Digital Theses Archive


Tesi etd-03272020-115046

Type of thesis
Magnetic Localization Strategy of Robotic Endoscopic Devices
Scientific disciplinary sector
Istituto di Biorobotica
Istituto di Biorobotica - BIOROBOTICS
relatore Prof. CIUTI, GASTONE
Tutor Prof. DARIO, PAOLO
  • Nessuna parola chiave trovata
Exam session start date
This thesis aims to provide scientific and technological advances to improve clinical practice in the vision of achieving painless semi-autonomous navigation of a magnetically guided robotic capsule in colonoscopy. The development of such a semi-autonomous robotic system would contribute to increase the acceptability of the procedure for patients and would provide advanced tools to support clinicians in diagnosis. In particular, the reduction of invasiveness and discomfort perceived by patients is identified as the key element to improve the acceptability of colonoscopic diagnosis and to encourage participation in mass screening campaigns. Endoscopic robots seek to address this need by changing the paradigm of rear-wheel drive with manual locomotion to front-wheel drive with active locomotion. In current procedures, the clinician manually moves the colonoscope from the outside by pushing and pulling it against the walls of the colon, which deforms the anatomical curves and the mesentery muscles, thus causing pain. Thanks to the introduction of active magnetic locomotion solutions, the clinician moves the soft tether colonoscopic capsule directly from its distal side by means of safe magnetic interaction. The capsule communicates with the external environment through the soft tether itself that adapts to the anatomical curves without stretching the mesentery. This paradigm shift contributes to the reduction of perceived pain but eliminates the hand-instrument control, requiring knowledge of the configuration of the endoscopic capsule along the procedure. For this reason, it is necessary to develop localization strategies that ensure 1) optimal alignment between the external magnetic driving source and the capsule through an external localization strategy, and 2) the alignment between the endoscopic capsule and the colonic lumen through an internal localization strategy. The core of this thesis lays in this framework: the conception, design and implementation of a 6-DoFs external localization system compatible with high-field magnetic locomotion. Technical specifications and key reference technologies about the main localization strategies for endoscopic capsules have been thoroughly analysed and reported. Starting by this extensive literature review, it was decided to develop a localization strategy based on the triangulation of electromagnetic fields generated outside the patient. This approach ensures 1) better performance of radio frequency localization systems, commonly used for wireless endoscopic capsules, 2) does not interfere with the external permanent magnet used for locomotion, and 3) contribute to limit the required space inside the capsule. The hybrid localization system presented in this work combines electromagnets used for localization purpose and an external permanent magnet used for locomotion. The implemented system exploits the locomotion source without being limited and connected. The localization system developed in this work exploits a triangulation-based approach with two localization steps with the aim to improve localization accuracy and reduce update rate. The first step is based on magnetic field triangulation according to two mathematical approximations, i.e. spheroidal and ellipsoidal. The second step is based on minimizing the root mean square error between the measured and estimated magnetic field. Experimental results show accuracy in terms of position and orientation <5 mm and <5° along each axis, respectively. The accuracy obtained is comparable to the state of the art, but the developed localization system demonstrates an improvement in terms of applicability in additional medical fields, such as laparoscopy or gastroscopy. In conclusion, the localization system provides an efficient support for the locomotion of the endoscopic capsule, thus allowing to develop magnetic navigation strategies that reduce the discomfort perceived by the patient. Moreover, this thesis proposes the development of an innovative diagnostic tool able to support the clinician in the evaluation of the severity of injuries, a key-element towards semi-autonomous diagnosis. The proposed system is able to measure the size of a lesion from a single image (using the embedded camera) without the need for reference objects or multiple images of the lesion. The results demonstrate the good applicability of the tool and its ability to measure the size of various objects in endoscopic images with an absolute average error of 1.10 mm ± 0.89 mm. In conclusion, by introducing new features in terms of external localization and diagnosis, this work takes a step forward to the integrated the vision of a painless semi-autonomous diagnostic system that ensures a high acceptability and an accurate early diagnosis.