2012 Proceedings - International Tissue Elasticity Conference

037 ACQUISITON OF FREEHAND ELASTOGRAPHY VOLUMES IN BRAIN TUMOR SURGERY:
PRELIMINARY RESULTS.
Tormod Selbekk 1,2 , Frank Lindseth 1,2 , Geirmund Unsgård 2,3 .
1 SINTEF, Trondheim, NORWAY; 2 The Norwegian University of Science and Technology,
Trondheim, NORWAY; 3 St. Olav Hospital, Trondheim University Hospital, Trondheim, NORWAY.
Background: Ultrasound imaging is an established method for intraoperative guidance and monitoring in
surgery of brain tumors. Some commercial systems also offer the possibility of performing freehand
acquisition of ultrasound image volumes. In such systems, an ultrasound scanner is integrated with a
navigation system which enables spatial tracking of the ultrasound probe equipped with a position sensor
device. The ultrasound volume is generated by tilting and translating the ultrasound probe. After acquisition
the ultrasound image volume is stored and subsequently displayed on the navigation system. This enables
navigation and simultaneous display of intraoperative ultrasound and preoperative images as, e.g., MRI.
Several research groups have explored ultrasound elastography or strain imaging of brain tumors [1–3], and
real time 2D ultrasound elastography images have also been compared with co–registered MR–images using a
navigation system [4]. Elastography (strain magnitude) images of glial brain tumors have been reported to
have higher image contrast than corresponding B–mode images and may, therefore, serve as a complement in
distinguishing resectable cancerous tissue from normal brain tissue [5]. It can be speculated that navigation
of surgical instruments based on ultrasound elastography image volumes could contribute to detecting and
localizing residual tumor tissue during surgery and thereby increase the proportion of gross total resection.
We present our initial experience with freehand acquisition of elastography image volumes in brain surgery
and neuronavigation based on simultaneous display of intraoperative elastography, B–mode ultrasound and
preoperative, registered Magnetic Resonance image volumes.
Aims: The aim of the study was to investigate whether or not it is possible to acquire ultrasound
elastography image volumes of brain tumors using a simple freehand technique.
Methods: Data have been acquired using the Ultrasonix MDP scanner (Vancouver, BC, Canada) with a flat
linear probe (L14–5/38) and the standard elastography module. The navigation system consisted of the
in–house developed CustusX research navigation software and the Polaris tracking system (NDI, Ontario,
Canada). So far, data have been acquired in two clinical cases, a glioblastoma and a meningioma.
Results: It was possible to acquire ultrasound elastography volumes of the brain tumor in both cases.
Various display techniques like volume rendering and image fusion of ultrasound elastography volumes,
conventional ultrasound and preoperative MRI has been explored.
Conclusions: The initial test shows that it is possible to acquire and use ultrasound elastography volumes
for neuronavigation purposes. The method must be further developed and refined for further clinical use.
Acknowledgements: This work was financed by the National Centre for Ultrasound and Image Guided Therapy at St.
Olav’s Hospital, Trondheim, Norway. We acknowledge the work of the CustusX development team: Christian
Askeland, Ole Vegard Solberg, Janne B. Bakeng, Lars E. Bø and Erlend Hofstad (all SINTEF).
References:
[1] Selbekk T, Bang J, Unsgaard G: Strain Processing of Intraoperative Ultrasound Images of Brain Tumours: Initial
Results. Ultrasound in Medicine and Biology, 31 (1), pp. 45–51, 2005.
[2] Scholz M, Lorenz A et al.: Current Status of intraoperative Real-Time Vibrography in Neurosurgery. Ultraschall
Med, 28 (5), pp. 493–497, 2007.
[3] Uff CE, Garcia L, et al.: Real Time Ultrasound Elastography in Neurosurgery. Proceedings of the IEEE
International Ultrasonics Symposium, pp. 467–470, 2009.
[4] Chakraborty A, Berry G et al.: Intra–Operative Ultrasound Elastography and Registered Magnetic Resonance
Imaging of Brain Tumours: A Feasibility Study. Ultrasound, 14 (1), pp. 43–49, 2006.
[5] Selbekk T, Brekken R, Indergaard M, Solheim O, Unsgård G: Comparison of Contrast in Brightness Mode and
Strain Ultrasonography of Glial Brain Tumours. BMC Med Imaging, 12(11), 2012.
Figure 1: Display from navigation system during surgery of
a meningioma showing (A) volume rendering of MR
FLAIR;, (B) reformatted ultrasound image slice
overlaid on corresponding MR; (C) reformatted
ultrasound elastography image slice overlaid on
corresponding MR. Tumor is indicated with a
bright arrow in (B) and (C).
indicates Presenter 115