Medical oxygen is crucial for effective treatment of patients, yet many low- and middle-income countries (LMICs) without a good healthcare infrastructure have been unable to provide sufficient oxygen therapy for years now. The COVID-19 pandemic highlighted the critical need for more oxygen, leading to supply shortages and rising prices even in developed countries. Currently, most medical oxygen is produced by a few large companies using centralized Cryogenic Air Separation Units (CAS). Pressure Swing Adsorption (PSA) offers a promising alternative, enabling local production of medical oxygen without reliance on suppliers. PSA leverages the pressure dependency of adsorption isotherms to selectively adsorb nitrogen, concentrating the oxygen.

This research has investigated the possibilities of designing a system that not only meets the specific oxygen demands of a Dutch hospital but also complies with the Dutch legal frameworks and forms an economically feasible case. A case study at Reinier de Graaf hospital (RdGG) in Delft used real oxygen consumption data. The applicable regulatory frameworks have been obtained by research in literature and with help of a representative at RdGG. For the technical design and optimisation, a numerical model of the PSA-cycle has been developed. This model is based on the Ideal Adsorption Solution Theory (IAST) and makes use of the Linear Driving Force model for adsorption kinetics. The model behaviour has been validated by experiments within a self-built, small-scale PSA-unit in the Process & Energy (P&E) lab. After this, the setup was scaled to hospital size within the model. A schematic PSA-plant has been designed based on the regulatory frameworks and system requirements which came from the numerical modelling. The economic viability has been addressed based on quotes, consumption data and electricity prices which were provided by RdGG.

Dutch regulations require hospitals to have three oxygen sources, each capable of independently providing the full design flow, with PSA units obligated to produce 93% oxygen concentration (± 3%) and meet strict impurity limits. To achieve the required oxygen purity, a vacuum pressure of 0.05 bar and an adsorption pressure of 6 bar with Oxysiv MDX zeolite are optimal. Depressurization should occur close to atmospheric pressure (1.05 bar) for efficiency. The adsorption column is most effective with a diameter-to-length ratio of 0.1 and a dimensionless time, tc, of 9.56 seconds for maximum oxygen production. The dimensionless time represents the time it takes for the gas to pass through the length of the column based on its inlet velocity.
The PSA unit at RdGG must handle a normal demand of 10 Nm³/h and a peak demand of 80 Nm³/h for three consecutive days. The second source can handle peak demand for three days, while the backup source can manage only 9 hours (tvital). If the PSA-storage has been depleted and the second source fails, tvital is the maximum refill time of the PSA-storage. This requires a production rate of 0.40 mol/s and two packages of storage cylinders (1.6 m³) which store the oxygen at 200 bar. This setup necessitates two 336L columns (3.5m height, 0.35m diameter, 0.36 m/s inlet velocity) and an air inlet flow of 126 m³/hr, supported by a vacuum pump and a compressor. The cycle steps for the adsorption, depressurization and vacuum (tAD = 79 s, tDP = 67 s, tVC = 112.1 s) total 258.7 s, allowing two columns to run in parallel. A 3 m³ air pressure vessel at 10 bar maintains PSA operation for three minutes during compressor disturbances. This setup achieves 93.61% oxygen purity with 41% recovery for 93% oxygen concentration, increasing to 58% recovery for 90% oxygen concentration. Each column requires 127 kg of zeolite, producing 5.75 mol O₂ kg⁻¹h⁻¹ (0.66 m³ O₂ kg⁻¹h⁻¹ at adsorption pressure), with an energy consumption of 29.38 kJ per mole of oxygen, totalling 255 kWh/tO₂.

The total investment for a PSA plant is estimated at 215,190 EUR, with fixed equipment costs of 176,800 EUR. Using straight-line depreciation over 20 years results in annual depreciation of 9,890 EUR. Annual costs also include energy and maintenance.
For an oxygen demand of 234 tons in 2023, the annual cost would be 25,590 EUR using PSA, significantly less than the current 60,840 EUR with the Liquefied Oxygen (LOX) installation. The levelized cost of oxygen over a period of 20 years for PSA is 128.61 EUR/ton, which is 2.1 times lower than the LCOO of LOX which is 270.52 EUR/ton.

The implementation of PSA plants for localized oxygen production in the Netherlands is both technically and economically feasible. A case study at Reinier de Graaf hospital shows significant cost savings compared to current liquid oxygen setups, with potential annual savings of 35,250 EUR. Required equipment is available and the setup size allows it to be installed inside or next to the hospital. Regulatory frameworks are already present and define clear requirements for using a PSA system as primary source. When implementing the right flow and pressure mechanisms the PSA plant can be connected to the current second and backup source, minimizing system adjustments for a smooth integration.

Future research should focus on several key areas to enhance the feasibility of using PSA in Dutch hospitals. Regulatory frameworks need approval or revision by experts in medical oxygen production. Analysing zeolite degradation and validating its performance are crucial for simulating the PSA unit's lifecycle. Improved modelling techniques, considering temperature variations, research on the validity of current assumptions and preventing backflow in the experimental setup will yield more accurate results. Additionally, industry practices should be reviewed to refine the proposed setup and obtaining precise cost estimates from quotes or hospital bills will improve the economic analysis.

Herniorrhaphy, the closure of an abdominal wall hernia, is one of the most performed general surgeries worldwide. However, approximately one-third of these patients require revision surgery due to hernia recurrence, possibly caused by excess tension on the aponeurotic edge. Currently, there is no standardized method to quantify this tension. This thesis aims to design a device for use in minimally invasive herniorrhaphy to provide intraoperative information on fascial tension to assist surgeons in intraoperative decision-making.
This thesis builds upon the work of E.F. van Koten, who designed an initial device called MINT based on a linear force spring to assess tension. However, her design was not yet suitable for intraoperative use due to small components and a high component count. Therefore, this thesis focuses on redesigning the MINT to reduce the complexity of the device.
Through the redesign of the connection mechanism, the component count was reduced from fourteen (and one tool) to five. This reduction has several advantages: it simplifies the device assembly and disassembly and reduces the risk of losing components. Consequently, the new design is more suitable for use in the operating room.
Further studies should investigate the reusability of the device made from selective laser sintered PA-12, and clinical testing is required before clinical implementation.

Gastroschisis, a congenital abdominal wall defect located to the right of the intact umbilical cord (UC), results in the herniation of fetal abdominal organs into the amniotic cavity without a protective membrane covering these structures. Complex gastroschisis (CG), comprising approximately 10% of cases, is associated with significantly higher morbidity and mortality rates compared to simple gastroschisis. Fetoscopic repair of CG offers the potential to improve gastrointestinal health at birth, but thus far, no procedure has been successfully demonstrated as safe and feasible. Therefore, the goal of this graduation project was to provide a proof of principle for a novel dedicated method that enables the swift closure of the abdominal wall defect during a fetoscopic repair procedure for CG.

The development of this method began with an analysis of the clinical context, including the characteristics of the abdominal wall defect, the adjacent umbilical cord and vessels, and the fetoscopic surgical setup, which provided a clear design direction. After generating various concept solutions, the key concept — a silicone ring with membrane — was selected using the Harris Profile methodology. This concept was designed for insertion into the fetal abdominal cavity, with the membrane effectively covering the opening of the defect.

Eight configurations of the silicone ring with a membrane were then prototyped through injection molding of liquid silicone rubber in a 3D-printed mold. The rings varied in shape (round or rusk), diam- eter (20 mm and 30 mm), and stiffness (shore hardness A25 and A40). Additionally, a validation model simulating a 24-week-old fetus with CG was developed with input from medical experts.

The validation experiments demonstrated that the silicone ring with a membrane securely remained in place, effectively closing the abdominal wall defect under intra-abdominal pressure conditions ranging from 0 to 40 mmHg. These experiments, conducted using the validation model, simulated conditions during and immediately after fetal intervention in a 24-week-old fetus with CG following intestinal repositioning. These experiments provided proof of principle for the silicone ring with membrane as a novel method that enables the swift closure of the abdominal wall defect in CG during a fetoscopic repair procedure. Notably, round-shaped rings were favored, and larger diameters allowed for coverage of larger defects. However, it’s noteworthy that the 20 mm round ring effectively covered an oval-shaped defect measuring 13.5 × 12.7 mm, aligning with the reported mean defect size in CG. Furthermore, the experiments demonstrated the feasibility of introducing the rings through a 12 Fr (20 mm rings) or 14 Fr (30 mm rings) surgical port, aligning with the preferred surgical setup.

Future research is required to clinically investigate the defect diameter in CG and optimize the silicone ring with membrane’s design. Additionally, enhancing the validation model to serve dual purposes as both a validation and training model will facilitate user tests. Moreover, developing an instrument for introducing the ring into the uterus and refining the surgical technique for precise ring positioning will be essential steps toward the clinical application of this innovative approach.

Distal cement plug removal in total hip arthroplasty revision is a time-consuming and technically challenging procedure. There is a risk of perforating the femur while drilling in the cement plug. This risk increases when the orientation of the prosthesis tip is excentric. The aim of this study was to design a reusable drill guide that facilitates centric drilling in the cement plug and to evaluate this design. The extremity of the drill guide contains two centralizers. Activation of the centralizers results in the centralization of the drill guide in the femur. A set of requirements was defined for the drill guide. To check if the drill guide meets these requirements, different tests were performed. The centralizers were tested in a fatigue test and a radial force test. The usability and functionality of the drill guide were tested in a simulation of the cement plug removal procedure performed by an orthopaedic surgeon. In this simulation was a cement plug in a bone sample drilled in three different conditions. The first condition was without the drill guide. The second condition was with the drill guide by which the handle was kept pressed during the drilling. The third condition was with the drill guide but the handle was released after activation. Furthermore, the disassembly and assembly of the drill guide were tested by five inexperienced test subjects, and the cleaning and sterilization of the drill guide were discussed with experts. This study's results show that the drill guide prototype meets the requirements. The centralizers could be activated ten times without breaking and will not apply a force on the bone that exceeds the yield stress of cortical bone. The absolute deviation of the position of the drilled hole from the centre of the cement plug was significantly lower in the tests with the drill guide compared to the tests without the drill guide. The same test showed that the generated temperature by the drill guide will not cause bone necrosis. Furthermore, the (dis)assembly of the drill guide was performed in less than 110 s. However, the drill guide would benefit from some design adjustments and further testing, such as testing the durability after multiple sterilization cycles. When this is included in the design, the drill guide could be a valuable addition to the standard tools in THA revision.

Introduction: Trauma-induced rib fractures are a common injury, affecting millions of individuals globally each year. Although anteroposterior thoracic radiographs are part of the standard posttraumatic screening, the most sensitive modality, and therefore golden standard for diagnosing rib fractures, is computed tomography (CT). Still, between 19.2% and 26.8% of rib fractures are missed. Another problem encountered in rib fracture treatment management is the large interobserver variability on their taxonomy. This thesis aims to automate rib fracture detection and improve consistency in their classification by developing a Deep Learning (DL) model, using CT data.

Methods: The rib fractures were classified according to the Chest Wall Injury Society (CWIS) taxonomy, evaluating rib fracture’s type, displacement and location. Furthermore, the ribs were numbered from 1 up to and including 12 from cranio-caudal direction. For the detection and three CWIS labels, three classification models of the nnDetection framework were trained. The rib numbering consisted of a trained nnU-Net segmentation model. The four models were combined to obtain the proposed DCRibFrac model.

Experiments and results: The dataset is composed of retrospectively collected and anonymized CT scans of 100 randomly selected patients (1010 rib fractures) who were admitted to the Erasmus MC following blunt chest trauma. On the internal test set, DCRibFrac achieved a detection sensitivity of 77%, precision of 79%, and F1-score of 78%, with a mean false-positives per scan of 2.26. The type labels had the lowest scores, with sensitivities between 17% and 90%. The displacement labels had sensitivities between 43% and 91%. The location labels had the highest scores, with sensitivities between 88% and 96%. The rib number was correct in 72% of the rib fractures when wrong segmentations were excluded.

Conclusion: The proposed DL model automates acute rib fracture detection and reaches a sensitivity that is on par with clinicians. This model is the first, to the authors’ knowledge, to incorporate the CWIS taxonomy and shows its potential for achieving a consistent classification.

Currently, morphological measurements on conventional radiographs are used to assess calcaneal fractures. The two most commonly used angles for determining the degree of depression and displacement of such a fracture are Böhler’s angle (BA) and the Critical angle of Gissane (CAG). However, conventional radiographs only provide limited amount of information and are increasingly being omitted, while computerized tomography (CT) scans are increasingly being used as they contain much more information regarding fracture configuration and displacement. It is therefore important that morphological measurements can be performed using CT-scans. The purpose of this thesis were to design a novel method to perform semi-automated morphological measurements based on 3D models of the calcaneus. The results of the novel method were compared with conventional 2D measurements of the same calcaneus.

119 lateral foot radiographs and CT-scan of the same foot were obtained. The data consisted out of three populations: 40 non-fractured, 39 fractured and 40 reconstructed calcanei. Based on the CT-scans, 3D models were reconstructed through interactive segmentation processes. Measurements on the radiographs and 3D models were performed in a specially designed Graphical User Interface. Three observers measured BA and the CAG, after which they repeated the measurements after a minimum of one week. The inter- and intra-observers reliability were calculated separately for all three populations, using the intra-class correlation coefficient (ICC). Additionally, the frequency of consensus given an allowed discrepancy was calculated.

The ICC for inter- and intra-observer reliability of the 3D measurements showed an improvement for BA and the CAG for all populations compared with the ICC of the 2D measurements. The ICC for inter- and intra-observer reliability of the 3D measured BA ranged from 0.97 to 1.00, indicating an almost perfect agreement between the observers. For the CAG, the inter- and intra-observer ICC ranged from 0.89 to 0.92 and from 0.87 to 0.96, respectively. To achieve 80% consensus for the BA among the observers, an allowable discrepancy of 20 degrees was needed for the 2D measurements, while only 5 degrees was needed for the 3D measurements. To achieve 80% of consensus for the 2D CAG measurements, an allowable discrepancy of at least 20 degrees was needed. For the fractured and reconstructed population, even an allowed discrepancy of 30 degrees was needed. For the 3D CAG measurements, 80% of consensus was achieved with an allowable discrepancy of 5 degrees, 20 degrees and 10 degrees for the non-fractured, fractured and reconstructed calcanei populations, respectively.

3D morphological measurements based on 3D models of the calcaneus showed better reliability and repeatability compared to the 2D measurements. However, the novel method of performing the measurements is not yet safe for use in clinical practice, as the measurements first should be validated. Nevertheless, the method is well suited to be employed as a reference for the development of further (semi-)automated methods to perform morphological measurements.

In up to 30% of hernia patients revision surgery is needed due to infection, pain and defect recurrence. The role that abdominal wall tension plays in this is incontrovertible: most repair techniques in herniorrhaphy aim to reduce tension at the aponeurotic edge, as excess tension is directly related with local ischemia and recurrence of the hernia. Currently, fascial tension is subjectively observed by the surgeon and rarely quantified intra­-operatively. The choice of procedure is based on pre­operative characteristics of the defect, surgeon experience and preference, which can be highly variable. Research shows that an objective assessment of fascial tension can be a feasible adjunct to surgical decision making. Therefore, this thesis provides a proof of principle for MINT: minimally invasive tensiometry. MINT is an add­on tool for existing laparoscopic instruments, which enables an objective assessment of abdominal wall tension by the use of a linear spring. Universal applicability has been evaluated and confirmed in this research. MINT is fabricated using carbon fibre reinforced PA­12 (”Onyx”) at the TU Delft. The device’s safety and effectivity have been validated using several experiments and sterilisation test runs. MINT provides accurate and consistent results in Newton without further calibration. Forces up to 60N can be quantified, with an accuracy of 5.5+/­2%, expressed in Mean Absolute Percentage Error (MAPE). Results show that ”Onyx” and the silicon used can be sterilised using an autoclave at least five times. Moreover, its ease of use and functionality have been assessed in a clinical setting using an embalmed cadaver. Further testing will have to be done to substantiate the results from this research through a larger study. In addition, redesign will have to take place to decrease part count and further improve assembly of the device. The findings of this thesis provide a first step in the implementation of fascial tension measurements for intra­-operative decision making during laparoscopic surgery.

Problem: One of the biggest challenges in hospitals today is improving efficiency, (patient) safety and quality of care while cutting on costs. A current reoccurring challenge in the operation department is the coordination of the components involved in making a surgery successful. One of those components is the set of surgical instruments. They undergo a cyclic process using reprocessing methods during which various challenges arise. A few of these challenges are the complex and time-consuming instrument counts before, during and after surgery.
Research question: Various technological aids have been proposed to automate the instrument counts. Previous technologies all showed their own flaws when they were tested in the operation room (OR). A new research field for the purpose of instrument counting is the use of computer vision. Computer vision shows great promise as it is already widely used to detect and recognize objects in digital images. However, before developing an algorithm to be used specifically for surgical instrument counting in and around the OR, the various activities, working methods and environmental factors are investigated first. This is done using the following research question: "What is the feasibility of using a computer vision algorithm to automatically detect and count surgical instruments and what are potential factors that influence the performance and the implementation in the OR?".

Methods: The research question is answered using a converting thesis structure. Firstly,
the most general steps of the instrument cycle are outlined and a description is given of a SIFT computer vision algorithm. SIFT is the proposed algorithm type for the investigated application. Secondly, the more specific steps of the instrument cycle at the Reinier de Graaf Gasthuis (RdGG) are described. The result of this description are different application options and different design scenarios. Thirdly, one application type and design scenario is selected: instrument counts in the OR. A blueprint is given for testing a SIFT algorithm in the OR. This blueprint could result in numerical results, valuable observations in the OR and staff survey results.
Results: A total of 35 surgeries were attended. Only results from observations and the survey are shown as the algorithm itself was not tested yet. The observations showed factors that could negatively influence the algorithm’s performance. The survey results gave valuable insights into personal opinions on the value, use and implementation of the algorithm. 
Conclusion: The feasibility of a current SIFT algorithm in a current ORs is low as it will not be able to automatically detect and count all instruments. There are a lot of factors that need to be taken into account to improve performance and possible implementation. They are formulated in 5 design focus points: 1) a line of sight between camera and the instrument(s), 2) dealing with instruments being taken away from and added to the table, 3) controlling the light conditions around the instrument table, 4) recognizing the specific type of some instruments and 5) showing clear feedback.

Laparoscopy was shown to be highly effective in improving patients healthcare outcomes in comparison to traditional open surgery, ensuring faster healing, reduced scarring of the tissue and reduced pain. Laparoscopy has a great technological complexity, causing difficulties which make it of great interest to the engineering community. This research investigated whether colour filtering provides a better contrast during laparoscopic surgery, allowing for easier identification of tissues and vessels. A video of a gall bladder removal surgery was first carefully analysed for key moments when the hepatic vessels, gall duct and gallbladder vessels were visible. Three different reference images were selected from the original video and twelve different RGB (Red, Green, Blue) ratios were used to create new colour enhanced images for each of the selections in Darktable.

Hospitals are facing enormous financial pressure over the last years. To achieve lower costs, hospitals should invest in smart ways of working to make optimal use of the scarce capacities. A solution can be digitising processes in the hospital to prevent it from making more costs. In line with this founding, planning and scheduling of the operating room (OR) program during a day is a process that could be improved by digitising. Overtime and idle time are consequences of inaccurate planning and are both expensive elements that do not contribute to satisfaction of hospital personnel and patients. Radio Frequency Identification (RFID) is proven and proposed in previous research to be used to acquire data for surgical phase detection. Up until now, the detection accuracy for this model is too low and requires optimization before it can be implemented in the OR. This research uses a systematic approach to investigate the feasibility of implementation of RFID in the OR in Reinier de Graaf Gasthuis (RdGG) in Delft for the purpose of surgical phase recognition. The systematic approach is divided in four parts: theory, design, testing and evaluation. The first part presents an analysis of the OR in RdGG and the RFID technology and is used in the design part to compile a list of of design requirements. This list presents criteria that must be met in order to achieve succesful implementation of RFID in the OR. Based on the requirements an optimal position of the antenna is chosen above the surgical table, in the center of the plenum ventilation area and on a distance of 1.5 meter of the surgical table. On the basis of the optimal antenna position, an antenna, tag and reader is chosen. The proposed RFID system is tested in the MISIT-lab at the TU Delft and in an OR in RdGG. The goals of the experiments were to visualise the detection field and to compare the effect of the environment on the RFID performance. In the MISIT-lab, the antenna was able to detect a vast majority of tags up to a perpendicular distance (from the antenna to the surgical table) of 1.3 meter. At longer distances of 1.4 and 1.5 meter the antenna was still able to detect tags but to a lesser extent. The OR experiment yielded poor results compared to the laboratory experiment. None of the tags was detected on the predeterimined distances. The antenna was only able to detect tagged instruments on a distance of approximately 0.8 meter. The results are evaluated in the last part of this research. Normally, when facing poor performance of an RFID system the performance can be improved by increasing the antenna gain or choosing stronger RFID tags. These choices are both constrained by the dimensions of the antenna and the tag. An RFID antenna with a large surface cannot be placed in the airflow above the surgical table because this increases the risk on infections and large RFID tags do not fit on surgical instruments. The most probable reason for the decrease in performance between the two experiments is electromagnetic noise from surrounding electrical equipment and wires in the floor and ceiling. In conclusion, it is not possible to implement an RFID system in the OR for phase recognition purposes. RFID technology is fast evolving and new technologies can offer a solution. It is certainly possible that RFID can be implemented in the future when tags and antennas are more powerful while retaining small dimensions. In future, it is recommended to perform on site tests of RFID in the OR before further developing an application.