The Influence of CoO/P2O5 Substitutions on the Structural, Mechanical, and Radiation Shielding of Boro-Phosphate Glasses

A new glass system (50−x)P2 O5 –20B2 O3 –5Al2 O3 –25Na2 O–xCoO was manufactured using a standard melt quenching procedure, where 1≤ x ≤ 12 mol%. The characteristics of boro-phosphate-glasses containing CoO have been studied. The effect of CoO on the radiation-protective properties of glasses was established. The density of the prepared glasses as a function of CoO increased. XRD was used to check the vitreous structure of samples. Fourier-transform infrared (FTIR) spectroscopy was used to study the structure of each sample. FTIR demonstrated that connections grew as CoO/P2 O5 levels increased, and the FTIR spectra shifted to higher wavenumbers. The increment of CoO converts non-bridging oxygens associated with phosphate structural units into bridging oxygens. This process increases the concentration of BO4 structural units and creates new, strong and stable bonds B–O–P, i.e., there is polymerization of the boro-phosphate glass network. With an increase in the ratio of CoO/P2 O5 in the produced samples, ultrasonic velocities and elastic moduli were observed to increase. The coefficients of linear and mass attenuation, the transmittance of photons in relation to the photon energy, the efficiency of radiation protection in relation to the photon energy, and the thickness of the absorber were modeled using these two methods (experimental and theoretical). From the obtained values, it can be concluded that the 12Co sample containing 12 mol% will play the most influential role in radiation protection. An increase in the content of cobalt-I oxide led to a significant increase in the linear and mass attenuation coefficient values, which directly contributes to the development of the radiation-protective properties of glass. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This work funding by Deanship of Scientific at Jouf University through research grant no (DSR2020-02-504)

Effect of scattered electrons on the \u27Magic Plate\u27 transmission array detector response

Transmission type detectors can provide a measure of the energy fluence and if they are real-time systems that do not significantly attenuate the radiation beam have a distinct advantage over the current method as Quality Assurance (QA) could in principle be done during the actual patient treatment. The use of diode arrays in QA holds much promise due to real-time operation and feedback when compared to other methods e.g. films which are not real-time. The goal of this work is to describe the characterization of the radiation response of a silicon diode array called the Magic Plate (MP) when operated in transmission mode (MPTM). The response linearity of MPTM was excellent (R2=1). When the MP was placed in linac block tray position; the change in PDD at phantom surface (SSD 100 cm) for a 10 × 10 cm2 was -0.037 %, -0.178 % and -0.949 % for 6 MV, 10 MV and 18 MV beams. Therefore, MP does not provide a significant increase in skin dose to the patient and the percentage depth doses showed an excellent agreement with and without MPTM for 6 MV, 10 MV and 18 MV beams

Radiation response and basic dosimetric characterisation of the \u27Magic Plate\u27

Two Dimensional (2D) silicon diode arrays are often implemented in radiation therapy quality assurance (QA) applications due to their advantages such as: real-time operation (compared to the films), large dynamic range and small size (compared to ionization chambers). The Centre for Medical Radiation Physics, University of Wollongong has developed a multifunctional 2D silicon diode array known as the Magic Plate (MP) for real-time applications and is suitable as a transmission detector for photon flunce mapping (MPTM) or for in phantom dose mapping (MPDM). The paper focusses on the characterisation of the MPDM in terms of output factor and square field beam profiling in 6 MV, 10 MV and 18 MV clinical photon fields. We have found excellent agreement with three different ion chambers for all measured parameters with output factors agreeing within 1.2% and field profiles agreeing within 3% and/or 3mm. This work has important implications for the development of the MP when operating in transmission mapping mode

Optimisation of output factor measurements using the Magic Plate 512 silicon dosimeter array in small megavoltage photon fields

We evaluate the impact of an air gap and optimization of this air gap for the MP512 silicon detector array when operated in dosimetry mode for small photon field measurements in solid water. We present output factor measurements for 6MV and 10 MV photon beams with the square field sizes ranging from 0.5 to 10 cm2. The size of the air gap above the MP512 detector was changed from 0.5, 1.0, 1.2, 2.0 and 2.6 mm. We compare the output factors measurements of the MP512 with EBT3 film and the MOSkin dosimeter. For the two photon energies investigated, we find that the output factor measured by the MP512 reduce with increasing air gap and reducing of field size. The reduction in output factor is most pronounced for the 0.5 and 1 cm2 field sizes. The air gap of 0.5 mm and 1.2 mm showed good agreement with the EBT3 film and MOSkin output factor for 6 and 10 MV photon fields, respectively. The negligible effect on dosimetry for the field sizes larger than 4x4 cm2 demonstrates that the electronic disequilibrium caused by small air gap only influences the dosimetry measurements for small fields. The study shows that the output factor reduction is enhanced by increasing of air gap and demonstrates that the optimal air gap for the MP512 at 6 and 10 MV photon fields is 0.5mm

The effect of an air gap on a 2D monolithic silicon detector for relative dosimetry

Purpose: To evaluate the impact of an air gap on the Magic Plate (MP512) response and optimize this gap for relative dosimetry in photon and electron beams. Materials and methods: MP512 is a 2D monolithic silicon detector manufactured on a p-Type substrate. The array consists of 512 pixels with 0.5 x 0.5 mm2 size and 2 mm pitch with an overall dimension of 52 x 52 mm2. The signal ratio (SR) as a function of beam size and the percentage were measured with MP512 in 6 MV and 10 MV photon beams. The enhanced dynamic wedge (EDW) beam profile measurements were performed for 6 MV photon beams. In this work the signal ratio is defined as the ratio of central axis MP512 reading for field sizes ranging from 0.5 x 0.5 cm2 to 10 x 10 cm2 and for the reference square field of side 10 cm at a depth of 10 cm in solid water phantom. The measurements were performed with an air gap immediately above the detector array of 0.5, 1.0, 1.2, 2.0 and 2.6 mm, respectively. The PDD was measured for field sizes 2x 2 cm2, 5x 5 cm2 and 10x 10 cm2 by scanning the MP512 from the depth of 0.5 cm to 10 cm. The beam profiles were measured for Varian linac enhanced dynamic wedge (EDW) angles of 15, 45 and 60 for field size 5x 5 cm2. The PDD for 6, 12 and 20 MeV electron beams were performed for a standard applicator providing 10x 10 cm2 field size. Results: The signal ratio measured with MP512 reduces with increasing air gap above the detector. The strongest effect of the air gap size was observed for small fields of 0.5x 0.5 cm2 and 1x 1 cm2 while the effect was negligible within ± 2% (1 standard deviation) for field sizes larger than 4x 4 cm2. The signal ratio measured with MP512 with air gaps of 0.5 mm and 1.2 mm showed a good agreement with signal ratio measured with the EBT3 film (within ± 2%) and MOSkinTM for 6 MV and 10 MV, respectively. Similar results were observed for the PDD measurement for field size 5x 5 cm2 and 10x 10 cm2. The PDD measured with M512 was in good agreement with Markus Ionization chamber (IC) within ± 1.6% (1 standard deviation) for 6 MV and ± 1.5% (1 standard deviation) for 10 MV. The PDD discrepancy for 2x 2 cm2 was within ± 3% of the EBT3 for both photon energies. The EDW dose profile matched well with the EBT3 for the air gap of 0.5 mm within ± 2% (1 standard deviation) for all wedge angles. The PDD measured by electron beams demonstrated no significant effect of the air gap size above MP512 for all energies. The results showed similar variations (within ± 3%) compared to Markus IC for both 0.5 mm and 2.6 mm gap. Conclusion: The MP512 diode array was demonstrated to be suitable as an in-phantom dosimeter for QA in small radiation treatment fields. The study shows that air gap size has a significant effect on small field photon beam dosimetry due to a loss of electronic equilibrium. The small air gaps of 0.5 mm and 1.2 mm were the best air gaps for 6 MV and 10 MV, respectively. The effect of the air gap in electron beam fields is not significant due to the fact that an electronic equilibrium is fully established

Synthesis of graphene-based Ag-doped CuFe2O4 composite for improved photocatalytic activity against industrial effluents

Copper ferrite (CuFe2O4, CF) and silver-doped copper ferrite (Ag-CuFe2O4, ACF) were prepared via co-precipitation method. While nano-composite of ACF with rGO was prepared by ultra-sonication approach. Degradation of crystal violet (CV) and benzoic acid (BA) by CF, ACF, and ACF@rGO was conducted under sunlight. Because of tremendous stability and immense surface area of rGO, it shows good ability to transfer electrons during photocatalysis.Band gap for CF and ACF were tuned having values 1.36 and 1.67 eV. Ag-CuFe2O4@rGO has exhibited greater photo-catalytic activity than a bare and doped sample. 82.7% and 48.4% were degradation % of CV and BA by Ag-CuFe2O4@rGO respectively. Ag-CuFe2O4@rGO showed 1.3 times higher efficiency than bare CuFe2O4. ACF was sonicated with rGO and composite was formed which was not reported before and I was the novelty of this paper. The photodegradation ability and cyclic stability etc. was increased after the formation of composite

Impact of a monolithic silicon detector operating in transmission mode on clinical photon beams

Purpose To investigate the effect on surface dose, as a function of different field sizes and distances from the solid water phantom to transmission detector (Dsd), of using the monolithic silicon detector MP512T in transmission mode. Methods The influence of operating the MP512T in transmission mode on the surface dose of a phantom for SSD 100cm was evaluated by using a Markus IC. The MP512T was fixed to an adjustable stand holder and was positioned at different Dsd, ranging from 0.3 to 24 cm. For each Dsd, measurements were carried out for irradiation field sizes of 5 × 5cm2, 8 × 8 cm2 and 10 × 10 cm2. Measurements were obtained under two different operational setups, (i) with the MP512T face-up and (ii) with the MP512T face-down. In addition, the transmission factors for the MP512T and the printed circuit board were only evaluated using a Farmer IC. Results For all Dsd and all field sizes, the MP512T led to the surface dose increasing by less than 25% when in the beam. For Dsd \u3e18 cm the surface dose increase is less than 5%, and negligible for field size 5 × 5 cm2. The difference in the surface dose perturbation for the MP512T operating face up or operating face down is negligible (sd and field sizes. Conclusion The study demonstrated that positioning the MP512T in air between the Linac head and the phantom produced negligible perturbation of the surface dose for Dsd \u3e18 cm, and was completely transparent for 6 MV photon beams

Two-dimensional solid-state array detectors: A technique for in vivo dose verification in a variable effective area

Purpose:We introduce a technique that employs a 2D detector in transmission mode (TM) to verify dose maps at a depth of dmaxin Solid Water. TM measurements, when taken at a different surface‐to‐detector distance (SDD), allow for the area at dmax(in which the dose map is calculated) to be adjusted.Methods:We considered the detector prototype MP512 (an array of 512 diode‐sensitive volumes, 2 mm spatial resolution). Measurements in transmission mode were taken at SDDs in the range from 0.3 to 24 cm. Dose mode (DM) measurements were made at dmaxin Solid Water. We considered radiation fields in the range from 2x2cm2to 10x10 cm2, produced by 6 MV flattened photon beams;we derived a relationship between DM and TM measurements as a function of SDD and field size. The relationship was used to calculate, from TM measurements at 4 and 24 cm SDD, dose maps at dmaxin fields of 1x1cm 2 and 4x4cm2, and in IMRT fields. Calculations were cross‐checked (gamma analysis) with the treatment planning system and with measurements (MP512,films, ionization chamber).Results:In the square fields, calculations agreed with measurements to within±2.36%. In the IMRT fields, using acceptance criteria of 3%/3 mm, 2%/2 mm, 1%/1 mm, calculations had respective gamma passing rates greater than 96.89%,90.50%, 62.20% (for a 4 cm SSD); and greater than 97.22%, 93.80%, 59.00% (for a24 cm SSD). Lower rates (1%/1 mm criterion) can be explained by submillimeter misalignments, dose averaging in calculations, noise artifacts in film dosimetry. Conclusions:It is possible to perform TM measurements at the SSD which produces the best fit between the area at dmaxin which the dose map is calculated and the size of the monitored target

2D mapping of the MV photon fluence and 3D dose reconstruction in real time for quality assurance during radiotherapy treatment

the photon irradiation response of a 2D solid state transmission detector array mounted in a linac block tray is used to reconstruct the projected 2D dose map in a homogenous phantom along rays that diverge from the X-ray source and pass through each of the 121 detector elements. A unique diode response-to-dose scaling factor, applied to all detectors, is utilised in the reconstruction to demonstrate that real time QA during radiotherapy treatment is feasible. Purpose: to quantitatively demonstrate reconstruction of the real time radiation dose from the irradiation response of the 11x11 silicon Magic Plate (MP) detector array operated in Transmission Mode (MPTM). Methods and Materials: in transmission mode the MP is positioned in the block tray of a linac so that the central detector of the array lies on the central axis of the radiation beam. This central detector is used to determine the conversion factor from measured irradiation response to reconstructed dose at any point on the central axis within a homogenous solid water phantom. The same unique conversion factor is used for all MP detector elements lying within the irradiation field. Using the two sets of data, the 2D or 3D dose map is able to be reconstructed in the homogenous phantom. The technique we have developed is illustrated here for different depths and irradiation field sizes, (5 x 5 cm2 to 40 x 40 cm2) as well as a highly non uniform irradiation field. Results: we find that the MPTM response is proportional to the projected 2D dose map measured at a specific phantom depth, the sweet depth . A single factor, for several irradiation field sizes and depths, is derived to reconstruct the dose in the phantom along rays projected from the photon source through each MPTM detector element. We demonstrate that for all field sizes using the above method, the 2D reconstructed and measured doses agree to within ± 2.48% (2 standard deviation) for all in-field MP detector elements. Conclusions: a 2D detector system and method to reconstruct the dose in a homogeneous phantom and in real time has been demonstrated. The success of this work is an exciting development toward real time QA during radiotherapy treatment