Biomedical Engineering / Biomedizinische Technik

Published by De Gruyter

Volume 58 Issue 3

Issue of Biomedical Engineering / Biomedizinische Technik

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Contents
Journal Overview

Masthead

Publicly Available June 1, 2013

Masthead

Page range: i-iii

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Editorial

June 1, 2013

Intraoperative optical imaging in neurosurgery

Ute Morgenstern, Stephan B. Sobottka, Tobias Meyer, Matthias Kirsch, Hagen Malberg, Gabriele Schackert

Page range: 213-215

Special issue articles

June 1, 2013

SEP-induced activity and its thermographic cortical representation in a murine model

Klaus-Peter Hoffmann, Roman Ruff, Matthias Kirsch

Page range: 217-223

Abstract

This article is a methodical report on the generation of reproducible changes in brain activity in a murine model. Somatosensory evoked potentials (SEP) are used to generate synchronized cortical activity. After electrical stimulation of mice forelimbs, the potentials were recorded with a flexible thin-film polyimide electrode structure directly from the cortex. Every registration included a simultaneous recording from both hemispheres that repeated four times to reproduce and compare the results. The SEPs in the murine model were shown to generate a very stable signal. The latency of the second positive wave (P2 wave) ranged between 16 and 19 ms, and the N1-P2 amplitude ranged between 39 and 48 µV. In addition, the temperature distribution of the cortex was acquired using infrared thermography. Surface cortical temperature changed during electrical stimulation without a clear hemispheric correlation. These initial results could be a step toward a better understanding of the different synchronized cortical activities and basic methods of evaluation of various mathematical algorithms to detect them.

May 10, 2013

Intraoperative optical imaging of functional brain areas for improved image-guided surgery

Tobias Meyer, Stephan B. Sobottka, Matthias Kirsch, Gabriele Schackert, Ralf Steinmeier, Edmund Koch, Ute Morgenstern

Page range: 225-236

Abstract

Intraoperative optical imaging of intrinsic signals can improve the localization of functional areas of the cortex. On the basis of a review of the current state of technology, a setup was developed and evaluated. The aim was to implement an easy-to-use and robust imaging setup that can be used in clinical routine with standard hardware equipment (surgical microscope, high-resolution camera, stimulator for peripheral nerve stimulation) and custom-made software for intraoperative and postoperative data analysis. Evaluation of different light sources (halogen, xenon) showed a sufficient temporal behavior of xenon light without using a stabilized power supply. Spatial binning (2×2) of the camera reduces temporal variations in the images by preserving a high spatial resolution. The setup was tested in eight patients. Images were acquired continuously for 9 min with alternating 30-s rest and 30-s stimulation conditions. Intraoperative measurement and visualization of high-resolution two-dimensional activity maps could be achieved in <15 min. The detected functional regions corresponded with anatomical and electrophysiological validation. The integration of optical imaging in clinical routine could successfully be achieved using standard hardware, which improves guidance for the surgeon during interventions near the eloquent areas of the brain.

June 1, 2013

Evaluation of the clinical practicability of intraoperative optical imaging comparing three different camera setups

Stephan B. Sobottka, Tobias Meyer, Matthias Kirsch, Edmund Koch, Ralf Steinmeier, Ute Morgenstern, Gabriele Schackert

Page range: 237-248

Abstract

Intraoperative optical imaging (IOI) is a method to visualize functional activated brain areas during brain surgery using a camera system connected to a standard operating microscope. Three different high-resolution camera systems (Hamamatsu EB-CCD C7190-13W, Hamamatsu C4742-96-12G04, and Zeiss AxioCam MRm) have been evaluated for suitability to detect activated brain areas by detecting stimulation-dependent blood volume changes in the somatosensory cerebral cortex after median nerve stimulation. The image quality of the camera systems was evaluated in 14 patients with tumors around the somatosensory cortex. The intraoperative images of the brain surface were continuously recorded over 9 min. With all three camera systems, the activity maps of the median nerve area could be visualized. The image quality of a highly sensitive electron-bombarded camera was up to 10-fold lower compared with two less sensitive standard cameras. In each IOI-positive case, the activated area was in accordance with the anatomical and neurophysiological location of the corresponding cortex. The technique was found to be very sensitive, and several negative influencing factors were identified. However, all possible artifacts seem to be controllable in the majority of the cases, and the IOI method could be well adapted for routine clinical use. Nevertheless, further systematic studies are needed to demonstrate the reliability and validity of the method.

February 18, 2013

Assessment of visual function during brain surgery near the visual cortex by intraoperative optical imaging

Stephan B. Sobottka, Tobias Meyer, Matthias Kirsch, Gilfe Reiss, Edmund Koch, Ute Morgenstern, Gabriele Schackert

Page range: 249-256

Abstract

Several functional brain imaging and mapping techniques have been used for the intraoperative identification and preservation of the sensory, motor, and speech areas of the brain. However, intraoperative monitoring and mapping of the visual function is less frequently performed in the clinical routine. To our knowledge, here we demonstrate for the first time that the individual visual cortex can be mapped to the brain surface using a contact-free optical camera system during brain surgery. Intraoperative optical imaging (IOI) was performed by visual stimulation of both eyes using stobe-light flashes. Images were acquired by a camera mounted to a standard surgical microscope. Activity maps could reproducibly be computed by detecting the blood volume-dependent signal changes of the exposed cortex. To the preliminary experience, the new technique seems to be suitable for mapping the visual function in any neurosurgical intervention that requires exposure of the visual cortex. However, the clinical relevance and reliability of the technique need to be confirmed in further studies.

May 23, 2013

Evaluation of intraoperative optical imaging analysis methods by phantom and patient measurements

Martin Oelschlägel, Tobias Meyer, Hannes Wahl, Stephan B. Sobottka, Matthias Kirsch, Gabriele Schackert, Ute Morgenstern

Page range: 257-267

Abstract

Intraoperative optical imaging (IOI) is a localization method for functional areas of the human brain cortex during neurosurgical procedures. The aim of the current work was to develop of a new analysis technique for the computation of two-dimensional IOI activity maps that is suited especially for use in clinical routine. The new analysis technique includes a stimulation scheme that comprises 30-s rest and 30-s stimulation conditions, in connection with pixelwise spectral power analysis for activity map calculation. A software phantom was used for verification of the implemented algorithms as well as for the comparison with the commonly used relative difference imaging method. Furthermore, the analysis technique was tested using intraoperative measurements on eight patients. The comparison with the relative difference algorithm revealed an averaged improvement of the signal-to-noise ratio between 95% and 130% for activity maps computed from intraoperatively acquired patient datasets. The results show that the new imaging technique improves the activity map quality of IOI especially under difficult intraoperative imaging conditions and is therefore especially suited for use in clinical routine.

June 1, 2013

Quantitative fluorescence angiography for neurosurgical interventions

Claudia Weichelt, Philipp Duscha, Ralf Steinmeier, Tobias Meyer, Julia Kuß, Peter Cimalla, Matthias Kirsch, Stephan B. Sobottka, Edmund Koch, Gabriele Schackert, Ute Morgenstern

Page range: 269-279

Abstract

Present methods for quantitative measurement of cerebral perfusion during neurosurgical operations require additional technology for measurement, data acquisition, and processing. This study used conventional fluorescence video angiography – as an established method to visualize blood flow in brain vessels – enhanced by a quantifying perfusion software tool. For these purposes, the fluorescence dye indocyanine green is given intravenously, and after activation by a near-infrared light source the fluorescence signal is recorded. Video data are analyzed by software algorithms to allow quantification of the blood flow. Additionally, perfusion is measured intraoperatively by a reference system. Furthermore, comparing reference measurements using a flow phantom were performed to verify the quantitative blood flow results of the software and to validate the software algorithm. Analysis of intraoperative video data provides characteristic biological parameters. These parameters were implemented in the special flow phantom for experimental validation of the developed software algorithms. Furthermore, various factors that influence the determination of perfusion parameters were analyzed by means of mathematical simulation. Comparing patient measurement, phantom experiment, and computer simulation under certain conditions (variable frame rate, vessel diameter, etc.), the results of the software algorithms are within the range of parameter accuracy of the reference methods. Therefore, the software algorithm for calculating cortical perfusion parameters from video data presents a helpful intraoperative tool without complex additional measurement technology.

June 1, 2013

Autostereoscopic 3D visualization and image processing system for neurosurgery

Tobias Meyer, Julia Kuß, Falk Uhlemann, Stefan Wagner, Matthias Kirsch, Stephan B. Sobottka, Ralf Steinmeier, Gabriele Schackert, Ute Morgenstern

Page range: 281-291

Abstract

A demonstrator system for planning neurosurgical procedures was developed based on commercial hardware and software. The system combines an easy-to-use environment for surgical planning with high-end visualization and the opportunity to analyze data sets for research purposes. The demonstrator system is based on the software AMIRA. Specific algorithms for segmentation, elastic registration, and visualization have been implemented and adapted to the clinical workflow. Modules from AMIRA and the image processing library Insight Segmentation and Registration Toolkit (ITK) can be combined to solve various image processing tasks. Customized modules tailored to specific clinical problems can easily be implemented using the AMIRA application programming interface and a self-developed framework for ITK filters. Visualization is done via autostereoscopic displays, which provide a 3D impression without viewing aids. A Spaceball device allows a comfortable, intuitive way of navigation in the data sets. Via an interface to a neurosurgical navigation system, the demonstrator system can be used intraoperatively. The precision, applicability, and benefit of the demonstrator system for planning of neurosurgical interventions and for neurosurgical research were successfully evaluated by neurosurgeons using phantom and patient data sets.

Research articles

May 4, 2013

Evaluation of a semi-automatic segmentation algorithm in 3D intraoperative ultrasound brain angiography

Claire Chalopin, Karl Krissian, Jürgen Meixensberger, Andrea Müns, Felix Arlt, Dirk Lindner

Page range: 293-302

Abstract

In this work, we adapted a semi-automatic segmentation algorithm for vascular structures to extract cerebral blood vessels in the 3D intraoperative contrast-enhanced ultrasound angiographic (3D-iUSA) data of the brain. We quantitatively evaluated the segmentation method with a physical vascular phantom. The geometrical features of the segmentation model generated by the algorithm were compared with the theoretical tube values and manual delineations provided by observers. For a silicon tube with a radius of 2 mm, the results showed that the algorithm overestimated the lumen radii values by about 1 mm, representing one voxel in the 3D-iUSA data. However, the observers were more hindered by noise and artifacts in the data, resulting in a larger overestimation of the tube lumen (twice the reference size). The first results on 3D-iUSA patient data showed that the algorithm could correctly restitute the main vascular segments with realistic geometrical features data, despite noise, artifacts and unclear blood vessel borders. A future aim of this work is to provide neurosurgeons with a visualization tool to navigate through the brain during aneurysm clipping operations.

May 10, 2013

Recommendations for accurate numerical blood flow simulations of stented intracranial aneurysms

Gábor Janiga, Philipp Berg, Oliver Beuing, Mathias Neugebauer, Rocco Gasteiger, Bernhard Preim, Georg Rose, Martin Skalej, Dominique Thévenin

Page range: 303-314

Abstract

The number of scientific publications dealing with stented intracranial aneurysms is rapidly increasing. Powerful computational facilities are now available; an accurate computational modeling of hemodynamics in patient-specific configurations is, however, still being sought. Furthermore, there is still no general agreement on the quantities that should be computed and on the most adequate analysis for intervention support. In this article, the accurate representation of patient geometry is first discussed, involving successive improvements. Concerning the second step, the mesh required for the numerical simulation is especially challenging when deploying a stent with very fine wire structures. Third, the description of the fluid properties is a major challenge. Finally, a founded quantitative analysis of the simulation results is obviously needed to support interventional decisions. In the present work, an attempt has been made to review the most important steps for a high-quality computational fluid dynamics computation of virtually stented intracranial aneurysms. In consequence, this leads to concrete recommendations, whereby the obtained results are not discussed for their medical relevance but for the evaluation of their quality. This investigation might hopefully be helpful for further studies considering stent deployment in patient-specific geometries, in particular regarding the generation of the most appropriate computational model.

April 16, 2013

No influence of simultaneous bone-substitute application on the success of immediately loaded dental implants: a retrospective cohort study

Sigmar Kopp, Detlef Behrend, Günther Kundt, Peter Ottl, Bernhard Frerich, Mareike Warkentin

Page range: 315-321

Abstract

Purpose: To examine the influence of bone-substitute application during implantation on the success of immediately placed and loaded dental implants. Materials and methods: A total of 147 consecutive patients (age, 16.5–80.4 years) were provided with 696 immediately loaded implants. The mean follow-up time was 34.1 months. Of these implants, 50.4% (n=351) were immediately placed into extraction sockets. A total of 119 implants were added by simultaneous bone-substitute application (NanoBone, Artoss GmbH, Rostock Germany), whereas the other implants were placed in healed bone. Univariate and multivariate analysis was performed using IBM SPSS V.20. Results: The overall implant success rate was 96.1%. Implants with simultaneous bone replacement had a hazard ratio of 0.877 (p=0.837); 95% CI, 0.253–3.04). Factors found to be statistically significant modifiers of success on multivariate analysis (p<0.05) included type of superstructure (p<0.001), implant-abutment connection (p<0.001), membrane use (p=0.010), and jaw (p=0.026). None of the other factors investigated were significant modifiers. Conclusions: The present study demonstrates high success rates for immediately loaded implants and their superstructures independent of the simultaneous application of bone substitute. The declared aim of socket preservation, the prevention avoiding bone loss, is achieved in the immediate implant placement scenario under immediate-loading conditions.

About this journal

Objective
Biomedical Engineering / Biomedizinische Technik (BMT) is a high-quality forum for the exchange of knowledge in the fields of biomedical engineering, medical information technology and biotechnology/bioengineering. As an established journal with a tradition of more than 60 years, BMT addresses engineers, natural scientists, and clinicians working in research, industry, or clinical practice. All articles are peer-reviewed. All manuscripts must be submitted in English.

Topics

diagnostic imaging
image processing
biosignal processing
modelling and simulation
biomechanics
information and communication in medicine
telemedicine and e-health
surgery
minimum invasive interventions
endoscopy and image-guided therapy
diagnostic and therapeutic instrumentation
clinical engineering
micro- and nanosystems in medicine
active implants
biosensors
neuro-engineering
neural systems
rehabilitation and prosthetics
biomaterials
cellular and tissue engineering
artificial organs
biomedical engineering for audiology, ophthalmology, emergency and dental medicine
general subjects (e.g., education and training, health technology assessment)
special topics (e.g., linking proteomics and genomics with biomedical engineering, emergency medicine)

Article formats
Reviews, Research Articles, Short Communications