Browsing by Author "Gregory, Thomas S."

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    Development of a Deflection Measurement System for the Hybrid III Six-Year Old Biofidelic Abdomen
    Gregory, Thomas S. (Virginia Tech, 2012-12-17)
    Despite advancements in automotive safety, motor vehicle collisions remain the leading cause of unintentional death for children ages 5 to 14. Enhancement of child occupant protection depends on the ability to accurately assess the effectiveness of restraint systems. Booster seat design and proper belt fit require evaluation using child anthropomorphic test devices, yet biofidelity of the abdomen and pelvis of the current anthropomorphic test device, the Hybrid III 6-year-old, needs improvement. Further, measurement of abdominal deflection is needed for quantification of the degree of submarining and associated potential injury risk. A biofidelic abdomen for the Hybrid III 6-year-old dummy is being developed by the Ford Motor Company. A practical measurement system for the biofidelic abdominal insert has been developed and demonstrated for three dimensional determination of abdominal deflection. Quantification of insert deflection is achieved via differential signal measurement using electrodes mounted within a conductive medium. Signal amplitude is proportional to the distance between the electrodes. A microcontroller is used to calculate distances between ventral electrodes and a dorsal electrode in three dimensions. This system has been calibrated statically, as well as evaluated dynamically. Its performance has also been demonstrated in a series of sled tests. Deflection measurements from the instrumented abdominal insert showed clear differences between two booster seat designs, yielding an average peak anterior to posterior displacement of the abdomen of 1.0 ± 3.4 mm and 31.2 ± 7.2 mm for the seats, respectively. Implementation of a 6-year-old abdominal insert with the ability to evaluate submarining potential will likely advance the effectiveness of booster seat design and restraint performance, and help mitigate child occupant injury severity in automobile collisions.
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    Therapeutic ultrasound as a potential male contraceptive: power, frequency and temperature required to deplete rat testes of meiotic cells and epididymides of sperm determined using a commercially available system
    Tsuruta, James K.; Dayton, Paul A.; Gallippi, Caterina M.; O'Rand, Michael G.; Streicker, Michael A.; Gessner, Ryan C.; Gregory, Thomas S.; Silva, Erick J. R.; Hamil, Katherine G.; Moser, Glenda J.; Sokal, David C. (2012-01-30)
    Background Studies published in the 1970s by Mostafa S. Fahim and colleagues showed that a short treatment with ultrasound caused the depletion of germ cells and infertility. The goal of the current study was to determine if a commercially available therapeutic ultrasound generator and transducer could be used as the basis for a male contraceptive. Methods Sprague-Dawley rats were anesthetized and their testes were treated with 1 MHz or 3 MHz ultrasound while varying power, duration and temperature of treatment. Results We found that 3 MHz ultrasound delivered with 2.2 Watt per square cm power for fifteen minutes was necessary to deplete spermatocytes and spermatids from the testis and that this treatment significantly reduced epididymal sperm reserves. 3 MHz ultrasound treatment reduced total epididymal sperm count 10-fold lower than the wet-heat control and decreased motile sperm counts 1,000-fold lower than wet-heat alone. The current treatment regimen provided nominally more energy to the treatment chamber than Fahim's originally reported conditions of 1 MHz ultrasound delivered at 1 Watt per square cm for ten minutes. However, the true spatial average intensity, effective radiating area and power output of the transducers used by Fahim were not reported, making a direct comparison impossible. We found that germ cell depletion was most uniform and effective when we rotated the therapeutic transducer to mitigate non-uniformity of the beam field. The lowest sperm count was achieved when the coupling medium (3% saline) was held at 37 degrees C and two consecutive 15-minute treatments of 3 MHz ultrasound at 2.2 Watt per square cm were separated by 2 days. Conclusions The non-invasive nature of ultrasound and its efficacy in reducing sperm count make therapeutic ultrasound a promising candidate for a male contraceptive. However, further studies must be conducted to confirm its efficacy in providing a contraceptive effect, to test the result of repeated use, to verify that the contraceptive effect is reversible and to demonstrate that there are no detrimental, long-term effects from using ultrasound as a method of male contraception.