Simulations and Measurements of radiation doses from patients treated with I-131.

University essay from Umeå universitet/Radiofysik

Abstract: The aim of this work is to introduce a couple of new exposure scenariosof interest when personnel, family members and general public are externally irradiated from patients treated with Iodine-131. A series of modied ORNL matematical phantoms were used in Monte-Carlo simulations in PENELOPE-2011 to determine dose rates to: a cab driver where thepatient sits in the back seat at opposite side, a newborn child held by an adult patient, a doctor giving treatment to a patient while leaning over the hospital bed and collective effective dose to bus passengers if the patient travels home by bus. The cost to order taxi instead of a public transport ticket for the patient is put in relation to the lowered collective effective dose to general public and compared with other companies price per lowered manSv. Dose rate measurements and the effective half-life of I-131 are used to determine the retained whole body activity at different times post administration. This in combination with the simulations are used to estimate effective doses to the cab driver, bus passengers, newborn and personnel. Whole body-, abdominal- and thyroid source distributions were considered in the patients during simulations. Dose rates within 99.7 % condence intervals were up to: 23.7 ± 0.4, 62.7 ± 0.3, 530 ± 71, 96.8 ± 0.5 µSv/h/GBq, for the cab driver, closest bus passenger, newborn and physician respectively. Collective effective dose to bus passengers is estimated to 291 ± 2 µmanSv/h/GBq. A patient specic tool for estimating more reasonable restriction times on how long to avoid small children is developed, taking into account retained body activity and the home situation for the patient. Effective dose estimations suggest that dose constraints are very unlikely exceeded for the taxi driver, and public transport should be a considered option for thyrotoxicosis patients of lower administered activities and some cancer patients. It is also estimated that hospitals in Sweden are paying 7.6 - 31 MSEK per lowered collective effective dose of 1 manSv by sending patients by taxi instead of bus.

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