The performance of hydrostatic bearings is in part decided by their lubrication-film height shape. Imaging the shape can be done by dissolving fluorescent dyes in the layer. However, current imaging techniques are rooted in heuristics, and as such, their physics, design parameters, and error sources are not quantitively understood. To fully grasp and consequently design the ultimate measurement system, the governing equation—the fluorescent radiative transfer equation—is solved analytically for a plane-parallel system. The new solution method assumes that fluorescent radiative transfer is well-described by the first two photon generations. Verification is done experimentally and by a concurrent Monte Carlo method. The model also successfully predicted the response of a real measurement setup. Further model analysis led to the understanding of factors such as: camera positioning; light source design; and the effect of the reflective background on which the lubrication layer lays. The insights suggest a practical implementation for a dynamic imaging setup.

The investigation of the interaction between lasers and brain tissue holds significant theoretical and practical significance in the field of brain physiology studies. A two-dimensional finite element-based simulation model was constructed using the commercial finite element simulation software COMSOL Multiphysics to investigate the propagation of light and photon correlation in tissues. The simulations included static and dynamic conditions of light propagation in tissue. In both cases this diffuse light propagation itself was studied along with photon correlation using the solution of the diffusion equation. Subsequently, the obtained simulation results are assessed and summarized by considering the outcomes of data fitting. The findings indicate that the accuracy of simulating light propagation is higher for larger sizes, although satisfactory results can be achieved for correlation propagation simulations in the small size range. The simulation results remain unaffected by the refinement of the mesh, provided that the fundamental criteria for mesh size are satisfied.

Atrial fibrillation is a cardiac arrhythmia resulting from abnormal electrical conduction and impulse formation within the atria. To address this condition, a minimally invasive procedure called cardiac ablation is performed. Real-time visual feedback during this procedure plays a critical role in determining its success. Photoacoustic imaging is a technique capable of providing real-time visual feedback. Integrating photoacoustic capabilities into existing Radiofrequency ablation catheters poses a significant challenge, which this thesis addresses. The proposed integrated solution employs optical fibers for light delivery and an ultrasound transducer for signal reception. This work investigates the design of two light delivery systems for integrated photoacoustic-guided surgery. Monte Carlo simulations are employed to study three-dimensional light propagation in tissue, informing the catheter design specifications. Optimal fiber distances and orientations within the catheter are determined based on normalized fluence values and illumination spot size—critical parameters for assessing the amount of delivered light, its area of coverage, and depth of penetration. The methodology presented applies to various photoacoustic applications. The simulation study was able to successfully inform design specifications and it was able to establish a relation between design variables and the evaluation criteria such that it can be referred to for future designs. The comparative study yielded a better-performing design configuration and its optimal specifications were found out. This proves the use of a simulation-based evaluation to design a photoacoustic intracardiac catheter. In the final phase of this research, an experiment is set up to validate the light delivery of the design, which provides a clear outlook for the future of these designs into fabricated products.

This work investigates low-cost three-dimensional (3D) ultrasound reconstruction from a two-dimensional (2D) hand-held probe with motion tracking. The best available motion tracking is an optical tracking system, which is expensive and requires external tracking hardware. Here, a low-cost manoeuvrable motion tracker, an inertial measurement unit (IMU) sensor, has been tested by comparing it with an optical tracking system. The motion of the probe has been divided into a rotation and translation movement. Comparing the IMU sensor rotation tracking with the optical tracking, while rotating 40 degrees, resulted in an average Pearson’s correlation of 0.99 ± 0.0056. The average Pearson’s correlation between the translation tracking of the IMU sensor and the optical tracking system, in a translation of 15 centimetres, was 0.13 ± 0.78. The rotation and translation tracking is used to reconstruct the ultrasound volume of a phantom. In a rocking motion reconstructed volume the horizontal distance between phantom features had a mean error of 45%, a vertical distance was reconstructed with a mean error of 0.25%. In a translation motion reconstructed volume these errors were 29% and 1.4% for respectively horizontal feature distance and vertical feature distance. This study demonstrates that an IMU sensor can be used to track the motion of the probe. The rotation tracking of the IMU sensor is comparable with the rotation tracking of an optical tracking system. The translation tracking of the IMU sensor is on average not comparable with an optical tracking system, however some translations have been tracked with a high correlation. A reason to explain the low average correlation of the translation tracking of the IMU sensor is the method of gravity vector correction in the accelerometer data. Future research should focus on the clinical evaluation of the rotation tracking and the development of an accurate translation tracking method by studying the initial gravity vector or looking at different translation tracking methods.

Treatment methods for spinal disorders involving spinal fusion surgery often entail lengthy and expensive procedures, with a risk of damage to surrounding tissues. Breach detection tools aid in precise pedicle screw placement, thereby reducing the risk of complications or misalignment, and minimizing the need for follow-up surgeries. Accurate placement of pedicles in the vertebrae is crucial in spinal fusion surgery, as improper positioning can result in breaches that potentially harm neural tissues. This study proposes a handheld bone sensing device capable of measuring real-time reflected light from tissue using carefully selected optical elements. The selection of these optical elements was guided by analyzing porcine absorption spectra and conducting Monte Carlo light reflectance simulations. The device is designed to provide consistent real-time feedback by incorporating an electronic circuit optimized to minimize environmental signal interference. A prototype, named the optics-based bone quality sensing device, was developed using electrical discharge machining parts, 3D printed parts, an Arduino Uno, a custom-made printed circuit board (PCB), and off-the-shelf optical components such as laser and photodiodes coupled into optical fibers. Experimental validation with ex vivo porcine vertebrae revealed that the device could not detect sufficient reflected light to differentiate between cortical and cancellous bone. Despite this, the study marks significant progress in creating a handheld bone sensing device that utilizes real-time reflected light sensing minimizing interference. This device represents an important step towards developing tools to assist in precise pedicle screw placement for the treatment of spinal disorders.

Treatment methods for spinal disorders involving spinal fusion surgery often entail lengthy and expensive procedures, with a risk of damage to surrounding tissues. Breach detection tools aid in precise pedicle screw placement, thereby reducing the risk of complications or misalignment, and minimizing the need for follow-up surgeries. Accurate placement of pedicles in the vertebrae is crucial in spinal fusion surgery, as improper positioning can result in breaches that potentially harm neural tissues. This study proposes a handheld bone sensing device capable of measuring real-time reflected light from tissue using carefully selected optical elements. The selection of these optical elements was guided by analyzing porcine absorption spectra and conducting Monte Carlo light reflectance simulations. The device is designed to provide consistent real-time feedback by incorporating an electronic circuit optimized to minimize environmental signal interference. A prototype, named the optics-based bone quality sensing device, was developed using electrical discharge machining parts, 3D printed parts, an Arduino Uno, a custom-made printed circuit board (PCB), and off-the-shelf optical components such as laser and photodiodes coupled into optical fibers. Experimental validation with ex vivo porcine vertebrae revealed that the device could not detect sufficient reflected light to differentiate between cortical and cancellous bone. Despite this, the study marks significant progress in creating a handheld bone sensing device that utilizes real-time reflected light sensing minimizing interference. This device represents an important step towards developing tools to assist in precise pedicle screw placement for the treatment of spinal disorders.

Integrated operating rooms (OR) have shown to be promising in meeting the challenges created by the increased complexity in the OR, by improving the quality of care, simplifying the clinical workflows, and reducing equipment-related incidents and surgical errors. Although several systems that integrate medical devices have been developed, surgical energy devices have yet to be integrated into these systems. Current measurement systems of surgical energy devices are not yet suitable for this integration, due to a lack of being manufacturer-independent and being limited in the amount of measured information. Therefore, the main objective of this thesis is the development of a manufacturer-independent measuring system that can estimate and communicate the state of any surgical energy device in real time. To realize this goal, a measurement system has been developed that measures the state of any surgical energy device through image recognition. The system is integrated into the OPeLiNK system of the Smart Cyber Operating Theatre, SCOT. It can however, be integrated in any of the other integrated ORs. The system has been tested through several experiments, showing that the accuracy and measuring speed meet the requirements of 90% and 0.2s. The system outperforms the state of the art in the amount of data that is being measured in real time at the cost of a small delay of 0.07s. Currently the bottleneck is the communication through the OPeLiNK system, where the communication frequency has a set limit of 1Hz. It can be concluded that the developed measurement system can be used for the integration of surgical energy devices in the integrated operating room. The next step is to further improve the system in terms of robustness, easier use, and increased measurement capabilities.

3D-multi-electrode arrays (3D-MEAs) are needed to overcome the limitations of 2D-multi-electrode arrays (2D-MEAs) and enable the electrical characterization of 3D neuronal cultures in in vitro brain models, advancing the understanding of neurological disorders and paving the way to personalized medicine. The aim of this thesis was to overcome some of the limitations of current 3D-MEA devices and develop structures approaching the stiffness of the brain microenvironment, by using materials softer than conventional Silicon.A polymeric 3D-MEA was designed and developed by means of an innovative combination of two-photon polymerization (2PP), a 3D printing technology with sub-micrometer resolution, and standard wafer-level microfabrication methods from the semiconductor industry. Two novel fabrication protocols were developed, the first being a combination of 2PP with high-aspect ratio photolithography, which, though feasible, proved to require an inconveniently laborious process flow. The second fabrication process employed instead 2PP to fabricate the polymeric structures, pattern the microelectrodes, and provide electrical insulation. The 2PP-based process flow was ultimately preferred due to its potential for fabrication of structures of higher aspect ratio and geometrical complexity for 3D-MEA, extending their measurement resolution. Furthermore, a wafer-level alignment routine was developed with an alignment repeatability of 2PP structures of ±5 µm, which enabled the multi-step 2PP fabrication process. A novel maskless photolithography via 2PP process was also developed to pattern thin films over slanted surfaces, utilizing photoresist and glycerol-based immersion optics. The resulting 3D-MEA consisted of 15 printed polymeric pyramids featuring a total of 60 gold microelectrodes. The electrical insulation of the traces was partially successful, and will require further process development.The results demonstrate the feasibility of merging, for the first time, the 2PP process with standard wafer-level microfabrication techniques, specifically for the fabrication of a 3D-MEA for in vitro studies of human induced pluripotent stem cell (hiPSC) neuronal cultures. The 2PP-based solutions provided in this thesis show a promising pathway for the development of more complex and biomimetic 3D-MEAs. More generally, the developed wafer-level alignment routine and maskless photolithography via 2PP process for high-aspect ratio structures contribute to advance the field of microfabrication, and may enable the development of other types of innovative microdevices.

Bio-imaging plays an essential role in life sciences and medicine. Recently, structured illumination has emerged as a promising super-resolution technique. However, in the case of thick scattering media, the benefits of structured illumination can be significantly reduced compared to conventional illumination methods, resulting in significant degradation of imaging quality. Therefore, the question of dealing with the challenges posed by structured illumination in scattering media has become a topic of considerable focus. In this thesis, an experimental setup aimed at achieving super-resolution imaging using structured illumination is developed. The factors influencing the imaging process are systematically analyzed. At the same time, machine learning methods for recovering structured illumination patterns propagated through scattering media are explored. Overall, this research tackles the challenge of improving super-resolution imaging through scattering medium thereby contributing to the development of biological and medical imaging technologies.

Cerebral oxygen saturation is an important indicator that reflects the oxygen metabolism of the brain tissues in such patients. The utilization of near-infrared spectroscopy (NIRS) enables the identification of the oxygen saturation levels in nearby tissues by analyzing the distinct oxygenation states of hemoglobin-oxyhemoglobin (HbO2) and the distinctive molecular spectrum of deoxygenated hemoglobin (Hb). It is helpful to realize the objective of noninvasive continuous detection on cerebral oxygen saturation because near-infrared radiation can directly penetrate the skull to obtain the characteristics of the average oxygen saturation of the brain tissues. This also allows a noninvasive way to monitor blood flow in the brain. A frequency comb is a pulsed laser in the time domain and a sequence of discrete, uniformly spaced frequency lines in the frequency domain. Applying the frequency comb to NIRS has the potential to develop a high-speed and fs-level time-of-flight resolution blood flow measurement system. The objective of this thesis is to utilize a chip-based optical frequency comb as an illuminating source in order to conduct time-of-flight measurements of a single target, employing a Michelson interference experiment. The establishment of the time of flight in the single-layer case and the investigation of the non-ambiguity range form the fundamental basis for future experiments multi-layer.

Background: Bilateral tubal ligation (BTL) is the most common method of contraception worldwide because it is safe and effective. However, its accessibility remains unequal among women in rural India, in part due to a lack of laparoscopic equipment. Rural hospitals therefore resort to gas insufflation-less laparoscopic surgery (GILLS) because it requires less complex equipment. The pneumoperitoneum is replaced by an abdominal wall lift (AWL) device, but these devices suffer from limitations concerning visibility and working space. Methods: Initiated by the identified medical needs in rural India, a novel AWL device with an integrated imaging system is designed based on methods from literature and input from local end-users. It is a stainless steel hollow circular hook housing an LED lighting system and a 5 MP camera module. It can be connected to any laptop with a USB-A port. The device substitutes for both the traditional AWL device and currently used laparoscopes. The design is exemplified by a fully functional aluminium prototype used for verification and validation. Results: The selected camera module is the key technology of this design because it provides state-of-the-art imaging at an unmatched price point. The lighting system used for the prototype does not provide enough light, has an asymmetric illumination distribution, and generates too much heat. A structural strength test showed that the strength of the prototype exceeds the material-adjusted design load by 30%. Furthermore, the prototype is cost-effective, lightweight, compatible with current AWL systems, and has limited waterproofness. User tests with an expert rural surgeon confirmed that this design has the potential to improve surgical outcomes of BTL and other procedures, and can increase access to specialized medical care in rural India. Conclusions: It is strongly recommended to continue the development of this AWL device. The focus points should be the shape and size of the loop (and related cost-effective production techniques), a new lighting system, and the waterproofness of the device. Collaboration with rural surgeons and local biomedical engineers is crucial for context-driven development and implementation.