A. Naber, and W. Nahm. Video magnification for intraoperative assessment of vascular function. In Current Directions in Biomedical Engineering, vol. 3(2) , pp. 175-178, 2017
In neurovascular surgery the intraoperative fluorescence angiography has been proven to be a reliable contact-free optical imaging technique to visualize vascular blood-flow. This angiography is obtained by injecting a fluorescence dye e.g. indocyanine green and using an infrared camera system to visualize the fluorescence inside the vessel. Obviously this requires a medical approved dye and an additional camera setup and therefore generating risks and costs. Hence, the aim of our research is to develop a comparable technique for assessing the vascular function. This approach would not require dye nor an additional infrared camera setup. It is achieved by first preprocessing the video data of a camera that records only the visible spectrum and then filter it spatially as well as temporally. The prepared data is again processed to extract information about the vascular function and visualize it. This method would provide an option to compute and visualize the vascular function using the data recorded in the visible spectrum by the surgical microscopes. Given this contact-free optical imaging system, physiological information can be easily provided to the surgeon without an additional setup. In the case of comparable results with the state-of-the-art, this technique provides a straightforward optical intraoperative angiography. Further no drug approval is needed since no dye is injected.
A. Naber, and W. Nahm. Bi - Domain Intraoperative Registration of Vessels. In Current Directions in Biomedical Engineering, vol. 4(1) , pp. 25-28, 2018
The segmentation and registration of structures are gaining importance due to the increasing demand of auto- mated image enhancement and understanding. Especially in medicine and life science, assistance systems could have a large impact on diagnosis, treatment and quality control. Dye driven procedures, such as uorescence imaging with Indocya- nine green (ICG), are nowadays indispensable because they enhance contrast, reveal structures and deliver the operator with important information. The contact free ICG angiography is providing the surgeon spatial and temporal information on blood ow w ithin a v essel. T he p rocessing o f t hose informa- tion is done manually or semi automated but is very helpful for the surgeon. Extending the degree of automatism, the amount of information processed and even augment or transfer it into another domain could deliver the operator useful support and improve surgical work ow. Using, analyzing and transferring those information from ICG-IR domain into the RGB domain is the focus of this project. We are introducing a vessel regis- tration method in the RGB domain driven by the spatial u- orescence behavior of the vessel in the ICG-IR domain. The method includes Superpixel based segmentation of the vessel in the ICG-IR domain, the spatial gradient based transfer and registration in the RGB domain and the continuous segmen- tation of the vessel in a RGB video. This paper show a proof of concept of the method. The results show an successful in- ter domain information transfer and registration of the vessel. Further tracking of the vessel over all frames is possible. Nev- ertheless limitations are revealed and discussed.
A miniaturized ceramic atmospheric plasma source for the utilization in life sciences has been developed. It is manufactured in LTCC-technology (low temperature cofired ceramic). The plasma generation is based on buried electrodes which lead to a Dielectric Barrier Discharge (DBD). The employed technology allows small feature sizes (electrode width 150 μm, barrier thickness 40μm etc.) as well as precision in the μm range, resulting in a very low power consumption of the system (approx. 5 W). Thus, the maximum temperature at the point of use can be kept below 40 °C. The flexibility of the manufacturing process (layer lamination, screen printing, patterning with picosecond laser etc.) offers additional features like robust fluidic structures (channels, chambers, gas distribution etc.) as well as the direct implementation of electronic components. The technology concept as well as the design of the ceramic parts and the handhold matched to the multi-well plate format is demonstrated. The plasma of the system can be tuned depending on the assembly of the system and the electric excitation. To prove the biocompatibility and the experimental compatibility with cell cultures (low temperature at the point of use), a method for temperature measurements on the bottom of a multi-well plate was developed. First results of the impact of the plasma source on cell cultures are presented. The effects occurring in the plasma, as well as their effects on the cell cultures (ozone formation, ultraviolet radiation etc.) are separately considered. Furthermore, the cell tolerability of the treatment with the micro-plasma source is investigated with L929 fibroblast cells.
T. Wirth, A. Naber, and W. Nahm. Combination of Color and Focus Segmentation for Medical Images with Low Depth-of-Field. In Current Directions in Biomedical Engineering, vol. 4(1) , pp. 345-349, 2018
Image segmentation plays an increasingly important role in image processing. It allows for various applications including the analysis of an image for automatic image understanding and the integration of complementary data. During vascular surgeries, the blood flow in the vessels has to be checked constantly, which could be facilitated by a segmentation of the affected vessels. The segmentation of medical images is still done manually, which depends on the surgeon’s experience and is time-consuming. As a result, there is a growing need for automatic image segmentation methods. We propose an unsupervised method to detect the regions of no interest (RONI) in intraoperative images with low depth-of-field (DOF). The proposed method is divided into three steps. First, a color segmentation using a clustering algorithm is performed. In a second step, we assume that the regions of interest (ROI) are in focus whereas the RONI are unfocused. This allows us to segment the image using an edge-based focus measure. Finally, we combine the focused edges with the color RONI to determine the final segmentation result. When tested on different intraoperative images of aneurysm clipping surgeries, the algorithm is able to segment most of the RONI not belonging to the pulsating vessel of interest. Surgical instruments like the metallic clips can also be excluded. Although the image data for the validation of the proposed method is limited to one intraoperative video, a proof of concept is demonstrated.