PhD Defense by Oliver Zettinig

Speaker: Oliver Zettinig Date: Friday, October 6th, 2017 Time: 14:00 PM Location: FMI-Building, Room 02.13.010

Advanced Ultrasound Imaging Techniques for Computer Assisted Interventions

Abstract:

Ultrasound imaging is commonplace in clinical routine and has become the standard of care for a plethora of diagnostic scenarios. Due to issues such as limited image quality or obstructed visibility of anatomy, the exclusive use of this modality for interventional guidance purposes has, however, not yet reached a comparable level of maturity. This thesis addresses several challenges associated with ultrasound imaging by proposing advanced techniques for interventional use. Although applied to a broad spectrum of clinical fields and anatomies, their underlying methodology is generic and can be transferred to other medical scenarios.

First, a framework for multi-modal prostate biopsy guidance is introduced, allowing urologists to accurately target suspicious lesions by combining trans-rectal ultrasound information with complementary functional tomographic data. The crucial part of this fusion consisting of deformable image registration is solved by two novel algorithms based on automatically segmented prostate surfaces or a preconditioned intensity similarity metric and a statistical deformation model.

To overcome the challenges of manual acquisitions, in particular navigation to and maintenance of appropriate location and suitable acoustic window, robotic solutions are studied. Based on multi-modal image registration, a visual servoing control scheme for neurosurgical navigation is introduced. While compensating for target anatomy movements in real-time, it allows for automatic needle guide alignment for accurate manual insertions. The suitability of such systems for reliable robotic acquisitions even in absence of planning data is demonstrated by applying the developed methods, including image quality optimizations using confidence maps, for automated abdominal aortic aneurysm screenings.

Through Doppler modes, ultrasound physics uniquely allows fast analysis of blood flow dynamics, albeit limited to 2D projections. This thesis introduces a novel technique to recover 3D velocity information in combination with a temporal flow profile using measurements from multiple directions. Due to the importance of accurate and linearly independent sampling, the advantages of robotic acquisition schemes can be hereby fully exploited.

Results of phantom experiments, volunteer studies and clinical patient evaluations, all in close collaboration with medical partners, demonstrate the great potential benefit of advanced ultrasound imaging techniques in interventional settings in terms of both efficacy and efficiency.