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Gregory J. Gerling, Ph.D.
Associate Professor
Systems and Information Engineering
gregory-gerling
virginia edu
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News Updates
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Paper
with NLM STTP student Michael Cary accepted by JAMIA
January 29th, 2010
Dunn Lopez, K., Gerling, G. J., Cary, M. P., Kanak, M. F., Cognitive
Work Analysus to Evaluate the Problem of Patient FAlls in the Inpatient
Setting (JAMIA: Journal of the American Medical Informatics
Association, accepted)
Abstract: Objective. Cognitive work analysis was
used to identify factors in the
nursing work domain that contribute to the problem of inpatient falls,
aside from patient risk. Design. A mix of qualitative and
quantitative
methods were used to identify work constraints imposed on nurses, which
may underlie patient falls. Measurements. Data collection was
done on
a neurology unit staffed by 27 registered nurses and utilized field
observations, focus groups, time-motion studies and written surveys
(AHRQ Hospital Survey on Patient Culture, NASA-TLX, and custom Nursing
Knowledge of Fall Prevention Subscale). Results. Four major
constraints were identified that inhibit nurses' ability to prevent
patient falls. All constraints relate to work processes and the
physical work environment, opposed to safety culture or nursing
knowledge, as currently emphasized. The constraints were:
cognitive
"head data", temporal workload, inconsistencies in written and verbal
transfer of patient data, and limitations in the physical environment.
To deal with these constraints, the nurses tend to employ four
workarounds: written and mental chunking schemas, bed alarms, informal
querying of the previous care nurse, and informal video and audio
surveillance. These workarounds reflect systemic design flaws and may
only be minimally effective in decreasing risks to patients.
Conclusion. Cognitive engineering techniques helped identify
seemingly
hidden constraints in the work domain that impact the problem of
patient falls. System redesign strategies aimed at improving work
processes and environmental limitations hold promise for decreasing the
incidence of falls in inpatient nursing units. |
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Presented poster with
Angie Lee at 2010 Simulation and Healthcare Society Annual Meeting in
Pheonix, Arizona
January 25,
2010
Lee, A.J.
and Gerling, G.J., Applying Computerized Adaptive Testing to the
Virginia Prostate Examination Simulator
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Paper of
Miki Wang accepted by IEEE Transactions on Information Technology in
Biomedicine
January 14, 2010
Wang, N., Gerling, G.J., Moyer Childress, R., and Martin M.L.
"Quantifying Palpation Techniques in Relation to Performance in a
Clinical Prostate Exam (IEEE Transactions on Information Technology in
Biomedicine, in press)
Abstract: This work seeks to
quantify finger palpation techniques
in the prostate clinical exam, determine their relationship with
performance in detecting abnormalities, and differentiate the
tendencies of nurse practitioner students and resident physicians. One
issue with the digital rectal examination (DRE) is that performancn
detecting abnormalities varies greatly and agreement between-examiners
is low. The utilization of particular palpation techniques may be
one
way to improve clinician ability. Based on past qualitative
instruction, this work algorithmically defines a set of palpation
techniques for the DRE, i.e., global finger movement, local finger
movement, and average intentional finger pressure, and utilizes a
custom-built simulator to analyze finger movements in an experiment
with two groups: 18 nurse practitioner students and 16 resident
physicians. Although technique utilization varied, some elements
clearly impacted performance. For example, those utilizing the local
finger movement of vibration were significantly better at detecting
abnormalities. Also, the V global finger movement led to greater
success, but finger pressure played a lesser role. Interestingly, while
the residents were clearly the superior performers, their techniques
differed only subtly from the students. In summary, the quantified
palpation techniques appear to account for examination ability at some
level but not entirely for differences between groups. |
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Paper with Leigh
Baumgart and Ellen Bass accepted by Cancer Epidemiology
December 8,
2009
Baumgart,
L.A., Gerling, G.J., and Bass, E.J. "Characterizing the range
of simulated prostate abnormalities palpable by digital rectal
examination" (Cancer Epidemiology, 34 (1), 79-84 2010)
Abstract: Background: Although the
digital rectal exam (DRE) is
a common method of screening for prostate cancer and other
abnormalities, the limits of ability to perform this hands-on exam are
unknown. Perceptible limits are a function of the size, depth, and
hardness of abnormalities within a given prostate stiffness. Methods:
To better understand the perceptible limits of the DRE, we conducted a
psychophysical study with 18 participants using a custom-built
apparatus to simulate prostate tissue and abnormalities of varying
size, depth, and hardness. Utilizing a modified version of the
psychophysical method of constant stimuli, we uncovered thresholds of
absolute detection and variance in ability between examiners. Results:
Within silicone-elastomers that mimic normal prostate tissue (21 kPa),
abnormalities of 4 mm diameter (20 mm3 volume) and greater were
consistently detectable (above 75% of the time) but only at a depth of
5 mm. Abnormalities located in simulated tissue of greater stiffness
(82 kPa) had to be twice that volume (5 mmdiameter, 40 mm3 volume) to
be detectable at the same rate. Conclusions: This study finds that the
size and depth of abnormalities most influence detectability, while the
relative stiffness between abnormalities and substrate also affects
detectability for some size/depth combinations. While limits identified
here are obtained for idealized substrates, this work is useful for
informing the development of training and allowing clinicians to set
expectations on performance. |
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Conference papers of
Isabelle Rivest, Elmer Kim and Leigh Baumgart accepted for 2010 Haptics
Symposium
November 30,
2009
Rivest, I.I.
and Gerling, G.J., Evaluating Populations of Tactile
Sensors for Curvature Discrimination, to appear in the Proceedings of
the 2010 IEEE Haptic Interfaces for Virtual Environment and
Teleoperator Systems.
Abstract: The high density of
receptors in fingertip skin is a
limiting factor for replicating tactile feedback for neural
prosthetics. At present, the large size of engineered sensors and the
dense network of neural connections from finger to brain inhibit
duplicating the approximately 100 receptors/cm2. The objective of this
work is to build a model of the skin and neural response with which
populations of sensors can be positioned and evaluated when
discriminating spheres. The effort combines a 3D finite element model
of the fingertip, a bi-phasic transduction model, and a
leaky-integrate-and-fire neuronal model. Populations of sensors are
configured with three average densities (10,000/cm2, 1,000/cm2, and
100/cm2). For these populations, the firing rates for the dynamic
(40-70 ms) and static (650 ms-900 ms) phases and first spike latencies
are predicted. The model can differentiate indenters at a level similar
to human performance at each sampling density, including of the human
finger (100/cm2).
Kim, E.K, Gerling, G.J. Wellnitz, S.A., and Lumpkin, E.A., Using Force
Sensors and Neural Models to Encode Tactile Stimuli as Spike-based
Response, to appear in the Proceedings of the 2010 IEEE Haptic
Interfaces for Virtual Environment and Teleoperator Systems.
Abstract: Tactile sensors will
augment the next generation of
prosthetic limbs. However, currently available sensors do not produce
biologically-compatible output. This work seeks to illustrate that a
force sensor combined with a bi-phasic, neural spiking algorithm, or
spiking-sensor, can produce spiking patterns similar to that of the
slowly adapting type I (SAI) mechanoreceptor. Experiments were
conducted where first spike latency and inter-spike interval, in
response to a rapidly delivered (100 ms) sustained displacement (1.1,
1.3, 1.5 mm for 5 s), were compared between the spiking-sensor and SAI
recording. The results indicated that the predicted spike times were
similar, in magnitude and increasing linear trend, to those observed
with the SAI. Over the three displacements, average dynamic ISIs were
7.3, 4.2, 3.8 ms for the spiking-sensor and 6.2, 6.9, 4.1 ms for the
SAI, while average static ISIs were 69.0, 45.2, 35.1 ms and 159.9,
69.6, 38.8 ms. The predicted first spike latencies (74.3, 73.9, 96.3
ms) lagged in comparison to those observed for the SAI (26.8, 31.7,
28.8 ms), which may be due to both the different applied force ramp-ups
and the SAI's exquisite dynamic sensitivity range and rapid response
time.
Baumgart,
LA, Gerling, GJ, and Bass, EJ, Psychophysical
Detection of Inclusions with the Bare Finger amidst Softness
Differentials, to appear in the Proceedings of the 2010 IEEE Haptic
Interfaces for Virtual Environment and Teleoperator Systems.
Abstract: Softness discrimination
and the detection of inclusions
are important in surgery and other medical tasks. To better understand
how the characteristics of an inclusion (size, depth, hardness) and
substrate (stiffness) affect their tactile detection and discrimination
with the bare finger, we conducted a psychophysics experiment with
eighteen participants. The results indicate that within a more
pliant
substrate (21 kPa), inclusions of 4 mm diameter (20 mm3 volume) and
greater were consistently detectable (above 75% of the time) but only
at a depth of 5 mm. Inclusions embedded in stiffer substrates (82 kPa)
had to be twice that volume (5 mm diameter, 40 mm3 volume) to be
detectable at the same rate. To analyze which tactile cues most impact
stimulus detectability, we utilized logistic regression and generalized
estimating equations. The results indicate that substrate stiffness
most contributes to inclusion detectability, while the size, depth, and
hardness of the stimulus follow in individual importance, respectively.
The results seek to aid in the development of clinical tools and
information displays and more accurate virtual haptic environments in
discrimination of soft tissue. |
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Paper accepted by Acta
Biomaterialia
November 12,
2009
Yin, J.,
Gerling, G. J. and Chen, X.. "Mechanical modeling of a
wrinkled fingertip immersed in water." (Acta Biomaterialia, in press)
Abstract: Fingertips often wrinkle
after extended exposure to water. The
underlying mechanics issues, in particular the critical parameters
governing the wrinkled morphology, are studied by using both finite
element simulation and analytical modeling. The wrinkling behaviors,
characterized by the wrinkle-to-wrinkle distance (wavelength), wrinkle
depth (amplitude) and critical wrinkling stress/strain, are
investigated as the geometry and material parameters of the fingertip
are varied. A simple reduced model is employed to understand the effect
of finger curvature and skin thickness, whereas a more refined full
anatomical model provides the basis for analyzing the effect of a
multilayered skin structure. The simulation results demonstrate that
the stiffness of the stratum corneum and the dermal layer in the skin
has a large effect on the wrinkling behavior, which agrees well with
the analytical predictions. From the uncovered mechanical principles,
potential ways for effectively slowing down and suppressing skin
wrinkles are proposed; among them, increasing the modulus of the dermal
layer in the skin appears to be the most effective. |
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Lesniak
conference paper accepted to IEEE
EMBC
July 8, 2009
Lesniak, DL, Wellnitz, SA, Gerling, GJ, and Lumpkin, EA, Statistical
analysis and modeling of variance in the SA-I mechanoreceptor response
to sustained indentation (accepted for IEEE EBMS Engineering in
Medicine and Biology Conference, Minneapolis, MN September 6, 2009)
Abstract:
The slowly-adapting type I mechanoreceptor (SA-I) exhibits variability
in its steady-state firing rate both within an afferent upon repeated
stimulation and between afferents. Additionally, inter-spike
intervals of the SA-I are extremely variable during this steady-state
firing. While variability of the SA-I response has been noted
previously, the work presented herein provides a finer analysis of the
impact of force and fiber on the SA-I response. Specifically, we
test two hypothesis, that 1) fiber-to-fiber variation will
significantly impact firing rate over the range of applied forces, and
that 2) fiber-to-fiber variation will significantly impact the
coefficient of variation (CV) of inter-spike intervals over the range
of applied forces. Utilizing an ex vivo skin nerve preparation in
the mouse, experiments were conducted with six SA-I fibers from five
mice, and with compressive stimuli with force magnitudes up to 9.59 mN.
We found fiber to significantly impact both firing rate and CV.
These findings motivated the construction of a generalized input
(force) - output (firing rate) model composed of a baseline response
profile and a multiplicative fiber sensitivity factor. This work
will inform future efforts to attribute variability to differences in
skin, neuron, and receptor properties, and will contribute to the
understanding of how much variability is acceptable in systems designed
to provide tactile feedback to the nervous system.
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Paper accepted by
Applied Bionics and Biomechanics
May 22, 2009
Gerling,
G.J., "SA-I mechanoreceptor position in fingertip skin may
impact sensitivity to edge stimuli" (Applied Bionics and Biomechanics,
in press)
Abstract:
Background:
The skin plays a role in conditioning mechanical indentation into
distributions of stress/strain that mechanoreceptors convert into neural signals. Solid
mechanics methods have modeled the skin to predict the in vivo neural
response from mechanoreceptors.
Despite their promise, current models cannot explain the role that
anatomical positioning and receptor organ morphology play in producing
differences in neural response. This work hypothesizes that the skin's
intermediate ridges may help explain, in part, the sensitivity of
slowly adapting type I (SA-I) mechanoreceptors to edge stimuli. Method: Two finite element
models of the fingertip were built, validated, and used to analyze the
functionality of the intermediate ridges. One of the 2D,
cross-sectional models included intermediate ridges, while the second
did not. The analysis sought to determing if intermediate ridges a)
increase the magnitude of strain energy density were found near the
SA-I location and b) help differentiate one 2.0 mm indenter from two
0.5 mm wide indenters with a 1.0 mm gap.
Results:
Higher concentrations of strain energy density were found near the tips
of the intermediate ridges, the anatomical location that coincides with
the SA-I receptors. The first result suggested that the location of the
SA-Is in the stiffer epidermal tissue helps magnify their response to
edge stimuli. The second result was that both models were equally
capable of predicting the spatial structure within the in vivo neural
responses, and therefore the addition of intermediate ridges did not
help in differentiating the indenters.
Conclusions:
The finding, a 15-35% increase in response when the sampling point lies
within the stiffer tissue at the same depth, seeks to inform the
positioning of force sensors in robotic skin substrates. |
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Capstone team wins
best paper in the Human Factors in Healthcare Track at the 2009 SIEDS
conference
May 18, 2009
Everett, KA, Exon, RE, Rosales, SH, Gerling, GJ, Virtual Reality
Interface to Provide Point Interaction and Constriction to the Finger
(SIEDS Conference, 2009, Charlottesville, VA, pp. 203-207)
Abstract: Virtual reality (VR)
simulation of tube
thoracostomy may improve the procedural training for medical and
nursing students. Current VR simulators, however, do not provide
tactile feedback, which is essential for enabling certain tasks (e.g.,
surface palpation to identify rib location, blunt dissection for access
to pleural space surrounding the lungs, and finger sweep to confirm
location in the pleural space). This work develops a physical apparatus
that provides users with point feedback at the fingertip when palpating
an external surface and a sensation of constriction around the finger
during insertion into a body. The physical apparatus is composed of two
components that separately control the constriction on the tip and
middle of the finger. Each constriction component is made of two nylon
casings coated with a silicone-elastomer that enclose about the top and
bottom of the finger. DC gearhead motors control the magnitude of
pressure in proportion to feedback from force transducers embedded in
the silicone-elastomer. The device is intended to communicate with a
virtual environment (written in H3D). The apparatus augments
traditional stick-based force feedback and should enhance the learning
of tactile tasks in tube thoracostomy. |
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Paper
with Lumpkin Lab, Baylor Col. of Medicine accepted by Science
May 2, 2009
Maricich, S.M., Wellnitz, S.A., Aislyn M., Nelson, A.M., Lesniak, D.R.,
Gerling, G.J., Lumpkin, E.A., and Zoghbi, H.Y., "Merkel Cells are
Essential for Light Tough Responses."
The article can be seen here.
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Bill
Carson presents on device built to measure prostate stiffness
May 1, 2009
Bill Carson was one of 7 individual finalists in the 2009 Spring
Undergraduate Research and Design Symposium at the University of
Virginia. His talk was titled "Using spherical indentation to compare
the material properties of synthetic and ex vivo prostate tissue in a
clinical setting." His involvement at the conference was written
up
in a story by the Cavalier Daily which can be seen here.
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Journal
paper by Daine Lesniak accepted by Mathematical Biosciences
April 1, 2009
Mathematical Biosciences accepted the journal paper "Predicting SA-I
mechanoreceptor spike times with a skin-neuron model" written by Daine
R. Lesniak and Gregory J. Gerling.
Abstract: Slowly adapting type I (SA-I) mechanoreceptors encode the
edges and curvature of touched objects by generating neural spikes in
response to indentation of the skin. Beneath this general
input-output relationship, models are of great utility for
understanding the sub-processes, as SA-I transduction sites are
inaccessible to whole-cell recording. This work develops and
validates a SA-I skin-receptor model that combines a finite element
model of skin mechanics, a sigmoidal function of transduction, and a
leaky integrate-and-fire model of neural dynamics. The model produced a
R2=0.80 goodness of fit between predicted and observed firing rates for
3 mm and 5 mm grating stimuli. In addition, modulation indices of
predicted firing rates for 3 mm and 5 mm gratings are 0.46 and 0.59
respectively, compared to the 0.71 and 0.72 found in vivo. An analysis
of predicted first spikes indicates their latency may also be enhanced
by edges, as edge proximity shortened first spike latencies by 26.2 and
41.8 ms for the 3 mm and 5 mm gratings, respectively. The model
described here bridges the gap between those models that transform
sustained indentation to firing rates and those that transform
vibration to spike times.
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Paper
published on a simulator for training clinical prostate exams
February
26, 2009
Greg
Gerling, Sarah Rigsbee, Reba Childress, and Marcus Martin published
their research titled The Design
and Evaluation of a Computerized and Physical Simulator for Training
Clinical Prostate Exams in IEEE Transactions on Systems, Man, and
Cybernetics – Part A: Systems and Humans. |
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Cavalier Daily
Article: New Simulator
Provides Unique Practice
January
27th, 2009
"An ongoing collaboration involving the University's
Nursing, Medicine and Engineering schools has resulted in the creation
of a simulator designed to help fight prostate cancer. The
simulator, known as the Virginia Prostate Exam Simulator, is a human
patient simulator created by professors, undergraduate students and
graduate students that is designed to help teach students how to
effectively detect prostate cancer."
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NBC 29 Interview: Simulator Helps UVA
Doctors Detect
Cancer
January 26th, 2009
"The University of
Virginia is home to a one of a kind, high-tech teaching tool training
doctors and nurses to diagnose prostate cancer.
The Virginia Prostate Examination Simulation (VPES) uses a prostate
made of silicone full of tiny water balloons that act as tumors.
Sensors tell with the student finds a tumor, allowing professors
to give instant feedback to students giving the exam.
Doctors say the simulations are vital to help rising medical
professionals save lives in the future."
Click
here to view the entire NBC 29 interview on the prostate cancer
simulator designed by our team. |
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Two papers presented at AMIA conference
November 10, 2008
Daine Lesniak and Michael Cary presented
two papers
at
the AMIA Conference: An Engineering Work Analysis to Patient Falls in
the Nursing Domain (Michael Cary) and Modeling the
Data Transformations Underlying Touch Sensation to Further Tactile
Feedback in Neural Prosthesis (Daine Lesniak). |
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Journal paper accepted by IEEE SMC, Part A
October 24th, 2008
Rigsbee, S., Gerling, G.J., Moyer Childress, R. and Martin, M. L., "The
Design and Evaluation of a Computerized Physical Simulator for Training
Clinical Prostate Palpation Skills." (in press, IEEE Transactions on
Systems, Man, Cybernetics, Part A) |
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Six students
participated at Virginia Tech HFES Student Conference
October 15th, 2008
Daine Lesniak, Miki Wang, Elmer Kim, Angela Lee, Isabelle Rivest and
Bill Carson participated at the Virginia Tech Human Factors and
Ergonomics Society Student Conference in Blacksburg, Virginia. |
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Miki Wang
presents paper at HFES conference in NYC
September 25th, 2008
Miki Wang
presented a paper on the characterization of finger
palpation.
Wang, M.,
Gerling, G.J., Moyer Childress, R., and Martin, M.L.,
"Characterizing Finger Palpation in the Detection of Prostate Cancers
and Abnormalities" (Human Factors and Ergonomics Society, 2008, New
York City, NY). |
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Gerling gives talk at Department of Industrial and
Systems Engineering (ISE) at the University of Buffalo
September 15, 2008 |
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Charlottesville
Community Health Fair
July
26th, 2008
Greg
Gerling participated in the Charlottesville Community Health Fair on
Saturday along with graduate students Miki Wang and Leigh Baumgart. |
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Lesniak presents
work at National Library of Medicine
July
8th, 2008
Daine
Lesniak presented work "Modeling the Data Transformations Underlying
Touch Sensation to Further Tactile Feedback in Neural Prosthesis" at
the National Library of Medicine Informatics Training Conference in
Bethesda, Maryland. |
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UVa Today story on
Michael Cary
May 21st,
2008
Michael
Cary is
working with Greg Gerling on a project under the National Library of
Medicine diversity award to apply systems engineering to analyze
the nursing problem of patient falls.
Click
here to read the entire UVa Today article on Michael Cary. |
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Invited Presentation
at UVa
Medical School
April
24th, 2008
Marcus
Martin, Greg Gerling, Reba Childress, Ninghuan
Wang, Sarah Risgbee, Isabelle Rivest, and Angela Lee presented at the UVa Medical School on A
Physical Simulator for Training
Clinical Palpation Skills in Exams of the Prostate Gland, Clinical
Connections Session |
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Invited Talk at Old Dominion University
February
29th, 2008
Greg
Gerling
spoke at Old Dominion University on Neural Prosthetic Touch and
Simulation for Medical/Surgical Tasks. |
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Grant from DARPA received
February 29, 2008
Greg Gerling receives a grant from DARPA entitled "Enabling the Sense
of Touch:
Mimicking Responses from Single-Receptors and Optimizing Populations."
Dr. Gregory Gerling , PI, and Dr. Ellen Lumpkin (Baylor School of
Medicine, Houston, Texas), Co -I, receive notice of award from DARPA
for their proposal, "Enabling the Sense of Touch: Mimicking Responses
from Single-Receptors and Optimizing Populations." Graduate students,
Daine Lesniak and Matt Wagner, in particular, contributed. The
grant is for approximately $500,000 and will run for two years starting
in June 2008. |
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Receive grant for
prostate cancer simulation work
November 9, 2007
Greg
Gerling, PI, along with Dr. Reba Childress (Nursing) and Dr.
Marcus Martin (Emergency Medicine) receive notice of award from the
Congressional Directed Medical Research Program for their proposal "The
Development of Prostate Palpation Skills through Simulations Training
may Impact Early Detection of Prostate Abnormalities and Early
Management." The grant is for approximately $391,000 and will run for
three years starting in May 2008. |
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Article published in IMPACT on
Gerling
Fall
2007
An
article was published in IMPACT (UVA Engineering) on Greg Gerling
and
his lab. The story
included a photo of Greg Gerling and a feature on graduate student
Daine
Lesniak.
Click here to view the entire IMPACT article
on the intersection of people and computers. |
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Invited Talk at
Navy Research Labs in Washington, D.C.
September
24, 2007
Greg
Gerling
spoke at the Navy Research Lab in Washington, D.C. on Neural Prosthetic
Touch and Simulation for Medical/Surgical Tasks. |
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Granted provisional
patent for computerized and physical simulator
Greg Gerling along
with Marcus Martin
(Emergency Medicine) and Reba Childress (Nursing) were granted a provisional patent through
the
University
of Virginia with the U.S. Patent Office for their
computerized and physical simulator for training clinical prostate
palpation skills. |
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