In patients with oral cavity cancer invading the mandible, a segmental bone resection is performed and the original contour of the mandible is reconstructed with a free fibula flap. Virtual surgical planning is performed prior to surgery to determine the locations and orientations of the osteotomy planes on the mandible and fibula. Currently, patient-specific cutting guides are designed and three-dimensional printed to translate the virtual surgical plan to the patient in the operating room. However, these cutting guides are not ideal; they lack adaptability when the intraoperative situation is different than expected, e.g. due to tumor progression. Alternatively, surgical navigation could be used to translate the virtual surgical plan to the patient. To enable surgical navigation, accurate alignment of the preoperative imaging data, including the virtual surgical plan, and the patient is required, i.e. image-to-patient registration. In this thesis, a simple, accurate, and noninvasive registration method for electromagnetic navigation of the mandible is introduced and assessed. Chapter 1 gives an introduction to the clinical background of mandible reconstruction surgery and the technical background of surgical navigation. The clinical problem, a potential solution and the thesis objectives are also discussed. The systematic review in Chapter 2 gives an overview of currently used registration methods in navigated mandibular surgery: point registration, surface registration, hybrid registration, and computer vision based registration. The main conclusion of the review was that there is always a tradeoff between the usability, registration time, accuracy, and invasiveness of a registration method. Chapter 3 introduces a simple and noninvasive registration method for mandible navigation: hybrid registration. This method consists of two steps: 1) point registration; performed for initialization using three anatomic landmarks on the mandible, and 2) surface registration; performed for optimization using the surgically exposed mandibular bone surface after removal of soft tissue. In previous research in the NKI-AvL, an applicator was used to fixate an electromagnetic sensor to the mandible to track its movements during navigated surgery. The design of this applicator, however, enabled movement of the sensor in the applicator, which resulted in inaccurate navigation. Therefore, in Chapter 4, a renewed design for the sensor applicator is proposed. In Chapter 5, the optimal approach for hybrid registration of the mandible is determined in phantom experiments. Different registration configurations, i.e. different surface point areas and number and configuration of surface points, were evaluated as well as registration with different patient anatomies. In all experiments, the target registration error (TRE) was below 2.0 mm, which meets the practical clinical requirements for mandible reconstruction surgery. The results suggest that only a small surface area of the mandible, marked by limited surface points, is required to obtain accurate registration. Chapter 6 describes the preliminary results of hybrid registration of the mandible in four patients during surgery. Registration could be performed within on average 4.5 minutes. Mean TRE values of 3.4 mm for anatomic landmarks and 2.3 mm for cutting guide landmarks were obtained, indicating that the registration procedure should be further optimized to achieve clinically acceptable registration accuracy. Chapter 7 provides an overall conclusion and future perspectives. Although the preliminary results of the patient study for mandible navigation are promising, the registration method should be further optimized and evaluated in more patients before implementation into clinical practice is possible. Ultimately, we want to use electromagnetic navigation to position a universal cutting guide during mandible reconstruction surgery. Multiple challenges still lie ahead before this can become reality in the NKI-AvL.  

The operating room and central sterile supply department (CSSD) are two resource-intensive healthcare departments. Reducing the environmental and financial impact of these departments is of great importance in the global debate on sustainability. Removing unnecessary items from instrument trays may provide a partial solution. However, improvements to tray compositions are often time-consuming, not permanent and not using the full reduction potential. This research compares different methods of medical instrument tray optimization and combines different aspects to create a new methodology. Three models compared and evaluated objective and subjective instrument use percentages and different suggestions for tray optimizations. New tray compositions, based on objective use rates, were discussed with the medical specialists and attuned to their requirements. The result was then reviewed by the OR-assistants, before making any final adjustments. This methodology is tested for abdominal instrument trays at the gynaecology department of the Leiden University Medical Center (LUMC). The new trays were evaluated over a test period and missing items were registered during follow-up. Risks to patient safety as a result of missing individual instruments and chances of missing instruments for different reduction methods are discussed and quantified. Mean use rates of the designated instrument sets are 28.4% (SD=6.43%) for open surgery (n=16) and 47.6% (SD=8.16%) for minimally invasive procedures (n=12). A 37% reduction of instruments is reached across three abdominal trays by removing unnecessary items. Weight of the tray contents is reduced by 31%. During the evaluation (n=7 procedures), mean instrument use for abdominal procedures increased from 28.4% (SD=6.43%) to 46.47% (SD=10.96%) after tray optimization. A reduction based on use rates with a 10% cut-off or based on the recommendations of the medical specialists, induces an 8.7% or 3.9% chance of missing any instrument during the procedure, respectively. Tray content reductions based on OR-assistant suggestions and objective use rates with a 0% cut-off are safe, but do not utilize the complete reduction potential. Different tray optimization methods were compared. Use rates were measured in the OR and expert recommendations were discussed in group sessions. A combination of objective use rates and subjective expert considerations can lead to a significant reduction of the amount of unnecessary items in the medical instrument cycle without harming patient safety. Group consensus amongst medical specialists suggests the most radical reduction of instruments on the tray, but increases chances of missing instruments during surgery. Recommendations based on use rates have to be supplemented by reduction efforts based on the clustering of equivalent instruments. Future work should focus on ways to scale reduction efforts to an autonomous hospital-wide system and teach optimization models to mimic human expert input. It should also focus on exact measurements in the CSSD to estimate reductions in costs and CO2-footprint reliably.

Absorbent mats, abundantly used in hospitals, are integral to maintaining hygiene and cleanliness by effectively collecting and retaining patient's bodily fluids. absorbent mats are available as disposable and reusable products. In the Netherlands, predominantly disposable products are used, and approximately 23 million absorbent mats are employed each year. The abundant use contributes to the Dutch healthcare sector’s substantial impact to the country’s greenhouse gas emissions, waste generation, material extraction, water consumption, and land use. Hospitals and policy makers within the healthcare sector striving to implement environmentally sustainable practices, require current data for informed decision-making. Yet, only two studies have determined the environmental impact of absorbent mats; however, critical environmental metrics are lacking and detail on the contributions of life cycle stages are insufficient. This study addresses these issues by conducting a comparative Life Cycle Assessment, examining eighteen environmental metrics of both disposable and reusable absorbent mats. The primary objective is to not only assess the environmental impact across all their life cycle stages but also to facilitate the redesign of these absorbent mats to reduce their environmental impact. An in-depth cradle-to-grave Life cycle Assessment, utilizing the ReCiPe impact assessment method, was conducted to compare and evaluate the environmental impact of three different disposable absorbent mats and one reusable absorbent mat. The identification of major contributors to their environmental impact, combined with the application of eco-design strategies, facilitated the sustainable absorbent mat redesign. The Life Cycle Assessment findings indicate that reusable absorbent mats are environmentally superior compared to their disposable counterparts, even if the impact of disposable absorbent mats is mitigated by sustainable product redesign. The reusable absorbent mat demonstrates a lower environmental impact score in fifteen out of eighteen environmental metrics when compared to the disposable absorbent mats. The environmental impact of absorbent mats is largest in the use stage for reusable absorbent mats, and in the material production and manufacturing stage for disposable absorbent mats. The redesigned disposable and reusable absorbent mat concepts exhibit a reduced environmental impact, among other factors, attributed to product recycling. Both concepts facilitate recycling by utilizing a single material for the entire absorbent mat, namely wood-derived materials for the disposable redesign and polyethylene terephthalate-derived materials for the reusable redesign. This study has demonstrated the versatility of Life Cycle Assessment in aiding informed decisions-making and providing valuable insights for sustainable product redesign. The outcomes of the Life Cycle Assessment suggest that hospitals should transition to the use of reusable absorbent mats. Furthermore, the redesign findings offer valuable insights into the environmental benefits achievable through the recycling of medical products.

Climate change is a large and global concern. The healthcare sector contributes between 6% and 10% to national carbon emissions in developed countries. Within the healthcare sector, operation rooms are very resource-intensive. A lot of energy, medical products, equipment and pharmaceuticals are required to perform surgery on a daily basis. This report explores methods to calculate the carbon footprint of Dutch operation rooms. Based on these, a tool is developed to calculate total carbon footprint and identify contributing processes. A data collection trial is completed during this development, identifying difficulties in the data collection and calculation process as well as generating some emission results. A tool is designed from the results of this trial. It is based on life cycle analysis, while also including emission factors calculated from sector carbon disclosures. Differences from either one of these carbon emission calculation methods are evaluated and if possible, compared. A final selection of calculation methods for each process is selected and used in the tool. The tool is capable of both internally monitoring carbon emissions over different time periods and comparing emission results with other hospitals. Both these functions can be used to identify emission hotspots, inspire improvements and monitor changes in emissions. Sensitivity of the model to different characterization methods and scope definitions is tested. Ultimately, this tool is aimed to aid in reducing CO2-eq emissions within operation rooms. Recommendations are made to further improve this tool and its data collection procedure.