Engineering is the process by which a subset of The World’s Many Problems are carefully observed and diligently solved. This is done by listening to those affected by the problems, determining how causally those problems manifest, studying enough of some subset of the world’s functions (be they mechanical, electrical, etc.) to understand the cause-problem relationship, creatively exploring means/methods of changing that problematic situation, designing safe means/methods of that change, experimentally verifying the efficacy of a proposed solution, refining those means/methods when presented with new data, and implementing (at a scale sufficient) a proposed solution, knowing that all solutions are temporary, but that not all problems are.
Below are a few examples of my engineering experience amongst The World’s Many Problems.
Material Characterization
Case Study: Multimodal Analysis of Tissue Phantom Material
The mechanical and imaging properties of polyvinyl chloride (PVC) can be adjusted to meet the needs of researchers as a tissue-mimicking material. Examples include adjusting the hardness my changing the ratio of a softener to the PVC polymer, adding mineral oil for lubrication for needle insertion experiments, and mixing in glass beads to scatter acoustic energy similar to biological materials. Below are several techniques used to characterize the properties appropriate to various investigations including mechanical (hardness, elastic modulus, needle insertion friction) and medical imaging (optical clarity, ultrasound, magnetic resonance, and x-ray). (READ MORE)
Process Modeling
Case Study: Sequential Bone Drilling
Experimental techniques (using a portion of ex vivo human shin bones) and finite element analysis (using a 3D axisymmetric advection inverse heat transfer model) were used to understand the process of heat spread during bone drilling. (READ MORE)
Results of the techniques described below can be found in both the Journal of Orthopaedic Research (Heat accumulation during sequential cortical bone drilling) and Medical Engineering & Physics (Numerical evaluation of sequential bone drilling strategies based on thermal damage).
Experimental Instrumentation
Case Study: Electrical Impedance of Novel Materials
In an effort to develop a reusable phantom for high-channel electrical impedance tomography experimentation, a custom tetrapolar probe was designed and built. The probe consists of four 0.02” diameter platinum wires spaced 5mm apart, housed in a PEEK block. Sample measurements were taken using a LCR meter (Hioki IM3536). Contact between samples and probe was facilitated using a small droplet of ionic solution (1 M KCl, ~11 S/m) at each platinum wire tip. To assess anisotropy, the probe was randomly oriented on the surface of a sample for at least five individual measurements, each comprising of 10 repeated frequency sweeps (1-200 kHz). (READ MORE)
Electrical Engineering
Case Study: Wearable Bioimpedance Sensor
Bioimpedance is uniquely suited to measure several “vital signs” including heart rate, respiratory rate, and intravascular volume status. (There is also some evidence that the arterial waveform present in the signal correlates to blood pressure.) Most clinically available measurement apparatuses require bedside monitoring and a stationary subject. To test that viability of bioimpedance as a signal in situ, a wearable bioimpedance monitor was developed using a reconfigurable frontend (to assess interface effects between bipolar and tetrapolar configurations) and low-power electronics (to enable long-term measurements). (READ MORE)
Multimodal (Medical) Imaging
Case Study: IVC Ultrasound Feature Tracking
Using established and novel image processing techniques (Harris corner thresholding, KLT feature-tracking, pyramidal segmentation, etc.) I developed algorithms for automating inferior vena cava (IVC) measurements via subcostal ultrasound. In this way the dynamic interplay of the respiratory and cardiac cycles as a function of volume status could be studied rigorously. (READ MORE)
Published results: B Belmont, R Kessler, N Theyyunni, C Fung, R Huang, M Cover, KR Ward, AJ Shih, M Tiba, “Continuous inferior vena cava diameter tracking trough an iterative Kanade-Lucas-Tomasi based algorithm” Ultrasound in Medicine and Biology, 44: 12, Pages 2793-2801, Dec 2018.
Case Study: Cardiac/Respiratory Mixed-Signal Separation
Blood volume shifts in venous systems correspond to major pressure drivers: blood pressure generated by the heart beating and intrathoracic pressure from the diaphragm exerting influence on the lungs. By frequency band limiting
Case Study: Clinical bioimpedance evaluation
Much of my research has been in developing and validating an impedance plethysmographic technique to assess intravascular volume status (the amount of blood a person has available to work with). To this point, volume status has proven an elusive metric for most currently available techniques, sporting predictive powers between total guessing (AUROC = 0.54) and educated guessing (AUROC = 0.84). The technique I investigated along with researchers from the Department of Emergency Medicine at the University of Michigan proved to correctly assess volume status over 95% of the time over the entire phsyiological range (with many regions of near perfect prediction, AUROC = 1.00). (READ MORE)
Open-source MATLAB-based GUI for vascular ultrasound DICOM image evaluation
Refined a clinically-used GUI with user-friendly tools to assess mechanical properties of peripheral blood vessels, including local environment strain, wall stiffness, vessel distensibility, wall shear rate of blood flow
Published result: B Belmont, DW Park, WF Weitzel, AJ Shih, “An Open-Source Ultrasound Software for Diagnosis of Fistula Maturation”, ASAIO Journal, January 2018.
Optimization of mechanical parameters of dialysis fistula via vascular ultrasound image evaluation
Worked with clinical members of Nephology to enroll end-stage renal disease patients to measure mechanical parameters (diameter, strain, distensibility) at inflow artery, post-arterial anastomotic segment, and outflow vein at initial and follow-up evaluation of surgically related arteriovenous fistula using software I helped create and develop.
Published result: B Belmont, DW Park, A Shih, M Leavitt, B Plattner, PK Henke, WF Weitzel, “A pilot study to measure vascular compliance changes during fistula maturation using open-source software”, The Journal of Vascular Access, May 2018
Arteriovenous fistula blood flood simulations
Using automated ultrasound acquisition, three-dimensional reconstructions of vessels were made (using in-house MATLAB code), from these the geometry was imported into a multi-physics program (COMSOL) and given realistic biological values for viscoelastic properties to aid in further arteriovenous fistula optimization experiments
Minimizing heat accumulation during bone drilling procedures
AC Palmisano, BL Tai, B Belmont, TA Irwin, A Shih, JR Holmes. “Heat accumulation during sequential cortical bone drilling”, Journal of Orthopedic Research, March 2016.
BL Tai, AC Palmisano, B Belmont, TA Irwin, J Holmes, AJ Shih. “Numerical evaluation of sequential bone drilling strategies based on thermal damage”, Medical Engineering and Physics, September 2015.
AC Palmisano, BL Tai, B Belmont, TA Irwin, A Shih, JR Holmes. “Comparison of cortical bone drilling induced heat production among common drilling tools”, Journal of Orthopedic Trauma, May 2015.
Micromachining K-wire tips
Published: Y Liu, B Belmont, Y Wang, B Tai, J Holmes, A Shih. “Notched K-wire for low thermal damage bone drilling”, Medical Engineering and Physics, July 2017.
Optical point tracking correlated to force measurement during high-speed atherectomy
Developed image processing algorithm to measure key angular frequencies during high-speed (200,000 rpm) orbital atherectromy
Published: Y Zheng, B Belmont, AJ Shih. “Experimental investigation of the abrasive crown dynamics in orbital atherectomy”, Medical Engineering and Physics, July 2016.
Measurement of needle tip deflection due to bevel orientation for pediatric patients
Conference paper: W Li, B Belmont, L Jing, A Shih. “Investigation of Needle Bevel Face Up and Down Orientation on Pediatric Intravenous Access”, Int’l Workshop on Microfactories, 2014.
Mechanically realistic anatomical simulators for surgical education
Conference paper: A Price, L Savastano, WC Lin, B Belmont, A Shih. “Manufacturing of Anatomically Accurate Cerebral Arteries for the Brain Aneurysm Surgical Simulator”, ASME 2016 11th International Manufacturing Science and Engineering Conference, June 2016.
Experimental investigation of dry electrodes with novel surface etchings
Measured electrode-electrolyte surface polarization of dry-electrodes of common materials with novel surface patterns as a possible low-cost solution for wearable electrocardiograph, quantifying effects of material and surface parameters
Verification and validation of world’s highest-channel-count electrical impedance tomograph
Worked as a member of a small team responsible for determining nominal operating parameters of a 256-channel electrical impedance tomography in preparation for potential clinical testing in maternal and neonatal care environments.
Particle image velocimetry to determine CTC settling patterns in aortic blood flow
Created computer vision algorithms to cross-correlate experimental PIV images of a tissue-mimic to assess where circulating tumor cells would settle within a patient’s aorta
Silicon neural probe tip strength optimization
Performed rudimentary analytic and finite-element analysis on the insertion point of a silicon neural probe, design-of-experiment (DoE) based on laboratory’s available nanofabrication and packaging capabilities for the tip’s rake and inclination angles