Sameer Al-Maisary

Computer-assisted analysis of annuloplasty rings

Over 40.000 annuloplasty rings are implanted each year in the United States to treat mitral regurgitation. The rings come in different sizes and shapes. However it is unclear, which ring is most suitable for the individual patient. Here we present a preoperative annuloplasty planning software to determine an eligible ring. It provides fast interactive methods to create 4D mitral annulus models based on arbitrary image data. Created models can be analyzed geometrically and compared to existing annuloplasty ring models. This way, forces caused by a specific annuloplasty ring can visualized, which enables preoperative simulation and eventually improves operation results. Using our software, we evaluated the size changes caused by five commercially available annuloplasty rings on the mitral annuli of 39 patients. The results suggest that the annuloplasty ring should be selected for each patient specifically.

Intraoperative Quantitative Mitral Valve Analysis Using Optical Tracking Technology

PURPOSE Analysis of mitral valve morphology during reconstruction is routinely based on visual assessment and subjective, poorly reproducible measurements. We prove the feasibility of a new intraoperative system for quantitative mitral valve analysis. DESCRIPTION The proposed computer-based assistance system enables accurate intraoperative localization of anatomic landmarks on the mitral valve apparatus using optical tracking technology. Measurement and visualization strategies were specifically developed and tailored for mitral valve operations. EVALUATION The feasibility of intraoperative quantitative measurements was successfully shown for 9 patients. Precise geometric descriptions of the valve were obtained and adequately visualized, providing valuable decision support during the intervention. The mean annular area obtained from the intraoperative measurements was 736 ± 266 mm(2), in good agreement with the mean area of the implanted prosthetic rings of 617 ± 124 mm(2), which are slightly smaller due to annular downsizing. Comparison with preoperative three-dimensional echocardiography revealed differences between the beating heart, with transverse and septolateral annular diameters of 40.6 ± 15.4 mm and 41.2 ± 8.2 mm, and the intraoperative cardioplegic condition, with corresponding diameters of 34.3 ± 6.9 mm and 27.4 ± 5.6 mm. CONCLUSIONS Mitral valve analysis by optical tracking represents a unique technologic advance in intraoperative assessment, providing the surgeon with an extended quantitative perception of surgical target. This technology promotes a major philosophical change from an empirical procedure toward a quantitatively predictable modern reconstructive operation.

Gestaltung patientenspezifischer Annuloplastieringe

Mitralinsuffizienz ist eine weit verbreitete Krankheit, welche durch die Implantation von Annuloplastieringen behandelt werden kann. Die Wahl eines geeigneten Ringes gestaltet sich aufgrund uneindeutiger Mess- und Selektionskriterien jedoch schwierig. Durch das vorgestellte Verfahren zur patientenspezifischen Gestaltung von Annuloplastieringen wird eine gute Passgenauigkeit gewahrleistet. Das individuelle Ringdesign ermoglicht eine geringere maximale Deformation des Mitralannulus uber den Herzzyklus gegenuber den untersuchten kommerziellen Ringe, wodurch die Gefahr einer Ringdehinszenz gemindert werden kann. Durch die Herstellung eines entsprechenden implantierfahigen Annuloplastierings mit Hilfe von Rapid-Prototyping Technologien wird zus atzlich gezeigt, dass eine Einbindung in die Klinik zeitlich und preislich vertretbar ist.

Elastic Mitral Valve Silicone Replica Made from 3D-Printable Molds Offer Advanced Surgical Training

Reconstructive mitral valve surgeries are demanding cardiac surgeries that are conducted in the mid-age of a surgical career at the earliest. Receiving years of training in patients is required to gain the experiences and skills necessary for surgical success. On top of that, the number of such surgeries is limited per hospital, therefore other means of training should be offered to facilitate a steep learning curve. Within the scope of this work, we equipped an existing physical simulator with patient-specific flexible replica of the mitral valve. We developed software to automatically produce a 3D-printable casting mold for silicone material, as this mimics properties of the valve tissue in terms of stitching and cutting. We show the feasibility of the approach and the usefulness of these models is evaluated by an experienced cardiac surgeon, successfully conducting reconstructive surgery on pathological silicone valves.

Computer-based comparison of different methods for selecting mitral annuloplasty ring size

BackgroundRing sizing for mitral valve annuloplasty is conventionally done intraoperatively using specific ‘sizer’ instruments, which are placed onto the valve tissue. This approach is barely reproducible since different sizing strategies have been established among surgeons. The goal of this study is to virtually apply different sizing methods on the basis of pre-repair echocardiography to find out basic differences between sizing strategies.MethodsIn three-dimensional echocardiographs of 43 patients, the mitral annulus and the contour of the anterior mitral leaflet were segmented using MITK Mitralyzer software. Similarly, three-dimensional virtual models of Carpentier-Edwards Physio II annuloplasty rings and their corresponding sizers were interactively generated from computer tomography images. For each patient, the matching annuloplasty ring was selected repeatedly according to popular sizing strategies, such as the height of anterior mitral leaflet, the intercommissural distance and the surface area of anterior mitral leaflet. The areas of the selected rings were considered as the neo-surface area of the mitral annulus after implantation.ResultsThe sizing of the mitral valve according to the height of anterior mitral leaflet (mean ring size = 29.9 ± 3.90), intercommissural distance (mean ring size = 37.5 ± 1.92) or surface area of anterior mitral leaflet (mean ring size = 32.7 ± 3.3) led to significantly different measurements (p ≤ 0.01). In contrary to intercommissural distance, height and surface area of the anterior mitral leaflet exhibited significant variations between the patients (p ≤ 0.01). The sizing according to the height of anterior mitral leaflet led to the maximal reduction of the mitral annulus surface area followed by the sizing according to the surface area of anterior mitral leaflet and finally by the intercommissural distance.ConclusionsThis novel comprehensive computer-based analysis reveals that the surveyed sizing methods led to the selection of significantly different annuloplasty rings and therefore underscore the ambiguity of routinely applied annuloplasty sizing strategies.

Towards Automatic Assessment of the Mitral Valve Coaptation Zone from 4D Ultrasound

The coaptation zone is the part of the two mitral valve leaflets that collide during the cardiac cycle. It is an important parameter for the valve’s function and closing capability, but difficult to assess. In this work, we present an automatic approach for leaflet segmentation from 4D ultrasound images, which incorporates steps for coaptation zone modelling and allows determining the coaptation zone from the resulting leaflet surface. The method segments the leaflets over the whole cardiac cycle given a previously segmented annulus model. To provide a meaningful analysis of the coaptation line assessment, the mean error between ground truth model and segmented model has been computed for each leaflet separately. For the anterior leaflet, we achieved a mean error of \(1.16 \pm 0.38\) mm and \(1.24 \pm 0.37\) mm for the posterior leaflet, respectively.

Augmented reality-enhanced endoscopic images for annuloplasty ring sizing

Mitral valve annuloplasty is done in patients with mitral valve insufficiency in order to stabilize, remodel or downsize the often symmetrical or asymmetrical dilated annulus by stitching a prosthetic ring on this anatomical structure. Prosthetic rings are available in different shapes and sizes. State-of-the-art intraoperative sizing techniques for determination of the appropriate ring prosthesis are ambiguous and highly depend on the surgeon’s expertise. We propose a new augmented reality environment for visualizing the prosthetic ring in-situ on endoscopic images and therefore aid in ring selection. The superimposed ring gives quantitative information and visual cues allowing to compare the selected ring prosthesis with the patient’s annulus. Furthermore, it helps in determination of regions where an asymmetrical dilatation can be observed. Our method identifies 2D points on the endoscopic images by detecting the entry points of the mattress sutures into the annular tissue for ring fixation. 3D shape information of the annulus are obtained from ultrasound images of the patient. The pose estimation problem of the 3D annulus model is solved using an adapted iterative closest point algorithm. Neither additional hardware nor placement of artificial fiducial markers are required by the proposed approach.

Statistische 3D-formmodelle mit verteilter erscheinungsmodellierung segmentierung per abstimmung

Die Segmentierungsfahigkeit 3D Statistischer Formmodelle wird durch eine limitierte, typischerweise unidirektionale Landmarkensuche und durch schwaches Lernen auf lokal begrenzter Bildinformation erheblich eingeschrankt. Wir prasentieren eine Erweiterung 3D Statistischer Formmodelle um eine verteilte Erscheinungsmodellierung auf der Grundlage randomisierter Regressionswalder. Diese schatzen von unterschiedlichen Bildpositionen aus die Lage gesuchter Oberflachenlandmarken und ziehen dabei einen ganzheitlicheren Nutzen aus verteilter Bildinformation. Schlieslich werden alle Schatzungen in einem Abstimmungsverfahren zu einer robusten Positionsschatzung gebundelt. Nach erfolgreichen Anwendungen bei der Multi-Organ-Segmentierung aus fruheren Arbeiten demonstrieren wir die Segmentierungsfahigkeit der Methode auf besonders herausfordernden Daten. Fur diesen Zweck fuhren wir Segmentierungen des linken Herzventrikels auf 32 transosophagealen 3D-Ultraschalldaten durch. Ergebnisse werden quantitativ in 4-facher Kreuzvalidierung evaluiert und mit veroffentlichten Ergebnissen hochspezialisierter Methoden verglichen. Ohne zusatzliche Parameteroptimierung, Bildvorverarbeitung und Modellinitialisierung werden hierbei Ergebnisse erzielt, die sich im Bereich spezialisierter Methoden bewegen.

Computerunterstütztes „ring sizing“ für die Anuloplastie

ZusammenfassungHintergrundDie gegenwärtigen Methoden zur Bestimmung der Ringgröße und -form bei Mitralklappenanuloplastien sind semiquantitativ und unterliegen oft der subjektiven Einschätzung des Operateurs. Hierzu ist große chirurgische Erfahrung erforderlich.Ziel der ArbeitDurch das computerunterstützte Ring sizing sollen dem Operateur quantitative Messwerkzeuge an die Hand gegeben werden, die ihn bei einer objektiven Ringauswahl unterstützen.Material und MethodeEntwickelt wurde eine schnelle und klinisch leicht integrierbare Modellierungsmethode des Mitralklappenrings. Dadurch werden präzise Vermessungen und präoperative Deformationsanalysen für Anuloplastieringe ermöglicht. Zusätzlich lassen sich Ringimplantate, basierend auf den individuellen anatomischen Eigenschaften des Patienten, anfertigen.ErgebnisseDurch die Nutzung computerunterstützter Modellierungs- und Messwerkzeuge kann eine objektive und nachvollziehbare Ringselektion erfolgen. Die Möglichkeit zur Herstellung von patientenspezifisch gestalteten Ringen eröffnet den Weg zu einer neuartigen individualisierten Patientenversorgung.AbstractBackgroundCurrent methods to determine the size of an annuloplasty ring for mitral valve reconstruction are semi-quantitative and dependent on the subjective assessment by the surgeon which requires a high degree of professional experience.AimComputer-assisted ring sizing supports the surgeon with a quantitative measurement tool for an objective ring selection.Material and methodsA fast modeling method for the annulus of the mitral valve was developed, which is easy to integrate into the clinical workflow. It enables precise measurement and preoperative deformation analysis of annuloplasty rings. Additionally, ring implants can be created based on the patient’s individual anatomy.ResultsComputer-assisted modeling and measurement tools enable an objective and reproducible ring selection. The possibility of manufacturing patient-specific designed rings can lead to a novel patient-centered treatment.