The Development of a Patient-Specific, Open Source Computational Fluid Dynamics Tool to Comprehensively and Innovatively Study Coarctation of the Aorta in a Limited Resource Clinical Context

Congenital heart disease (CHD) has a global prevalence of 8 per 1000 births [1] and coarctation of the aorta (CoA) is one of the most common defects with a prevalence of 7% of all cases. The occurrence of CHD in Africa is estimated to be significantly lower, which is attributed to a lack of data [2]. This emphasises the restricted human resources, as well as diagnostic and intervention capacity of specialists in Africa which leads to delayed treatment, presentation with established severity and, consequently, a worse prognosis. Computational Fluid Dynamics (CFD) is seen as the tool that will lead to a better understanding of the haemodynamic effects caused by the malformations related to CoA and provide insights into post-repair morbidity. In addition, the development of a computational tool is envisaged to improve the clinical capacity for diagnosis as well as provide a tool to conduct in silico repair planning. In a low and lower-middle income country healthcare facility, the supplementary data that CFD can provide can add diagnostic value, plan interventions to be more effective and efficient, as well as provide data that may improve postrepair patient management. The aim of this project is to develop a patient-specific, open source, computational fluid dynamics toolchain that is able to study the haemodynamics relating to CoA. In order to do so, a protocol for the collection of doppler echocardiography (echo) and CTA data is proposed. The method for processing the echo data and manually segmenting the CTA data is presented and evaluated. The open source, OpenFOAM code is used to simulate a patient-specific CoA case as well as two in silico designs of coarctation repairs based on expanding the coarctation from the original dataset. The CFD toolchain was developed such that patient data collected from the hospital could be processed to present key haemodynamic metrics such as velocities in the field at the coarctation zone, the pressure gradient across the coarctation and volumetric flow rates through each supra-aortic branch. These results are obtained for each case's geometry, and the trends and impacts that increasing the coarctation ratio has on each of the haemodynamic metrics is presented. The results show that the coarctation pressure gradient and maximum coarctation velocity decrease while perfusion of the lower limbs recovers with expanding coarctation ratio. Following an analysis of the results, it is evident that the pipeline is capable of running patient-specific CFD simulations and can present clinically relevant results. It is noted that this work is a proof of concept and so several steps are discussed that will improve the pipeline

Data Analysis and Curve Fitting to Determine the Regener-Pfotzer Maximum

Various data analysis methods were explored to more accurately and consistently determine the Regener-Pfotzer (RP) maxima for high altitude cosmic radiation. The radiation has been measured during 15 balloon flights using Geiger counters with five second accumulation times. Of the 15 flights, 10 of them included omni-directional counts data, and 8 of them included vertical coincidence counts data. Count data from altitudes greater than 10 km were analyzed to determine the maxima. The data analysis methods used were moving average filtering and summation of Geiger counts into one minute intervals. Moving average filtering did not give reliable results, so the summation method was chosen. Once the data were summed, several different curves were fit to determine where the RP maximum occurred. The curves tested include second and third order polynomials as well as cubic spline interpolation of the data averaged over 1 km intervals. Second order polynomial fitting did not fit the data well. Third order polynomials and cubic splines gave better results. Third order polynomial fitting was chosen due to its ease of use and the similarity of the results given by the cubic spline interpolation (within 1%). The omni-directional RP maxima occurred at an average altitude of 21.8 km ± 1.7 km, while the vertical coincidence RP maxima occurred at an average altitude of 18.5 km ± 1.1 km. In addition, the vertical coincidence RP maximum occurred at 65 hPa ± 9 hPa, while the omni-directional coincidence RP maximum occurred at 38 hPa ± 13 hPa

The Regener-Pfotzer Maxima during a Total Solar Eclipse

The Regener-Pfotzer (RP) maximum is the altitude at which cosmic radiation intensity is the greatest. A reduction of the altitude of the interaction layer, assumed to be measured by the RP maximum, has been suggested to account for a reduction in the secondary cosmic ray flux measured at the surface of the Earth during a total solar eclipse. To investigate this suggestion, high altitude cosmic radiation was measured using Geiger Mueller (GM) counters carried beneath weather balloons both before and during the total solar eclipse on August 21st, 2017. The pre-eclipse omnidirectional RP maxima occurred at an average altitude of 20.2 km and 20.4 km during the eclipse. The vertical coincidence pre-eclipse RP maxima occurred at an average altitude of 18.3 km and 18.0 km during the eclipse. Our results do not show any reduction in the altitude of neither the omnidirectional nor the vertical coincidence RP maxima outside the range of our observations before the eclipse

Design of an Imaging Payload for Earth Observation from a Nanosatellite

A compact imaging payload consisting of visible-near infrared and short-wave infrared capability is being developed to demonstrate low-cost wildfire monitoring among other Earth observations. Iris is a 1U multispectral push-broom imager that is capable of generating spectral data pertinent for wildfire science and wildfire risk analysis from a CubeSat platform. This payload is slated to fly on-board Ex-Alta 2, the University of Alberta’s second CubeSat and Alberta’s contribution to the Canadian CubeSat Project, to be deployed from the International Space Station in 2022. Iris features four closely integrated designs: optical, structural, electronics, and firmware. The mechanical and electronic interfaces of Iris are suited for modular integration into 1U of other generic CubeSat structures. The design has significant constraints on mass, size, performance, and cost. The current optical design features two compact lightpaths within the housing for imaging in short-wave infrared, near-infrared, blue, and red bands (center wavelengths at 2100, 865, 490, and 665 nm, respectively). Design simulations suggest achievement of a signal-to-noise ratio greater than 20 dB across all bands and a spatial resolution of 360 mor better averaged across the field-of-view. Taken together, this demonstrates significant scientific value for minimized cost and instrument volume. This design uses exclusively commercially available lenses, providing significant overall cost savings. The structural housing of Iris consists of 6061 T6 Aluminum, which provides a light-tight optical path for the visible to near-infrared and short-wave infrared light paths, as well as mounting for the optics and printed circuit board to the CubeSat structure within the required tolerances. A 45-degree folding mirror is employed to provide an extended optical lightpath within 1U with no deployable optics. The lens and mirror mounts are fitted with manual adjustment mechanisms for post-assembly alignment of the optical elements. This feature allows the team to perform small modifications to the axial position of the lenses as well as the folding mirror plane without having to re-manufacture the structure, saving time and cost. Within Iris, a subsystem named Electra features a custom filtered CMV4000 CMOS detector from ams AG integrated alongside a custom filtered G11478-512WB InGaAs linear array from Hamamatsu. Electra is a custom printed circuit board which houses an Intel Cyclone V system-on-chip field-programmable gate array, 512 MB of DDR3 synchronous dynamic random-access memory, and other supporting infrastructure for controlling Iris imaging operations and handling spectral data. An in-house software and VHDL suite is implemented within Electra for sensor control, memory management, and all off-board communications. Software functionality includes data compression and a cloud detection algorithm, wherein images are ranked based on heuristic value of relative cloud content, together increasing scientific value per spacecraft link time. A full proto-flight model of Iris is scheduled for manufacturing and testing in Q4 2021. Following manufacturing, comprehensive validation analysis and characterization will be performed, confirming ability to meet mission requirements

Computational fluid dynamics modelling for medical applications

Slides of presentation given by Malebogo Ngoepe and Liam Swanson with the title 'Computational fluid dynamics modelling for medical applications', presented on Thursday, 14 March 2019 as part of the Inaugural PROTEA (Partnerships for Children with Heart Disease in Africa) Workshop in Cape Town, South Africa.The 13th-16th March 2019 marked the Inaugural PROTEA (Partnerships for Children with Heart Disease in Africa) Workshop hosted by the Children’s Heart Disease Research Unit under the directorship of A/Prof Liesl Zuhlke and in conjunction with the Paediatric Cardiology Service of the Western Cape. A first in Africa, this workshop combined four events: a research methods workshop, a basic echocardiography (echo) workshop, two days of advanced echo as well as a rheumatic heart disease research think-tank. 130 delegates from 19 different countries representing all six continents attended the event, making it truly global and giving attendees the opportunity to meet and network with experts in the fields of rheumatic and congenital heart disease.</div

The Regener-Pfotzer Maxima during a Total Solar Eclipse

The Regener-Pfotzer (RP) maximum is the altitude at which cosmic radiation intensity is the greatest. A reduction of the altitude of the interaction layer, assumed to be measured by the RP maximum, has been suggested to account for a reduction in the secondary cosmic ray flux measured at the surface of the Earth during a total solar eclipse. To investigate this suggestion, high altitude cosmic radiation was measured using Geiger Mueller (GM) counters carried beneath weather balloons both before and during the total solar eclipse on August 21st, 2017. The pre-eclipse omnidirectional RP maxima occurred at an average altitude of 20.2 km and 20.4 km during the eclipse. The vertical coincidence pre-eclipse RP maxima occurred at an average altitude of 18.3 km and 18.0 km during the eclipse. Our results do not show any reduction in the altitude of neither the omnidirectional nor the vertical coincidence RP maxima outside the range of our observations before the eclipse

The Regener-Pfotzer Maximum During a Total Solar Eclipse

The Regener-Pfotzer (RP) maximum is the altitude at which cosmic radiation intensity is the greatest. A decrease of the altitude of the interaction layer, assumed to be measured by the RP maximum, has been suggested to account for a reduction in the secondary cosmic ray flux measured at the surface of the Earth during a total solar eclipse. To investigate this suggestion, high altitude cosmic radiation was measured using Geiger Mueller (GM) counters carried beneath weather balloons both before and during the total solar eclipse on 21 August 2017. The 19 and 20 August 2017 omnidirectional RP maxima occurred at an average altitude of 20.2 km ± 0.9 km. During the eclipse of 21 August 2017 the omnidirectional RP maxima occurred at an altitude of 20.4 km ± 0.8 km. The 19 and 20 August 2017 vertical coincidence RP maxima occurred at an altitude of 18.3 km ± 1.0 km. During the eclipse the vertical coincidence RP maxima occurred at 18.0 km ± 1.0 km. Our results do not show any decrease in the altitude of either the omnidirectional or the vertical coincidence RP maximum outside the range of our measurements before the eclipse