Image-guided Neurosurgery 

Non-invasive neurosurgical treatment of functional brain disorders using transcranial MRI-guided Focused Ultrasound

The aim of our project is the introduction of Transcranial Magnetic Resonance-guided Focused Ultrasound (TcMRgFUS) into clinical medicine for neurosurgical treatment of brain diseases in a fully non-invasive manner.

MR-guided focused ultrasound (MRgFUS) works on the same principle as a magnifying glass that focuses sunlight to burn holes into paper sheets. High intensity ultrasound beams from a phased array transducer are focused into a hotspot with a volume of only a few cubic millimeters where the heating is high enough to induce thermal tissue ablation.

MRgFUS technology is already in clinical use to handle soft tissue tumors in gynaecology, e.g. for the coagulation fibro-adenomas of the breast, and being established as a routine method for non-invasive tissue ablation uterine fibroids (www.InSightec.com).

Fig. 1: The InSightec ExAblate 4000 system interfaced to the 3.0T high field MR-scanner. The half-spherical ultrasound transducer and the positioning mechanics are in the center, a stereotactic frame for immobilizing the patient head is mounted in front of the transducer.

In this project we aim to extend the use of MRgFUS technology to applications in the human brain by developing technologies and protocols for non-invasive treatment of different diseases through the intact skull. Transcranial MR-guided Focused Ultrasound (TcMRgFUS) will extend the minimally invasive functional operative techniques by higher precision (image guided), multifocal possibilities, on-line thermal control. Moreover, it will overcome limitations of any penetration procedure, such as the risk of damaging surrounding healthy brain tissue, and the risk of hemorrhage and infection.

The field of functional neurosurgery will benefit decisively from this new development. Thus the first clinical application for TcMRgFUS will be the neurosurgical treatment of functional brain disorders, such as Parkinson's disease, dystonia and tremors, neurogenic pain and tinnitus, neuro-psychiatric disorders and epilepsy. In spite of obvious differences in clinical presentation, there is evidence that a distortion of the normal dynamics between thalamus and cortex, named thalamo-cortical dysrhythmia (TCD), is the underlying basic mechanism of these diseases.

Theoretical understanding of TCD in terms of basic cellular and network oscillatory dynamics has allowed developing a selective and minimally invasive surgical approach against these disorders. Specific stereotactic targets in the medial thalamus, or in the pallidum allow the retuning of brain rhythmicity without reduction of the thalamocortical function.

The goal to conduct these surgical procedures non-invasively by tcMRgFUS will require support by new advanced tools and significant methodological developments in two main areas:

1. the current method for intervention planning (targeting) will be refined by using statistical shape models of the relevant part of the thalamus and the basal ganglia, which will allow to fully utilize the morphological knowledge provided by the available histological data.
   
2. theoretical modeling is carried out to identify the pertinent anatomical and physiological mechanisms that underlie the normal and abnormal functioning of the thalamo-cortical system. This knowledge allows optimizing the application of existing stereotactic targets and eventually leading to the development of new stereotactic targets.

Fig. 2: Simulated patient treatment with transcranial MR-guided focused ultrasound. Non-invasive functional neurosurgery will overcome many limitations of even minimal invasive neurosurgical methods.

Methodological developments and experimental work at the University Children's Hospital aim at the optimization of MR sequences for high-resolution imaging and for high precision real time temperature mapping. Technical work will be done to ensure compatibility of the FUS- and the MR-system and balance individual system component performance.

The InSightec ExAblate 4000 clinical research platform was installed in June 2006 at the 3.0T high-field MR system of the MR-Center. Experimental work started with compatibility testing and the integration of the installed TcMRgFUS-prototype system into the existing clinical 3.0T MR-environment.

After calibration and performance testing of the high-energy ultrasound transducer we started to investigate ultrasound propagation and target focusing in adult and pediatric skulls. In the course of these experiments we will verify phase prediction models for ultrasound wave propagation through the skull and observe heat dissipation in relation to the energy deposition at the focal point.

For the verification of theoretical findings artificial and biological phantoms are developed. Using these phantoms we could successfully demonstrate the technical feasibility to create clinically relevant localized tissue ablations in the thalamus of the human brain using TcMRgFUS.

For a detailed project description see NCCR CO-ME Project 5
http://co-me.ch/projects/phase2/p05/index.en.html

Collaborations

Prof. Daniel Jeanmonod, Labor für funktionelle Neurochirurgie, Neurochirurgische Klinik, Universitätsspital Zürich, Zürich

Prof. Gabor Székely, Institut für Bildverarbeitung, Eidgenössische Technische Hochschule Zürich, Zürich

PD Dr. Daniel Kiper, Institut für Neuroinformatik, Universität Zürich und Eidgenössische Technische Hochschule Zürich, Zürich

Prof. Dr. Niels Kuster, IT'IS Foundation, Zürich

Prof. Peter Groscurth, Anatomisches Institut der Universität Zürich

InSightec, Haifa, Israel (http://www.insightec.com)

Contact

Prof. Dr. Ernst Martin
ernst.martinkispi.uzh.ch

Funding Source

NCCR CO-ME (National Centre of Competence in Research for Computer Aided and Image Guided Medical Interventions),  http://co-me.ch

Publications

Martin E, Jeanmonod D, Zadicario E, Werner B (2009). High-intensity focused ultrasound for noninvasive functional neurosurgery. Ann Neurol, 66(6): 858-861.

 Medienmitteilung Systeminstallation 15. Juni 2006 [508.5 KB]

Tagesschaubeitrag über Systeminstallation 15. Juni 2006

 "Hirnoperation mit Ultraschall", Unipublic 07.07.2006 [67 KB]

 "Ohne Skalpell", Unimagazin 2/2007, Seite 16-19 [4528.9 KB]