AbstractMagnetic Resonance Imaging (MRI) provides unique advantages such as superior soft tissue contrast, true multiplanar imaging, variable contrast mechanisms, measurement of temperature changes, perfusion and diffusion, and no ionizing radiation. Despite considerable research efforts in the field of interventional MRI, numerous challenges remain including restricted access to the patient, high acoustic noise and a shortage of MRI-safe devices.
Novel methods and devices are presented in this thesis with the primary objective of enabling effective MRI-guided interventions, particularly abdominal needle and common catheter-based endovascular interventions. Firstly, a set of MRI-safe devices (guidewires, micro guidewires, catheters and micro catheters) were developed with passive or inductively coupling resonant markers for MRI visualisation. Secondly, a method was implemented for wireless tracking and dynamic guidance of instruments. Thirdly, a framework of technologies was developed for in-room display, wireless MRI remote control and multi-user communication along with a dedicated user interface and imaging protocol.
These implementations were assessed in regards to MRI-safety, performance and usability and evaluated for MRI-guided liver biopsies, balloon angioplasty procedures and also for mechanical thrombolysis. Flow phantoms, Thiel soft-embalmed human cadavers with partially re-established perfusion and a porcine model were used for in vitro, ex vivo and in vivo validation, respectively.
The results demonstrate that these interventions are experimentally feasible and practical when using the presented developments: automated device tracking and equipment designed for MRI-guided interventions streamlined procedural workflow. Specifically, it was shown that fast and accurate needle placements along complex trajectories were feasible using a wireless interactive display and control device with a dedicated user interface for interventions. Moreover, safe and efficacious balloon angioplasties of the iliac artery were practical using the described framework of technologies along with a dedicated MRI protocol. Finally, it was demonstrated that these developments could be adapted and applied to MRI-guided endovascular mechanical thrombolysis of the middle cerebral artery.
The technologies, described in this thesis have been shown to overcome many of the present limitations and should therefore be useful for enabling MRI-guided interventions while not further constraining the operating physician in an already complex environment. Nevertheless, it is acknowledged that many crucial issues remain to be solved in the field of iMRI and in the context of the presented research. In particular further device optimisations, improvements of the tracking implementation along with further in vivo evaluations are required before moving towards clinical evaluation. This thesis sets the groundwork for moving ahead with the eventual clinical realisation of optimised MRI-guided interventions.
|Date of Award||2014|
|Supervisor||Andreas Melzer (Supervisor) & Graeme Houston (Supervisor)|
- interventional MRI
- endovascular interventions
- real-time imaging
- MR-guided balloon angioplasty
- device localization
- catheter tracking
- image-guided liver intervention
- MR remote control
- mobile web technology