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Virtual surgery planning systems have demonstrated great potential to help surgeons achieve a better functional and aesthetic outcome for the patient, and at the same time reduce time in the operating room resulting in considerable cost savings. However, the two-dimensional tools employed in these systems today, such as a mouse and a conventional graphical display, are difficult to use for interaction with three-dimensional anatomical images. Therefore surgeons often outsource virtual planning which increases cost and lead time to surgery.

Haptics relates to the sense of touch and haptic technology encompasses algorithms, software, and hardware designed to engage the sense of touch. To demonstrate how haptic technology in combination with stereo visualization can make cranio-maxillofacial surgery planning more efficient and easier to use, we describe our haptics-assisted surgery planning (HASP) system. HASP supports in-house virtual planning of reconstructions in complex trauma cases, and reconstructions with a fibula osteocutaneous free flap including bone, vessels, and soft-tissue in oncology cases. An integrated stable six degrees-of-freedom haptic attraction force model, snap-to-fit, supports semi-automatic alignment of virtual bone fragments in trauma cases. HASP has potential beyond this thesis as a teaching tool and also as a development platform for future research.

In addition to HASP, we describe a surgical bone saw simulator with a novel hybrid haptic interface that combines kinesthetic and vibrotactile feedback to display both low frequency contact forces and realistic high frequency vibrations when a virtual saw blade comes in contact with a virtual bone model. 

We also show that visuo-haptic co-location shortens the completion time, but does not improve the accuracy, in interaction tasks performed on two different visuo-haptic displays: one based on a holographic optical element and one based on a half-transparent mirror. 

Finally, we describe two prototype hand-worn haptic interfaces that potentially may expand the interaction capabilities of the HASP system. In particular we evaluate two different types of piezo-electric motors, one walking quasi-static motor and one traveling-wave ultrasonic motor for actuating the interfaces.

Interactive systems for exploring and analysing medical three dimensional (3D) volume image data using techniques such as stereoscopic rendering and haptics can lead to new workflows for virtual surgery planning. This includes the design of patient-specific surgical guides and plates for additive manufacturing (3D printing). Our applications, medical visualization and cranio-maxillofacial surgery planning, involve large volume data such as computed tomo\-graphy (CT) images with millions of data points. This motivates the development of fast and efficient methods for visualization and haptic rendering, as well as the development of efficient modeling techniques for simplifying the design of 3D printable parts. In this thesis, we develop methods for visualization and haptic rendering of isosurfaces in volume image data, and show applications of these methods to medical visualization and virtual surgery planning. We further develop methods for modeling surgical guides and plates for cranio-maxillofacial surgery, and integrate them into our system for haptics-assisted surgery planning called HASP. This system is now installed at the department of surgical sciences, Uppsala University, and is being evaluated for use in clinical research.