SINTEF Open
Not a member yet
11374 research outputs found
Sort by
Vessel-based CTA-image to spatial anatomy registration using tracked catheter position data: preclinical evaluation of in vivo accuracy
Get PDFElectromagnetic tracking of endovascular instruments has the potential to substantially decrease radiation exposure of patients and personnel. In this study, we evaluated the in vivo accuracy of a vessel-based method to register preoperative computed tomography angiography (CTA) images to physical coordinates using an electromagnetically tracked guidewire. Centerlines of the aortoiliac arteries were extracted from preoperative CTA acquired from five swine. Intravascular positions were obtained from an electromagnetically tracked guidewire. An iterative-closest-point algorithm registered the position data to the preoperative image centerlines. To evaluate the registration accuracy, a guidewire was placed inside the superior mesenteric, left and right renal arteries under fluoroscopic guidance. Position data was acquired with electromagnetic tracking as the guidewire was pulled into the aorta. The resulting measured positions were compared to the corresponding ostia manually identified in the CTA images after applying the registration. The three-dimensional (3D) Euclidean distances were calculated between each corresponding ostial point, and the root mean square (RMS) was calculated for each registration. The median 3D RMS for all registrations was 4.82 mm, with an interquartile range of 3.53–6.14 mm. A vessel-based registration of CTA images to vascular anatomy is possible with acceptable accuracy and encourages further clinical testing.publishedVersio
Incidence, risk factors, and clinical implications of postoperative blood in or near the resection cavity after glioma surgery
Get PDFIntroduction: Postoperative hematomas that require reoperation are a serious, but uncommon complication to glioma surgery. However, smaller blood volumes are frequently observed, but their clinical significance is less known.
Research question: What are the incidence rates, risk factors, and patient-reported outcomes of all measurable blood in or near the resection cavity on postoperative MRI in diffuse glioma patients?
Material and methods: We manually segmented intradural and extradural blood from early postoperative MRI of 292 diffuse glioma resections. Potential associations between blood volume and tumor characteristics, demographics, and perioperative factors were explored using non-parametric methods. The assessed outcomes were generic and disease-specific patient-reported HRQoL.
Results: Out of the 292 MRI scans included, 184 (63%) had intradural blood, and 212 (73%) had extradural blood in or near the resection cavity. The median blood volumes were 0.4 mL and 3.0 mL, respectively. Intradural blood volume was associated with tumor volume, intraoperative blood loss, and EOR. Extradural blood volume was associated with age and tumor volume. Greater intradural blood volume was associated with less headache and cognitive improvement, but not after adjustments for tumor volume.
Discussion and conclusions: Postoperative blood on early postoperative MRI is common. Intradural blood volumes tend to be larger in patients with larger tumors, more intraoperative blood loss, or undergoing subtotal resections. Extradural blood volumes tend to be larger in younger patients with larger tumors. Postoperative blood in or near the resection cavity that does not require reoperation does not seem to affect HRQoL in diffuse glioma patients.publishedVersio
Security-by-design challenges for medical device manufacturers
Get PDFThe European health care system is moving toward personalised, distributed, and home-based services, made possible via new and improved connected medical devices (CMDs). Cyber security will clearly be important in this context. In this paper we present 15 challenges that the manufacturers of CMDs face when trying to “build security in” for the devices that they produce. The challenges have been identified in a qualitative research study, including interview data from healthcare stakeholders combined with document analysis of four relevant CMD case studies.publishedVersio
Scaling up 3D printed hybrid sorbents towards (cost) effective post-combustion CO2 capture: A multiscale study
Get PDFpublishedVersio
LX-mixers for QAOA: Optimal mixers restricted to subspaces and the stabilizer formalism
Get PDFWe present a novel formalism to both understand and construct mixers that preserve a given subspace. The method connects and utilizes the stabilizer formalism that is used in error correcting codes. This can be useful in the setting when the quantum approximate optimization algorithm (QAOA), a popular meta-heuristic for solving combinatorial optimization problems, is applied in the setting where the constraints of the problem lead to a feasible subspace that is large but easy to specify. The proposed method gives a systematic way to construct mixers that are resource efficient in the number of controlled not gates and can be understood as a generalization of the well-known X and XY mixers and a relaxation of the Grover mixer: Given a basis of any subspace, a resource efficient mixer can be constructed that preserves the subspace. The numerical examples provided show a dramatic reduction of CX gates when compared to previous results. We call our approach logical X-Mixer or logical X QAOA (LX-QAOA), since it can be understood as dividing the subspace into code spaces of stabilizers S and consecutively applying logical rotational X gates associated with these code spaces. Overall, we hope that this new perspective can lead to further insight into the development of quantum algorithms.publishedVersio
A dynamic modelling approach to explore zero emission building stock opportunities towards 2050 – Case study of a university campus
Get PDFThe building sector has a significant influence on energy use and environmental impact. When observing a university campus, reduction of energy use is a complex issue due to the variety of building types, usage, building construction age, and different implementation of improvement measures. To investigate how energy efficiency measures on a single building may influence the entire campus, a combination of building energy simulation and a scenario-based aggregation method using dynamic material flow analysis principles was implemented. This study investigated possible energy efficiency measures at a university campus in Trondheim, Norway. Scenario analysis was used to identify the most critical factors for future development and to evaluate to what extent the campus might develop towards a net zero-emission campus during the period 2017–2050. Four scenarios were introduced including two aspects: renovation of the existing building stock and changes in campus energy supply systems. The results on energy efficiency packages highlighted that saving potentials were highly dependent on the construction period of the buildings. The package combining envelope renovation and operation improvements showed the highest savings. The findings indicated that advanced renovation, including extensive use of heat pumps, might be the most promising strategy for reducing energy demand by 26 %.publishedVersio
The reliability of a resilient power system: Service restoration time in reliability analysis
Get PDFNeglecting service restoration in reliability analyses can lead to overestimation of energy not supplied (ENS) due to contingencies, and subsequently also the associated interruption costs. Estimating accurate interruption costs is of high importance as it serves as input into power system operation and planning. In this paper a method of accounting for service restoration in reliability analysis is proposed. Literature covering restoration strategies is surveyed, and a minimalistic method of modeling service restoration is developed. The method describes the restoration process in a generalizable manner using steady state analysis. The results of the case study indicate that incorporating service restoration in reliability analysis can have a large impact on the estimated annual expected ENS of the system. The developed method can serve as a platform for further work.The reliability of a resilient power system: Service restoration time in reliability analysisacceptedVersio
Effects of Different Doping Strategies on Cubic Li<inf>7</inf>La<inf>3</inf>Zr<inf>2</inf>O<inf>12</inf> Solid-State Li-Ion Battery Electrolytes
No full textSolid-state Li-ion conductors based on cubic Li7La3Zr2O12 (LLZO) garnets have received much attention in recent years as potential next-generation battery electrolytes, enabling safer and more energy-dense Li-ion batteries. Aliovalent doping of the LLZO structure is usually necessary to stabilize the cubic garnet phase and increase the ionic conductivity by increasing the concentration of Li vacancies. Here, we report on the synthesis, characterization, and testing of Li7−3xAlxLa3Zr2O12 ceramics with different amounts of Al doping (x = 0.20−0.40). Phase-pure LLZO with a cubic crystal structure was prepared by an aqueous synthesis route, and dense (>93%) ceramic samples were fabricated by conventional sintering at 1200 °C. By analyzing the composition, microstructure, and electrochemical performance, we found that the optimal Al content in LLZO is x = 0.2, the lowest content needed to stabilize the cubic structure in our series. For the composition with x = 0.2, we found a Li-ion conductivity at room temperature of 3.7 × 10−4 S cm−1 and an activation energy of Ea = 0.3 eV. At a higher doping concentration, the conductivity decreases, and the activation energy increases; for x ≥ 0.35, secondary Al-rich phases appear. These results indicate an inverse relationship between Li-ion conductivity and Al doping, where the optimal amount of doping is the minimum amount necessary to stabilize the cubic LLZO phase. Additionally, we present an analysis of the available literature on chemical modification of LLZO to compare how different doping strategies affect Li conductivity. Based on our literature review, Ga and Ta doping gives the highest conductivities (≤2 × 10−3 S cm−1). The literature analysis also supports our findings that the primary objective of the dopant is to stabilize the cubic structure rather than create Li vacancies.publishedVersio
Prediction of mass transfer regimes in a steelmaking ladle
Get PDFThe paper deals with the prediction of the mass transfer between liquid steel and slag in a steelmaking ladle. Predictions are realized with OpenFOAM® and Volume of Fluid (VoF) method is selected for the interface modeling. Two mass transfer regimes are observed in water models and industrial configurations when the gas flow rate increases. The transition between them depends on formation of slag droplets. It is observed that the average shear stress between liquid steel and slag is not the key parameter affecting the mass transfer. The interface area between liquid steel and slag is the driving mechanism for the mass transfer.publishedVersio
