BEE 4530 - 2006 Student Papers

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https://hdl.handle.net/1813/3048

Student research papers for Professor Ashim Datta's Biomed BEE 4530/Computer-aided Engineering course for 2002.

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Heating of Nanoshells by Near-infrared Radiation: A Rapid and Minimally-invasive method for destroying tumors
Arquiza, Apollo; Holt, Brendan; Lai, Kay; Mak, Hester; Mendelson, Avital (2006-05-24T20:21:48Z)
The purpose of this project is to model a novel and promising cancer treatment that involves the destruction of tumor cells by the direct injection of biocompatible nanoparticles (gold-silicon nanoshells) and their subsequent heating with near-infrared radiation. The use of near infra-red radiation gives this procedure an advantage over other thermal ablation treatments for cancer since light at this range (700-900 nm) is not significantly absorbed by chromopores in human tissue and can therefore penetrate more deeply (Hirsch et al., 2003). The method is also quick and minimally invasive. Using the simulation software FIDAP, we analyzed the diffusion of the nanoshells into a spherical tumor after being injected into its center. The change in temperature of the tumor due to the exposure of the nanoshells to near-infrared light was also studied. We found out that when 50 microliters of nanoshell solution (concentration of 1.5 e10 nanoshells/ml) is introduced to a 1-cm diameter tumor, it takes 29 hours for the nanoshells to fill up the tumor. At this point, exposure of the tumor with a laser (800 nm, power = 5.6 W/m2) for 10 min raised the temperature of the entire tumor to at least 45?C, effectively destroying it. Further analysis on the effect of nanoshell distribution on the temperatures obtained showed that it has negligible effect. All distributions tested (0%, 25%, 50%, 75% and 100%) resulted in the entire tumor being heated above 45?C. The laser can therefore be immediately applied to the tumor right after injection. Nanoshell concentration vs. time and temperature vs. time profiles for the tumor for various treatment conditions were also obtained. The results of the mathematical modeling will help further studies of this treatment. Although the method still needs to be refined, it should provide an effective new treatment for the destruction of breast carcinomas and other localized tumors.
The Effect of a Cooler on the Rate of Heat Loss from a Horse Post-Exercise
Gates, Megan; Perkins, Luke; Salvat, Regina; Tang, Zhouwen (2006-05-24T20:17:03Z)
Coolers are large wool blankets put on horses after exercising or bathing during cold weather. They are intended to allow moisture to travel away from the body of the horse while providing an insulating layer to help stabilize their body temperature and to prevent them from getting a chill. We tested the effectiveness of these wool coolers by comparing the rate of heat loss from a horse's skin with and without the added wool layer. Using the modeling software of FIDAP we were able to simulate the coupled processes of heat transfer from the horse?s skin and sweat evaporation. The model was run in FIDAP after determining an optimized mesh size and time step, which allowed accurate finite element modeling but maintained a reasonable run time. The model shows that the wool helps maintain a constant body temperature post exercise by providing an insulating layer. Since accurate diffusivity and conductivity values for wool and hair were hard to find, a sensitivity analysis was performed to determine the effect of an error on the temperature and mass profiles. After varying the diffusivities by one order of magnitude and the conductivities by 10%, the model determined that errors in these variables have little to no effect on horse body temperature approximations after one half hour.
Hormone Delivery System: The Contraceptive Ring
Antisell, Joanna; Poon, Tiffany; Borey, Adam; Briddell, Jenna; Palesch, Seth (2006-05-24T20:08:59Z)
Many women use contraceptive methods that involve the hormones estrogen and progestin, which prevent the ovaries from developing and releasing mature eggs. This, therefore, prevents conception. Currently there are two well established types of birth control on the market. These possibilities are the pill form where the user ingests a large dose once a day for 21 days or the birth control patch is placed on the skin every week for three weeks out of the month. Women can also receive hormone shots or implants that last for four months. However, these methods only allow a menstrual cycle every four months, so they are difficult to compare to the other methods. All of these other methods can cause side effects such as headaches, blood clots, nausea, and breakthrough bleeding. However, there is a new form of birth control that comes in a flexible thin ring that is inserted into the vagina below the cervix. This ring is designed to releases a continuous low dose of hormone that is absorbed by the vagina and distributed into the blood stream. The ring actually releases two derivatives of estrogen and progestin known as etonogestrel and ethinyl estradiol (Organon USA Inc. 2005). See Figure 1 for the chemical structures of both of these compounds. Because the ring is only changed once a month, it ceases the fluctuation of hormone levels that is normal in the other birth control methods.
Cold Therapy of Sporting Injury in Upper Thigh Region: A Comprehensive Study on the Time Required to Achieve Optimal Cooling and the Effects of Swelling
Chen, Jack; Chiang, Ian; Hu, Alex; Huland, David; Youn, Paul (2006-05-24T20:01:35Z)
One of the most common injuries amongst athletes is soft tissue injury due to impact, and the traditional treatment for this is cold therapy using an ice pack. While this treatment is effective, inexpensive, and easily accessible, there is very little quantitative data available on the actual effects of ice on the muscle. The most common advice found in medical textbooks and literature is a 20 minute on, 20 minute off icing cycle. In this study we model the temperature distribution in the upper leg region after one and a half cycles of ice therapy. Our axisymmetric model consists of three layers: skin, fat, and muscle, and we include an initial swelling of the muscle layer that decreases as a function of the muscle temperature. After an initial 20 minutes of cooling, the desired temperature change of 10?C penetrated to only 4 mm into the muscle layer, but after a 60 minute cycle, the desired cooling increased to 1 cm. Our sensitivity analysis revealed that slight changes in properties such as density, specific heat and conductivity did not alter the results significantly. Also, using a fixed muscle thickness independent of temperature yielded a lower temperature drop in the muscle layer. It was concluded that ice therapy, though slow, is effective in cooling some of the muscle to the desired temperature, and its main advantages stem from its inexpensiveness and ease of application.
An Analysis of the Ortho Evra Birth Control Patch
Fields, Rachel; Fisher, Elana; Kramer, Scott; Kwan, Elaine; Wong, Angela (2006-05-24T19:54:37Z)
The Ortho Evra Birth Control Patch is an effective alternative method of birth control. It releases two drugs, norelgestromin and ethinyl estradiol, and these two drugs diffuse through a person?s skin and into their bloodstream. In order to analyze this process, we developed a 2-D, axisymmetric model of the diffusion of norelgestromin from the patch and through the skin. Through the use of a sensitivity analysis to determine the correct patch diffusivity, we were able to get an accurate representation of the physical process. We then modeled what would happen if the patch were removed for various periods of time, and we were able to determine that if the patch were removed for 24 hours or less, no significant disruption to the delivery of the drugs would occur. Finally, we also ran a simulation of wearing two different patches over the course of two weeks, and we determined that the concentration would normally encounter periodic rises and falls over the two-week period.
Heat Loss in the Carotid Artery During Selective Brain Cooling in Humans
Attygalle, Suneth; Girnary, Hussein; Jeffrey, Natalie; Lee, Sean; Torre, Rosa (2006-05-24T19:28:56Z)
Heat flow in the neck was simulated in FLUENT to study countercurrent effects of cooling blood in the carotid artery during selective brain cooling. The simulation was performed in order to verify Zhu?s theory (used as a basis for our methodology) and to determine the contribution of countercurrent exchange by comparing results to a heat flow model without exchange. The surface temperature of the neck and flow rates within the vessels were varied to determine the specific effects of countercurrent exchange. With ambient skin temperature (25?C) and normal blood flow rate (120 ml/min); our model demonstrates that the average temperature of the arterial blood reaching the brain drops by 1.18?C while traveling through the neck. The effect of the countercurrent exchange alone contributes 0.88?C to this temperature decay. Placing an ice pack on the neck surface can further decrease the arterial blood temperature by as much as 1.0?C. This indicates that placing an ice pack on the neck does aid in selective brain cooling and that countercurrent exchange has a significant impact in cooling as well. The overall temperature drop of blood between the inlet to the carotid artery and the outlet was found to decrease with increasing blood flow rates and surface temperatures, verifying the trends modeled in Zhu?s analysis. Zhu?s theoretical study, however showed a temperature drop of 0.35?C at a blood flow rate of 240 ml/min with vein inlet blood temperature at 29?C and neck temperature at 19?C whereas ours showed a temperature drop above 0.85?C. Sensitivity analysis was performed to test the stability of our solution and to discover factors that might affect arterial outlet temperature. The factors that had the most influence on penetration depth were the specific heat of the blood and varying the thermal conductivity of the tissue. This project could be expanded upon by considering more variations in geometry, such as center-to center spacing, vessel eccentricity and modeling multiple vessels. This would allow for a better model of the true behavior of heat flow in the neck.
Ex Vivo Maintenance of Heart Viability: Comparison of Two Methods
Bridgen, Devin; Hagens, John; Brink, Rob; Gregg, Peter; Aridgides, Dan; Faghri, Ali (2006-05-24T19:08:41Z)
Currently established methods of tissue preservation for heart transplantation involve placing the harvested donor heart in a cold, nutrient-rich cardioplegic solution. Clinically, methods like these have only been shown to preserve heart tissue for a matter of hours. A new solution for tissue preservation developed by Transmedics Inc involves placing the heart in a chamber that mimics the physiological conditions of the human chest cavity. This solution maintains the heart in a beating state and pumps blood and nutrients through the myocardial circulation. This preservation technique has been clinically shown to improve the length of time that a heart can be preserved ex-vivo and when properly implemented, could theoretically preserve a donor heart indefinitely. A computer simulation using Finite-Element analysis was performed with the intention of comparing how well these two methods work to perfuse heart tissue with oxygen over a long period of time. As expected, it was shown that the Transmedics cart could keep the concentration of oxygen in the heart tissue at optimal levels indefinitely while the immersion technique could only keep the concentrations of oxygen in the tissue above healthy levels for around 5.5 hours. Investigations into the effect of temperature on each preservation technique found that the Transmedics preservation is most effective at 37 degrees Celsius, body temperature; while the immersion technique is most effective at 4 degrees Celsius. Though the Transmedics device was shown to be far superior in many areas, other considerations, like the cost and the ease of implementation of each technique have lead us to conclude that there are still certain situations in which tissue preservation by cooling is the best option for heart transplantation.
The Advantage of Under Armour for Winter Sports Performance
Allen, Lisa; Chen, Brenda; Pokwal, Sonam; Graunke, Steve (2006-05-24T19:03:33Z)
Under Armour produces apparel designed for winter sports athletes. This apparel aims to keep athletes comfortable by retaining body heat and removing moisture due to perspiration. Special wicking properties are claimed to enable the material to remove moisture quickly and provide insulation. This study will propose a mechanism by which the Under Armour clothing material achieves these effects. We will model moisture transfer and heat transfer through the cloth, considering skin surface temperature and moisture content as measures of comfort. Additionally, we will compare the effects of Under Armour to cotton clothing which has different material properties, considering diffusivity, conductivity, partition coefficient, and porosity. The goal of this study is to use our proposed model to show the advantages of Under Armour for winter sports performance.
Angina Patch: Drug Delivery for Chest Pain
Lee, Jessica; Morgan, Lee; Yee, Jackie (2006-05-24T18:58:22Z)
Angina pectoris is defined as chest pain due to lack of blood and oxygen to the heart. Nitroglycerin is an organic nitrate which treats angina by vasodilating both arteries and veins to increase blood flow to the heart. It is easy to develop nitroglycerin drug tolerance, and therefore drug application must occur at intervals of about 12 hours. While commercial products such as Deponit are suitable for treating mild cases of angina, a larger, daily dose of 40 mg of nitroglycerin is needed to treat the most acute cases. The purpose of this study is to model the diffusion of nitroglycerin from a transdermal patch into the blood stream using the Deponit drug delivery system. We determined that Deponit was indeed unable to deliver the necessary 40 mg of drug. We therefore suggested a new patch which could treat acute angina, by modifying both patch geometry and the initial amount of drug in the reservoir. We also simulated drug delivery for a 36 hour period of wearing the patch for 12 hours, not wearing the patch for 12 hours, and then reapplying a new patch for another 12 hours. We found that drug continued to be delivered even in absence of patch and after 36 hours, only ~125 mg of drug was delivered. The modified Thicker Patch with a 10x thicker drug reservoir than Deponit can physically hold 142 mg of drug and deliver 40 mg within 12 hours. The modified patch is safe, non-toxic, cost effective, and capable of treating recalcitrant angina. To determine whether our assumptions were appropriate for our parameters, we performed two specific sensitivity analyses: varying the diffusivity of the skin and varying the diffusivity of the patch and the skin. From the sensitivity analysis we found that the amount of drug delivered to body is very sensitive to the diffusivity of the skin but insensitive to the diffusivity of the patch
Laser Interstitial Thermo-Therapy in Hepatic Tissue
Ahyow, Patrick; Lee, Brian; Wong, Kevin (2006-05-24T18:54:25Z)
Laser Interstitial ThermoTherapy (LITT) is a well establish surgical method used in the treatment of tumors. This study analyzes the extent of tissue damage when using LITT in a liver. GAMBIT and FIDAP was used to model a spherical tumor with a diameter of 4cm in a 12cm spherical liver. The mesh that was used contained 14326 nodes which were shown to converge using our mesh convergence analysis. From our sensitivity analysis, the optimal time the laser would be on was determined to be 40 seconds, because this was the time where most of the cancerous tissue was destroyed while keeping healthy tissue damage at a minimum. The optimal laser power was determined to be 30W, which provided the correct amount of heating needed to induce necrosis in the most of the tumor, and maintain a safe temperature below 40oC for healthy liver tissue. However, there a small amount of healthy liver was destroyed, but this could not be avoided due to the cylindrical geometry of the laser applicator. In our sensitivity analysis, we determined that varying the thermal conductivity caused very little change in the average tumor temperature. This indicates that thermal conductivity parameter is relatively insensitive to changes and using our values for thermal conductivity would accurately model the process.

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