Kenyatta National Hospital (KNH) is the largest public referral hospital with a comprehensive cancer treatment facility in East and Central Africa. Occupational radiation monitoring is a significant technique for demo...Kenyatta National Hospital (KNH) is the largest public referral hospital with a comprehensive cancer treatment facility in East and Central Africa. Occupational radiation monitoring is a significant technique for demonstrating compliance of radiation regulatory limits. The objective of the study was to carry out assessment of occupational radiation exposure among radiotherapy personnel at KNH using thermoluminescence dosimeter, TLD. KNH staff were monitored using dosimeter type TLD-100 made of LiF:Mg,Ti, on monthly basis. The reader system used for analysis was Harshaw 8800. The measurement established the average monthly accumulated occupational personnel dose for KNH to be 0.21 mSv and 0.29 mSv for Hp (10) and Hp (0.07) respectively. The accumulated dose results were within the maximum acceptable dose of 1.67 mSv/month and 41.6 mSv/month for Hp (10) and Hp (0.07) respectively. The investigation results were higher than the acceptable public limit of 0.08 mSv/month. Moreover, incidences were noted where the fetus dose limit 0.42 was also exceeded. Evaluation of statistical dose exposure among doctors, nurses and radiographers’ measurement results were within ±0.02 mSv. The study established the average KNH occupational radiation exposure levels for both Hp (10) and Hp (0.07) were within the ICRU recommendation, validating radiation protection safe practice. Data analysis of healthcare workers did not indicate exposure trend biased to any healthcare profession. Hence radiation risk cut across all professional categories. It is recommended that Radiation Monitoring program be reviewed to include non-clinical staff who access the facility. Radiation reporting should not be limited to one facility, but reflect cases where workers are involved in multiple multiple jobs.展开更多
This study presents the intercomparison of the outdoor environmental gamma dose rates measured using a Nal （TI） based survey meter along with thermoluminescent dosimeters （TLDs） and estimation of excess lifetime c...This study presents the intercomparison of the outdoor environmental gamma dose rates measured using a Nal （TI） based survey meter along with thermoluminescent dosimeters （TLDs） and estimation of excess lifetime cancer risk （ELCR）, for the inhabitants of Poonch division of the Azad Kashmir, Pakistan. CaF2： Dy （TLD-200） card dosimeters were installed at height of 1 m from ground at fifteen different locations covering the entire Poonch division comprising of three districts.展开更多
The aim of this study was to study the technical factors affecting the reading of TLD (LiF:Mg:Ti) for radiation dosimetry. The method adapted was an exposure of LiF:Mg:Ti crystal with?γ-ray with the following filters...The aim of this study was to study the technical factors affecting the reading of TLD (LiF:Mg:Ti) for radiation dosimetry. The method adapted was an exposure of LiF:Mg:Ti crystal with?γ-ray with the following filters (Hp 0.07 and Hp?10), before and after usage of filter Hp?(0.07), annealing, cooling by nitrogen flux and crystal morphology by scanning electron microscope. The collected data analyzed by EXCELL software showed that: TLD average count/second (C/s) with filter Hp?(10) was greater than that obtained with filter Hp?(0.07) with an amount of 1191 c/s?(19%). Also the analysis showed that: the average C/s without filter Hp?(0.07) was greater than that with filter by an amount of 994.5 C/s (16.4%), and there was proportional linear relationship;as the applied dose increased the TLD C/s increased significantly (R2?=?0.9) based on the equations: y = 885.1x???286.5 and y = 860.5x?+ 856.8 for filtered and without filtered beam respectively, where?x?refers to applied dose in mGy and?y?refers to C/s. Also the average C/s without nitrogen flux (cooling) was greater than with nitrogen count with an amount of 52.4 C/s (11%). The annealing (without filter) causes a reduction in dose by 82.2?μGy (19.2%), and in case of annealing with filter, the dose reduced by 66.7?μGy (21.9%) relative to annealing without filter. The morphology of TLD crystal shown by scanning electron microscope SEM was a darkening surface after irradiation.展开更多
A track structure model has been applied to calculate the relative thermoluminescent efficiency of TLD- 100 irradiated with energetic heavy ions. In earlier work we proposed that the response of TLD- 100 to γ-ray ari...A track structure model has been applied to calculate the relative thermoluminescent efficiency of TLD- 100 irradiated with energetic heavy ions. In earlier work we proposed that the response of TLD- 100 to γ-ray arises from a combination of 1- hit and 2- hit trap structures. The supralinear (2- hit) response is now known to diminish with a decrease in the energy of incident electrons. Since the delta rays of slow particles are of low energy, diminishing with a reduction in ion speed, we calculate the response to slow heavy ions by track theory as due to the 1- hit targets alone and obtain good agreement between theory and experiment. The branching of the experimental curves is principally caused by the kinematic limit in delta ray production for ions approaching the end of their range, an effect which is called "thidown" when seen in the tracks of heavy ions approaching the end of their range in electron sensitive nuclear emulsion.展开更多
文摘Kenyatta National Hospital (KNH) is the largest public referral hospital with a comprehensive cancer treatment facility in East and Central Africa. Occupational radiation monitoring is a significant technique for demonstrating compliance of radiation regulatory limits. The objective of the study was to carry out assessment of occupational radiation exposure among radiotherapy personnel at KNH using thermoluminescence dosimeter, TLD. KNH staff were monitored using dosimeter type TLD-100 made of LiF:Mg,Ti, on monthly basis. The reader system used for analysis was Harshaw 8800. The measurement established the average monthly accumulated occupational personnel dose for KNH to be 0.21 mSv and 0.29 mSv for Hp (10) and Hp (0.07) respectively. The accumulated dose results were within the maximum acceptable dose of 1.67 mSv/month and 41.6 mSv/month for Hp (10) and Hp (0.07) respectively. The investigation results were higher than the acceptable public limit of 0.08 mSv/month. Moreover, incidences were noted where the fetus dose limit 0.42 was also exceeded. Evaluation of statistical dose exposure among doctors, nurses and radiographers’ measurement results were within ±0.02 mSv. The study established the average KNH occupational radiation exposure levels for both Hp (10) and Hp (0.07) were within the ICRU recommendation, validating radiation protection safe practice. Data analysis of healthcare workers did not indicate exposure trend biased to any healthcare profession. Hence radiation risk cut across all professional categories. It is recommended that Radiation Monitoring program be reviewed to include non-clinical staff who access the facility. Radiation reporting should not be limited to one facility, but reflect cases where workers are involved in multiple multiple jobs.
文摘This study presents the intercomparison of the outdoor environmental gamma dose rates measured using a Nal （TI） based survey meter along with thermoluminescent dosimeters （TLDs） and estimation of excess lifetime cancer risk （ELCR）, for the inhabitants of Poonch division of the Azad Kashmir, Pakistan. CaF2： Dy （TLD-200） card dosimeters were installed at height of 1 m from ground at fifteen different locations covering the entire Poonch division comprising of three districts.
文摘The aim of this study was to study the technical factors affecting the reading of TLD (LiF:Mg:Ti) for radiation dosimetry. The method adapted was an exposure of LiF:Mg:Ti crystal with?γ-ray with the following filters (Hp 0.07 and Hp?10), before and after usage of filter Hp?(0.07), annealing, cooling by nitrogen flux and crystal morphology by scanning electron microscope. The collected data analyzed by EXCELL software showed that: TLD average count/second (C/s) with filter Hp?(10) was greater than that obtained with filter Hp?(0.07) with an amount of 1191 c/s?(19%). Also the analysis showed that: the average C/s without filter Hp?(0.07) was greater than that with filter by an amount of 994.5 C/s (16.4%), and there was proportional linear relationship;as the applied dose increased the TLD C/s increased significantly (R2?=?0.9) based on the equations: y = 885.1x???286.5 and y = 860.5x?+ 856.8 for filtered and without filtered beam respectively, where?x?refers to applied dose in mGy and?y?refers to C/s. Also the average C/s without nitrogen flux (cooling) was greater than with nitrogen count with an amount of 52.4 C/s (11%). The annealing (without filter) causes a reduction in dose by 82.2?μGy (19.2%), and in case of annealing with filter, the dose reduced by 66.7?μGy (21.9%) relative to annealing without filter. The morphology of TLD crystal shown by scanning electron microscope SEM was a darkening surface after irradiation.
文摘A track structure model has been applied to calculate the relative thermoluminescent efficiency of TLD- 100 irradiated with energetic heavy ions. In earlier work we proposed that the response of TLD- 100 to γ-ray arises from a combination of 1- hit and 2- hit trap structures. The supralinear (2- hit) response is now known to diminish with a decrease in the energy of incident electrons. Since the delta rays of slow particles are of low energy, diminishing with a reduction in ion speed, we calculate the response to slow heavy ions by track theory as due to the 1- hit targets alone and obtain good agreement between theory and experiment. The branching of the experimental curves is principally caused by the kinematic limit in delta ray production for ions approaching the end of their range, an effect which is called "thidown" when seen in the tracks of heavy ions approaching the end of their range in electron sensitive nuclear emulsion.
