BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Collimator-Free Non-Collinear Cascade Gamma Coincidence Imaging: A GATE-Based Study Achieving Sub-Millimeter Resolution and High Sensitivity DTSTART;VALUE=DATE-TIME:20260522T095000Z DTEND;VALUE=DATE-TIME:20260522T101000Z DTSTAMP;VALUE=DATE-TIME:20260624T123128Z UID:indico-contribution-657-3845@indico.tlabs.ac.za DESCRIPTION:Speakers: Enock Mtatiro Mwita (University of Dar es Salaam)\nT his study presents the GATE-based Monte Carlo model and performance evalua tion of a non-time-of-flight\, collimator-free tomographic medical imaging system based on non-collinear cascade gamma-ray Coincidence (CGC) imaging . A CGC imaging model was developed to reconstruct three-dimensional decay vertices from valid coincidence events. A custom geometric back-projectio n reconstruction algorithm was implemented to generate tomographic images in transverse\, coronal\, and sagittal views\, enabling quantitative asses sment of spatial resolution\, sensitivity\, and coincidence detection effi ciency (CDE). The results show\, with 111In-ion point source at the center of field of view (FoV)\, the modeled imaging system achieved sub-millimet er isotropic spatial resolution of approximately 0.477 mm (FWHM) along all axes and demonstrated resolving capability between 1.5-2.0 mm for closely spaced point sources. The CGC imager achieved a coincidence efficiency of 1.50588 × 10⁻2 and sensitivity of 15\,058.8 cps/MBq for a 111In source at the center of the FoV in air\, their corresponding values for source i n PMMA phantom were 1.25279 × 10-2 and 12\,527.9 cps/MBq\, respectively. These values were significantly higher than those reported for conventiona l parallel-hole\, focused\, and hybrid collimator-based systems\, represen ting improvements of several orders of magnitude. For positional reconstru ction\, the analysis confirmed the reconstructed source position within ± 16 mm transaxially and ±17 mm axially resembles to simulated position. To evaluate the impact of radionuclide decay characteristics on imaging perf ormance\, four cascade gamma emitters (43K\, 73Se\, 111In and 177Lu) were simulated under identical conditions. 111In and 73Se exhibit the highest C DEs\, followed by 177Lu\, while 43K shows the lowest due to its extremely short intermediate-state half-life of 46 ps\, which is below the detector timing resolution (~0.549 ns)\, leading to missed valid coincidence events . The higher CDE for 111In is partly from random coincidences caused by it s longer half-life and wider timing window. These results emphasize that d etector timing resolution\, isotope selection\, and coincidence window des ign are critical for optimizing cascade gamma imaging performance. On the other hand\, spatial resolution remained the same (~0.477 mm FWHM) across radionuclides. This finding confirms that system resolution is governed by detector geometry and reconstruction parameters rather than decay propert ies. The findings demonstrate that non-collinear CGC imaging enables the s imultaneous achievement of both high sensitivity and sub-millimeter spatia l resolution. However\, experimental testing of the system should be condu cted to assess its practical performance.\n\nhttps://indico.tlabs.ac.za/ev ent/139/contributions/3845/ LOCATION:NRF-iThemba LABS\, Old Faure Road\, Cape Town Auditorium URL:https://indico.tlabs.ac.za/event/139/contributions/3845/ END:VEVENT BEGIN:VEVENT SUMMARY:Monte Carlo-Based Optimization of Occupational Radiation Protectio n in a Diagnostic Radiology Facility at Kitui County Level V Hospital\, Ke nya DTSTART;VALUE=DATE-TIME:20260522T093000Z DTEND;VALUE=DATE-TIME:20260522T095000Z DTSTAMP;VALUE=DATE-TIME:20260624T123128Z UID:indico-contribution-657-3819@indico.tlabs.ac.za DESCRIPTION:Speakers: Muthama Matsitsi (South Eastern Kenya University)\nA ccurate occupational dose estimation is essential for optimizing radiation safety and ensuring compliance with regulatory guidelines. The spatial di stribution of scatter radiation in the radiography room was characterized using Monte Carlo simulations based on Geant4. A diagnostic X-ray system w as accurately modeled and validated using experimental measurements to eva luate the magnitude and distribution of scattered radiation. Simulated and measured dose rates showed good agreement within ±10%\, with a root mean square error of 0.08 µSv h⁻¹\, indicating strong model reliability. S catter dose exhibited a general decrease with distance from the source\, a pproximately following the Inverse Square Law\, although deviations were o bserved due to distributed scatter sources and attenuation in air. The sca tter dose decreased from 1.51 µSv h⁻¹ at 0.25 m to 0.36 µSv h⁻¹ at 2.0 m from the source\, representing approximately a 76% reduction. Incre asing the field size from 10 × 10 cm² to 20 × 20 cm² and 30 × 30 cm² significantly increased scatter dose even at far-field positions. The com bined use of lead protective clothing and 0.5 mm mobile lead shielding red uced scatter dose by approximately 90–96%. Overall\, the estimated occup ational dose levels were within internationally recommended limits. The ob served distribution and variability of scatter radiation highlight the imp ortance of continuous radiation protection optimization. The study therefo re recommends routine indoor radiation monitoring\, particularly for staff working in radiology departments. Strict implementation of the ALARA prin ciple through appropriate positioning and effective shielding using lead a prons is strongly recommended.\n\nKeywords: Occupational dose\, Monte Carl o simulation\, X-ray dosimetry\, Scatter Dose\, radiation safety.\n\nhttps ://indico.tlabs.ac.za/event/139/contributions/3819/ LOCATION:NRF-iThemba LABS\, Old Faure Road\, Cape Town Auditorium URL:https://indico.tlabs.ac.za/event/139/contributions/3819/ END:VEVENT BEGIN:VEVENT SUMMARY:Organ-Specific Dosimetric Assessment of Radon Exposure via Drinkin g Water in a Selected Population DTSTART;VALUE=DATE-TIME:20260522T083500Z DTEND;VALUE=DATE-TIME:20260522T085500Z DTSTAMP;VALUE=DATE-TIME:20260624T123128Z UID:indico-contribution-657-3805@indico.tlabs.ac.za DESCRIPTION:Speakers: Ibrahim Ayodeji Bello (Kabba College of Agriculture\ , Ahmadu Bello University)\nThis study evaluated organ-specific annual eff ective doses and excess lifetime cancer risk (ELCR) from radon exposure th rough 20 groundwater samples in a selected population. The experiment was analysised using Liquid Scintillation Counter (LSC). Radon concentrations ranged from 10.6 to 43.1 Bq/L\, with over 90% of samples exceeding the U. S. EPA limit of 11.1 Bq/L\, though remaining below the WHO limit of 100 Bq /L. Total annual effective doses ranged from 34.4 to 140.1 µSv/year\, wit h the lungs receiving the highest organ-specific dose (up to 13.0 µSv/yea r)\, followed by the stomach. Estimated ELCR values (1.21 × 10⁻⁴ to 4 .90 × 10⁻⁴) exceeded the EPA's acceptable threshold of 1.00 × 10⁻ ⁴ in most samples\, suggesting a notable radiological health risk. Inhal ation was the dominant exposure pathway. These findings underscore the nee d for regular monitoring\, public awareness\, and mitigation measures in a reas with elevated groundwater radon levels.\n\nhttps://indico.tlabs.ac.za /event/139/contributions/3805/ LOCATION:NRF-iThemba LABS\, Old Faure Road\, Cape Town Auditorium URL:https://indico.tlabs.ac.za/event/139/contributions/3805/ END:VEVENT BEGIN:VEVENT SUMMARY:Establishment of Local Diagnostic Reference Levels for Adult and P ediatric Patients in Intraoral Radiography at South African Oral Health Ca re Center DTSTART;VALUE=DATE-TIME:20260522T081500Z DTEND;VALUE=DATE-TIME:20260522T083500Z DTSTAMP;VALUE=DATE-TIME:20260624T123128Z UID:indico-contribution-657-3832@indico.tlabs.ac.za DESCRIPTION:Speakers: Sello Mashinini ()\nThis work contributes to the Rad iation and Health Physics theme through the application of dose quantifica tion and optimization methodologies in intraoral radiography. By establish ing locally relevant Diagnostic Reference Levels (DRLs) for both adult and pediatric populations\, the study addresses a key gap in South African ra diological protection practice. The findings support standardization effor ts and provide a framework for future national DRL development and optimiz ation strategies in medical imaging.\n\nhttps://indico.tlabs.ac.za/event/1 39/contributions/3832/ LOCATION:NRF-iThemba LABS\, Old Faure Road\, Cape Town Auditorium URL:https://indico.tlabs.ac.za/event/139/contributions/3832/ END:VEVENT BEGIN:VEVENT SUMMARY:Estimation of radiation exposure to family members of patients tre ated with I-131 in Tanzania DTSTART;VALUE=DATE-TIME:20260522T075500Z DTEND;VALUE=DATE-TIME:20260522T081500Z DTSTAMP;VALUE=DATE-TIME:20260624T123128Z UID:indico-contribution-657-3809@indico.tlabs.ac.za DESCRIPTION:Speakers: Penina Mbago (University of Dar es Salaam)\, Innocen t Lugendo (University of Dar es Salaam)\nAbstract\nRadiation therapy using Iodine-131 (I-131) is a widely employed treatment for thyroid disorders\; however\, it poses potential radiation exposure risks to patient caregive rs due to gamma emissions from treated patients. This study estimates the radiation doses received by family members of patients undergoing I-131 th erapy in Tanzania\, where cultural practices and living conditions complic ate adherence to international safety guidelines. Using the Particle and H eavy Ions Transport-code System (PHITS)\, exposure scenarios during hospit alization and post-discharge phases were modelled\, accounting for proximi ty\, activity levels\, and caregiver-patient interactions. These models we re utilized to estimate the radiation exposure to family members of patien ts treated with I-131 in Tanzania. Results indicate that family members as sisting dependent patients during hospitalization received doses of 1.53\, 2.33\, and 2.99 mSv for 3700\, 5550\, and 7400 MBq\, respectively. These doses are below the 5 mSv/episode limit but exceed the 1 mSv/year public d ose limit. Post-hospitalization\, the doses decreased significantly\, with the highest exposure caused by close-contact activities. Meanwhile\, tran sportation scenarios showed the exposure to be less than 1 mSv/year for sh ort durations. Nevertheless\, strict adherence to maintaining a one-meter distance and minimizing the duration of close contact is emphasized. These findings provide critical insights for maintaining public health while en suring effective thyroid cancer treatment. \nKeywords: Caregiver safety\, family members\, Iodine-131 therapy\, PHITS simulation\, radiation exposu re\, Tanzania\, thyroid cancer.\n\nhttps://indico.tlabs.ac.za/event/139/co ntributions/3809/ LOCATION:NRF-iThemba LABS\, Old Faure Road\, Cape Town Auditorium URL:https://indico.tlabs.ac.za/event/139/contributions/3809/ END:VEVENT BEGIN:VEVENT SUMMARY:Estimation of Annual Effective Dose and Excess Lifetime Cancer Ris k from Background Ionizing Radiation at Udege Mbeki Abandoned Excavated Mi ning Site\, Nasarawa State\, Nigeria DTSTART;VALUE=DATE-TIME:20260522T073000Z DTEND;VALUE=DATE-TIME:20260522T075500Z DTSTAMP;VALUE=DATE-TIME:20260624T123128Z UID:indico-contribution-657-3807@indico.tlabs.ac.za DESCRIPTION:Speakers: Michael Adeleye (Bingham University\, Nigeria)\nThis study evaluates the radiological health implications of human exposure to background ionising radiation (BIR) at the mining site\, with particular emphasis on the Annual Effective Dose Equivalent (AEDE) and Excess Lifetim e Cancer Risk (ELCR). Soil samples were collected from four distinct zones \; dumps\, farmland\, surface soil and the processing site\, and analyzed using a gamma-ray spectrometer to determine the activity concentrations of naturally occurring radionuclides 40K\, 226Ra\, and 232Th. Radiological h azard indices\, including absorbed dose rate\, AEDE\, and ELCR were subseq uently computed. At the processing site\, mean activity concentrations of 40K\, 226Ra\, and 232Th were 218.58 Bq kg⁻¹\, 114.35 Bq kg⁻¹\, and 4 20.06 Bq kg⁻¹\, respectively. These elevated radionuclide levels result ed in a mean absorbed dose rate of 315.66 ± 9.72 nGy h⁻¹\, correspondi ng to a mean AEDE of 161.30 ± 4.97 mSv y⁻¹ and a mean ELCR of 564.56 × 10⁻³. The highest values were recorded at sample point P7\, with AED E and ELCR reaching 387.03 mSv y⁻¹ and 1354.59 × 10⁻³\, respectivel y. In the dumps\, mean AEDE and ELCR were 148.81 ± 4.49 mSv y⁻¹ and 52 0.83 × 10⁻³\, respectively\, while farmland soils showed comparatively lower values with mean AEDE of 67.12 ± 2.67 mSv y⁻¹ and ELCR of 234.9 2 × 10⁻³. Surface soils exhibited intermediate radiological characteri stics\, with mean AEDE and ELCR of 121.49 ± 3.48 mSv y⁻¹ and 425.22 × 10⁻³\, respectively. Overall\, the estimated AEDE and ELCR values acro ss the studied locations exceeded internationally recommended safety limit s for public exposure\, indicating significant radiological risk\, particu larly within the processing and dump sites. The elevated ELCR values sugge st an increased probability of cancer development over a lifetime of expos ure. These findings underscore the need for continuous environmental monit oring\, restriction of prolonged human activities within high-exposure zon es of the mined area to mitigate long-term health risks and enforcement of land reclamation agreement to restore excavated mining sites into usable land for agriculture or residential purposes.\n\nhttps://indico.tlabs.ac.z a/event/139/contributions/3807/ LOCATION:NRF-iThemba LABS\, Old Faure Road\, Cape Town Auditorium URL:https://indico.tlabs.ac.za/event/139/contributions/3807/ END:VEVENT END:VCALENDAR