MSc., Faculty of Science, University of the Witwatersrand, 2011 / Wild animals are captured for management, health, translocation and research purposes. Capture is an unnaturally stressful event, which may result in morbidity or mortality. An attributing cause of the morbidity and mortality is capture-induced hyperthermia; the larger the magnitude and the longer the duration of this captured-induced hyperthermia, the greater the likely risk to the animal. The most common practice currently used in the field to lower body temperature is to douse hyperthermic animals with water. However, the water used is often at ambient temperatures and its efficacy is not known. We investigated whether this method and alternative methods are effective at lowering the body temperature of hyperthermic animals. To achieve these aims we implanted 19 blesbok with miniature temperature-sensitive data loggers in their abdomens and into their subcutaneous layers (at the sites of the flank, groin, lower neck and upper neck). The loggers continuously recorded core body temperatures of the blesbok throughout the study period at an interval of six minutes. We successfully retrieved complete data sets from 12 blesbok. The animals were captured on six separate occasions using a technique which elicited hyperthermia. Five animals were cooled by dousing with water of different temperatures (4°C, 17°C, 28°C) and fanning after dousing with 28°C water, in random order. Seven animals were cooled by ice packs, spraying a fine mist spray, intravenous (IV) infusion of one litre of 4°C water and 28°C water-dousing. Through the use of our continuous logging of body temperature we established the normal body temperature of the blesbok, which displayed a regular 24 hour body temperature pattern. The average daily body temperature of the blesbok was 38.8°C ± 0.4°C, with a minimum body temperature of 37.9°C ± 0.1°C and a maximum body temperature of 39.4°C ± 0.1°C. The body temperature after capture was as high as 41°C-42°C, which was significantly higher than the normal body temperature (Student’s t-test, P < 0.05). The animals were cooled once they were immobilised and the start of cooling was denoted as time zero. In the control (no active cooling) intervention the body temperature decreased to only about 40°C. Dousing animals with water, irrespective of its temperature, resulted in significant cooling (P < 0.05) of the animals, as indicated by their minimum body temperature reached, change in body temperature and rate of cooling. The water-dousing interventions decreased the body temperature to about 38°C after an hour, which was significantly lower than the control (RM-ANOVA, P < 0.05) but there was no significant difference in the minimum body temperature reached between the different water temperatures or by the addition of fanning (RM-ANOVA, P > 0.05). The water-dousing interventions cooled the animals more quickly than did the control (RM-ANOVA, P < 0.05), and the coldest water (4°) cooled the animals quicker than did the 28°C water-dousing (RM-ANOVA, P < 0.05). The core body temperature minus the subcutaneous temperature was calculated, and revealed a peak difference of about 3.5°C after the 4°C water-dousing. Ice-packs also resulted in significant cooling (P < 0.05) of the animals, as depicted by their minimum body temperature reached, change in body temperature and rate of cooling. The ice-packs lowered the body temperature to a minimum of about 38°C, which was significantly lower than the control (RM-ANOVA, P < 0.05). The ice-packs also cooled the animals significantly faster than did the control, intravenous infusion and mist spray (RM-ANOVA, P < 0.05) but cooled as quickly as the 28°C water-dousing (RM-ANOVA, P > 0.05). The core body temperature minus the subcutaneous temperature for the ice-packs peaked at a difference of about 3°C. The IV infusion and mist spray were ineffective cooling methods and did not significantly (P > 0.05) alter the minimum body temperature or rate of cooling. Even though the IV infusion caused a significant reduction in body temperature by 1°C, the cooling effect from the IV infusion was short-lived because the minimum body temperature reached after the intravenous infusion and mist spray was ultimately similar to the body temperature seen in animals receiving the control (RM-ANOVA P > 0.05). Also, the intravenous infusion and mist-spray cooled as slowly as did the control (RM-ANOVA P > 0.05). Therefore, water-dousing in this study was the most effective and practical method to cool hyperthermic blesbok. Although all the water temperatures (4°C, 17°C and 28°C) that we tested were effective, the coldest water (4°C) cooled the animals quickest. The addition of fanning to the 28°C water-dousing did not increase cooling. Ice-packs were also effective but may be not as easy to use as the water-dousing method as ice-packs are large and need to be kept frozen, and therefore are cumbersome for use in the field.

Using the computer code Monte Carlo N-Particle (MCNP), doses were calculated for organs of interest such as the large intestine, urinary bladder, testes, and kidneys while patients were undergoing prostate brachytherapy. This research is important because the doses delivered to the prostate are extremely high and the organs near the prostate are potentially at risk for receiving high doses of radiation, leading to increased probabilities of adverse health effects such as cancer. In this research, two MCNP version 4C codes were used to calculate the imparted energies to the organs of interest delivered by 125I and 103Pd. As expected, the organs nearest to the prostate received the highest energy depositions and the organs farthest from the prostate received the lowest energy depositions. Once the energy depositions were calculated, the doses to the organs were calculated using the known volumes and densities of the organs. Finally, the doses to the organs over an infinite time period were calculated.

No description available.

Intravascular brachytherapy is the primary treatment for coronary in-stent restenosis. We hypothesized that differences in dose delivered to target may contribute to treatment failures. We compared dose distribution between arteries that developed recurrent restenosis (treatment failures) and those that remained patent at nine-months (treatment success). A cohort of 207 patients receiving brachytherapy for coronary in-stent restenosis with four radiation delivery devices was followed to identify treatment failures and successes. This cohort was examined to establish which patient and lesion characteristics had an effect on outcome. A nested case-control construct was then used in which treatment failures (n=14) were compared 1:2 to treatment successes (n=28) matched by two variables: radiation delivery system and angiographic pattern of in-stent restenosis. At baseline, the groups had similar patient and lesion characteristics. The dose absorbed by 90% of the artery encompassed by the external elastic membrane (D90EEM) was calculated using intravascular ultrasound (IVUS) images taken at 2-mm intervals along the treated lesion. Dose calculations were performed using dose kernel integration techniques; the dose kernels were generated from Monte Carlo simulations. The mean D90EEM minimum dose in treatment failures was 7.46±1.98 Gy, while for treatment success the mean D90EEM minimum dose was significantly higher: 8.87±1.13 Gy (p=0.007). Using a dose threshold of 8.4 Gy, a D90EEM minimum dose < 8.4 Gy occurred in 13 (93%) patients with treatment failure, but in only 9 (32%) with treatment success (p<0.001). No confounding variables were found to be statistically significant. In conclusion, current brachytherapy dose prescriptions result in significant inter- and intra-lesion variation in dose at the EEM. Arteries that receive < 8.4 Gy at any point along the EEM are more likely to be treatment failures. IVUS guided dosimetry may be critical to assure adequate dose regardless of radiation delivery system.

Using the computer code Monte Carlo N-Particle (MCNP), doses were calculated for organs of interest such as the large intestine, urinary bladder, testes, and kidneys while patients were undergoing prostate brachytherapy. This research is important because the doses delivered to the prostate are extremely high and the organs near the prostate are potentially at risk for receiving high doses of radiation, leading to increased probabilities of adverse health effects such as cancer. In this research, two MCNP version 4C codes were used to calculate the imparted energies to the organs of interest delivered by 125I and 103Pd. As expected, the organs nearest to the prostate received the highest energy depositions and the organs farthest from the prostate received the lowest energy depositions. Once the energy depositions were calculated, the doses to the organs were calculated using the known volumes and densities of the organs. Finally, the doses to the organs over an infinite time period were calculated.

Prostate brachytherapy, a treatment for prostate cancer, was a procedure that typically involved placing radioactive sources in a cancerous prostate using percutaneous needles. The placement of these sources determined the dose that the prostate and healthy tissues surrounding it received. However, because a needle could bend, tissue could deform, and a patient could move, each source may have been displaced from its planned position. This source misplacement could later cause some cancer to be spared or healthy organs to be further damaged. To better understand patterns of source misplacement, and eventually reduce the phenomenon, this work matched and registered implanted sources with their planned positions. Each implant was registered to its plan using a sequence of four successive registrations. A rough initial registration was first found, using features known in the planned dataset and estimated from the implanted dataset. Second, subsets of sources were reconstructed in the implanted dataset. The implanted sources were next matched to the planned sources using the subsets as constraints. Finally, the optimal rigid transformation between the implants and the plan was found. The algorithm was tested on both simulated and clinical datasets. Simulations placed limits on how properties of the subsets affected registration accuracy. When tested on 9 clinical datasets, the algorithm found 100% of correct plan-implant source matches within seconds on commonly available computers. When the implanted strands were reconstructed as sine waves, 97% of t strands had an amplitude of less than 2mm. The clinical accuracy result generally agreed with simulation: subsets with amplitudes less than 2mm were expected to produce an accuracy >90%. The high accuracy of the algorithm may enable its use in finding patterns of source misplacement. The fast run-time of the algorithm may additionally make it useful for use in a clinical setting. / Thesis (Master, Computing) -- Queen's University, 2011-12-23 13:28:07.348

No description available.

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2007. / Härtill 4 uppsatser.

Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2006. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Western Australia, 2005.