ложного просветов, а также их сочетание позволяют с высокой долей вероятности выполнить быструю и безошибочную маркировку просветов аорты. Ряд из описанных КТ-признаков коррелируют со стадией расслоения аорт

Multi-stage learning for segmentation of aortic dissections using a prior aortic anatomy simplification

Aortic dissection (AD) is a life-threatening cardiovascular disease with a high mortality rate. The accurate and generalized 3-D reconstruction of AD from CT-angiography can effectively assist clinical procedures and surgery plans, however, is clinically unavaliable due to the lacking of efficient tools. In this study, we presented a novel multi-stage segmentation framework for type B AD to extract true lumen (TL), false lumen (FL) and all branches (BR) as different classes. Two cascaded neural networks were used to segment the aortic trunk and branches and to separate the dual lumen, respectively. An aortic straightening method was designed based on the prior vascular anatomy of AD, simplifying the curved aortic shape before the second network. The straightening-based method achieved the mean Dice scores of 0.96, 0.95 and 0.89 for TL, FL, and BR on a multi-center dataset involving 120 patients, outperforming the end-to-end multi-class methods and the multi-stage methods without straightening on the dual-lumen segmentation, even using different network architectures. Both the global volumetric features of the aorta and the local characteristics of the primary tear could be better identified and quantified based on the straightening. Comparing to previous deep learning methods dealing with AD segmentations, the proposed framework presented advantages in segmentation accuracy

Morphologic evaluation of ruptured abdominal aortic aneurysm by 3D modeling

This thesis was created in Word and converted to PDF using Mac OS X 10.7.5 Quartz PDFContext.Abdominal aortic aneurysm (AAA) is defined as a dilatation of the abdominal aorta exceeding the normal diameter by more than 50%. The standard and widely used approach to assess AAA size is by measuring the maximal diameter (Dmax). Currently, the main predictors of rupture risk are the Dmax, sex, and the expansion rate of the aneurysm. Yet, Dmax has some limitations. AAAs of vastly different shapes may have the same maximal diameter. Dmax lacks sensitivity for rupture risk, especially among smaller AAAs. Thus, there is a need to evaluate the susceptibility of a given AAA to rupture on a patient-specific basis. We present the design concept and workflow of the AAA segmentation software developed at our institution. We describe the previous validation steps in which we evaluated the reproducibility of manual Dmax, compared software Dmax against manual Dmax, validated reproducibility of software Dmax and volume in cross-sectional and longitudinal studies for detection of AAA growth, and evaluated the reproducibility of software measurements in unenhanced computed tomographic angiography (CTA) and in the presence of stent-graft. In order to define new geometric features associated with rupture, we performed a case-control study in which we compared 63 cases with ruptured or symptomatic AAA and 94 controls with asymptomatic AAA. Univariate logistic regression analysis revealed 14 geometric indices associated with AAA rupture. In the multivariate logistic regression analysis, adjusting for Dmax and sex, the AAA with a higher bulge location and higher mean averaged surface area were associated with AAA rupture. Our preliminary results suggest that incorporating geometrical indices obtained by segmentation of CT shows a trend toward improvement of the classification accuracy of AAA with high rupture risk at CT over a traditional model based on Dmax and sex alone. Larger longitudinal studies are needed to verify the validity of the proposed model. Addition of flow and biomechanical simulations should be investigated to improve rupture risk prediction based on AAA modeling.Un anévrysme de l'aorte abdominale (AAA) est défini par une dilatation de plus de 50% par rapport au diamètre normal. La méthode standard et largement répandue pour mesurer la dimension d'un AAA consiste à mesurer le diamètre maximal (Dmax). Présentement, les principaux prédicteurs de risque de rupture sont le Dmax, le sexe et le taux d'expansion d'un anévrysme. Toutefois, le Dmax a certaines limitations. Des AAAs de formes très différentes peuvent avoir le même diamètre maximal. Le Dmax manque de sensibilité pour détecter le risque de rupture, en particulier pour les petits anévrysmes. Par conséquent, il y a un besoin d'évaluer de manière spécifique et individuelle la susceptibilité de rupture d'un AAA. Nous présentons le concept et le flux de travail d'un logiciel de segmentation des AAAs développé à notre institution. Nous décrivons les étapes antérieures de validation: évaluation de la reproductibilité du Dmax manuel, comparaison de Dmax par logiciel avec Dmax manuel, validation de la reproductibilité du Dmax et volume par logiciel dans des études transversale et longitudinale pour la détection de croissance et évaluation de la reproductibilité de mesures sur angiographie par tomodensitométrie et en présence d'endoprothèse. En vue d’identifier de nouveaux paramètres géométrique associés avec le risque de rupture, nous avons réalisé une étude cas-témoin comparant 63 cas avec AAA rompu ou symptomatique et 94 contrôles avec AAA asymptomatique. Une analyse de régression logistique univariée a identifié 14 indices géométriques associés avec une rupture de AAA. Dans l'analyse de régression logistique multivariée, en ajustant pour le Dmax et le sexe, les AAA avec un bombement plus haut situé et une surface moyenne plus élevée étaient associés à une rupture. Nos résultats préliminaires suggèrent que l'inclusion d'indices géométriques obtenus par segmentation de tomodensitométrie tend à améliorer la classification de AAA avec un risque de rupture par rapport à un modèle traditionnel seulement basé sur le Dmax et le sexe. De plus larges études longitudinales sont requises pour vérifier la validité du modèle proposé. Des simulations de flux et biomécaniques devraient être envisagées pour améliorer la prédiction du risque de rupture basée sur la modélisation d'anévrysmes

Optimization of CT scanning protocol of Type B aortic dissection follow-up through 3D printed model

This research aims to develop and evaluate a human tissue-like material 3D printed model used as a phantom in determining optimized scanning parameters to reduce the radiation dose for Type B aortic dissection patients after thoracic endovascular aortic repair. The results show that radiation risk for follow-up Type B aortic dissection patients can be potentially reduced. Further, the value of using 3D printed model in studying CT scanning protocols was further validated

Development of a Surgical Assistance System for Guiding Transcatheter Aortic Valve Implantation

Development of image-guided interventional systems is growing up rapidly in the recent years. These new systems become an essential part of the modern minimally invasive surgical procedures, especially for the cardiac surgery. Transcatheter aortic valve implantation (TAVI) is a recently developed surgical technique to treat severe aortic valve stenosis in elderly and high-risk patients. The placement of stented aortic valve prosthesis is crucial and typically performed under live 2D fluoroscopy guidance. To assist the placement of the prosthesis during the surgical procedure, a new fluoroscopy-based TAVI assistance system has been developed. The developed assistance system integrates a 3D geometrical aortic mesh model and anatomical valve landmarks with live 2D fluoroscopic images. The 3D aortic mesh model and landmarks are reconstructed from interventional angiographic and fluoroscopic C-arm CT system, and a target area of valve implantation is automatically estimated using these aortic mesh models. Based on template-based tracking approach, the overlay of visualized 3D aortic mesh model, landmarks and target area of implantation onto fluoroscopic images is updated by approximating the aortic root motion from a pigtail catheter motion without contrast agent. A rigid intensity-based registration method is also used to track continuously the aortic root motion in the presence of contrast agent. Moreover, the aortic valve prosthesis is tracked in fluoroscopic images to guide the surgeon to perform the appropriate placement of prosthesis into the estimated target area of implantation. An interactive graphical user interface for the surgeon is developed to initialize the system algorithms, control the visualization view of the guidance results, and correct manually overlay errors if needed. Retrospective experiments were carried out on several patient datasets from the clinical routine of the TAVI in a hybrid operating room. The maximum displacement errors were small for both the dynamic overlay of aortic mesh models and tracking the prosthesis, and within the clinically accepted ranges. High success rates of the developed assistance system were obtained for all tested patient datasets. The results show that the developed surgical assistance system provides a helpful tool for the surgeon by automatically defining the desired placement position of the prosthesis during the surgical procedure of the TAVI.Die Entwicklung bildgeführter interventioneller Systeme wächst rasant in den letzten Jahren. Diese neuen Systeme werden zunehmend ein wesentlicher Bestandteil der technischen Ausstattung bei modernen minimal-invasiven chirurgischen Eingriffen. Diese Entwicklung gilt besonders für die Herzchirurgie. Transkatheter Aortenklappen-Implantation (TAKI) ist eine neue entwickelte Operationstechnik zur Behandlung der schweren Aortenklappen-Stenose bei alten und Hochrisiko-Patienten. Die Platzierung der Aortenklappenprothese ist entscheidend und wird in der Regel unter live-2D-fluoroskopischen Bildgebung durchgeführt. Zur Unterstützung der Platzierung der Prothese während des chirurgischen Eingriffs wurde in dieser Arbeit ein neues Fluoroskopie-basiertes TAKI Assistenzsystem entwickelt. Das entwickelte Assistenzsystem überlagert eine 3D-Geometrie des Aorten-Netzmodells und anatomischen Landmarken auf live-2D-fluoroskopische Bilder. Das 3D-Aorten-Netzmodell und die Landmarken werden auf Basis der interventionellen Angiographie und Fluoroskopie mittels eines C-Arm-CT-Systems rekonstruiert. Unter Verwendung dieser Aorten-Netzmodelle wird das Zielgebiet der Klappen-Implantation automatisch geschätzt. Mit Hilfe eines auf Template Matching basierenden Tracking-Ansatzes wird die Überlagerung des visualisierten 3D-Aorten-Netzmodells, der berechneten Landmarken und der Zielbereich der Implantation auf fluoroskopischen Bildern korrekt überlagert. Eine kompensation der Aortenwurzelbewegung erfolgt durch Bewegungsverfolgung eines Pigtail-Katheters in Bildsequenzen ohne Kontrastmittel. Eine starrere Intensitätsbasierte Registrierungsmethode wurde verwendet, um kontinuierlich die Aortenwurzelbewegung in Bildsequenzen mit Kontrastmittelgabe zu detektieren. Die Aortenklappenprothese wird in die fluoroskopischen Bilder eingeblendet und dient dem Chirurg als Leitfaden für die richtige Platzierung der realen Prothese. Eine interaktive Benutzerschnittstelle für den Chirurg wurde zur Initialisierung der Systemsalgorithmen, zur Steuerung der Visualisierung und für manuelle Korrektur eventueller Überlagerungsfehler entwickelt. Retrospektive Experimente wurden an mehreren Patienten-Datensätze aus der klinischen Routine der TAKI in einem Hybrid-OP durchgeführt. Hohe Erfolgsraten des entwickelten Assistenzsystems wurden für alle getesteten Patienten-Datensätze erzielt. Die Ergebnisse zeigen, dass das entwickelte chirurgische Assistenzsystem ein hilfreiches Werkzeug für den Chirurg bei der Platzierung Position der Prothese während des chirurgischen Eingriffs der TAKI bietet