Accurate 3D-reconstruction and -navigation for high-precision minimal-invasive interventions
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Date
2016-02-03
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Abstract
The current lateral skull base surgery is largely invasive since it requires wide exposure and direct visualization
of anatomical landmarks to avoid damaging critical structures. A multi-port approach aiming to reduce
such invasiveness has been recently investigated. Thereby three canals are drilled from the skull surface
to the surgical region of interest: the first canal for the instrument, the second for the endoscope, and the
third for material removal or an additional instrument. The transition to minimal invasive approaches in the
lateral skull base surgery requires sub-millimeter accuracy and high outcome predictability, which results
in high requirements for the image acquisition as well as for the navigation.
Computed tomography (CT) is a non-invasive imaging technique allowing the visualization of the internal
patient organs. Planning optimal drill channels based on patient-specific models requires high-accurate
three-dimensional (3D) CT images. This thesis focuses on the reconstruction of high quality CT volumes.
Therefore, two conventional imaging systems are investigated: spiral CT scanners and C-arm cone-beam
CT (CBCT) systems. Spiral CT scanners acquire volumes with typically anisotropic resolution, i.e. the
voxel spacing in the slice-selection-direction is larger than the in-the-plane spacing. A new super-resolution
reconstruction approach is proposed to recover images with high isotropic resolution from two orthogonal
low-resolution CT volumes.
C-arm CBCT systems offers CT-like 3D imaging capabilities while being appropriate for interventional
suites. A main drawback of these systems is the commonly encountered CT artifacts due to several limitations
in the imaging system, such as the mechanical inaccuracies. This thesis contributes new methods
to enhance the CBCT reconstruction quality by addressing two main reconstruction artifacts: the misalignment
artifacts caused by mechanical inaccuracies, and the metal-artifacts caused by the presence of metal
objects in the scanned region.
CBCT scanners are appropriate for intra-operative image-guided navigation. For instance, they can be
used to control the drill process based on intra-operatively acquired 2D fluoroscopic images. For a successful
navigation, accurate estimate of C-arm pose relative to the patient anatomy and the associated
surgical plan is required. A new algorithm has been developed to fulfill this task with high-precision. The
performance of the introduced methods is demonstrated on simulated and real data.
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