In High Dose Rate (HDR) brachytherapy, treatment dose to patients is highly dependent on the accuracy of positioning and duration of the source. Source misplacement or wrong duration of treatment could potentially result in adverse clinical side effects to patients. In order to maintain successful treatment for patients, an independent Quality Assurance (QA) verification is crucial to measure the High Dose Rate (HDR) source positioning and dwell time periodically to ensure the prescribed dose is correct and safe for brachytherapy treatment. The current QA practice used to validate the accuracy of dwell time of the source is by using a stopwatch and measure the dwell position on the source position check ruler. Nevertheless, reaction time of human poses a major concern regarding the accuracy in these manual operating procedures. In this thesis, a new QA tool is proposed to acquire accurate information about time structure and source positioning in HDR brachytherapy. The tool consists of a consumer-grade webcam, a source position check ruler, a laptop computer and a custom-made combined camera-ruler mounting tool. The camera is used to capture the motion of the moving source in real time. Each frame contains positional and temporal information that are important to determine the difference between the measured and the actual HDR source position and time structure. Finally, a Graphical User Interface (GUI) application program is developed to receive the input from the camera for image processing. The measured results (time structure and positional information) are displayed on the computer screen as the output of the designed application. The tool was found to be able to reduce the time required significantly for the QA and minimize the impact of human errors. At the time of writing, the sensitivity of the system to luminous changes in the environment warrants further efforts to render the tool even more useful. Based on the experimental results, the accuracy of dwell time measured by the proposed system was ± 40 ms. The minimum detectable dwell time of the proposed system was 200 ms. The range of effective dwell position that could be measured by the system ranged from 1300 mm to 1500 mm (excluding 1300 mm and 1500 mm). The accuracy of dwell position measured by the proposed system was ± 1mm. / published_or_final_version / Diagnostic Radiology / Master / Master of Medical Sciences

No description available.

No description available.

Thesis (M. D.)--University of Hong Kong, 2007. / Also available in print.

published_or_final_version / abstract / Medicine / Master / Doctor of Medicine

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.

Current brachytherapy treatment planning systems are unable to accurately calculate dose distributions in the vicinity of brachytherapy sources having active lengths much greater than 5 mm. While low dose-rate ¹³⁷Cs sources are dosimetrically characterized using antiquated along-away tables with simple linear-linear interpolation errors in dose calculation exceeding 30% occur due to algorithm inadequacy. The method presented in this thesis permits dosimetric characterization of elongated brachytherapy sources with active lengths 0 < L < 10 cm for implementation on an FDA-approved clinical TPS. Low- and high-energy photon-emitting sources of Pd-103 and Ir-192, respectively, were examined.

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

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 98-107).

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Dr. C.-K. Chris Wang; Committee Member: Dr. Nolan E. Hertel; Committee Member: Dr. Sang Hyun Cho.