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Development of a Primary Standard fo...

Khan, Ahtesham Ullah.

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Development of a Primary Standard for Absorbed Dose to Water from Alpha-Emitting Radionuclides.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Development of a Primary Standard for Absorbed Dose to Water from Alpha-Emitting Radionuclides./
作者:	Khan, Ahtesham Ullah.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
面頁冊數:	235 p.
附註:	Source: Dissertations Abstracts International, Volume: 84-11, Section: B.
Contained By:	Dissertations Abstracts International84-11B.
標題:	Physics. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30490225
ISBN:	9798379511074

Development of a Primary Standard for Absorbed Dose to Water from Alpha-Emitting Radionuclides.
Khan, Ahtesham Ullah.

Development of a Primary Standard for Absorbed Dose to Water from Alpha-Emitting Radionuclides. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 235 p.

Source: Dissertations Abstracts International, Volume: 84-11, Section: B.

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2023.

This item must not be sold to any third party vendors.

Targeted radionuclide therapy (TRT) and brachytherapy with alpha particles has gained significant clinical relevance recently. Absorbed dose traceability to a standard is currently lacking in the dosimetry chain. The short range of alpha particles in water of <100 {phono}{aelig}m complicates the absorbed dose measurements in the form of significant attenuation and perturbation effects. The purpose of this work was to develop and validate absorbed dose to water standards for alpha-emitting radionuclides. Dosimetric formalisms to measure surface absorbed dose to water per radioactivity using windowless cylindrical parallel-plate extrapolation chambers (ECs) were introduced.{A0}Monte Carlo (MC) investigations were launched to probe the alpha transport mechanism using a Fano cavity test. Optimal electromagnetic transport parameters were extracted from this study. The assumptions of the cavity theories were evaluated and the impact of source parameters on absorbed dose was studied. Following the construction of the apparatus, a thin film 210Po source was employed with a radioactivity of 1.253 {phono}{aelig}Ci for evaluation. A parallel-plate EC with a 4.00 mm collector diameter composed of D400 polystyrene-equivalent material was utilized as a standard. Addtionally, a printed circuit board (PCB) with a segmented guard was constructed to align the detector and the source plates using a differential capacitance technique. The PCB EC aimed to enhance the repeatability of the ionization current measurements. EC-based and MC-based correction factors were calculated for a planar circular 210Po alpha emitter. Lateral and rotational alignment between the EC and the source was performed using translational and rotational shifts applied to the source using a hexapod motion stage. The initial air gap was determined using a contactless capacitance method. Ionization charge was collected as a function of applied voltage, varied between 1-200 V for a 0.3 mm air gap, to calculate the recombination correction. The polarity correction was measured by reversing the polarity of the applied bias. Multiple measurement trials were performed to measure ionization current at air gaps in the 0.3-0.525 mm range. The proposed dosimetric formalisms were employed to calculate the surface absorbed dose to water from a point-like 210Po source.Negligible self-attenuation was found for the 210Po source and the radius of the source was measured to be 1.60 mm. Lateral and rotational offsets of up to 0.20 mm and 1.50 deg were measured, respectively, when aligning the EC parallel to the source with their centers coincident with each other. The recombination and polarity correction factors were measured to be <0.50% when a 150 V/mm electric field strength was applied. The MC-calculated and measured absorbed dose to air agreed within 2.05% and 4.50% for the D400 and the PCB IC, respectively. Using the extrapolation method, the surface absorbed dose to water for the 210Po was measured to be 2.8913x10{acute}{88}{92}6 Gy/s/Bq and 2.304x10{acute}{88}{92}6 Gy/s/Bq with a combined uncertainty of 3.74% and 3.55% for the D400 and the PCB IC, respectively. Large uncertainties, above 7% at k=1, were reported for the absorbed dose calculated using the cylindrical shell dosimetric formalism. Therefore, the extrapolation method was preferred to measure the surface absorbed dose to water.This work demonstrated the ability of two windowless parallel-plate ECs as absorbed dose standards for alpha-emitting radionuclides.

ISBN: 9798379511074Subjects--Topical Terms:

516296
Physics.
Subjects--Index Terms:

Alpha-emitting radionuclides

Development of a Primary Standard for Absorbed Dose to Water from Alpha-Emitting Radionuclides.
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260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2023
300 $a 235 p.
500 $a Source: Dissertations Abstracts International, Volume: 84-11, Section: B.
500 $a Advisor: DeWerd, Larry A.
502 $a Thesis (Ph.D.)--The University of Wisconsin - Madison, 2023.
506 $a This item must not be sold to any third party vendors.
520 $a Targeted radionuclide therapy (TRT) and brachytherapy with alpha particles has gained significant clinical relevance recently. Absorbed dose traceability to a standard is currently lacking in the dosimetry chain. The short range of alpha particles in water of <100 {phono}{aelig}m complicates the absorbed dose measurements in the form of significant attenuation and perturbation effects. The purpose of this work was to develop and validate absorbed dose to water standards for alpha-emitting radionuclides. Dosimetric formalisms to measure surface absorbed dose to water per radioactivity using windowless cylindrical parallel-plate extrapolation chambers (ECs) were introduced.{A0}Monte Carlo (MC) investigations were launched to probe the alpha transport mechanism using a Fano cavity test. Optimal electromagnetic transport parameters were extracted from this study. The assumptions of the cavity theories were evaluated and the impact of source parameters on absorbed dose was studied. Following the construction of the apparatus, a thin film 210Po source was employed with a radioactivity of 1.253 {phono}{aelig}Ci for evaluation. A parallel-plate EC with a 4.00 mm collector diameter composed of D400 polystyrene-equivalent material was utilized as a standard. Addtionally, a printed circuit board (PCB) with a segmented guard was constructed to align the detector and the source plates using a differential capacitance technique. The PCB EC aimed to enhance the repeatability of the ionization current measurements. EC-based and MC-based correction factors were calculated for a planar circular 210Po alpha emitter. Lateral and rotational alignment between the EC and the source was performed using translational and rotational shifts applied to the source using a hexapod motion stage. The initial air gap was determined using a contactless capacitance method. Ionization charge was collected as a function of applied voltage, varied between 1-200 V for a 0.3 mm air gap, to calculate the recombination correction. The polarity correction was measured by reversing the polarity of the applied bias. Multiple measurement trials were performed to measure ionization current at air gaps in the 0.3-0.525 mm range. The proposed dosimetric formalisms were employed to calculate the surface absorbed dose to water from a point-like 210Po source.Negligible self-attenuation was found for the 210Po source and the radius of the source was measured to be 1.60 mm. Lateral and rotational offsets of up to 0.20 mm and 1.50 deg were measured, respectively, when aligning the EC parallel to the source with their centers coincident with each other. The recombination and polarity correction factors were measured to be <0.50% when a 150 V/mm electric field strength was applied. The MC-calculated and measured absorbed dose to air agreed within 2.05% and 4.50% for the D400 and the PCB IC, respectively. Using the extrapolation method, the surface absorbed dose to water for the 210Po was measured to be 2.8913x10{acute}{88}{92}6 Gy/s/Bq and 2.304x10{acute}{88}{92}6 Gy/s/Bq with a combined uncertainty of 3.74% and 3.55% for the D400 and the PCB IC, respectively. Large uncertainties, above 7% at k=1, were reported for the absorbed dose calculated using the cylindrical shell dosimetric formalism. Therefore, the extrapolation method was preferred to measure the surface absorbed dose to water.This work demonstrated the ability of two windowless parallel-plate ECs as absorbed dose standards for alpha-emitting radionuclides.
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650 4 $a Nuclear physics. $3 517741
650 4 $a Health sciences. $3 3168359
650 4 $a Electrical engineering. $3 649834
653 $a Alpha-emitting radionuclides
653 $a Dosimetry
653 $a Extrapolation chamber
653 $a Monte Carlo investigations
653 $a Radiopharmaceutical therapy
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690 $a 0544
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710 2 $a The University of Wisconsin - Madison. $b Medical Physics. $3 2097834
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793 $a English
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30490225