Section: New Results
Image Guided Intervention
Intraoperative 3D Free-Hand Ultrasound in Neurosurgery
We have continued our efforts in using ultrasound images during neurosurgical procedures. More specifically, we have adressed the problem of non-rigid registration of 3 D intraoperative ultrasound data to preoperative MR images. We have extended our previous approach on rigid registration with a parametric representation of the deformation. Results on synthetic and real data have shown promising results.
Preoperative brain deformation in neurosurgery
To our knowledge, there is no study that discusses the possible intraoperative brain deformations before skull opening. The study that we proposed is set within the context of brain tumor surgery. We demonstrated the existence of deformation in preoperative phase of IGNS and necessity to update preoperative images in order to allow the recovery of registration error for MIGNS systems due to a new phenomenon that we call " preoperative brain shift ". Respecting the " VisAGeS " point of view for planning in IGNS, preoperative brain shift requires to specify a new clinical protocol for IGNS planning procedures in order to improve the surgical workflow. Description and demonstration of the phenomenon are available on our web site (http://www.irisa.fr/visages/demo/Demo-PBS/PreoperativeBrainShift-eng.html )
Models of surgical procedures
In collaboration with the german ICCAS group, we have started this year a validation study of surgical models acquisition involving about 20 people during two weeks and providing about 1000 surgical models descriptions for analysis. We defined metrics for comparing surgical models based on measurement of structural outliers, content outliers, structural equivalence, and sequential completeness. Completion time, skills level, knowledge level, and software usability were also acquired during this study. In collaboration with the L. Morrineau at the GRESICO lab of University of South Brittany in Vannes, we have defined a methodology for identifying differences in cognitive behavior between neurosurgeons with different expertise levels. Nine neurosurgeons were interviewed. First results indicate a clear distinction between surgeons and provide a basis for further analysis. Main objective is the optimisation of information display and retrieval. Discussions and works with the ICCAS group started in November 2004 were used as a basis for the creation of a new DICOM group (WG 24: "DICOM in Surgery").
Transcranial magnetic stimulation
We have started a collaboration with the psychiatric hospital in Rennes (Prof. B. Millet) concerning transcranial magnetic stimulation for the treatment of depression. More specifically, we have developed a neuronavigation system that is coupled with the magnetic simulation system. This enables to localize in real-time the stimulation locus on the MR image. Compared to the standard empirical localization, we have shown that the neuronavigation is more reliable to stimulate the interface between areas 9 and 46 of the Brodmann atlas.