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

Interfaces for Modular Surgical Planning and Assistance Systems

Modern surgery of the 21st century relies in many aspects on computers or, in a wider sense, digital data processing. Department administration, OR scheduling, billing, and - with increasing pervasion - patient data management are performed with the aid of so called Surgical Information Systems (SIS) or, more general, Hospital Information Systems (HIS). Computer Assisted Surgery (CAS) summarizes techniques which assist a surgeon in the preparation and conduction of surgical interventions. Today still predominantly based on radiology images, these techniques include the preoperative determination of an optimal surgical strategy and intraoperative systems which aim at increasing the accuracy of surgical manipulations. CAS is a relatively young field of computer science. One of the unsolved "teething troubles" of CAS is the absence of technical standards for the interconnectivity of CAS system. Current CAS systems are usually "islands of information" with no connection to other devices within the operating room or hospital-wide information systems. Several workshop reports and individual publications point out that this situation leads to ergonomic, logistic, and economic limitations in hospital work. Perioperative processes are prolonged by the manual installation and configuration of an increasing amount of technical devices. Intraoperatively, a large amount of the surgeons'' attention is absorbed by the requirement to monitor and operate systems. The need for open infrastructures which enable the integration of CAS devices from different vendors in order to exchange information as well as commands among these devices through a network has been identified by numerous experts with backgrounds in medicine as well as engineering. This thesis contains two approaches to the integration of CAS systems: - For perioperative data exchange, the specification of new data structures as an amendment to the existing DICOM standard for radiology image management is presented. The extension of DICOM towards surgical application allows for the seamless integration of surgical planning and reporting systems into DICOM-based Picture Archiving and Communication Systems (PACS) as they are installed in most hospitals for the exchange and long-term archival of patient images and image-related patient data. - For the integration of intraoperatively used CAS devices, such as, e.g., navigation systems, video image sources, or biosensors, the concept of a surgical middleware is presented. A c++ class library, the TiCoLi, is presented which facilitates the configuration of ad-hoc networks among the modules of a distributed CAS system as well as the exchange of data streams, singular data objects, and commands between these modules. The TiCoLi is the first software library for a surgical field of application to implement all of these services. To demonstrate the suitability of the presented specifications and their implementation, two modular CAS applications are presented which utilize the proposed DICOM extensions for perioperative exchange of surgical planning data as well as the TiCoLi for establishing an intraoperative network of autonomous, yet not independent, CAS modules.Die moderne Hochleistungschirurgie des 21. Jahrhunderts ist auf vielerlei Weise abhängig von Computern oder, im weiteren Sinne, der digitalen Datenverarbeitung. Administrative Abläufe, wie die Erstellung von Nutzungsplänen für die verfügbaren technischen, räumlichen und personellen Ressourcen, die Rechnungsstellung und - in zunehmendem Maße - die Verwaltung und Archivierung von Patientendaten werden mit Hilfe von digitalen Informationssystemen rationell und effizient durchgeführt. Innerhalb der Krankenhausinformationssysteme (KIS, oder englisch HIS) stehen für die speziellen Bedürfnisse der einzelnen Fachabteilungen oft spezifische Informationssysteme zur Verfügung. Chirurgieinformationssysteme (CIS, oder englisch SIS) decken hierbei vor allen Dingen die Bereiche Operationsplanung sowie Materialwirtschaft für spezifisch chirurgische Verbrauchsmaterialien ab. Während die genannten HIS und SIS vornehmlich der Optimierung administrativer Aufgaben dienen, stehen die Systeme der Computerassistierten Chirugie (CAS) wesentlich direkter im Dienste der eigentlichen chirugischen Behandlungsplanung und Therapie. Die CAS verwendet Methoden der Robotik, digitalen Bild- und Signalverarbeitung, künstlichen Intelligenz, numerischen Simulation, um nur einige zu nennen, zur patientenspezifischen Behandlungsplanung und zur intraoperativen Unterstützung des OP-Teams, allen voran des Chirurgen. Vor allen Dingen Fortschritte in der räumlichen Verfolgung von Werkzeugen und Patienten ("Tracking"), die Verfügbarkeit dreidimensionaler radiologischer Aufnahmen (CT, MRT, ...) und der Einsatz verschiedener Robotersysteme haben in den vergangenen Jahrzehnten den Einzug des Computers in den Operationssaal - medienwirksam - ermöglicht. Weniger prominent, jedoch keinesfalls von untergeordnetem praktischen Nutzen, sind Beispiele zur automatisierten Überwachung klinischer Messwerte, wie etwa Blutdruck oder Sauerstoffsättigung. Im Gegensatz zu den meist hochgradig verteilten und gut miteinander verwobenen Informationssystemen für die Krankenhausadministration und Patientendatenverwaltung, sind die Systeme der CAS heutzutage meist wenig oder überhaupt nicht miteinander und mit Hintergrundsdatenspeichern vernetzt. Eine Reihe wissenschaftlicher Publikationen und interdisziplinärer Workshops hat sich in den vergangen ein bis zwei Jahrzehnten mit den Problemen des Alltagseinsatzes von CAS Systemen befasst. Mit steigender Intensität wurde hierbei auf den Mangel an infrastrukturiellen Grundlagen für die Vernetzung intraoperativ eingesetzter CAS Systeme miteinander und mit den perioperativ eingesetzten Planungs-, Dokumentations- und Archivierungssystemen hingewiesen. Die sich daraus ergebenden negativen Einflüsse auf die Effizienz perioperativer Abläufe - jedes Gerät muss manuell in Betrieb genommen und mit den spezifischen Daten des nächsten Patienten gefüttert werden - sowie die zunehmende Aufmerksamkeit, welche der Operateur und sein Team auf die Überwachung und dem Betrieb der einzelnen Geräte verwenden muss, werden als eine der "Kinderkrankheiten" dieser relativ jungen Technologie betrachtet und stehen einer Verbreitung über die Grenzen einer engagierten technophilen Nutzergruppe hinaus im Wege. Die vorliegende Arbeit zeigt zwei parallel von einander (jedoch, im Sinne der Schnittstellenkompatibilität, nicht gänzlich unabhängig voneinander) zu betreibende Ansätze zur Integration von CAS Systemen. - Für den perioperativen Datenaustausch wird die Spezifikation zusätzlicher Datenstrukturen zum Transfer chirurgischer Planungsdaten im Rahmen des in radiologischen Bildverarbeitungssystemen weit verbreiteten DICOM Standards vorgeschlagen und an zwei Beispielen vorgeführt. Die Erweiterung des DICOM Standards für den perioperativen Einsatz ermöglicht hierbei die nahtlose Integration chirurgischer Planungssysteme in existierende "Picture Archiving and Communication Systems" (PACS), welche in den meisten Fällen auf dem DICOM Standard basieren oder zumindest damit kompatibel sind. Dadurch ist einerseits der Tatsache Rechnung getragen, dass die patientenspezifische OP-Planung in hohem Masse auf radiologischen Bildern basiert und andererseits sicher gestellt, dass die Planungsergebnisse entsprechend der geltenden Bestimmungen langfristig archiviert und gegen unbefugten Zugriff geschützt sind - PACS Server liefern hier bereits wohlerprobte Lösungen. - Für die integration intraoperativer CAS Systeme, wie etwa Navigationssysteme, Videobildquellen oder Sensoren zur Überwachung der Vitalparameter, wird das Konzept einer "chirurgischen Middleware" vorgestellt. Unter dem Namen TiCoLi wurde eine c++ Klassenbibliothek entwickelt, auf deren Grundlage die Konfiguration von ad-hoc Netzwerken während der OP-Vorbereitung mittels plug-and-play Mechanismen erleichtert wird. Nach erfolgter Konfiguration ermöglicht die TiCoLi den Austausch kontinuierlicher Datenströme sowie einzelner Datenpakete und Kommandos zwischen den Modulen einer verteilten CAS Anwendung durch ein Ethernet-basiertes Netzwerk. Die TiCoLi ist die erste frei verfügbare Klassenbibliothek welche diese Funktionalitäten dediziert für einen Einsatz im chirurgischen Umfeld vereinigt. Zum Nachweis der Tauglichkeit der gezeigten Spezifikationen und deren Implementierungen, werden zwei modulare CAS Anwendungen präsentiert, welche die vorgeschlagenen DICOM Erweiterungen zum perioperativen Austausch von Planungsergebnissen sowie die TiCoLi zum intraoperativen Datenaustausch von Messdaten unter echzeitnahen Anforderungen verwenden

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

Dynamic Image Processing for Guidance of Off-pump Beating Heart Mitral Valve Repair

Compared to conventional open heart procedures, minimally invasive off-pump beating heart mitral valve repair aims to deliver equivalent treatment for mitral regurgitation with reduced trauma and side effects. However, minimally invasive approaches are often limited by the lack of a direct view to surgical targets and/or tools, a challenge that is compounded by potential movement of the target during the cardiac cycle. For this reason, sophisticated image guidance systems are required in achieving procedural efficiency and therapeutic success. The development of such guidance systems is associated with many challenges. For example, the system should be able to provide high quality visualization of both cardiac anatomy and motion, as well as augmenting it with virtual models of tracked tools and targets. It should have the capability of integrating pre-operative images to the intra-operative scenario through registration techniques. The computation speed must be sufficiently fast to capture the rapid cardiac motion. Meanwhile, the system should be cost effective and easily integrated into standard clinical workflow. This thesis develops image processing techniques to address these challenges, aiming to achieve a safe and efficient guidance system for off-pump beating heart mitral valve repair. These techniques can be divided into two categories, using 3D and 2D image data respectively. When 3D images are accessible, a rapid multi-modal registration approach is proposed to link the pre-operative CT images to the intra-operative ultrasound images. The ultrasound images are used to display the real time cardiac motion, enhanced by CT data serving as high quality 3D context with annotated features. I also developed a method to generate synthetic dynamic CT images, aiming to replace real dynamic CT data in such a guidance system to reduce the radiation dose applied to the patients. When only 2D images are available, an approach is developed to track the feature of interest, i.e. the mitral annulus, based on bi-plane ultrasound images and a magnetic tracking system. The concept of modern GPU-based parallel computing is employed in most of these approaches to accelerate the computation in order to capture the rapid cardiac motion with desired accuracy. Validation experiments were performed on phantom, animal and human data. The overall accuracy of registration and feature tracking with respect to the mitral annulus was about 2-3mm with computation time of 60-400ms per frame, sufficient for one update per cardiac cycle. It was also demonstrated in the results that the synthetic CT images can provide very similar anatomical representations and registration accuracy compared to that of the real dynamic CT images. These results suggest that the approaches developed in the thesis have good potential for a safer and more effective guidance system for off-pump beating heart mitral valve repair

New techniques and principles in acute aortic pathologies requiring emergency surgical interventions

Aortic surgery, especially for pathologies requiring urgent surgical intervention has undergone significant changes in the past twenty years, leading to major improvement in short- and long-term outcomes. This thesis aims to provide a comprehensive, up-to-date overview on clinical characteristics of acute aortic syndrome, with special emphasis on current operative treatment possibilities, including well-established and novel, innovative surgical approaches. Within this scheme, further specific goals are to analyse different cannulation and perfusion options, the role of core temperature management during hypothermic circulatory arrest and impact of age-related differences in surgical approach of AAS. Ultrasound-guided direct cannulation on the concavity of aortic arch applying Seldinger technique is a reliable method in dissection repairs. Prompt antegrade perfusion provides not only cerebral, but also peripheral organ and tissue protection, which is an advantage in this high-risk group of patients. This alternative arterial inflow technique can be applied for prompt establishment of cardiopulmonary bypass in type A dissections or other aortic emergencies, especially during haemodynamic instability. We have proven that tympanic temperature measurements correlate with arterial blood temperature monitoring during aortic surgery applying hypothermic circulatory arrest, therefore, should replace bladder and rectal measurements. Early diagnosis and aggressive surgical approach without delay is a key factor in effective treatment for aortooesophageal fitulas. Endovascular treatment is essential to save the patient, but as a standalone procedure often ends-up with life threatening mid-term graft infection. Eliminating the source of bleeding as an emergency, resecting the oesophagus urgently to prevent sepsis and reconstructing the gastrointestinal continuity as an elective case after having the inflammatory processes settled seems to justify the sequence of endovascular aortic repair and subtotal oesophageal resection, followed by a gastro-oesophageal reconstruction, as an effective surgical approach. More frequent proximal and distal progression of the dissection flap occurs in younger patients with acute type A aortic dissection. Older age is associated with a lower probability of an intimal tear at the level of sinus of Valsalva. These findings, associated with prognostic implications, account for the choice of more radical proximal procedures for repair of aortic dissection in younger patients

Pacing with restoration of respiratory sinus arrhythmia improved cardiac contractility and the left ventricular output: a translational study

Introduction: Respiratory sinus arrhythmia (RSA) is a prognostic value for patients with heart failure and is defined as a beat-to-beat variation of the timing between the heart beats. Patients with heart failure or patients with permanent cardiac pacing might benefit from restoration of RSA. The aim of this translational, proof-of-principle study was to evaluate the effect of pacing with or without restored RSAon parameters of LV cardiac contractility and the cardiac output

Studies on the Efficacy of Transcatheter Aortic Valve Replacement : Results from the FinnValve Registry

Aortic valve stenosis (AS) is the most prevalent valvular heart disease in the developing world and becomes more common due to ageing population and increased life expectancy. Severe symptomatic AS carries a dismal prognosis without operative treatment. Transcatheter aortic valve replacement (TAVR) has revolutionized the treatment of patients at high or prohibitive risk for surgical aortic valve replacement (SAVR). TAVR has been tested in randomized clinical trials which have shown superiority in comparison to medical treatment in inoperable patients, and comparable results in comparison to SAVR in intermediate- to high-risk patients. Recently, the ongoing clinical trials in low-risk patients have reported equivalent 2-year results after TAVR and SAVR. This thesis is based on five original articles from the FinnValve registry, which is is a nationwide registry including data on all patients who underwent TAVR or SAVR with a bioprosthesis for severe aortic stenosis from 2008 to 2017. The aim of this thesis was to investigate the efficacy of TAVR with a focus on important adverse effects. Study I examined the incidence of PVR and its impact on survival after TAVR and SAVR. In this study, both mild and moderate-to-severe PVR were associated with increased mortality in mid-term follow-up. Study II studied major vascular complications (MVC) after transfemoral TAVR. The rate of MVC declined significantly during the study period. Non-access-site related MVC increased mortality to threefold in 3-year follow-up. Access-site related MVC was associated with increased mortality if severe bleeding occurred. Study III investigated acute kidney injury (AKI) following TAVR and SAVR in patients without chronic kidney disease. In propensity score matched cohorts, the risk of AKI was significantly lower after TAVR. Mortality was significantly increased with increasing severity of AKI. Study IV examined the risk endocarditis after TAVR and SAVR. There was no difference in the risk of prosthetic valve endocarditis between TAVR and SAVR in mid-term follow-up. Study V assessed the efficacy of TAVR with newer generation prostheses in preventing 1-year mortality. The vast majority of patients underwent TAVR with acceptable risk in Finland. The accuracy of risk scores in estimating mortality risk were also investigated. In conclusion, TAVR has transformed the outlook for high-risk AS patients. Complication rates have decreased significantly with increased operator experience and better devices. Still, there are issues of concern and together with the lack of long-term valve durability data, TAVR is not yet the first choice in low-risk patients with longer life expectancy.Aorttastenoosi yleistyy väestön ikääntyessä ja eläessä pidempään. Vaikea-asteinen oireinen aorttastenoosi on huonoennusteinen sairaus. Katetriteitse asennettava aorttakeinoläppä (TAVI) on mullistanut korkean leikkausriskin potilaiden hoidon. Leikkaukseen soveltumattomilla potilailla TAVI on osoitettu paremmaksi kuin konservatiivinen hoito. TAVI-toimenpidettä on verrattu kirurgiseen aorttaläppäleikkaukseen useissa satunnaistetuissa tutkimuksissa. Tulokset ovat olleet verrattavissa kirurgiaan. Tämä väitöskirja koostuu viidestä tutkimusartikkelista, jotka ovat osa FinnValve-monikeskustutkimusta. FinnValve on kansallinen rekisteri, joka käsittää tiedot yliopistosairaaloissa aorttaläpän ahtauman vuoksi TAVI:lla tai kirurgisesti biologisella aorttakeinoläpällä hoidetuista potilaista vuosina 2008-2017. Väitöskirjan tavoitteena oli tutkia TAVI:n tehokkuutta keskittyen tärkeisiin haittavaikutuksiin. Osatyö I selvitti läppäkehikon ulkopuolisen vuodon (paravalvulaarivuodon) yleisyyttä ja vaikutusta ennusteeseen TAVI:n ja kirurgisen leikkauksen jälkeen. Tässä tutkimuksessa sekä lievä että keskivaikea paravalvulaarivuoto heikensivät TAVI-potilaiden ennustetta. Osatyö II tutki merkittävien verisuonikomplikaatioiden esiintyvyyttä ja niiden vaikutusta ennusteeseen reisivaltimon kautta tehdyissä TAVI-toimenpiteissä. Verisuonireitin sisäänmenokohtaan liittyvät komplikaatiot huononsivat ennustetta, jos niihin liittyi merkittävää verenvuotoa. Muualla kuin verisuonireitin sisäänmenokohdassa tapahtuvat verisuonikomplikaatiot lisäsivät kuolleisuutta kolminkertaiseksi. Osatyö III vertaili akuutin munuaisvaurion esiintyvyyttä ja vaikutusta ennusteeseen TAVI:n ja kirurgisen aorttaläppäleikkauksen jälkeen. Akuutti munuaisvaurio oli merkittävästi harvinaisempi TAVI:n jälkeen. Kuolleisuus lisääntyi huomattavasti munuaisvaurion vaikeusasteen lisääntyessä. Osatyö IV tarkasteli läppätulehduksen (endokardiitti) esiintyvyyttä TAVI:n ja kirurgisen aorttaläppäleikkauksen jälkeen. Endokardiitin riski ei eronnut ryhmien välillä. Osatyö V arvioi uudemman polven katetriläppien tehokkuutta varhaisen kuoleman estämisessä. Valtaosa potilaista katetriläppä asennettiin hyväksyttävällä riskillä. Osatyössä arvioitiin myös riskilaskureiden toimivuutta kuolemanriskin ennustamisessa. Yhteenvetona TAVI on mullistanut aorttaläppäahtaumaa sairastavien potilaiden hoidon. Komplikaatiot vähenivät seurannassa lisääntyneen kokemuksen ja kehittyneen teknologian myötä. Pitkäaikaistulosten puuttuessa kirurginen aorttaläppäleikkaus on edelleen ensisijainen hoitomuoto nuoremmilla matalamman leikkausriskin potilailla