Bioengineering Seminar Schedule
Spring Semester, 2001 (For prior semesters, click here: Fall 1999, Spring 2000 , Fall 2000, Click here to return to current semester)
Friday, Jan 12, Room 110 Hallowell Building (Univ Park) & CG624 (HMC)
2:30-3:30 pm
Norman R. Harris
Department of Bioengineering, Penn State
Transvascular Exchange in the Microcirculation
Thursday, Jan 18, Room 110 Hallowell Building (Univ Park) & CG623 (HMC)
2:30 - 3:30 pm
David B. Geselowitz, Ph.D.
Department of Bioengineering, Penn State
The Electrocardiogram
Friday, January 26, Room 110 Hallowell Building (Univ Park) & CG623 (HMC)
2:30 - 3:30 pm
Peter J. Butler, Ph.D.
Department of Bioengineering, University of California San Diego
Probing the Biophysical Origins and Physiological Implication of Endothelial Cell Sensitivity to Shear Stress
Friday, February 2, Room 110 Hallowell Building (Univ Park) & CG623 (HMC)
2:30 - 3:30 pm
Keefe B. Manning, Ph.D.
Bioengineering Program, Virginia Commonwealth University
Flow Irregularities in an Outlet Cannula of a Rotary Ventricular Assist Device
Thursday, February 8, 2001, Room 110 Hallowell Building (University Park) and CG623 (Hershey Medical Center)
2:30 - 3:30 pm
Jeffrey D. Zahn
Graduate Research Assistant, Dept of Electrical and Computer Engineering, Carnegie Mellon University and Depts of Mechanical Engineering and Bioengineering, UC Berkeley
Microfabricated Microneedles for Minimally Invasive Biomedical Devices
(Refreshments to follow in Room 234 Hallowell Bldg.)
Thursday, February 15, 2001, Room 110 Hallowell Building (University Park) and CG623 (Hershey Medical Center)
2:30 - 3:30pm
Christopher Collins, Ph.D.
Post Doctoral Fellow, Department of Radiology, Hershey Medical Center
Numerical Calculations of Interactions between Electromagnetic Fields and Tissues for MRI
Thursday, February 22, 2001, Room 110 Hallowell Building (University Park) and CG623 (Hershey Medical Center)
2:30 - 3:30pm
C. Forbes Dewey, Jr.
Professor of Mechanical Engineering and Bioengineering
Massachusetts Institute of Technology
Cell Dynamics are Influenced by Fluid Flow
Special Seminar
Wednesday, March 14, 2001, 110 Hallowell Building
12:00 Noon
Tao Lu Lowe, Ph.D.
Department of Chemical Engineering
University of Wisconsin
Design and Characterization of Non-Natural Compounds and Polymers for a better Life
Thursday, March 15, 2001, Room 110 Hallowell Building (University Park) and CG623 (Hershey Medical Center)
2:30 - 3:30 pm
Maria I. Klapa
Graduate Research Assistant
Department of Chemical Engineering
Massachusetts Institute of Technology
High Resolution Flux Determination by Stable Isotopes and Mass Spectrometry
Thursday, April 5, 2001, Room 110 Hallowell Building (University Park) and CG623 (Hershey Medical Center)
2:30 - 3:30 p.m.
James S. Ultman
Distinguished Professor of Chemical Engineering and Bioengineering, Pennsylvania State University
Quantifying the Distribution of Inhaled Air Pollutant Gases
Thursday, April 12, 2001, Room 110 Hallowell Building (University Park) and CG623 (Hershey Medical Center)
2:30 - 3:30 p.m.
Alan J. Snyder
Associate Professor of Surgery and Bioengineering, Hershey Medical Center
Penn State College of Medicine
Biomedical Applications of Electroactive Polymers
Friday, April 20, 2001, Room 110 Hallowell Building (University Park) and CG623 (Hershey Medical Center)
2:30 - 3:30 p.m.
Emad Ebbini
Associate Professor of Electrical and Computer Engineering
University of Minnesota
Filter-based Multi-modal Pulse-echo Imaging with Ultrasound Arrays
Bioengineering 590 Colloquium
Graduate Student Presentations, Part I.
Thursday, April 26, 2:30 - 4:00pm, Room 110 Hallowell Building (University Park)
and CG623 (Hershey Medical Center)
Wo-Hsing Chen
Development of Sector Scanning Ultrasonic Backscatter Microscope
Emanuel Gottlieb
High Frequency Ultrasound Phantoms
Bin Huang
Characterization of High-Frequency Transducers Using
Hewlett-Packard Membrane Hydrophone
Nirmal Kari
Potassium Niobate Single Crystal in Ultrasonic Transducers
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ABSTRACTS
Development of Sector Scanning Ultrasonic Backscatter Microscope
by
Wo-Hsing Chen
The Ultrasound Backscatter Microscope (UBM) is a noninvasive high frequency imaging tool used frequently for imaging
the eye, skin and blood vessels. Currently, most UBM systems employ a linear motor control to obtain a transverse
scan. This paper reports the implementation of a UBM that performs sector scan with a servo-controlled motor to
manipulate a single element transducer. The advantage of applying a sector scan versus a transverse linear scan
is that the transducer needs to travel less distance to acquire an image of the same area. The transducer sector
movement is achieved by a brief sweep that needs only a small open area for scanning. The servomotor’s sweep angle
has a small arc of 5 degrees and provides enough width for an image. Because of the small angle sweeping, the image
can be displayed in a linear format as the image in transverse scan without further calculation. The UBM system
can be operated within the 50-100 MHz frequency range. Images have been acquired with this approach on excised
human eye specimen. The quality of the image compares favorably with that obtained with the conventional UBM. The
results indicate that the sector scan is an alternative method for UBM scanning. Future work includes the development
of a hand held probe that houses a small transducer and servomotor capable of sector scanning.
High Frequency Ultrasound Phantoms
by
Emanuel Gottlieb
Design of high frequency ultrasound phantoms is crucial for assessing imaging performance of high frequency imaging
systems. Quality assurance for ultrasound imaging systems is essential to ensure optimal patient care and diagnosis.
The use of ultrasound phantoms can evaluate imaging parameters of a clinical Ultrasound Backscatter Microscope
(UBM). These imaging parameters are defined as lateral resolution, axial resolution, depth of penetration, dead
zone, image uniformity, vertical and horizontal distance accuracy. Each of these imaging parameters furnishes valuable
information to the clinician about the imaging performance of the system. Routine testing will reduce maintenance
costs and improve the efficiency of quality care.
Characterization of High-Frequency Transducers Using Hewlett-Packard Membrane Hydrophone
by
Bin Huang
Hydrophone method is the gold standard for characterizing ultrasound fields. Typical hydrophones often suffer from
spatial averaging due to their large geometric spot size, and can not fulfil the task of characterizing high-frequency
transducers. A commercial available hydrophone made by Hewlett-Packard Company is used to characterize high-frequency
transducers. It has a measured effective spot diameter of less than 100 um, and a -3dB bandwidth of 150 MHz. It
suffers less in spatial averaging and is expected to achieve desirable results. This hydrophone is used to measure
a 50MHz transducer and its performance is evaluated. Future work will focus on its comparison with other hydrophones.
Potassium Niobate Single Crystal in Ultrasonic Transducers
by
Nirmal Kari
The use of single crystals in the design and fabrication of high frequency single element ultrasonic transducers
offer the possibility of dramatic improvements in transducer performance. The merits of these materials stem from
their high coupling coefficients, a range of "designer" dielectric constants, the ability to optimize
crystallographic and absence of scaling limitations associated with grain size and porosity. Fabrication of high
frequency ( > 25 MHz ) transducers was done using potassium niobate single crystals. The effect of variation
of material parameters such as acoustic impedance, coupling coefficient, and dielectric constant on performance
parameters of importance such as pulse echo sensitivity and bandwidth are discussed. The KLM model was employed
to optimize the design of all the transducers for 50 ohm electrical impedance matching. All transducers were constructed
with the same fabrication technique, 3mm aperture size and f numb! er between 2 and 3, silver epoxy backing ( with
acoustic impedance of 5.9 Mrayls) , two matching layers and lensing as well as press focusing was used to achieve
desired focal depths. Pulse echo testing was performed to determine insertion loss, bandwidth, and depth of focus.
Experimental results show fairly broad bandwidths ( 58%) and high sensitivity ( -15dB insertion loss) for operating
frequencies as high as 36 MHz.
Bioengineering 590 Colloquium
Graduate Student Presentations, Part II.
Friday, April 27, 2:30 - 4:00pm, Room 110 Hallowell Building (University Park)
and CG623 (Hershey Medical Center)
Traci R. Haut
Mechanosensitivity of Bone Cells to Oscillating Fluid Flow (OFF)
Depends on Both Shear Stress and Flow Rate
Branka Lukic
Hemolysis Studies Associated with the Arrow LionHeart TM LVAD
Brent Margerum
The Relation between Mean Filtration Pressure of Endothelial Cell Suspensions
and Their Passage through Nucleopore Filters
Kavitha Nellore
L-Arginine Restores Arterio-Venular Communication
in Hypercholesterolemic Rats
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ABSTRACTS
Mechanosensitivity of Bone Cells to Oscillating Fluid Flow (OFF) Depends on Both Shear Stress and Flow Rate
by
Traci R. Haut
It has been demonstrated that bone adapts to its physical loading environment, however, the biophysical signals
that regulate bone cells are not known. The aim of this study was to examine effects of shear stress and chemotransport,
generated as a consequence of OFF, on cytosolic Ca2+ concentration ([Ca2+]i) and PGE2 production in mouse osteoblastic
MC3T3-E1 cells.
Ca2+ imaging: MC3T3-E1 cells cultured in monolayer were loaded with Fura-2 AM and placed in a parallel plate flow
chamber. Following a 1min no flow period, cells experienced OFF at 1Hz for 3 min generated using a materials testing
machine. 3 flow regimes were studied by altering flow rate and/or increasing fluid viscosity with neutral dextran:
1) constant peak shear stress (PSS), varied flow rate, 2) constant flow rate, varied PSS, 3) varied PSS with nutrient
free HBSS. Image analysis software was used to capture and convert fluorescent signals into [Ca2+]i values. Ca2+i
transients of 50 nM or greater were considered responses.
PGE2: Cells were exposed to 1hr OFF using 3 flow regimes, all producing a PSS of 20 dynes/cm2 but with altered
flow rates. Following flow, cells were incubated in fresh media for 1 hr, which was then collected for PGE2 analysis.
PGE2 production was also measured in no flow, control cells.
At constant PSS (20 dynes/cm2), reducing flow rate from 18 ml/min to11.5 ml/min decreased the percent of cells
responding with an increase in [Ca2+]i from 87.7±4.9% to 75.2±3.5%. At a constant flow rate of 4.5
ml/min, increasing PSS from 5 dynes/cm2 to 8.7 dynes/cm2 increased the percent of cells responding from 14.6±13%
to 33.6±7.1%. In nutrient free HBSS only 10.8±7% of cells responded at 20 dynes/cm2 and 8.4±1.6%
at 40 dynes/cm2. At a constant PSS of 20 dynes/cm2, decreasing flow rates from 43 to 28 to 18ml/min significantly
decreased PGE2 production from 34±3.1 to 25.8±6.8 to 9.1±1.8 pg/µg of total protein,
respectively (p<0.05).
OFF elicited Ca2+i transients and increased PGE2 production in MC3T3-E1 cells. Decreasing flow rate while maintaining
PSS decreased both Cai and PGE2 responses to OFF. The Cai response was increased when PSS was increased at a constant
flow rate, and was significantly reduced in nutrient free HBSS. These data suggest that the cellular responses
to OFF result from an interaction between shear stress and chemotransport. Further studies will determine whether
this interaction occurs at a defined “mechanoreceptor” or is the result of convergence of two distinct signaling
pathways.
Hemolysis Studies Associated with the Arrow LionHeart TM LVAD
by
Branka Lukic
A new mock circulatory loop has been developed for hemolysis studies associated with the Arrow LionHeart TM LVAD.
This loop has a small priming volume of 440 ml which reduces the quantity of blood required for experiments and
also minimizes the effect of loop blood-material contact. It has been constructed to simulate the hemodynamics
seen by the LVAD in clinical use. Clinical length cannulae are used.
Inlet and outlet compliance elements (arterial and venous) are provided by pneumatic LVADs (valves removed) in
which the pneumatic drive tube of the arterial chamber is connected to 1 liter air bottle. Mean arterial pressure
of approximately 100 mmHg is controlled by pressure regulator that bleeds air into the bottle. A venous compliance
chamber is open to air maintaining pressure of the venous chamber close to atmospheric.
The LVAD compliance chamber, which functions as a reservoir for the gas displaced by the blood sac during pump
filling, is not used. Instead, the compliance chamber tube from the energy converter is connected by a ¼
in. ID tube to a 10 liters air chamber. Positive mean pressure supplied by another pressure regulator is injected
into the air chamber and thus into the pump in order to control LVAD filling rate. The LVAD rate is controlled
by setting the systolic and diastolic factors to certain values via the telemetry system. A standard Arrow LVAD
with Bjork-Shiley monostrut Delrin disk valves is used. The entire loop is submerged in a 37°C water bath.
While pumping, the following parameters are acquired: outlet (arterial) pressure, inlet pressure, LVAD intraventricular
pressure, inlet flow, outlet flow, and inlet valve cavitation intensity (as measured by a hydrophone).
The primary objective of this study is to measure index of hemolysis (IH) under various operating conditions and
to determine the effect of LVAD rate and Loadpoint (equivalent to %fill) on hemolysis. A secondary objective is
to determine the correlation between hemolysis and physical parameters including: the LVAD intraventricular dP/dt
and maximum pressure, inlet and outlet flow dQ/dt, and inlet valve cavitation intensity.
The Relation between Mean Filtration Pressure of Endothelial Cell Suspensions
and Their Passage through Nucleopore Filters
by
Brent Margerum
Angiogenesis, the growth and development of new capillary blood vessels, occurs in numerous physiological and pathological
conditions, including embryonic development, wound healing, growth of solid tumors, and development of atherosclerotic
plaques. The angiogenesis process begins with the degradation of the basement membrane by proteases secreted by
activated endothelial cells that will migrate and proliferate, leading to the formation of solid endothelial cell
sprouts into the stromal space. Then, vascular loops are formed and capillary tubes develop with formation of tight
junctions and deposition of new basement membrane. During this migration process into the stromal space, the activated
endothelial cells experience forces that result in the deformation of their membranes.
To investigate the mechanical properties of these cells, methods of in vitro transient and steady state filtration
were used to determine the average deformability of a population of Rat Lung Microvascular Endothelial Cells (RLMEC)
in terms of the mean yield pressure necessary to push a trapped cell through a Nucleopore filter. To assess the
role that activation has in the cell's ability to deform, RLMECs were treated with different agents known to affect
the cell's membrane properties, such as membrane contraction, leukocyte adhesion molecule expression, and the loss
of surface anticoagulant molecules.
L-Arginine Restores Arterio-Venular Communication in Hypercholesterolemic Rats
by
Kavitha Nellore
In a previous study (Am J Physiol 277:H669-75, 1999), it was found that in normocholesteremic rats a correlation
existed between baseline fluid filtration rate (Jv/S) and the percent of the feeding arteriole length that was
paired (<15 µµm) with a postcapillary venule (A-V pairing). Additionally, a correlation was also
found between baseline red blood cell velocity (VRBC) and A-V pairing. However, these correlations did not exist
in hypercholesterolemic (HC) rats. It is known that endothelial cells in HC rats have a reduced capacity to release
nitric oxide (NO). In this study, it was hypothesized that NO is used in the communicated arteriovenular response,
and that L-Arginine can increase the levels of NO available in HC rats. Jv/S and VRBC were measured in individual
mesenteric capillaries of two groups of HC rats. One group of rats was given regular drinking water along with
the HC diet over a period of 2-3 weeks. The other group of rats were given 1% L-Arginine in drinking water along
with the diet. In the HC rats that had regular drinking water, no correlation was found between either Jv/S and
A-V pairing or VRBC and A-V pairing. However, in the other group of rats that were given L-Arginine water, both
the correlations were restored (P<0.05). These findings suggest that the arterio-venular communication is restored
in HC rats having 1% L-Arginine in drinking water by the enhanced release of NO. Further studies may help determine
how capillary perfusion and filtration might be better controlled in hypercholesterolemia.
For additional information, contact Ms. Brenda Bixler, Bioengineering Program, Tel: 814.865.1407 or E-Mail: bsb1@psu.edu