Please use this identifier to cite or link to this item: http://prr.hec.gov.pk/jspui/handle/123456789/13143
Title: DESIGN AND ANALYSIS OF SHIELDING CERROBEND BLOCKS AND INVESTIGATION OF PERFORMANCE OF THERMOLUMINESCE / PHOTOLUMINESCENCE-BASED DETECTORS DURING IN-VIVO DOSIMETRY
Authors: Ahmad, Habib
Keywords: Physics
Issue Date: 2017
Publisher: University of Peshawar, Peshawar.
Abstract: The actual dose delivery in radiotherapy is of prime importance, which can only be achieved by using an accurate dosimeter. This work reflects the fabrication of three types of dosimeters that can be applied in radiation dose measurement during radiotherapy and other areas of radiation measurements. LiF is a special material, which when doped with some activators produces a single crystal that acts as a highly sensitive nanophosphor. These nanophosphors have several applications, such as, color center laser, integrated optics and radiation dosimetry. It is widely used in personal dosimetry because of its low energy dependence, tissue equivalency, stability and sensitivity. In this work, we have locally fabricated monocrystalline cubes of LiF doped with Mg, Ti, Dy3+ and Eu3+ by simple chemical coprecipitation method. These dosimeters were annealed at two unique temperatures i.e. at 400ºC and at 600ºC. The synthesized samples were characterized by XRD, SEM, and FESEM, EDX, FTIR for structural and morphological studies. XRD showed the phase of LiF and crystallite size was found around 30 nm. SEM studied the surface morphology of the samples as cubic, while EDX indicated the chemical composition of the nanophosphor. FE-SEM was employed to see the grain and grain boundaries more clearly. Furthermore, FTIR spectra were recorded in order to see the different molecular species and functional groups in these nanophosphors. The spectra revealed the presence of hydroxyl group (–O–H) of the metal hydroxide such as Mg (OH)2, stretching vibrations of rare-earth cations (Dy3+ and Eu3+) and metals oxides, Li-O and Mg-O. To study the PL properties of the two dosimeters (LiF: Mg, Dy3+ and LiF: Eu3+), PL spectroscopy was performed, which confirmed the emission spectra in the visible region of 685 nm for Dy3+and 610 nm for Eu3+. Both emissions occurred in the red portion of electromagnetic spectrum. Finally, the core property of these dosimeters i.e. the TL property was studied from their glow curves. All the obligatory parameters for these dosimeters were carried out; for example, dose sensitivity, dose linearity response, dose fading, dose rate dependency, angle dependency, and energy dependency. The fabricated TLDs and commercially available TLDs were compared both in sensitivity and glow curve peak temperatures. The glow peak temperature was 285 °C to 290 °C while the sensitivity of the fabricated TLDs was about 8 times less than that of commercial ones to lower doses and vice versa. In-vivo dosimetry was performed using Rando-phantom in 5 common radiotherapy treatment sights having Organ at Risk. The OARs were shielded with customized blocks. The shielded OAR dose and the in-field target doses were measured, using the TL dosimeters (LiF: Mg, Ti). The measured dose and the Treatment Planning System (eclipse point dose version) results were compared and both were found well correlated in open areas, and shielded regions.
Gov't Doc #: 16373
URI: http://prr.hec.gov.pk/jspui/handle/123456789/13143
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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