24 results on '"Alqathami, Mamdooh"'
Search Results
2. Dose variations caused by setup errors in intracranial stereotactic radiotherapy: A PRESAGE study
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Teng, Kieyin, Gagliardi, Frank, Alqathami, Mamdooh, Ackerly, Trevor, and Geso, Moshi
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- 2014
- Full Text
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3. Novel Multicompartment 3-Dimensional Radiochromic Radiation Dosimeters for Nanoparticle-Enhanced Radiation Therapy Dosimetry
- Author
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Alqathami, Mamdooh, Blencowe, Anton, Yeo, Un Jin, Doran, Simon J., Qiao, Greg, and Geso, Moshi
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- 2012
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- View/download PDF
4. DVH analysis using a transmission detector and model‐based dose verification system as a comprehensive pretreatment QA tool for VMAT plans: Clinical experience and results
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Mohamed Yoosuf, Ahamed B., primary, AlShehri, Salem, additional, Alhadab, Abdulrahman, additional, and Alqathami, Mamdooh, additional
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- 2019
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5. Iron-based radiochromic systems for UV dosimetry applications
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Lee, Hannah J, primary, Alqathami, Mamdooh, additional, Blencowe, Anton, additional, and Ibbott, Geoffrey, additional
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- 2018
- Full Text
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6. Using 3D dosimetry to quantify the Electron Return Effect (ERE) for MR-image-guided radiation therapy (MR-IGRT) applications
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Lee, Hannah J, primary, Won Choi, Gye, additional, Alqathami, Mamdooh, additional, Kadbi, Mo, additional, and Ibbott, Geoffrey, additional
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- 2017
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7. Quantitative 3D Determination of Radiosensitization by Bismuth-Based Nanoparticles
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Alqathami, Mamdooh, primary, Blencowe, Anton, additional, Geso, Moshi, additional, and Ibbott, Geoffrey, additional
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- 2016
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- View/download PDF
8. Feasibility of hydrogel fiducial markers forin vivoproton range verification using PET
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Cho, Jongmin, primary, Campbell, Patrick, additional, Wang, Min, additional, Alqathami, Mamdooh, additional, Mawlawi, Osama, additional, Kerr, Matthew, additional, and Cho, Sang Hyun, additional
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- 2016
- Full Text
- View/download PDF
9. Experimental determination of the influence of oxygen on the PRESAGE®dosimeter
- Author
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Alqathami, Mamdooh, primary, Blencowe, Anton, additional, and Ibbott, Geoffrey, additional
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- 2016
- Full Text
- View/download PDF
10. Gel dosimetry enables volumetric evaluation of dose distributions from an MR-guided linac
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Ibbott, Geoffrey S., primary, Roed, Yvonne, additional, Lee, Hannah, additional, Alqathami, Mamdooh, additional, Wang, Jihong, additional, Pinsky, Lawrence, additional, and Blencowe, Anton, additional
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- 2016
- Full Text
- View/download PDF
11. Evaluation of ultra-sensitive leucomalachite dye derivatives for use in the PRESAGE® dosimeter
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Alqathami, Mamdooh, primary, Adamovics, John, additional, Benning, Ron, additional, Qiao, Greg, additional, Geso, Moshi, additional, and Blencowe, Anton, additional
- Published
- 2013
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- View/download PDF
12. Optimizing the sensitivity and radiological properties of the PRESAGE® dosimeter using metal compounds
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Alqathami, Mamdooh, primary, Blencowe, Anton, additional, Qiao, Greg, additional, Adamovics, John, additional, and Geso, Moshi, additional
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- 2012
- Full Text
- View/download PDF
13. Optimization of the sensitivity and stability of the PRESAGE™ dosimeter using trihalomethane radical initiators
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Alqathami, Mamdooh, primary, Blencowe, Anton, additional, Qiao, Greg, additional, Butler, Duncan, additional, and Geso, Moshi, additional
- Published
- 2012
- Full Text
- View/download PDF
14. Evaluation of ultra-sensitive leucomalachite dye derivatives for use in the PRESAGE® dosimeter
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Alqathami, Mamdooh, Adamovics, John, Benning, Ron, Qiao, Greg, Geso, Moshi, and Blencowe, Anton
- Subjects
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DYES & dyeing , *CHEMICAL derivatives , *DOSIMETERS , *SPECTROPHOTOMETERS , *COMPARATIVE studies , *SENSITIVITY analysis - Abstract
Abstract: In this study we carry out a comparison between the commercially available leucomalachite green (LMG) dye and three newly synthesised derivatives (with either methoxy, chloro or bromo substituents) incorporated into the PRESAGE® dosimeter to determine their effect on the sensitivity and post-response photostability of the dosimeter. In addition, the influence of the new LMG derivatives on the basic radiological properties of the PRESAGE® dosimeter was also investigated. The dosimeters were prepared in spectrophotometric cuvettes, irradiated with a 6MV X-ray beam, and the change in optical density of each dosimeter was measured using a spectrophotometer. For all of the new LMG derivatives investigated, the sensitivity of the resulting dosimeters to radiation dose increased significantly relative to the unmodified LMG dosimeter, and was dependent on the type of LMG derivative used, with the bromo substituted derivative showing the highest increase in sensitivity (450%), followed by chloro and methoxy substituted derivatives (340 and 200%, respectively). Overall, the new LMG derivatives had only a minimal influence on the radiological properties of the PRESAGE® dosimeter, with the exception of the bromo substituted LMG, which increased the effective atomic number (Z eff) of the dosimeter by 9%. All of the LMG dyes investigated showed similar post-response photostability characteristics, with the methoxy substituted LMG showing a slight improvement in post-response photoretention. [Copyright &y& Elsevier]
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- 2013
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15. Optimizing the sensitivity and radiological properties of the PRESAGE® dosimeter using metal compounds
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Alqathami, Mamdooh, Blencowe, Anton, Qiao, Greg, Adamovics, John, and Geso, Moshi
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DOSIMETERS , *METAL compounds , *RADIATION doses , *PHOTON beams , *COMPARATIVE studies , *POLYMERIZATION - Abstract
Abstract: The aim of this study is to investigate the radiation-modifying effects of incorporating commercially available bismuth-, tin- and zinc-based compounds in the composition of the PRESAGE® dosimeter, and the feasibility of employing such compounds for radiation dose enhancement. Furthermore, we demonstrate that metal compounds can be included in the formulation to yield water-equivalent PRESAGE® dosimeters with enhanced dose response. Various concentrations of the metal compounds were added to a newly developed PRESAGE® formulation and the resulting dosimeters were irradiated with 100kV and 6MV photon beams. A comparison between sensitivity and radiological properties of the PRESAGE® dosimeters with and without the addition of metal compounds was carried out. Optical density changes of the dosimeters before and after irradiation were measured using a spectrophotometer. In general, when metal compounds were incorporated in the composition of the PRESAGE® dosimeter, the sensitivity of the dosimeters to radiation dose increased depending on the type and concentration of the metal compound, with the bismuth compound showing the highest dose enhancement factor. In addition, these metal compounds were also shown to improve the retention of the post-response absorption value of the PRESAGE® dosimeter over a period of 2 weeks. Thus, incorporating 1–3mM (ca. 0.2wt%) of any of the three investigated metal compounds in the composition of the PRESAGE® dosimeter is found to be an efficient way to enhance the sensitivity of the dosimeter to radiation dose and stabilize its post-response for longer times. Furthermore, the addition of small amounts of the metal compounds also accelerates the polymerization of the PRESAGE® dosimeter precursors, significantly reducing the fabrication time. Finally, a novel water-equivalent PRESAGE® dosimeter formula optimized with metal compounds is proposed for clinical use in both kilovoltage and megavoltage radiotherapy dosimetry. [Copyright &y& Elsevier]
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- 2012
- Full Text
- View/download PDF
16. Quantitative 3D Determination of Radiosensitization by Bismuth-Based Nanoparticles
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Geoffrey Ibbott, Moshi Geso, M Alqathami, Anton Blencowe, Alqathami, Mamdooh, Blencowe, Anton, Geso, Moshi, and Ibbott, Geoffrey
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Radiation-Sensitizing Agents ,Materials science ,Biomedical Engineering ,Metal Nanoparticles ,Pharmaceutical Science ,Medicine (miscellaneous) ,Nanoparticle ,chemistry.chemical_element ,bismuth-based nanoparticles ,Bioengineering ,Nanotechnology ,02 engineering and technology ,Radiation ,Radiation Dosage ,Ionizing radiation ,Nanomaterials ,Bismuth ,dose enhancement ,03 medical and health sciences ,0302 clinical medicine ,Materials Testing ,Scattering, Radiation ,General Materials Science ,Irradiation ,Radiometry ,Absorption (electromagnetic radiation) ,radiotherapy ,Absorption, Radiation ,021001 nanoscience & nanotechnology ,chemistry ,Colloidal gold ,gold nanoparticles ,030220 oncology & carcinogenesis ,radiosensitization ,0210 nano-technology ,Biomedical engineering - Abstract
The nanoparticle-induced dose enhancement effect has been shown to improve the therapeutic efficacy of ionizing radiation in external beam radiotherapy. Whereas previous studies have focused on gold nanoparticles (AuNPs), no quantitative studies have been conducted to investigate the potential superiority of other high atomic number (Z) nanomaterials such as bismuth-based nanoparticles. The aims of this study were to experimentally validate and quantify the dose enhancement properties of commercially available bismuth-based nanoparticles (bismuth oxide (Bi2O3-NPs) and bismuth sulfide (Bi2S3-NPs)), and investigate their potential superiority over AuNPs in terms of radiation dose enhancement. Phantom cuvettes doped with and without nanoparticles where employed for measuring radiation dose enhancement produced from the interaction of radiation with metal nanoparticles. Novel 3D phantoms were employed to investigate the 3D spatial distribution of ionising radiation dose deposition. The phantoms were irradiated with kilovoltage and megavoltage X-ray beams and optical absorption changes were measured using a spectrophotometer and optical CT scanner. The radiation dose enhancement factors (DEFs) obtained for 50 nm diameter Bi2O3-NPs and AuNPs were 1.90 and 1.77, respectively, for 100 kV energy and a nanoparticle concentration of 0.5 mM. In addition, the DEFs of 5 nm diameter Bi2S3-NPs and AuNPs were determined to be 1.38 and 1.51, respectively, for 150 kV energy and a nanoparticle concentration of 0.25 mM. The results demonstrate that both bismuth-based nanoparticles can enhance the effects of radiation. For 6 MV energy the DEFs for all the investigated nanoparticles were lower (
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- 2016
17. Characterization of novel water-equivalent PRESAGE® dosimeters for megavoltage and kilovoltage x-ray beam dosimetry
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Moshi Geso, Geoffrey Ibbott, M Alqathami, Anton Blencowe, Alqathami, Mamdooh, Blencowe, Anton, Geso, Moshi, and Ibbott, Geoffrey
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Radiation ,Dosimeter ,dosimetry ,medicine.diagnostic_test ,Chemistry ,business.industry ,Attenuation ,Analytical chemistry ,Cuvette ,PRESAGE® ,Spectrophotometry ,3D dosimetry ,Measuring instrument ,medicine ,Dosimetry ,Irradiation ,Absorption (electromagnetic radiation) ,Nuclear medicine ,business ,water equivalency ,Instrumentation - Abstract
In this paper we introduce three novel PRESAGE ® dosimeters referred to as metal optimized dosimeters (MODs) 1, 2 and 3, and determine their sensitivity, as well as their water equivalency. All three formulations contained very small concentrations (0.01 wt%) of metal compounds. The radiological properties were key factors that were considered when designing and formulating the new dosimeters. The dosimeters were prepared in spectrophotometric cuvettes, irradiated with a 6 MV X-ray beam, and the change in optical density of each dosimeter was measured using a spectrophotometer. Results show that all three MOD formulations exhibit radiological properties closer to water than the recently introduced PRESAGE ® dosimeter formulation referred to as formulation A, with mass densities of the novel formulations varying by only 3.9% from that of water, as compared to 5.3% for the commercial formulation. Whereas the novel formulations have almost identical Z eff values to that of water (Z eff = 7.42), the Z eff for the commercial formulation was 3.7% higher than that of water. Comparison of mass energy coefficients for all MOD formulations showed a maximum variation of approximately 0.6 times closer to water especially MOD 3 whereas commercial formulation was 1.23 times larger than water at approximately 40 keV. The same effect was observed fo r mass attenuation coefficients comparison . MOD 3 was also more sensitive to radiation than MOD 1 and 2 as a result of the inclusion of bromine-based halocarbons in the formulation. All novel MOD formulations were comparable to commercial formulation in terms of probability of Compton scatter and pair production compared to water. However, the probability of photoelectric absorption in the three novel MOD formulations varied significantly less (1.3 times greater) from that of water as compared to the commercial formulation (1.8 times greater). Given that all three novel MOD formulations displayed improved radiological properties over any of the currently available PRESAGE ® dosimeter formulations makes them ideal candidates for tissue mimics in dosimetry of clinical megavoltage and kilovoltage x-ray beams.
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- 2015
18. Optimizing the sensitivity and radiological properties of the PRESAGE® dosimeter using metal compounds
- Author
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John Adamovics, Anton Blencowe, Greg G. Qiao, M Alqathami, Moshi Geso, Alqathami, Mamdooh, Blencowe, Anton, Qiao, Greg, Adamovics, John, and Geso, Moshi
- Subjects
metal compounds ,Radiation ,Dosimeter ,dosimetry ,Radiochemistry ,chemistry.chemical_element ,Bismuth ,radiation ,Metal ,chemistry ,visual_art ,visual_art.visual_art_medium ,Dosimetry ,Irradiation ,Tin ,Absorption (electromagnetic radiation) - Abstract
The aim of this study is to investigate the radiation-modifying effects of incorporating commercially available bismuth-, tin- and zinc-based compounds in the composition of the PRESAGE dosimeter, and the feasibility of employing such compounds for radiation dose enhancement. Furthermore, we demonstrate that metal compounds can be included in the formulation to yield water-equivalent PRESAGE dosimeters with enhanced dose response. Various concentrations of the metal compounds were added to a newly developed PRESAGE formulation and the resulting dosimeters were irradiated with 100 kV and 6 MV photon beams. A comparison between sensitivity and radiological properties of the PRESAGE dosimeters with and without the addition of metal compounds was carried out. Optical density changes of the dosimeters before and after irradiation were measured using a spectro- photometer. In general, when metal compounds were incorporated in the composition of the PRESAGE dosimeter, the sensitivity of the dosimeters to radiation dose increased depending on the type and concentration of the metal compound, with the bismuth compound showing the highest dose enhancement factor. In addition, these metal compounds were also shown to improve the retention of the post-response absorption value of the PRESAGE dosimeter over a period of 2 weeks. Thus, incorporating 1-3 mM (ca. 0.2 wt%) of any of the three investigated metal compounds in the composition of the PRESAGE dosimeter is found to be an efficient way to enhance the sensitivity of the dosimeter to radiation dose and stabilize its post-response for longer times. Furthermore, the addition of small amounts of the metal compounds also accelerates the polymerization of the PRESAGE dosimeter precursors, significantly reducing the fabrication time. Finally, a novel water-equivalent PRESAGE dosimeter formula optimized with metal compounds is proposed for clinical use in both kilovoltage and megavoltage radiotherapy dosimetry. Refereed/Peer-reviewed
- Published
- 2012
19. Novel Multicompartment 3-Dimensional Radiochromic Radiation Dosimeters for Nanoparticle-Enhanced Radiation Therapy Dosimetry
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Un Jin Yeo, Greg G. Qiao, M Alqathami, Simon J. Doran, Moshi Geso, Anton Blencowe, Alqathami, Mamdooh, Blencowe, Anton, Yeo, Un Jin, Doran, Simon J, Qiao, Greg, and Geso, Moshi
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Cancer Research ,Cone beam computed tomography ,Polymers ,medicine.medical_treatment ,nanoparticle-enhanced radiation therapy dosimetry ,Linear energy transfer ,Radiation Dosage ,Imaging phantom ,Imaging, Three-Dimensional ,Medicine ,Dosimetry ,Linear Energy Transfer ,Radiology, Nuclear Medicine and imaging ,Irradiation ,Radiometry ,Radiation ,Dosimeter ,Phantoms, Imaging ,business.industry ,Spectrophotometry, Atomic ,Equipment Design ,Cone-Beam Computed Tomography ,Radiation therapy ,Oncology ,Colloidal gold ,Nanoparticles ,Gold ,SMART dosimeter ,business ,Nuclear medicine ,Biomedical engineering - Abstract
Gold nanoparticles (AuNps), because of their high atomic number (Z), have been demonstrated to absorb low-energy X-rays preferentially, compared with tissue, and may be used to achieve localized radiation dose enhancement in tumors. The purpose of this study is to introduce the first example of a novel multicompartment radiochromic radiation dosimeter and to demonstrate its applicability for 3-dimensional (3D) dosimetry of nanoparticle-enhanced radiation therapy.A novel multicompartment phantom radiochromic dosimeter was developed. It was designed and formulated to mimic a tumor loaded with AuNps (50 nm in diameter) at a concentration of 0.5 mM, surrounded by normal tissues. The novel dosimeter is referred to as the Sensitivity Modulated Advanced Radiation Therapy (SMART) dosimeter. The dosimeters were irradiated with 100-kV and 6-MV X-ray energies. Dose enhancement produced from the interaction of X-rays with AuNps was calculated using spectrophotometric and cone-beam optical computed tomography scanning by quantitatively comparing the change in optical density and 3D datasets of the dosimetric measurements between the tissue-equivalent (TE) and TE/AuNps compartments. The interbatch and intrabatch variability and the postresponse stability of the dosimeters with AuNps were also assessed.Radiation dose enhancement factors of 1.77 and 1.11 were obtained using 100-kV and 6-MV X-ray energies, respectively. The results of this study are in good agreement with previous observations; however, for the first time we provide direct experimental confirmation and 3D visualization of the radiosensitization effect of AuNps. The dosimeters with AuNps showed small (3.5%) interbatch variability and negligible (0.5%) intrabatch variability.The SMART dosimeter yields experimental insights concerning the spatial distributions and elevated dose in nanoparticle-enhanced radiation therapy, which cannot be performed using any of the current methods. The authors concluded that it can be used as a novel independent method for nanoparticle-enhanced radiation therapy dosimetry.
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- 2012
20. Experimental determination of the influence of oxygen on the PRESAGE® dosimeter
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Geoffrey S. Ibbott, M Alqathami, Anton Blencowe, Alqathami, Mamdooh, Blencowe, Anton, and Ibbott, Geoffrey
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Materials science ,chemistry.chemical_element ,Oxygen ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Spectrophotometry ,medicine ,Radiology, Nuclear Medicine and imaging ,Irradiation ,Radiometry ,Deoxygenation ,Photons ,Dosimeter ,Radiological and Ultrasound Technology ,medicine.diagnostic_test ,PRESAGE ,business.industry ,Radiochemistry ,Oxygenation ,Cuvette ,chemistry ,030220 oncology & carcinogenesis ,3D dosimetry ,Radical initiator ,oxygenation ,Nuclear medicine ,business - Abstract
It is generally accepted that the PRESAGE(®) radiochromic dosimeter is not sensitive to oxygen, however, this claim has not been supported or verified experimentally. Therefore, the aim of this study was to experimentally determine the potential influence of oxygen on dose sensitivity of the PRESAGE(®) dosimeter and its reporting system. Batches of PRESAGE(®) and its radical initiator-leuco dye reporting system were prepared in aerobic and anaerobic conditions. The anaerobic batches were deoxygenated by bubbling nitrogen through the dosimeter precursors or reporting system for 10 min. The dosimeters and reporting systems were prepared in spectrophotometric cuvettes and glass vials, respectively, and were irradiated with 6 MV photons to various radiation doses. Changes in optical density of the dosimeters and reporting system before and after irradiation were measured using a spectrophotometer. The overall results show that oxygen has some influence on the dosimetric characteristics of PRESAGE(®), although the radical initiator does appear to oxidize the leucomalachite green even in the presence of oxygen. Deoxygenation of the reporting system leads to an increase in sensitivity to radiation dose by ~30% when compared to the non-deoxygenated system. A minor increase in sensitivity (~5%) was also achieved by deoxygenating the PRESAGE(®) precursor prior to casting. In addition, dissolved oxygen measurements revealed low levels of dissolved oxygen (0.40 ± 0.04 mg l(-1)) in the polyurethane precursor used to fabricate the PRESAGE(®) dosimeters, as compared to water (8.60 ± 0.03 mg l(-1)) and the reporting system alone (1.30 ± 0.10 mg l(-1)). The results suggest that the presence of oxygen does not inhibit the radiochromic properties of the PRESAGE(®) system. However, deoxygenation of the dosimeter precursors prior to casting improves the dosimeters dose sensitivity by ~5%, which might be particularly useful for measuring low radiation doses. Nevertheless, we believe this is not sufficient enough to recommend the deoxygenation of commercial PRESAGE(®) precursor prior to casting. In addition, there were no observed changes in the dose linearity, absorption spectrum and post-response photofading characteristics of the PRESAGE(®) under the conditions investigated.
- Published
- 2016
21. Gel dosimetry enables volumetric evaluation of dose distributions from an MR-guided linac
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Y. Roed, Lawrence Pinsky, Jihong Wang, Anton Blencowe, M Alqathami, Geoffrey S. Ibbott, Hannah J. Lee, XIV Mexican Symposium on Medical Physics Mexico City, Mexico 18-21 March 2016, Ibbott, Geoffrey S, Roed, Yvonne, Lee, Hannah, Alqathami, Mamdooh, Wang, Jihong, Pinsky, Lawrence, and Blencowe, Anton
- Subjects
Materials science ,Xylenol orange ,Dosimeter ,dosimetry ,conformal radiation therapy ,business.industry ,medicine.medical_treatment ,medical imaging ,Dose distribution ,Gel dosimetry ,gels ,Linear particle accelerator ,Radiation therapy ,chemistry.chemical_compound ,chemistry ,medicine ,Irradiation ,Nuclear medicine ,business ,polymers ,Mri guided ,Biomedical engineering - Abstract
Magnetic resonance-guided radiation therapy (MRgRT) benefits from performing treatment response assessments at the beginning and end of treatment and also during the treatment itself allowing for more normal tissue sparing and better tumor conformality. Gel dosimeters have been shown to demonstrate 3D dose distributions from conventional treatment units. This qualitative study assessed the value of gel dosimetry to measure volumetric dose distributions delivered by an MR-linac (MRL) while using the MR component for readout. Polymer gels in custom-designed glass cylinders of 5 cm diameter and 4 cm height were obtained from MGS Research Inc. (Madison, CT). In addition, Fricke-type dosimeters were prepared in-house with 0.05 mM xylenol orange. For this preliminary study, the dosimeters were irradiated in air, with a part of each dosimeter outside the treatment field to act as a reference. MR imaging was performed with the MRL to observe the change in paramagnetic properties pre and post irradiation using a T2 sequence for polymer gels and a T1-weighted sequence for Fricke gels. MRI during irradiation was done in the MRL using a fast sequence of TR = 5 ms and TE = 1.7 ms. Spin-spin relaxation rate (R2) maps were generated from the polymer gel images and line profiles across the penumbra were analyzed. R2 has previously been shown to be proportional to absorbed dose. When Fricke dosimeters are exposed to ionizing radiation, ferrous ions are oxidized to ferric ions. The paramagnetic spin changes, which are dependent on the concentrations of ferrous and ferric ion species, were observable on T1-weighted images due to changes in the spin-lattice relaxation rate (R1 = 1/T1). We observed a mean increase in pixel value of 53% from un-irradiated to irradiated regions of about 20 Gy. The increase in pixel value and corresponding dose was visible during irradiation using a fast MR sequence. The polymer gels also responded quickly. At 5 minutes after irradiation, the line profiles on the R2 map through the penumbra region showed the fall-off of the radiation field in both dosimeters. 20 hours after irradiation the polymerization of the gel was presumably completed. The overall signal was both higher on the R2 gray scale maps and more pronounced on the R2 color maps. The line profiles across the penumbra regions exhibited a similar trend for both field edges compared to the profiles at 5 minutes post-irradiation. Over the time frame tested, the dosimeter appears stable. These qualitative results indicate that gel dosimetry offers a promising means of measuring relative volumetric dose distributions delivered by an MR-Linac. Refereed/Peer-reviewed
- Published
- 2016
22. Evaluation of ultra-sensitive leucomalachite dye derivatives for use in the PRESAGE® dosimeter
- Author
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M Alqathami, Greg G. Qiao, John Adamovics, Moshi Geso, Ron Benning, Anton Blencowe, Alqathami, Mamdooh, Adamovics, John, Benning, Ron, Qiao, Greg, Geso, Moshi, and Blencowe, Anton
- Subjects
Radiation ,Dosimeter ,dosimetry ,PRESAGE ,Chemistry ,Radiochemistry ,Radiation dose ,food and beverages ,Optical density ,Leucomalachite green ,Leuco dyes ,Dosimetry ,Irradiation ,Effective atomic number ,radiotherapy ,Ultra sensitive - Abstract
In this study we carry out a comparison between the commercially available leucomalachite green (LMG) dye and three newly synthesised derivatives (with either methoxy, chloro or bromo substituents) incorporated into the PRESAGE dosimeter to determine their effect on the sensitivity and post- response photostability of the dosimeter. In addition, the influence of the new LMG derivatives on the basic radiological properties of the PRESAGEs dosimeter was also investigated. The dosimeters were prepared in spectrophotometric cuvettes, irradiated with a 6 MV X-ray beam, and the change in optical density of each dosimeter was measured using a spectrophotometer. For all of the new LMG derivatives investigated, the sensitivity of the resulting dosimeters to radiation dose increased significantly relative to the unmodified LMG dosimeter, and was dependent on the type of LMG derivative used, with the bromo substituted derivative showing the highest increase in sensitivity (450%), followed by chloro and methoxy substituted derivatives (340 and 200%, respectively). Overall, the new LMG derivatives had only a minimal influence on the radiological properties of the PRESAGE dosimeter, with the exception of the bromo substituted LMG, which increased the effective atomic number (Zeff) of the dosimeter by 9%. All of the LMG dyes investigated showed similar post-response photostability characteristics, with the methoxy substituted LMG showing a slight improvement in post-response photoretention. Refereed/Peer-reviewed
- Published
- 2013
23. Optimization of the sensitivity and stability of the PRESAGE™ dosimeter using trihalomethane radical initiators
- Author
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Greg G. Qiao, D. J. Butler, M Alqathami, Moshi Geso, Anton Blencowe, Alqathami, Mamdooh, Blencowe, Anton, Qiao, Greg, Butler, Duncan, and Geso, Moshi
- Subjects
Radiation ,Chloroform ,Dosimeter ,dosimetry ,Radical ,Radiochemistry ,Iodoform ,radiation ,chemistry.chemical_compound ,chemistry ,Radical initiator ,Dosimetry ,Irradiation ,radical initiators ,Bromoform - Abstract
The aim of this study is to investigate the effect of trihalomethane radical initiators on the radiological properties, radiation dose sensitivity and post response photo-stability of the PRESAGE dosimeter. Different PRESAGE dosimeters containing 50 and 100 mM of iodoform (CHI3), bromoform (CHBr3) or chloroform (CHCl3) radical initiators where fabricated and irradiated with 6 MV photons for a range of radiation doses from 0 to 30 Gy. A comparison between sensitivity and radiological properties of the PRESAGE dosimeters with the different radical initiators was carried out. Optical density changes of the dosimeters before and after irradiation were measured using a spectrophotometer. The incorporation of different radical initiators in the composition of the PRESAGE dosimeter resulted in variation of the radiation dose sensitivity and radiological properties of the dosimeters depending on the type and concentration of the radical initiator used, with iodoform showing the highest dose-response slope followed by bromoform and chloroform. However, at 100 mM iodoform, the effective atomic number was significantly higher than water (Zeff ¼ 16). This enhancement in dose-response was found to be directly related to the carbon-halogen bond dissociation energy and to the radiological properties of each individual radical initiator used in this study. Furthermore, the post-response stability of the PRESAGE dosimeters over two weeks remained stable regardless of the trihalomethane radical initiator employed, with negligible change in the post-response stability and linearity of the PRESAGE dosimeters. Refereed/Peer-reviewed
- Published
- 2012
24. Feasibility of hydrogel fiducial markers for in vivo proton range verification using PET.
- Author
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Cho J, Campbell P, Wang M, Alqathami M, Mawlawi O, Kerr M, and Cho SH
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- Hydrogels radiation effects, Oxygen Isotopes, Fiducial Markers adverse effects, Hydrogels chemistry, Positron-Emission Tomography methods, Protons
- Abstract
Biocompatible/biodegradable hydrogel polymers were immersed in 18O-enriched water and 16O-water to create 18O-water hydrogels and 16O-water hydrogels. In both cases, the hydrogels were made of ~91 wt% water and ~9 wt% polymer. In addition, 5-8 μm Zn powder was suspended in 16O-water and 18O-enriched water and cross-linked with hydrogel polymers to create Zn/16O-water hydrogels (30/70 wt%, ~9 wt% polymer) and Zn/18O-water hydrogels (10/90 wt%), respectively. A block of extra-firm 'wet' tofu (12.3 × 8.8 × 4.9 cm, ρ ≈ 1.05 g cm−3) immersed in water was injected with Zn/16O-water hydrogels (0.9 ml each) at four different depths using an 18-gauge needle. Similarly, Zn/18O-water hydrogels (0.9 ml) were injected into a second tofu phantom. As a reference, both 16O-water hydrogels (1.8 ml) and 18O-water hydrogels (0.9 ml) in Petri dishes were irradiated in a 'dry' environment. The hydrogels in the wet tofu phantoms and dry Petri dishes were scanned via CT and images were used for treatment planning. Then, they were positioned at the proton distal dose fall-off region and irradiated (2 Gy) followed by PET/CT imaging.Notably high PET signals were observed only in 18O-water hydrogels in the dry environment. The visibility of the Zn/16O-water hydrogels injected into the tofu phantom was outstanding in CT images, but these hydrogels provided no noticeable PET signals. The visibility of the Zn/18O-water hydrogels in the wet tofu were excellent on CT and moderate on PET; however, the PET signals were weaker than those in the dry environment, possibly owing to 18O-water leaching out. The hydrogel markers studied here could be used to develop universal PET/CT fiducial markers. Their PET visibility (attributed more to activated 18O-water than Zn) after proton irradiation can be used for proton therapy/range verification. More investigation is needed to slow down the leaching of 18O-water.
- Published
- 2016
- Full Text
- View/download PDF
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