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

Semiautonomous Robotic Manipulator for Minimally Invasive Aortic Valve Replacement

Aortic valve surgery is the preferred procedure for replacing a damaged valve with an artificial one. The ValveTech robotic platform comprises a flexible articulated manipulator and surgical interface supporting the effective delivery of an artificial valve by teleoperation and endoscopic vision. This article presents our recent work on force-perceptive, safe, semiautonomous navigation of the ValveTech platform prior to valve implantation. First, we present a force observer that transfers forces from the manipulator body and tip to a haptic interface. Second, we demonstrate how hybrid forward/inverse mechanics, together with endoscopic visual servoing, lead to autonomous valve positioning. Benchtop experiments and an artificial phantom quantify the performance of the developed robot controller and navigator. Valves can be autonomously delivered with a 2.0±0.5 mm position error and a minimal misalignment of 3.4±0.9°. The hybrid force/shape observer (FSO) algorithm was able to predict distributed external forces on the articulated manipulator body with an average error of 0.09 N. FSO can also estimate loads on the tip with an average accuracy of 3.3%. The presented system can lead to better patient care, delivery outcome, and surgeon comfort during aortic valve surgery, without requiring sensorization of the robot tip, and therefore obviating miniaturization constraints.</p

Quantitative imaging in cardiovascular CT angiography

In de afgelopen decennia is computertomografie (CT) een prominente niet-invasieve modaliteit om hart- en vaatziekten te evalueren geworden. Dit proefschrift heeft als doel de rol van CT in de therapeutische behandeling van coronaire hartziekte (CAD) en klepaandoeningen te onderzoeken.De relatie tussen kransslagadergeometrie (statisch en dynamisch) en aanwezigheid en omvang van CAD met CT werd onderzocht. De resultaten suggereren dat de statische geometrie van de kransslagader significant gerelateerd is aan de aanwezigheid van plaque en stenose. Er was echter geen verband tussen dynamische verandering van de coronaire arterie-geometrie en de ernst van CAD. Een algoritme om de invloed van intraluminair contrastmiddel op niet-verkalkte atherosclerotische plaque Hounsfield-Unit-waarden te corrigeren werd gepresenteerd en gevalideerd met behulp van fantomen.Diagnose en operatieplanning kunnen cruciale gevolgen hebben voor de klinische uitkomst van chirurgische ingrepen. In dit proefschrift wordt beschreven dat halfautomatische softwareprogramma’s het kwantificeren van het aortaklepgebied betere reproduceerbare resultaten toonden in vergelijking met handmatige metingen, en vergelijkbare resultaten met de huidige gouden standaard, de echocardiografie. Een systematische review over het dynamische gedrag van de aorta-annulus toont aan dat de vorm van de aorta-annulus tijdens de hartcyclus verandert, wat impliceert dat er bij het bepalen van een prothese rekening moet worden gehouden met meerdere fasen. Een andere review beschrijft het gebruik van 3D-printen in de chirurgische planning samen met andere toepassingen voor de behandeling van hartklepaandoeningen.CT is de belangrijkste beeldvormingsmodaliteit in deze onderzoeken, die gericht waren op de therapeutische behandeling van hart- en vaatziekten, van vroege risicobepaling tot diagnose en chirurgische planning.In the recent decades computed tomography (CT) has emerged as a dominant non-invasive modality to evaluate cardiovascular diseases. This thesis aimed to explore the role of CT in the therapeutic management of coronary artery disease (CAD) and valvular diseases.The relationship between both static and dynamic coronary artery geometry and presence and extent of CAD using CT was investigated. The results suggest that the static coronary artery geometry is significantly related to presence of plaque and significant stenosis. However, there were no such relationship between dynamic change of coronary artery geometry and severity of CAD. As part of this thesis an algorithm to correct the influence of lumen contrast enhancement on non-calcified atherosclerotic plaque Hounsfield-Unit values was presented. The algorithm was validated using phantoms. The diagnosis and surgical planning may have crucial impact on clinical outcome. Semi-automatic software for aortic valve area quantification presented in this thesis was proven to be more repeatable and similar to gold standard echocardiography in comparison to manual measurements. The systematic review regarding the dynamic behavior of aortic annulus revealed that aortic annulus geometry changes throughout the cardiac cycle which implies that multiple phases should be taken into account for prosthesis sizing. Another review in this thesis discusses the use of 3D printing in the surgical planning along with other applications for the treatment of valvular diseases.CT is the main imaging modality in these studies which were focused on the therapeutic management of cardiovascular diseases from early risk determination to diagnosis and surgical planning

Computer Vision Techniques for Transcatheter Intervention

Minimally invasive transcatheter technologies have demonstrated substantial promise for the diagnosis and treatment of cardiovascular diseases. For example, TAVI is an alternative to AVR for the treatment of severe aortic stenosis and TAFA is widely used for the treatment and cure of atrial fibrillation. In addition, catheter-based IVUS and OCT imaging of coronary arteries provides important information about the coronary lumen, wall and plaque characteristics. Qualitative and quantitative analysis of these cross-sectional image data will be beneficial for the evaluation and treatment of coronary artery diseases such as atherosclerosis. In all the phases (preoperative, intraoperative, and postoperative) during the transcatheter intervention procedure, computer vision techniques (e.g., image segmentation, motion tracking) have been largely applied in the field to accomplish tasks like annulus measurement, valve selection, catheter placement control, and vessel centerline extraction. This provides beneficial guidance for the clinicians in surgical planning, disease diagnosis, and treatment assessment. In this paper, we present a systematical review on these state-of-the-art methods.We aim to give a comprehensive overview for researchers in the area of computer vision on the subject of transcatheter intervention. Research in medical computing is multi-disciplinary due to its nature, and hence it is important to understand the application domain, clinical background, and imaging modality so that methods and quantitative measurements derived from analyzing the imaging data are appropriate and meaningful. We thus provide an overview on background information of transcatheter intervention procedures, as well as a review of the computer vision techniques and methodologies applied in this area

Quantitative evaluation of the mitral valve anatomy, geometry and spatial relationships in multiple cardiac phases by multi-slice computed tomography for planning of minimally invasive or percutaneous interventions

Objective: The objective of this study was to assess the mitral valve anatomy, geometry and mobility of control group and of patients with functional mitral regurgitation (FMR) by MSCT throughout the entire cardiac cycle in regards of optimizing the planning of transcatheter mitral valve procedures. Materials and methods: 24 healthy patients vs. 22 patients with varying degrees of FMR who had undergone ECG gated CTA were evaluated retrospectively. The mean age was 47 ± 11 vs. 63 ± 7 years (p<0.05), male gender 75% vs. 68% (ns), BMI 26 ± 2.8 kg/m² versus 26 ± 3.5 kg/m² (ns), LVEF 72 ± 6% vs. 31 ± 9% (p<0.05), LVEDD 55.3 ± 5.4 vs. 81 ± 11 mm (p<0.05). The evaluation of MA surface, entire circumference, projected circumference, trigone-to-trigone distance, and septal-to lateral distances for saddle-shaped and D-shaped mitral annulus, and annulus height for saddle-shaped annulus, aorto-mitral annular angle, LA to LV axis angle and MA to papillary muscles distance was carried out for all patients in both groups for ten 10% intervals throughout the cardiac cycle. Results: The mean MA saddle-shaped annular area averaged 12 ± 2 cm² in the control group, 14.6 ± 0.52 cm² in patients with FMR, the D-shaped annular area averaged 10.3 ± 1.6 cm² vs. 12.7 ± 0.5 cm², respectively, thus representing a significant difference between the two groups and both models. The trigone-to-trigone distance was slightly larger in patients with FMR than in healthy subjects, namely 33.7 ± 1.9 mm vs. 34.6 ± 0.4 mm (p<0.05). The aorto-mitral angle mean for healthy subjects was 55 ± 7° vs. 46 ± 6.8° in patients with FMR. The mobility of the mitral annulus was higher in healthy patients than in patients with FMR. Conclusion: This study showed that there are significant differences in the mitral annular morphology between controls and patients with FMR, as well as several changes between different sizing approaches of the mitral annulus throughout the entire cardiac cycle. Considering the low mobility of the mitral annulus in patients with FMR and its biggest size in diastolic phase, multiphase MSCT might be replaced by dual-phase scans for example when planning TMVI. This plays an important role in timing the pre-procedural analysis and in reducing radiation dose. However, using multiphase CTA should still be the favored mode in complicated cases. In summary, our study demonstrates that a non-invasive and comprehensive assessment of the mitral valve by MSCT is feasible.Ziel: Ziel dieser Studie war die Beurteilung der Mitralklappenanatomie, -geometrie und beweglichkeit von gesunden Probanden (Kontrollgruppe) und von Patienten mit funktioneller Mitralklappeninsuffizienz (FMR) durch MSCT über den gesamten Herzzyklus mit Fokus auf der Planung von Transkatheter-Mitralklappe Verfahren bei deren Planung das MSCT einen hohen Stellenwert hat. Material und Methoden: Datensätze von 24 Patienten ohne Mitralklappenerkrankung und 22 Patienten mit FMR, bei denen eine EKG-getriggerte MSCT durchgeführt wurde, wurden retrospektiv ausgewertet. Das Durchschnittsalter betrug 47 ± 11 gegenüber 63 ± 7 Jahren (p <0,05), männliches Geschlecht 75% gegenüber 68% (ns), BMI 26 ± 2,8 kg / m² gegenüber 26 ± 3,5 kg / m² (ns), LVEF 72 ± 6% vs. 31 ± 9% (p <0,05), LVEDD 55,3 ± 5,4 vs. 81 ± 11 mm (p <0,05). Die Ausmessung der Oberfläche des Mitralanulus (MA), des gesamten Umfangs, des projizierten Umfangs des Annulus, der Trigon-Trigon-Distanz und der Septum-zu-Lateralwand-Abstände für den sattelförmigen und D-förmigen Mitralanulus und die Anulushöhe für den sattelförmigen Anulus, den Aorto-Mitralen- Winkel, der Linker Vorhof (LA)-zu- Linker Ventrikel (LV)-Achsenwinkel und der Abstand zwischen MA und Papillarmuskeln wurde für alle Patienten in beiden Gruppen für zehn 10% Phasen Intervallen während des gesamten Herzzyklus durchgeführt. Ergebnisse: Die mittlere 3D MA-Fläche betrug 12 ± 2 cm² in der Kontrollgruppe und 14,6 ± 0,52 cm² bei Patienten mit FMR, die D-förmige Anulusfläche war 10,3 ± 1,6 cm² und 12,7 ± 0,5 cm². Diese Werte waren zwischen den zwei Gruppen und beiden Methoden signifikant unterschiedlich. Der Trigon-zu-Trigon-Abstand war bei Patienten mit FMR signifikant größer als bei gesunden Probanden; 33,7 ± 1,9 mm vs. 34,6 ± 4 mm (P <0,05). Der mittlere Aorten–Mitralwinkel lag bei gesunden Probanden bei 55 ± 7° gegenüber 46 ± 6,8° bei Patienten mit FMR. Darüber hinaus ist die Beweglichkeit des Mitralanulus bei gesunden Probanden höher als bei Patienten mit FMR. Schlussfolgerung: Es gibt signifikante Unterschiede in der Mitralanulus-Morphologie zwischen gesunden Probanden und Patienten mit FMR sowie der Morphologie bzw. Beweglichkeit des Mitralanulus während des gesamten Herzzyklus. Anbetracht der geringen Beweglichkeit des Mitralanulus bei Patienten mit FMR und seiner größten Größe in der diastolischen Phase könnte die mehrphasige MSCT bei der Planung einer TMVI beispielsweise durch zweiphasige Scans ersetzt werden. Dies spielt eine wichtige Rolle bei der präprozeduralen Analyse und bei der Reduzierung der Strahlendosis, jedoch ist die Verwendung von Mehrphasen-CTA in komplizierten Fällen sicher immer von Vorteil. Zusammenfassend zeigt unsere Studie, dass eine nicht-invasive und umfassende Beurteilung der Mitralklappe mittels MSCT möglich ist

Exploiting Temporal Image Information in Minimally Invasive Surgery

Minimally invasive procedures rely on medical imaging instead of the surgeons direct vision. While preoperative images can be used for surgical planning and navigation, once the surgeon arrives at the target site real-time intraoperative imaging is needed. However, acquiring and interpreting these images can be challenging and much of the rich temporal information present in these images is not visible. The goal of this thesis is to improve image guidance for minimally invasive surgery in two main areas. First, by showing how high-quality ultrasound video can be obtained by integrating an ultrasound transducer directly into delivery devices for beating heart valve surgery. Secondly, by extracting hidden temporal information through video processing methods to help the surgeon localize important anatomical structures. Prototypes of delivery tools, with integrated ultrasound imaging, were developed for both transcatheter aortic valve implantation and mitral valve repair. These tools provided an on-site view that shows the tool-tissue interactions during valve repair. Additionally, augmented reality environments were used to add more anatomical context that aids in navigation and in interpreting the on-site video. Other procedures can be improved by extracting hidden temporal information from the intraoperative video. In ultrasound guided epidural injections, dural pulsation provides a cue in finding a clear trajectory to the epidural space. By processing the video using extended Kalman filtering, subtle pulsations were automatically detected and visualized in real-time. A statistical framework for analyzing periodicity was developed based on dynamic linear modelling. In addition to detecting dural pulsation in lumbar spine ultrasound, this approach was used to image tissue perfusion in natural video and generate ventilation maps from free-breathing magnetic resonance imaging. A second statistical method, based on spectral analysis of pixel intensity values, allowed blood flow to be detected directly from high-frequency B-mode ultrasound video. Finally, pulsatile cues in endoscopic video were enhanced through Eulerian video magnification to help localize critical vasculature. This approach shows particular promise in identifying the basilar artery in endoscopic third ventriculostomy and the prostatic artery in nerve-sparing prostatectomy. A real-time implementation was developed which processed full-resolution stereoscopic video on the da Vinci Surgical System