Post-mortem interval estimation (PMI) is a key part of forensic investigation. Accurately obtaining a PMI early in the investigative process improves the reconstruction of events, directs follow-up research and narrows down suspects in case of homicide. Currently, PMI is determined using Henssge’s nomogram requiring ambient temperature, rectal temperature, an estimated body weight and an estimated correcting factor to account for the clothing of the deceased. These body weight and correcting factor estimates are subjective and can lead to errors of up to 14 hours from the actual PMI. To improve the accuracy of the PMI Academic Medical Centre (AMC) in Amsterdam, TU Delft, the Dutch Forensic Institute and the Dutch police initiated the Therminus project. Using the Wilks Model [1]with specialised equipment can increase the accuracy of the PMI by up to a 15-minute margin of error under ideal circumstances and up to 3.2 hours under non-ideal circumstances. For the Wilks model, the weight of the deceased remains an important input and the QuickScale was developed as a specialised tool to provide this information to forensic investigators at the crime scene. This report contains the development of the second iteration of the QuickScale, the QuickScale 2.0. Objectives of this development were: 1. To Finish the QuickScale prototype, design the modules needed for building in the electronics and for adding user-friendly, intuitive controls. 2. To design and conduct usability studies with forensic investigators and use the obtained information to further improve the QuickScale construction, electronics and usability. Using a design analysis and usability engineering approach for the QuickScale design and user interface respectively. The QuickScale design was calibrated, and validated and possible improvements were identified. Three different user interfaces were developed and usability studies were conducted for groups of students and forensic investigators. New design requirements were derived from both the design analysis and usability studies. The resulting QuickScale 2.0 design incorporated the user interface that resulted in the least user errors. It met 27 out of the total 30 design criteria and contains: • An ambidextrous user interface. • Correcting springs for the non-linearity of the load cell when measuring weights below 20kg. • Handlebars with improved grip which can easily be extended to accommodate more users. • Safety labels with an abbreviated guide on the field use and stickers indicating the controls The un-met design criteria were an indicator of remaining battery life and the possibility that both units can display a difference in weight larger than 0.5 kgs, especially at the start of weight measurements. As this design still needs to be produced, it needs to be tested and evaluated. Special care should be taken when calibrating the QuickScale 2.0 and altering the calibrating method might be necessary. Furthermore, it is recommended to integrate the QuickScale 2.0 with other Therminus equipment in future evaluations. All in all the QuickScale 2.0 is a user-oriented step toward more accurate post-mortem interval estimation.

When treating a Chronic Total Occlusion (CTO) via Percutaneous Coronary Intervention (PCI), a guidewire first needs to be passed through or around the occlusion, a task requiring considerable skill and clinician experience. Proper backup support for the guidewire being used by the clinician is a prerequisite to prevent buckling or uncontrolled movement. Three different concepts that can vary their stiffness were generated, prototyped and evaluated against each other. Finally, a mechanism was designed that can vary its stiffness drastically by radially jamming wires together between a braided sheath and a radially rigid core that is also flexible in bending. Friction between the wires and the steerable segment generates the stiff configuration. If the braided sheath is released the wires can move along each other and the mechanism is flexible. The variable stiffness ability was tested by clamping the mechanism into a frame while applying a load to the distal tip. This resulted in a force-displacement curve that was 20 times stiffer in the stiff state than in the flexible state. The use of a braided sheath in a Variable Stiffness Mechanism (VSM) is an effective and simple way to obtain variable stiffness. The proposed design is a step forward in the developing process for VSM for cardiovascular applications.

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.  

Worldwide 70-90% of hospitalised patients receive intravenous infusion at some stage during their stay. In many situations, a high degree of infusion accuracy is essential as deviation from the intended dose can quickly become dangerous and moreover costly. Electronic infusion pumps provide the most accurate way of infusion, but they require programming and frequent maintenance. Furthermore, they are unsuitable for austere environments, costly, and could even become scarce in times of a pandemic. Gravity infusion combined with a drop counter could pose an interesting alternative. However, this method appears to be inaccurate over time and setting an accurate flow rate is challenging. The typically used flow regulator, a roller clamp, is the cause of these complications. This study aimed to design and develop a precise and accurate manually controlled over-line flow regulator for gravity-driven infusion. The design process consisted out of three design phases: analysis, synthesis and evaluation. During the analysis, the design requirements were set up. The synthesis phase consisted of generating a morphological overview and several pincher experiments. A pincher is used to clamp the tubing to regulate the flow rate. Then, promising partial solutions were selected, and through rapid prototyping, a final design and prototype were developed. In the evaluation phase, the flow regulator prototype was evaluated based on the set requirements. The developed DropAdjust prototype demonstrated a major performance increase in terms of mean flow rate accuracy and regulation control compared to the roller clamp. In conclusion, the DropAdjust satisfies all tested design criteria and outperformed the roller clamp in terms of accuracy and precision. Moreover, it even showed a mean flow rate accuracy error comparable to the infusion pumps. Thus, the DropAdjust combined with a drop counter provides a more affordable and accessible alternative to the infusion pumps. The prototype is already practice-ready, but several steps are still needed to realise a market-ready device. For instance, conducting endurance tests and acquiring injection moulding advice from an experienced specialist are advised. Also, additional tests are necessary to verify its safety and functionality to qualify for a CE marking.

The project's purpose was to investigate the development of a medical sharps waste device appropriate for use and manufacture in Nepal. Medical sharps waste management in Nepal is still somewhat dangerous, despite the physical and environmental dangers. After considering several design directions, it was determined to create a mechanism capable of mechanically pulling the needle tube out of the hub. A device like this will render needles unusable while simultaneously opening up possibilities for the recycling of the materials of needle waste. Additionally a device that mechanically separates the materials of needles does not currently exist. Tensile tests were performed with various needle sizes and temperatures to better investigate this. There were no statistically significant differences between temperatures, although the results from 16 G needles differed significantly from the results from 20 G and 23 G needles. It was discovered that the device's minimum pulling force should be 500 N; this, along with information taken from several set standards and previous projects on needle devices, was then included into a set of requirements for the device. After exploring several clamping, pulling, and combined mechanisms, a roller mechanism was chosen for the device. A functional prototype capable of extracting a needle tube from its hub was created. This prototype was then tested, and various experiments were carried out to try to enhance the design because needle tubes were still slipping in between the rollers on occasion, and some needle tubes broke off. Adding other structures or a different material like rubber on the rollers did not result in better performance, and a knurling pattern worked best for creating grip on the needle tube. Adding a ridge did not improve the performance, however removing some material from both sides of the gap in Roller A did enhance performance temporarily. Making the rollers out of stainless steel 431 rather than 316 did not increase their performance; however, stainless steel 431 with a heat treatment did improve the performance and showed consistent test results. This final prototype, including the rollers made out of stainless steel 431 with a heat treatment was then used to do final verification and validation. 20 G needles could be pulled with the device consistently at a needle length of 33.8 mm, both wet and dry. 27 G needles however kept breaking off, both wet and dry. A design choice should be made here about if the device should be aimed at a smaller range of needles or a redesign should be made where different spring forces could be applied. The device showed not springback and no parts became trapped in the mechanism. It was impossible to insert needles of various diameters at greater angles from the vertical of the aperture and 16 G needles did not fit into the device at all. A redesign is needed for this. The average activation force of the device was 14.72 N and the distance from the hand holding the needle to the hand operating the device did not exceed 50 mm. The cycle time per needle was still too long for the device. Further research is required to improve these parameters. The prototype did meet the weight and size requirements. The device did not have a sharps box attached to it, this should be added in a redesign. If the rollers of the device are to be constructed of stainless steel 431, they should be made in India, since stainless steel 431 was not available in Nepal. The case, cubes, pushing plate, socket, spring axis, and lever may all be made in Nepal. Standard components, such as springs and bearings, may be obtained in India. However still choices and more research is needed in the area of where exactly the product should be produced and assembled. More research is needed to determine how the metal components of needles may be recycled and how a device like this would work with different types of needles. Also researching if applying force to both rollers and a redesign either with a different spring of multiple spring forces should still be done. More testing is needed to determine the pulling force and how many cycles the device can sustain. As well as a drop test, a tipping test on an angular surface and users tests. Lastly research into how to incorporate a redesign where the syringe is also rendered unusable is needed, since this study only focused on making the needle part unusable by separating the materials.

Infant shaking can cause serious damage (inflicted head injury by shaking trauma), it’s occurrence indicates the necessity for infant protection. To ensure reliable jurisprudence, it is important to know the exact consequences of shaking on an infant’s body. These consequences can be researched by the use of an anthropomorphic shake doll. With this doll, shake experiments can be performed in order to better understand the kinematics of the body and body parts during shaking. This study aims to establish design criteria for this doll as well as designing, producing and testing the joints for this model. A requirement list is presented, as well as a design for a joint that can be used for the limbs of the doll. To ensure structural integrity of this design, a representation of the joint was created and an indicative mechanical shake test was performed. Building further on this, real life prototypes have been made.

When sawing in bone for medical or medico-legal procedures, fine, airborne dust is produced (aerosols) that can pose a health hazard when inhaled by practitioners. The goal of the current study was to find the influence of saw blade frequency and saw blade contact load, the degree of skeletonisation of the bone, the test environment with external air flows such as ventilation systems, and the type of saw blade used on the production of aerosol particles. A custom test setup was designed and manufactured to test the sawing parameters in 8 experiments, with 2 to 9 experimental conditions tested in each, where a particle counter was used to determine the production of aerosol particles while varying the 5 chosen parameters. Results showed that the number of counted particles was highest with higher saw blade frequencies, lower saw blade contact loads, in dry completely skeletonised bone compared to fresh bone, and using an electrical oscillating saw compared to hand-sawing. Under all conditions, the high amount of aerosol counted posed potential health risks. The tested external ventilation system was adequate in removing the produced number of particles, but these high-tech systems are not always available in developing countries or emergency situations. In conclusion, the production of aerosols can be reduced by optimising the sawing parameters. However, even the lowest number of aerosol particles counted during the current study was high enough to cause potential health risks to practitioners. Safety precautions should be taken, such as external ventilation, proper breathing gear, and adequate protocols, to truly minimise the risk in all bone sawing scenarios.

Part I: Inflicted head injury by shaking trauma (IHI-ST) is often simulated to better understand the injury mechanisms and to analyze whether violent shaking can cause head injury in infants. Computational models are usually subjected to linear and rotational inputs to simulate shaking scenarios. In existing studies, the head’s rotation center is kept fixed over time during shaking. However, the infant’s head is unlikely to rotate around a fixed pivoting point in real life due to the flexibility of the infant’s neck and the external imposed shaking motion by the perpetrator. It is currently unknown how the location of the rotation center changes over time and how this manifests itself in the expression of the injury mechanisms associated with IHI-ST. In this study, the variation of the rotation center of an infant’s head during shaking and its potential effect on injury mechanisms were analyzed. First, dynamics of the infant’s head were obtained in shaking experiments with an infant surrogate. Next, the variation of the rotation center was calculated and relations between characteristics of the participants and shaking variables were analyzed. Key findings: during shaking the location of the head’s rotation center varied in both anterior-posterior and vertical direction with respect to the head, causing the head’s radius of curvature to vary six orders of magnitude. Therefore, head-dynamics and injury mechanisms underlying IHI-ST are possibly simulated incorrectly when using a fixed rotation center. It remains unclear how this affects the validity of IHI-ST injury risk assessments and the injury thresholds on which these assessments are based. Future research should therefore evaluate the performance of head-dynamic simulations regarding IHI-ST. Part II: Computational model simulations are extensively used to analyze inflicted head injury by shaking trauma in infants (IHI-ST). Infant head models are usually excited by dynamic inputs, which are applied to a specific point with respect to the head. In existing studies the load application point is assumed to be fixed over time; thereby neglecting spatiotemporal variation of the rotation center during shaking. Therefore, this assumption may be inappropriate, because the location of the heads’ rotation center is in fact not constant over time during shaking. It is unknown to what extent head dynamics are correctly simulated when using a fixed rotation center, hence simulation results regarding injury thresholds and shaking trauma assessment could be invalid. In this study, loading-methods used in IHI-ST simulations were evaluated for their temporal accuracy in replicating external head-dynamics. First, a mathematical model incorporating spatiotemporal variation of the head’s rotation center was proposed. Secondly, head dynamics were calculated using the proposed mathematical model and existing model-loading methods. Finally, the calculated head dynamics were compared to a reference dataset. Key findings: in all of the 29 cases from the reference dataset, implementation of a time-varying load application point resulted in an improved temporal replication of shaking dynamics compared to existing model-loading methods. Accelerations of the head in x- and z-direction had a two and four times smaller absolute error over a typical shake cycle than any previously existing finite element model (FEM) for IHI-ST. It remains unclear how implementation of a time-varying load application point affects the dynamics of fluids and tissues inside the skull. Future research should therefore focus on re-evaluating the results of IHI-ST assessment studies and injury threshold studies employing FEM head-models.

Implanted intra-peritoneal insulin infusion (‘i4’) devices administer insulin into the peritoneum of diabetic patients with extreme blood glucose swings, that are highly difficult to control. The flushing procedures of i4 devices to clear obstructions from its conduits caused by insulin degradation are not always fully effective. The goal of this research was to investigate how the flushing effectiveness can be increased by adapting conduit geometries and adapting the flush flow rate. It was hypothesized that flushing of conduits with complex geometries (featuring a.o. widened sections, or parallel flow paths) would be less effective than simple geometries, and that a higher flush flow rate would increase flushing effectiveness. An ex vivo laboratory experimental setup was created by producing polymethyl methacrylate (PMMA) test conduits of differing geometries that model the in vivo implanted intra-peritoneal insulin infusion (i4) device’s conduits, but are transparent to allow optical inspection. These test conduits were filled with acidified insulin, and precipitation thereof was artificially induced by heat incubation of the filled conduits, as a model for obstructed i4-device conduits. Experimental flushing procedures using sodium hydroxide (NaOH) as a flush liquid were performed on these test conduits at 2 different flush flow rates: 1.5mL/min, and at 20mL/min. After the flushing, the effectiveness of the procedure to clear the conduit of precipitates was evaluated by microscopically analysing the quantity of residual precipitates, and measuring Total Organic Carbon (TOC) of a liquid sample taken from the post-flushing conduit. All conduits with more complex geometries than straight tubes showed lower effectiveness of cleaning by flushing. The high flow rate showed an averaged 19% higher effectiveness of the flushing. In the sections of the conduits featuring widening, flushing often resulted in a narrow path being effectively cleaned, but significant regions of the conduit showed presence of residual precipitates. This research provides insight into the negative influence of complex geometries on effectiveness of flushing, and the positive influence of increased flush flow rate to improve effectiveness. Experimental repetition in this research is low, and the experimental methods were prone to much influence of material or measurement disturbances. This research merits elaboration and improvement of materials and methods to more precisely investigate the proposed relations. Outcomes suggest that future i4-devices should be designed to avoid complex conduit geometries as much as possible, and to be flushed with significantly higher flush flow rates than currently clinically applied.

Surgical aerosols in other words plumes are produced during thermal tissue destruction in medical operations. The cellular debris in the form of particulate matter may contain viruses and harmful chemical compounds which can lead to an infectious transmission in case of inhalation. The goal of this study was to design and produce an experimental setup to simulate Plasmajet (PJ) and ERBE experiments with minimal airflow disturbances. Such setup can lead to defining the lowest aerosol production conditions, investigating the production-affecting factors, and evaluating tissue effects to promote a safer and healthier surgical environment for both healthcare workers and patients. A clear correlation between the aerosol production affecting factors and particle counts was established for particle sizes 0.3, 0.5, 1.0, 2.0, 5.0, and 10.0 µm. The results of the experiments showed that among all experimental conditions, the PJ coagulation mode with fast operation yielded the lowest aerosol counts. In cutting mode, the lowest aerosol counts were also produced by PJ with fast operation speed. However, between speed and aerosol counts, no statistically significant correlation was found. Upon analyzing the correlation between aerosol counts and tissue effects, it was determined that, for ERBE device, higher aerosol counts were associated with darker tissue effects. In the case of the PJ device, this relationship persisted in the cutting mode, whereas no connection between tissue effect and particle counts was observed in the coagulation mode. Further investigation on the toxicity of the produced particulate matter and establishment of a clear minimal aerosol intake is recommended. Until then, preventive measures such as implementing local exhaust ventilation and using surgical N95 masks are strongly advised to minimize aerosol inhalation.