Nadine Warzée

Videomicroscopic extraction of specific information on cell proliferation and migration in vitro

In vitro cell imaging is a useful exploratory tool for cell behavior monitoring with a wide range of applications in cell biology and pharmacology. Combined with appropriate image analysis techniques, this approach has been shown to provide useful information on the detection and dynamic analysis of cell events. In this context, numerous efforts have been focused on cell migration analysis. In contrast, the cell division process has been the subject of fewer investigations. The present work focuses on this latter aspect and shows that, in complement to cell migration data, interesting information related to cell division can be extracted from phase-contrast time-lapse image series, in particular cell division duration, which is not provided by standard cell assays using endpoint analyses. We illustrate our approach by analyzing the effects induced by two sigma-1 receptor ligands (haloperidol and 4-IBP) on the behavior of two glioma cell lines using two in vitro cell models, i.e., the low-density individual cell model and the high-density scratch wound model. This illustration also shows that the data provided by our approach are suggestive as to the mechanism of action of compounds, and are thus capable of informing the appropriate selection of further time-consuming and more expensive biological evaluations required to elucidate a mechanism.

Automated tracking of unmarked cells migrating in three-dimensional matrices applied to anti-cancer drug screening.

In oncology, combating the spread of tumor cells is a clinical need which currently remains unsatisfied. Identifying anti-migratory compounds usually requires in vitro screening of a large number of molecules. Efficient and realistic (i.e., preferably 3D) in vitro tests are thus required in order to quantify the anti-migratory effects of anti-cancer drugs. To remain compatible with high-throughput screening, we focus on assays where unlabeled cells are migrating in 3D transparent gels and are observed under time-lapse 3D phase-contrast microscopy. In this context, we present a method for automatically tracking cells that combines a template matching preprocessing step with a mean-shift process. The preprocessing step consists in performing a correlation of a cell template with each observed volume in order to provide a phase-contrast artifact-free volume where the cells appear as correlation peaks surrounded by smooth gradients. This transformation enables the cells to be efficiently tracked by a mean-shift process. Robustness and efficiency of this approach are qualitatively and quantitatively shown in various experiments. Finally, we successfully applied our method to the quantitative characterization of the anti-migratory impact of cytochalasin-D on cancer cells. In conclusion, our method can efficiently be used for drug screening aiming to evidence drug-induced effects on cell migration in 3D transparent environments, such as matrix gels.

A Novel Technique for Distal Locking of Intramedullary Nail Based on Two Non-constrained Fluoroscopic Images and Navigation

Distal locking is one of the most difficult steps in intramedullary nailing. Numerous methods can help the surgeon, but all are time-consuming and involve much irradiation. We have developed and tested a new method based on only two fluoroscopic shots that do not need to be taken in the axes of the holes. This avoids requiring the presence of an experienced fluoroscopy operator to accurately adjust the imaging device in front of the locking holes, and decreases the exposure to radiation of the patient and medical team. A 3-D model of the distal nail and of its locking holes was constructed from a pair of calibrated fluoroscopic views. Prior to this, the contours of the nail and locking holes projections had to be determined. A 3-D optical localizer allowed the tracking of reference frames fixed to the nail, imaging device, and drilling motor. A navigation system based on the model guided the surgeon during distal targeting. The robustness, accuracy, and duration of the technique were evaluated in laboratory. The range of acceptable orientations of the X-ray beam has also been determined. Twenty drilling tests were carried out on sawbones. The accuracy and the duration required by our system to perform the distal targeting shows potential suitability for clinical use. The drill passed through the nail locking holes for all of them. The accuracy was about 1.5 mm in translation and 1deg in rotation. The total time spent on drilling did not exceed 15 min. The system was also assessed in vivo on three patients.

Development of a computer assisted system aimed at RFA liver surgery

Radio frequency ablation (RFA) is a minimally invasive treatment for either hepatocellular carcinoma or metastasis liver carcinoma. In order to resect large lesions, the surgeon has to perform multiple time-consuming destruction cycles and reposition the RFA needle for each of them. The critical step in handling a successful ablation and preventing local recurrence is the correct positioning of the needle. For small tumors, the surgeon places the middle of the active needle tip in the center of the tumor under intra-operative ultrasound guidance. When one application is not enough to cover the entire tumor, the surgeon needs to repeat the treatment after repositioning of the needle, but US guidance is obstructed by the opacity stemming from the first RFA application. In this case the surgeon can only rely on anatomical knowledge and the repositioning of the RFA needle becomes a subjective task limiting the treatment accuracy. We have developed a computer assisted surgery guidance application for this repositioning procedure. Our software application handles the complete process from preoperative image analysis to tool tracking in the operating room. Our framework is mostly used for this RFA procedure, but is also suitable for any other medical or surgery application.

Factors influencing the spatial precision of electromagnetic tracking systems used for MEG/EEG source imaging

OBJECTIVES The purpose of this study is to determine the factors influencing the spatial precision and the replicability of electromagnetic trackers (EMT) for the localization of electrodes and natural landmarks on the patients head. MATERIALS AND METHODS The effects of seven conditions on the measurement of the EMT were investigated with a Polhemus Fastrack: distance, contact between two components of the EMT, presence of magnetic object, localization of landmarks and electrodes on a phantom and a human subject without and with movements. RESULTS The EMT has a precision of 0.15mm+/-0.36mm for the measurements made on still objects in a non-magnetic environment. On a human subject, the mean variation of the nasion position is 1.6mm+/-1.46mm and 2.7mm+/-1.40mm for the tragus. The increase of the electrode measurement dispersions is significant between the phantom and the human subject with a mean variation of 2.39mm+/-1.26mm. In certain conditions, up to 15% of the measurements may be considered as outliers. CONCLUSION The precision significantly decreases for this application in the following cases: (1) physical contacts between the stylus/transmitter/receiver cables, (2) presence of magnetic objects in the surrounding of the EMT system, (3) skin and hair softness and (4) subjects head movements.

Computer-assisted needle positioning for liver tumour radiofrequency ablation (RFA).

The RFA procedures rely on a precise positioning of the radiofrequency electrode and the complete destruction of the tumour. This article presents new optimization techniques to improve such surgical procedures.

An environment for the analysis and reconstruction of archaeological objects

To assist archaeologists in their work of analysis and reconstruction of archaeological objects from their fragments, several environments have been developped in which virtual fragments can be manipulated. As a part of these environments, an important tool consists in automating the search for correct assemblages between two 3D objects by evaluating their matching surfaces. In this paper, we describe a new environment for computer aided reconstruction of archaeological objects and we propose a new method to estimate the quality of an association based on a surface area evaluation.

3D augmented reality mirror visual feedback therapy applied to the treatment of persistent, unilateral upper extremity neuropathic pain: a preliminary study

Objective: We assessed whether or not pain relief could be achieved with a new system that combines 3D augmented reality system (3DARS) and the principles of mirror visual feedback. Methods: Twenty-two patients between 18 and 75 years of age who suffered of chronic neuropathic pain. Each patient performed five 3DARS sessions treatment of 20 mins spread over a period of one week. The following pain parameters were assessed: (1) visual analogic scale after each treatment session (2) McGill pain scale and DN4 questionnaire were completed before the first session and 24 h after the last session. Results: The mean improvement of VAS per session was 29% (p < 0.001). There was an immediate session effect demonstrating a systematic improvement in pain between the beginning and the end of each session. We noted that this pain reduction was partially preserved until the next session. If we compare the pain level at baseline and 24 h after the last session, there was a significant decrease (p < 0.001) of pain of 37%. There was a significant decrease (p < 0.001) on the McGill Pain Questionnaire and DN4 questionnaire (p < 0.01). Conclusion: Our results indicate that 3DARS induced a significant pain decrease for patients who presented chronic neuropathic pain in a unilateral upper extremity. While further research is necessary before definitive conclusions can be drawn, clinicians could implement the approach as a preparatory adjunct for providing temporary pain relief aimed at enhancing chronic pain patients’ tolerance of manual therapy and exercise intervention. Level of Evidence: 4.

Real time L-system generated trees based on modern graphics hardware

Generation is a needful solution to render fractal objects like trees that have a complex geometry characterized by a huge quantity of details. This paper proposes a complete method for dynamic generation of botanical trees using L-Systems. The model integrates the dynamic generation combined with levels of detail, lighting and the animation under the wind influence. Moreover, every solution to these problems has been thought to take into account the GPU capabilities by taking advantage of its features like hardware transform and lighting and programmability.

Automatic fluoroscopic Image Calibration for Traumatology Intervention Guidance

Fluoroscopic images are often used in surgery but they are difficult to exploit in computer aided medical intervention because of their numerous disadvantages. A simple method, compatible with surgical use, is presented and applied to a common operation in traumatology: the distal targeting during intra-medullary nailing. We also show how calibrated data from fluoroscopy imaging system combined to virtual reality techniques can guide the surgeon in such difficult tasks