Gregory J. Gerling, Ph.D.

    Associate Professor

    Systems and Information Engineering

    gregory-gerling virginia edu

Greg Gerling     Gerling Lab Logo          
News Updates

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)

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.

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

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.

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.

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.

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.

        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.

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)

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.  

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.

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.

  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.

      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.

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.

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."

Click here to view the entire Cavalier Daily article on the prostate cancer simulator designed by our team.

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.  

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).

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)

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.  

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).

Gerling gives talk at Department of Industrial and Systems Engineering (ISE) at the University of Buffalo
September 15, 2008

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.

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.

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.

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 

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.

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.

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.

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.

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.

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.