Instrumentation of a Clinical Colonoscope for Surgical Simulation

This paper describes the instrumentation of a clinical colonoscope needed for a novel colonoscopy simulation framework. The simulator consists of a compact and portable haptic interface and a virtual reality environment to provide real-time visualization. The proposed instrumentation enables tracking different functions of the colonoscope while keeping the ergonomic unchanged

Development of A Kinetic Model For Loop-Free Colonoscopy Technology

The colonoscope is an important tool in diagnosis and management of diseases of the colon. One of the ongoing challenges with this device is that the colonoscope may form a loop together with the colon during the procedure. The result of the loop is that further insertion of the scope in the colon may not be possible. The loop may also cause risks of perforation of the colon and pain in the patient. There are currently several existing devices to overcome loop formation in colonoscopy, some of which have been introduced in clinical work. However, empirical assessment shows that these devices do not work very well. This is the motivation for the research presented in this thesis. In this thesis, a new paradigm of thinking, “doctor-assisted colonoscopy,” is proposed to overcome loop formation. In this new approach, the physician’s role is enhanced with new information that is acquired by sensors outside the human body and inferred from the mathematical model. It is referred to as a kinetic model due to the fact that this model describes the kinetic behaviour of the scope. This thesis is devoted to development of this kinetic model. In this study, the model of the colonoscope and the model of the colon are developed based on the Timoshenko beam theory, and parameters in both models are determined by the experiments. The following conclusions then are made: (1) self-locking of the colonoscope is the most basic cause for a loop to occur, while structural instability of the colonsocope is dependent on the self-locking; (2) both the scope and the colon can be well represented with the Timoshenko beam elements and the Linear Complementary Problem (LCP) formulation derived from Signorini’s law, and Coulom’s law for representation of interactions between the colon and scope is adequate; (3) there are effects from the location, looping, and tip deflection of the scope on flexural rigidity of the scope. Approximately, the flexural rigidity of the CF-Q160L colonoscope ranges from 300 to 650 N•cm2, and its accuracy is proven by a good agreement between the model predicted result and experimental result; (4) Rayleigh damping for the CF-Q160L colonoscope depends more on the mass matrix [M] of the colonoscope than the stiffness matrix [K], which is evident by the large coefficient value of “alpha” (0.3864) and the small coefficient value of “beta” (0.0164). The contributions of this thesis are: (1) the finding that the main cause of the loop is not structural instability of the colonoscope but rather self-locking of the colonoscope, which could lead to design of a “new-generation” colonoscope to avoid the loop; (2) a systematic evaluation of the existing colonoscopy technologies based on the well-proven Axiomatic Design Theory (ADT), which will serve as a guideline for the development of future new colonoscopes in future; (3) an approach to developing a kinetic model of the colonoscope useful to modeling similar objects such as a catheter guide-wire; (4) a novel ex-vivo colonoscopy test-bed with the kinetic and kinematic measurements useful for validation of new designs in colonoscopy technology and also useful for training physicians who perform the colonoscopy procedure; and (5) a new paradigm of thinking for colonoscopy called “doctor-assisted colonoscopy,” which has potential applications to other medical procedures such as catheter-based procedures

Entwicklung eines computergesteuerten Trainingssimulators für die Koloskopie mit aktivem Force-Feedback

Anhand der Entwicklung eines Trainingssimulators für die Koloskopie werden verschiedene Aspekte der Modellierung, des Interfacebaus, der Visualisierung und der Software-Architektur betrachtet. Im Gegensatz zu herkömmlichen Systemen werden sowohl am Endoskopschlauch als auch an den Bedienungsrädern aktive Kräfte generiert. Das System ermöglicht das Training der Navigation eines Endoskops im Darm und ist damit eine sinnvolle Ergänzung in der endoskopischen Ausbildung

Entwicklung eines Endoskopiesimulators mit spezieller Haptik für verschiedenartige neue Trainingsmethoden

Koloskopie ist ein endoskopisches Verfahren zur Untersuchung des Colons. Da das Erlernen der Untersuchung schwierig ist und für den Patienten gefährlich sein kann, wird versucht, durch den Einsatz von Trainingsmodellen oder Computersimulatoren ein patientenunabhängiges Training zu realisieren. Die Möglichkeiten und Grenzen dieser Methoden werden in der vorliegenden Arbeit aufgezeigt und daraus neuartige Methoden zur Verbesserung des Trainings abgeleitet. Um diese neuen Trainingsmöglichkeiten zu realisieren, wurde der vorhandene Simulator "EndoSim" um eine akustische Ausgabe ergänzt. Die Haptik wurde sowohl im Umfang als auch bezüglich der Funktionalität erweitert. Dadurch entstand der erste Koloskopiesimulator, welcher eine maximale Realitätstreue durch aktives Force-Feedback auf allen bei dieser Untersuchung möglichen Freiheitsgraden bietet. Des Weiteren ist dabei erstmals ein Koloskopiesimulator mit Positionierung auf den vier Freiheitsgraden realisiert worden. Dies wurde genutzt, um dem Trainierenden neue Möglichkeiten der Hilfe anzubieten: Ein Lernender kann sich anhand von Aufnahmen führen lassen, diesen Wiedergabemodus für eigene Versuche unterbrechen und sich bei Schwierigkeiten wieder auf den empfohlenen Weg zurücksetzen lassen. Für Nutzer des Force-Feedback-Modus wurde die Möglichkeit geschaffen, sich bei Problemen einen vorausberechneten Weg sowohl optisch als auch haptisch aufzeigen zu lassen. Die neu eingeführten Methoden erweitern in Ausbildung und Assessment den Einsatzbereich von Endoskopiesimulatoren. Zusätzlich ist es durch die neue Haptik einfach möglich, weitere Anwendungen zur Verbesserung des Trainings -- wie paralleles haptisches Training oder delokalisierte Anleitung durch einen Experten -- zu realisieren

Registration of prone and supine CT colonography images and its clinical application

Computed tomographic (CT) colonography is a technique for detecting bowel cancer and potentially precancerous polyps. CT imaging is performed on the cleansed and insufflated bowel in order to produce a virtual endoluminal representation similar to optical colonoscopy. Because fluids and stool can mimic pathology, images are acquired with the patient in both prone and supine positions. Radiologists then match endoluminal locations visually between the two acquisitions in order to determine whether pathology is real or not. This process is hindered by the fact that the colon can undergo considerable deformation between acquisitions. Robust and accurate automated registration between prone and supine data acquisitions is therefore pivotal for medical interpretation, but a challenging problem. The method proposed in this thesis reduces the complexity of the registration task of aligning the prone and supine CT colonography acquisitions. This is done by utilising cylindrical representations of the colonic surface which reflect the colon's specific anatomy. Automated alignment in the cylindrical domain is achieved by non-rigid image registration using surface curvatures, applicable even when cases exhibit local luminal collapses. It is furthermore shown that landmark matches for initialisation improve the registration's accuracy and robustness. Additional performance improvements are achieved by symmetric and inverse-consistent registration and iteratively deforming the surface in order to compensate for differences in distension and bowel preparation. Manually identified reference points in human data and fiducial markers in a porcine phantom are used to validate the registration accuracy. The potential clinical impact of the method has been evaluated using data that reflects clinical practise. Furthermore, correspondence between follow-up CT colonography acquisitions is established in order to facilitate the clinical need to investigate polyp growth over time. Accurate registration has the potential to both improve the diagnostic process and decrease the radiologist's interpretation time. Furthermore, its result could be integrated into algorithms for improved computer-aided detection of colonic polyps