Design and Material Characterization of an Inflatable Vaginal Dilator.

There are more than 13,000 new cases of cervical cancer each year in the United States and approximately 245,000 survivors. External beam radiation and brachytherapy are the front-line treatment modalities, and 60% of patients develop vaginal damage and constriction, i.e., stenosis of the vaginal vault, greatly impeding sexual function. The incidence of vaginal stenosis (VS) following radiotherapy (RT) for anorectal cancer is 80%. VS causes serious quality of life (QoL) and psychological issues, and while standard treatment using self-administered plastic dilators is effective, acceptance and compliance are often insufficient. Based on published patient preferences, we have pursued the design of a soft inflatable dilator for treating radiotherapy-induced vaginal stenosis (VS). The critical component of the novel device is the dilator balloon wall material, which must be compliant yet able to exert therapeutic lateral force levels. We selected a commercially available silicone elastomer and characterized its stress-strain characteristics and hyperelastic properties. These parameters were quantified using uniaxial tensile testing and digital image correlation (DIC). Dilator inflation versus internal pressure was modeled and experimentally validated in order to characterize design parameters, particularly the dilator wall thickness. Our data suggest that an inflatable silicone elastomer-based vaginal dilator warrants further development in the context of a commercially available, well-tolerated, and effective device for the graded, controlled clinical management of radiotherapy-induced VS.

Optical Surgical Navigation: A Promising Low-cost Alternative.

State-of-the-art computer-assisted surgery relies on infrared-based cameras for precise positional measurements. However, the cost of purchasing these systems acts as a barrier for smaller healthcare facilities to adopt them. Recently, low-cost optical tracking with cameras has emerged as a promising alternative, but differences in operating room conditions and patient anatomy can cause inconsistencies between procedures. Therefore, it is essential to identify and evaluate individual factors that may affect a procedure. In this study, we evaluate fiducial ArUco markers as a low-cost alternative to traditional markers. To evaluate their effectiveness, we designed a ground truth testing platform, which enables us to measure the real-time difference between the predicted and actual positions. We investigated the effects of warping, line-of-sight obstruction, and operating room lighting as variables that could influence marker tracking in the operating room. Each variable was isolated and simplified to quantifiable modifications to the physical marker and X-Y platform environment. We find that our navigation system is a promising approach for use in computer-navigated surgery, and future work will focus on implementing image processing techniques to improve the accuracy of optical marker tracking.

First Clinical Experience With Ophthalmic e-Device for Unaided Patient Self-Examination During COVID-19 Lockdown.

PURPOSE: The aim of this study was to describe a new type of medical device that allows for internet-enabled patient self-screening, without the aid of an ophthalmic professional, through biomicroscopy self-imaging and self-measurement of the best-corrected visual acuity (BCVA). METHODS: In this prospective nonrandomized comparative study, 56 patients were instructed to screen their own eyes using a custom-built e-Device containing miniaturized slitlamp optics and a visual acuity Snellen chart virtually projected at 20 ft. BCVA measurements were recorded, and biomicroscopic videos were scored for image quality of the anterior segment status on a scale from 1 to 5 (1 = poor and 5 = excellent) by a blinded observer. RESULTS: After a short instruction, all patients were able to self-image their eyes and perform a self-BCVA measurement using the e-Device. Patient self-image quality with the e-Device scored on average 3.3 (±0.8) for videos (n = 76) and 3.6 (±0.6) for photographs (n = 49). Self-BCVA measurement was within 1 Snellen line from routine BCVA levels in 66 of 72 eyes (92%). When compared with conventional biomicroscopy, patient self-biomicroscopy allowed for recognition of the relevant pathology (or absence thereof) in 26 of 35 eyes (74%); 9 cases showed insufficient image quality attributed to device operating error (n = 6) and mild corneal edema and/or scarring (n = 3). Patient satisfaction with the device was 4.4 (±0.9). CONCLUSIONS: An e-Device for combined BCVA self-measurement and biomicroscopy self-imaging may have potential as an aid in remote ophthalmic examination in the absence of an ophthalmic professional and may be considered for patients who are unable to visit an ophthalmic clinic for routine follow-up.

Design and Validation of an Automated Dilator Prototype for the Treatment of Radiation Induced Vaginal Injury.

Vaginal stenosis (VS) is a common late complication of radiation injury caused by cervical cancer radiotherapy. It is characterized by the narrowing or shortening of the vaginal canal, which is often detrimental to patient quality of life. To address this public health problem, an expandable vaginal dilator was designed for the prevention of VS in cervical cancer survivors. Modeling and benchtop experimentation were used to iteratively characterize the relationship among dilator pressure, expansion, and the load applied to the simulated vaginal wall. Both experimental and simulation results exhibited shared trends relating pressure, dilator expansion, applied load, and resultant displacement of the modeled vaginal walls. Future work will incorporate enhanced Mooney-Rivlin material assumptions and validation of the model with in vivo tests.Clinical Relevance- These results present a design opportunity and treatment paradigm shift to increase patient adherence to VS treatment after cervical cancer radiotherapy. Specifically, gradual expansion of the vaginal dilator increases comfort during the expansion of the vagina, while monitoring the dilator pressure enables the tracking of VS improvement and normalization of vaginal wall compliance.

A comparative study of experimental urinary catheters containing silver and zinc for biofilm inhibition.

Both commercial and experimental antibacterial urinary catheters were investigated for their efficacy in preventing planktonic growth and biofilm formation of Escherichia Coli bacteria in a synthetic urine solution. Experimental antibacterial catheters having thin (<500 µm) dispersions of Ag, Ag/Ag2O, or Zn/Ag2O in polydimethylsiloxane (PDMS) binder all exhibited significant antimicrobial activity, outperforming traditional commercial antibacterial catheters. All experimental catheters prevented planktonic growth of bacteria and did not exhibit biofilm formation during a six-day test period using a colony forming unit (CFU) measurement method. On the other hand, the best performing commercial catheters demonstrated efficacy for only 3 days in planktonic growth tests and formed multiple bacterial colonies in CFU measurements. The Zn/Ag2O/PDMS experimental catheter was the only catheter observed to produce hydrogen peroxide, a reactive oxygen species known to inhibit biofilm formation; lack of detectable hydrogen peroxide production by the Ag2O/PDMS and Ag/Ag2O/PDMS experimental catheters suggests that bactericidal action most likely arises from release of silver ions present in the PDMS coatings.

A Compact Optical Pressure Measurement System for Acquiring Intraocular Pressure and Ocular Pulse.

Frequent and accurate monitoring of intraocular pressure is an important aspect of glaucoma management and is central to timely therapeutic intervention and treatment optimization. Intraocular pressure is known to fluctuate not only throughout the day, but also as a function of the heart rate. This pulsatory pressure change behavior is known as the ocular pulse. In this study, we report on the measurement of the ocular pulse profile using a miniaturized intraocular pressure sensor implanted in the eye of a New Zealand White rabbit. The pressure sensor is based on the principle of interferometry and does not require an internal power source. The ocular pulse variation has been measured up to 5 Hz with an accuracy of +/- 0.15 mmHg using both a DSLR reader and a handheld smartphone reader.

A Wireless Handheld Pressure Measurement System for In Vivo Monitoring of Intraocular Pressure in Rabbits.

Intraocular pressure (IOP) is the leading modifiable risk factor for preventing vision loss in glaucoma patients. Direct and frequent IOP measurements are highly desirable to assess adequacy of treatment and prevent further vision loss. In this study, we report on successful in vivo measurements of intraocular pressure in rabbits using an optical IOP measurement system. The sensor was implanted during cataract surgery in two New Zealand white (NZW) rabbits and tested in vivo for ten weeks. Prior to implantation, the sensors were characterized in vitro in the physiologically relevant pressure range of 0-60 mmHg. A portable wireless handheld reader consisting of an internal beam splitter, a monochromatic light source, and a digital single-lens reflex (DSLR) camera was also designed and implemented to capture interference patterns from the sensor. The sensitivity and accuracy of the sensor was 30 nm/mmHg and ±0.2 mmHg, respectively. Ten weeks post-implantation, the two NZW rabbits continued to respond well to the implant with no observable inflammation, signs of infection, or biofouling. All IOP measurements were obtained using the portable DSLR handheld reader. Successful in vivo studies demonstrate biocompatibility of the IOP sensor and prove feasibility of the IOP measurement system. The system has the potential to be used in both clinical and patient point-of-care (home) settings to frequently and accurately measure pressure.

Macroscopic assessment of cartilage shear: effects of counter-surface roughness, synovial fluid lubricant, and compression offset.

During joint articulation, cartilage is subjected to compression, shear, and sliding, mechanical factors that regulate and affect cartilage metabolism. The objective of this study was to use an in vitro material-on-cartilage shear test to elucidate the effects of counter-surface roughness (Polished, Mildly rough, and Rough), lubricants (phosphate buffered saline (PBS) and bovine synovial fluid (bSF)), and compression offset on the shearing and sliding of normal human talar cartilage under dynamic lateral displacement. Peak shear stress (sigma(xz,m)) and strain (E(xz,m)) increased with increasing platen roughness and compression offset, and were 30% higher with PBS than with bSF. Compared to PBS, bSF was more effective as a lubricant for P than for M and R platens as indicated by the higher reduction in kinetic friction coefficient (-60% vs. -20% and -19%, respectively), sigma(xz,m) (-50% vs. -14% and -17%) and E(xz,m) (-54% vs. -19% and -17%). Cartilage shear and sliding were evident for all counter-surfaces either at low compression offset (10%) or with high lateral displacement (70%), regardless of lubricant. An increase in tissue shear occurred with either increased compression offset or increased surface roughness. This material and biomechanical test system allow control of cartilage sigma(xz,m) and E(xz,m), and hence, sliding magnitude, for an imposed lateral displacement. It therefore can facilitate study of cartilage mechanobiological responses to distinct regimes of cartilage loading and articulation, such as shear with variable amounts of sliding.

Long time spreading of a microdroplet on a smooth solid surface.

The long time spreading of microdroplets on a smooth solid surface is studied experimentally. An empirical expression is obtained for the spreading area as a function of time showing a final area when spreading stops. The mean film thickness of this final area appears to be independent of the initial volume of the droplet and of the spreading dynamics. A theoretical model is developed to predict this final uniform film thickness, based on volume conservation and the principle of minimum energy. Good agreement is found between the theoretical and experimental results.

A simple atomic force microscopy calibration method for direct measurement of surface energy on nanostructured surfaces covered with molecularly thin liquid films.

A simple calibration method is described for the determination of surface energy by atomic force microscopy (AFM) pull-off force measurements on nanostructured surfaces covered with molecularly thin liquid films. The method is based on correlating pull-off forces measured in arbitrary units on a nanostructured surface with pull-off forces measured on macroscopically smooth dip-coated gauge surfaces with known surface energy. The method avoids the need for complex calibration of the AFM cantilever stiffness and the determination of the radius of curvature of the AFM tip. Both of the latter measurements are associated with indirect and less accurate measurements of surface energy based on various contact mechanics adhesion models.