Magnetic Resonance Imaging for Percutaneous Interventions

The fundamental motivation for all percutaneous interventions is to improve patient care by reducing the invasiveness of the procedure. An increasing number of percu- taneous interventions from biopsies, targeted drug delivery to thermal ablations are performed under magnetic resonance (MR) guidance. Its excellent soft-tissue con- trast and multiplanar imaging capabilities make MRI an attractive alternative to computed tomography or ultrasound for real-time image-guided needle placement, in particular for targets requiring a highly angulated approach and non-axial scan pla- nes. MRI further provides the unique ability to monitor spatial temperature changes in real-time.

The research efforts of this dissertation were focused on improving and simplifying the workflow of MR-guided percutaneous procedures by introducing novel image- based methods without the need for any additional equipment. For safe and efficient MR-guided percutaneous needle placement, a set of methods was developed that allows the user to: 1) plan an entire procedure, 2) directly apply this plan to skin entry site localization without further imaging, and 3) place a needle under real-time MR guidance with automatic image plane alignment along a planned trajectory with preference to the principal patient axes. Methods for enhanced MR thermometry visualization and treatment monitoring were also developed to support an effective thermal treatment facilitating the ablation of tumor tissue without damaging adjacent healthy structures.

To allow for an extensive in-vitro and in-vivo validation, the proposed methods for both needle guidance and MR thermometry were implemented in an integrated prototype. The clinical applicability was demonstrated for a wide range of MR-guided percutaneous interventions emphasizing the relevance and impact of the conducted research.