Kris Verstreken

An image-guided planning system for endosseous oral implants

A preoperative planning system for oral implant surgery was developed which takes as input computed tomographies (CTs) of the jaws. Two-dimensional (2-D) reslices of these axial CT slices orthogonal to a curve following the jaw arch are computed and shown together with three-dimensional (3-D) surface rendered models of the bone and computer-aided design (CAD)-like implant models. A technique is developed for scanning and visualizing an eventual existing removable prosthesis together with the bone structures. Evaluation of the planning done with the system shows a difference between 2-D and 3-D planning methods. Validation studies measure the benefits of the 3-D approach by comparing plans made in 2-D mode only with those further adjusted using the full 3-D visualization capabilities of the system. The benefits of a 3-D approach are then evident where a prosthesis is involved in the planning. For the majority of the patients, clinically important adjustments and optimizations to the 2-D plans are made once the 3-D visualization is enabled, effectively resulting in a better plan. The alterations are related to bone quality and quantity (p<0.05), biomechanics (p<0.005), and esthetics (p<0.005), and are so obvious that the 3-D plan stands out clearly (p<0.005). The improvements often avoid complications such as mandibular nerve damage, sinus perforations, fenestrations, or dehiscences.

Single-cell recording and stimulation with a 16k micro-nail electrode array integrated on a 0.18 μm CMOS chip

To cope with the growing needs in research towards the understanding of cellular function and network dynamics, advanced micro-electrode arrays (MEAs) based on integrated complementary metal oxide semiconductor (CMOS) circuits have been increasingly reported. Although such arrays contain a large number of sensors for recording and/or stimulation, the size of the electrodes on these chips are often larger than a typical mammalian cell. Therefore, true single-cell recording and stimulation remains challenging. Single-cell resolution can be obtained by decreasing the size of the electrodes, which inherently increases the characteristic impedance and noise. Here, we present an array of 16,384 active sensors monolithically integrated on chip, realized in 0.18 μm CMOS technology for recording and stimulation of individual cells. Successful recording of electrical activity of cardiac cells with the chip, validated with intracellular whole-cell patch clamp recordings are presented, illustrating single-cell readout capability. Further, by applying a single-electrode stimulation protocol, we could pace individual cardiac cells, demonstrating single-cell addressability. This novel electrode array could help pave the way towards solving complex interactions of mammalian cellular networks.

Temperature Determination of Resonantly Excited Plasmonic Branched Gold Nanoparticles by X‐ray Absorption Spectroscopy

The fields of bioscience and nanomedicine demand precise thermometry for nanoparticle heat characterization down to the nanoscale regime. Since current methods often use indirect and less accurate techniques to determine the nanoparticle temperature, there is a pressing need for a direct and reliable element-specific method. In-situ extended X-ray absorption fine structure (EXAFS) spectroscopy is used to determine the thermo-optical properties of plasmonic branched gold nanoparticles upon resonant laser illumination. With EXAFS, the direct determination of the nanoparticle temperature increase upon laser illumination is possible via the thermal influence on the gold lattice parameters. More specifically, using the change of the Debye-Waller term representing the lattice disorder, the temperature increase is selectively measured within the plasmonic branched nanoparticles upon resonant laser illumination. In addition, the signal intensity shows that the nanoparticle concentration in the beam more than doubles during laser illumination, thereby demonstrating that photothermal heating is a dynamic process. A comparable temperature increase is measured in the nanoparticle suspension using a thermocouple. This good correspondence between the temperature at the level of the nanoparticle and at the level of the suspension points to an efficient heat transfer between the nanoparticle and the surrounding medium, thus confirming the potential of branched gold nanoparticles for hyperthermia applications. This work demonstrates that X-ray absorption spectroscopy-based nanothermometry could be a valuable tool in the fast-growing number of applications of plasmonic nanoparticles, particularly in life sciences and medicine.

A Flexible Environment for Image Guided Virtual Surgery Planning

We present an object-oriented environment built on top of OpenGL and intended for virtual planning of image-guided surgery. We enumerate typical requirements from this field and show how they are coped with by our developments. A number of already derived surgery planning applications demonstrates the flexibility of our environment.

A Double Scanning Procedure for Visualization of Radiolucent Objects in Soft Tissues: Application to Oral Implant Surgery Planning

A procedure for visualization of radiolucent objects in CT scan images is proposed and applied to endosseous oral implant surgery planning. Many of these patients have a removable prosthesis, and visualisation of this prosthesis proves to be advantageous during planning. Such a prosthesis is usually quite radiolucent and thus not distinguishable on CT. The technique glues small markers on the prosthesis, and then scans it, giving a first image set. A second image set of the patient with the intraoral marked prosthesis is then acquired. From the first set, a surface rendered model of the prosthesis can be constructed. From the second set, a surface model of the bone can be made, and the markers indicate the position of the prosthesis in the mouth of the patient. The prosthesis model is then orthogonally transformed so that it fits the bone model. The views obtained are clinically very relevant since they indicate where the teeth of a later fixed prosthesis will come, and the planner can orient the axes of the implants towards the occlusal plane of the teeth. This double scanning procedure is a low-cost technique that nevertheless has significant clinical benefits.

Image-Based Planning and Validation of C1-C2 Transarticular Screw Fixation Using Personalized Drill Guides

OBJECTIVE Posterior transarticular spine fusion is a surgical procedure used to stabilize the cervical bodies C1 and C2. Currently, spine screws are used most frequently, according to the procedure of Magerl. As the anatomy is rather complex and the view is limited, this procedure has a high risk factor. We present and validate a planning system for cervical screw insertion based on preoperative CT imaging. MATERIALS AND METHODS The planning system discussed allowed a neurosurgeon to interactively determine the desired position of the cervical screws, based on appropriate and real-time reslices through the preoperative CT image volume. From the planning, a personalized mechanical drill guide was derived as a means of transferring the plan intraoperatively. Eight cadaver experiments were performed to validate this approach. Postoperative CT was applied, and screw locations were extracted from the postoperative images after registering them to preoperative images. In this way, the deviations of the axes of the planned and inserted screws were determined. RESULTS From an initial cadaver series, it was observed that the drill guides were not stable enough to cope with the drilling forces, and tended to become displaced. Still, most of the inserted screws were reported to be placed adequately. No vascular compromise or invasion of the spinal canal was observed. For a second cadaver series, the design of the drill guide was altered. In this series, the displacement was no longer present, and all screws were optimally placed. CONCLUSIONS The preoperative planning system allowed the neurosurgeon to rehearse screw insertion in a way that is closer to surgical reality. The image-based validation technique allowed verification and enhancement of the template design on a cadaver study, giving accuracies comparable to those obtained with transfer by navigation.

Micro-sized syringes for single-cell fluidic access integrated on a micro-electrode array CMOS chip

Very-large scale integration and micro-machining have enabled the development of novel platforms for advanced and automated examination of cells and tissues in vitro. In this paper, we present a CMOS chip designed in a commercial 0.18 μm technology with integrated micro-syringes combined with micro-nail shaped electrodes and readout electronics. The micro-syringes could be individually addressed by a through-wafer micro-fluidic channel with an inner diameter of 1 μm. We demonstrated the functionality of the micro-fluidic access by diffusion of fluorescent species through the channels. Further, hippocampal neurons were cultured on top of an array of micro-syringes, and focused ion beam-scanning electron microscopy cross-sections revealed protrusion of the cells inside the channels, creating a strong interface between the membrane and the chip surface. This principle demonstrates a first step towards a novel type of automated in vitro platforms, allowing local delivery of substances to cells or advanced planar patch clamping.

Lable-free biosensor based on localized surface plasmon resonance in a multi-channel microfluidic chip

A label-free biosensor based on localized surface plasmon resonance (LSPR) was developed. A multi-channel microfluidic chip was integrated with the sensor, providing referencing channel to minimize noise level and improving the throughput. With a CCD as a detector, a sensitivity of 10™4 RIU was demonstrated. The adsorption of S-layer protein was detected successfully by the sensor system.

Active Content on the Web Using VRML and JAVA, and the Influence of WWW/JAVA on Modern Information Systems

The tremendous impact of the world wide web (WWW) on our society has, to a large extent, been made possible by two factors. The first is that the information on the Web is composed of the same elements as are traditional documents, i.e. text and images. The second factor is that the principles for accessing information and for navigating through it are universal. The information we want to disseminate can be accessed by anyone using any browser on any type of computer, not just by the specific group of users that have installed a particular software package. This is made possible by strict standardisation of the types of information and of the ways of interaction. However, this imposes restrictions on the kind of information that can be used, and causes the level of interactivity to be fairy low.