Publications by authors named "Moshi Geso"

35 Publications

Measuring the dose in bone for spine stereotactic body radiotherapy.

Phys Med 2021 Apr 25;84:265-273. Epub 2021 Mar 25.

Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia.

Purpose: Current quality assurance of radiotherapy involving bony regions generally utilises homogeneous phantoms and dose calculations, ignoring the challenges of heterogeneities with dosimetry problems likely occurring around bone. Anthropomorphic phantoms with synthetic bony materials enable realistic end-to-end testing in clinical scenarios. This work reports on measurements and calculated corrections required to directly report dose in bony materials in the context of comprehensive end-to-end dosimetry audit measurements (63 plans, 6 planning systems).

Materials And Methods: Radiochromic film and microDiamond measurements were performed in an anthropomorphic spine phantom containing bone equivalent materials. Medium dependent correction factors, k, were established using 6 MV and 10 MV Linear Accelerator Monte Carlo simulations to account for the detectors being calibrated in water, but measuring in regions of bony material. Both cortical and trabecular bony material were investigated for verification of dose calculations in dose-to-medium (D) and dose-to-water (D) scenarios.

Results: For D calculations, modelled correction factors for cortical and trabecular bone in film measurements, and for trabecular bone in microDiamond measurements were 0.875(±0.1%), 0.953(±0.3%) and 0.962(±0.4%), respectively. For D calculations, the corrections were 0.920(±0.1%), 0.982(±0.3%) and 0.993(±0.4%), respectively. In the audit, application of the correction factors improves the mean agreement between treatment plans and measured microDiamond dose from -2.4%(±3.9%) to 0.4%(±3.7%).

Conclusion: Monte Carlo simulations provide a method for correcting the dose measured in bony materials allowing more accurate comparison with treatment planning system doses. In verification measurements, algorithm specific correction factors should be applied to account for variations in bony material for calculations based on D and D.
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http://dx.doi.org/10.1016/j.ejmp.2021.03.011DOI Listing
April 2021

Differential Effects of Gold Nanoparticles and Ionizing Radiation on Cell Motility between Primary Human Colonic and Melanocytic Cells and Their Cancerous Counterparts.

Int J Mol Sci 2021 Jan 31;22(3). Epub 2021 Jan 31.

Discipline of Medical Radiation, School of Health and Biomedical Sciences, RMIT University, Bundoora, VIC 3083, Australia.

This study examined the effects of gold nanoparticles (AuNPs) and/or ionizing radiation (IR) on the viability and motility of human primary colon epithelial (CCD841) and colorectal adenocarcinoma (SW48) cells as well as human primary epidermal melanocytes (HEM) and melanoma (MM418-C1) cells. AuNPs up to 4 mM had no effect on the viability of these cell lines. The viability of the cancer cells was ~60% following exposure to 5 Gy. Exposure to 5 Gy X-rays or 1 mM AuNPs showed the migration of the cancer cells ~85% that of untreated controls, while co-treatment with AuNPs and IR decreased migration to ~60%. In the non-cancerous cell lines gap closure was enhanced by ~15% following 1 mM AuNPs or 5 Gy treatment, while for co-treatment it was ~22% greater than that for the untreated controls. AuNPs had no effect on cell re-adhesion, while IR enhanced only the re-adhesion of the cancer cell lines but not their non-cancerous counterparts. The addition of AuNPs did not enhance cell adherence. This different reaction to AuNPs and IR in the cancer and normal cells can be attributed to radiation-induced adhesiveness and metabolic differences between tumour cells and their non-cancerous counterparts.
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http://dx.doi.org/10.3390/ijms22031418DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7866826PMC
January 2021

Nanoparticle dose enhancement of synchrotron radiation in PRESAGE dosimeters.

J Synchrotron Radiat 2020 Nov 23;27(Pt 6):1590-1600. Epub 2020 Oct 23.

School of Health and Biomedical Sciences, RMIT University, Plenty Road, Bundoora, Victoria 3083, Australia.

The physical absorbed dose enhancement by the inclusion of gold and bismuth nanoparticles fabricated into water-equivalent PRESAGE dosimeters was investigated. Nanoparticle-loaded water-equivalent PRESAGE dosimeters were irradiated with superficial, synchrotron and megavoltage X-ray beams. The change in optical density of the dosimeters was measured using UV-Vis spectrophotometry pre- and post-irradiation using a wavelength of 630 nm. Dose enhancement was measured for 5 nm and 50 nm monodispersed gold nanoparticles, 5-50 nm polydispersed bismuth nanoparticles, and 80 nm monodispersed bismuth nanoparticles at concentrations from 0.25 mM to 2 mM. The dose enhancement was highest for the 95.3 keV mean energy synchrotron beam (16-32%) followed by the 150 kVp superficial beam (12-21%) then the 6 MV beam (2-5%). The bismuth nanoparticle-loaded dosimeters produced a larger dose enhancement than the gold nanoparticle-loaded dosimeters in the synchrotron beam for the same concentration. For the superficial and megavoltage beams the dose enhancement was similar for both species of nanoparticles. The dose enhancement increased with nanoparticle concentration in the dosimeters; however, there was no observed nanoparticle size dependence on the dose enhancement.
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http://dx.doi.org/10.1107/S1600577520012849DOI Listing
November 2020

Samarium doped titanium dioxide nanoparticles as theranostic agents in radiation therapy.

Phys Med 2020 Jun 12;75:69-76. Epub 2020 Jun 12.

Discipline of Medical Radiations, School of Health and Biomedical Sciences, RMIT University, Bundoora, Victoria 3083, Australia.

Purpose: Titanium dioxide nanoparticles (TiO NPs) have been investigated for their role as radiosensitisers for radiation therapy. The study aims to increase the efficiency of these NPs by synthesising them with samarium.

Methods: Samarium-doped TiO NPs (Ti(Sm)O NPs) were synthesised using a solvothermal method. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS) were performed for characterising of the Ti(Sm)O NPs. The intracellular uptake and cytotoxicity were assessed in vitro using A549 and DU145 cancer cell lines. Furthermore, the effect of dose enhancement and generation of reactive oxygen species (ROS) in response to 6 MV X-rays was evaluated. Additionally, the image contrast properties were investigated using computed tomography (CT) images.

Results: The synthesised Ti(Sm)O NPs were about 13 nm in diameter as determined by TEM. The XRD pattern of Ti(Sm)O NPs was consistent with that of anatase-type TiO. EDS confirmed the presence of samarium in the nanoparticles. At 200 μg/ml concentration, no differences in cellular uptake and cytotoxicity were observed between TiO NPs and Ti(Sm)O NPs in both A549 and DU145 cells. However, the combination of Ti(Sm)O NPs and X-rays elicited higher cytotoxic effect and ROS generation in the cells than that with TiO NPs and X-rays. The CT numbers of Ti(Sm)O NPs were systematically higher than that of TiO NPs.

Conclusions: The Ti(Sm)O NPs increased the dose enhancement of MV X-ray beams than that elicited by TiO NPs. Samarium improved the efficiency of TiO NPs as potential radiosensitising agent.
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http://dx.doi.org/10.1016/j.ejmp.2020.06.007DOI Listing
June 2020

Combined Effects of Gold Nanoparticles and Ionizing Radiation on Human Prostate and Lung Cancer Cell Migration.

Int J Mol Sci 2019 Sep 11;20(18). Epub 2019 Sep 11.

Discipline of Medical Radiation, School of Health and Biomedical Sciences, RMIT University, Bundoora 3083, Victoria, Australia.

The effect of 15 nm-sized gold nanoparticles (AuNPs) and/or ionizing radiation (IR) on the migration and adhesion of human prostate (DU145) and lung (A549) cancer cell lines was investigated. Cell migration was measured by observing the closing of a gap created by a pipette tip on cell monolayers grown in 6-well plates. The ratio of the gap areas at 0 h and 24 h were used to calculate the relative migration. The relative migration of cells irradiated with 5 Gy was found to be 89% and 86% for DU145 and A549 cells respectively. When the cells were treated with 1 mM AuNPs this fell to ~75% for both cell lines. However, when the cells were treated with both AuNPs and IR an additive effect was seen, as the relative migration rate fell to ~60%. Of interest was that when the cells were exposed to either 2 or 5 Gy IR, their ability to adhere to the surface of a polystyrene culture plate was significantly enhanced, unlike that seen for AuNPs. The delays in gap filling (cell migration) in cells treated with IR and/or AuNPs can be attributed to cellular changes which also may have altered cell motility. In addition, changes in the cytoskeleton of the cancer cells may have also affected adhesiveness and thus the cancer cell's motility response to IR.
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http://dx.doi.org/10.3390/ijms20184488DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770098PMC
September 2019

On the use of AAA and AcurosXB algorithms for three different stereotactic ablative body radiotherapy (SABR) techniques: Volumetric modulated arc therapy (VMAT), intensity modulated radiation therapy (IMRT) and 3D conformal radiotherapy (3D-CRT).

Rep Pract Oncol Radiother 2019 Jul-Aug;24(4):399-408. Epub 2019 Mar 23.

School of Health & Biomedical Sciences, RMIT University, Victoria, Australia.

Aim: The purpose of this study was to investigate the dosimetric characteristics of three stereotactic ablative body radiotherapy (SABR) techniques using the anisotropic analytical algorithm (AAA) and Acuros XB algorithm. The SABR techniques include coplanar volumetric modulated arc therapy (C-VMAT), non-coplanar intensity modulated radiation therapy (NC-IMRT) and non-coplanar three-dimensional conformal radiotherapy (NC-3D CRT).

Background: SABR is a special type of radiotherapy where a high dose of radiation is delivered over a short time. The treatment outcome and accuracy of the dose delivered to cancer patients highly depend on the dose calculation algorithm and treatment technique.

Materials And Methods: Twelve lung cancer patients underwent 4D CT scanning, and three different treatment plans were generated: C-VMAT, NC-IMRT, NC-3D CRT. Dose calculation was performed using the AAA and Acuros XB algorithm. The dosimetric indices, such as conformity index (CI), homogeneity index, dose fall-off index, doses received by organs at risk and planning target volume, were used to compare the plans. The accuracy of AAA and Acuros XB (AXB) algorithms for the lung was validated against measured dose on a CIRS thorax phantom.

Results: The CIs for C-VMAT, NC-IMRT and NC-3D CRT were 1.21, 1.28 and 1.38 for the AAA, respectively, and 1.17, 1.26 and 1.36 for the Acuros XB algorithm, respectively. The overall dose computed by AcurosXB algorithm was close to the measured dose when compared to the AAA algorithm. The overall dose computed by the AcurosXB algorithm was close to the measured dose when compared to the AAA algorithm.

Conclusion: This study showed that the treatment planning results obtained using the Acuros XB algorithm was better than those using the AAA algorithm in SABR lung radiotherapy.
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http://dx.doi.org/10.1016/j.rpor.2019.02.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6624189PMC
March 2019

Retrospective assessment of a single fiducial marker tracking regimen with robotic stereotactic body radiation therapy for liver tumours.

Rep Pract Oncol Radiother 2019 Jul-Aug;24(4):383-391. Epub 2019 Jun 21.

Division of Radiation Oncology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuou-ku, Kobe City, Hyogo 650-0017, Japan.

Aim: To investigate tumour motion tracking uncertainties in the CyberKnife Synchrony system with single fiducial marker in liver tumours.

Background: In the fiducial-based CyberKnife real-time tumour motion tracking system, multiple fiducial markers are generally used to enable translation and rotation corrections during tracking. However, sometimes a single fiducial marker is employed when rotation corrections are not estimated during treatment.

Materials And Methods: Data were analysed for 32 patients with liver tumours where one fiducial marker was implanted. Four-dimensional computed tomography (CT) scans were performed to determine the internal target volume (ITV). Before the first treatment fraction, the CT scans were repeated and the marker migration was determined. Log files generated by the Synchrony system were obtained after each treatment and the correlation model errors were calculated. Intra-fractional spine rotations were examined on the spine alignment images before and after each treatment.

Results: The mean (standard deviation) ITV margin was 4.1 (2.3) mm, which correlated weakly with the distance between the fiducial marker and the tumour. The mean migration distance of the marker was 1.5 (0.7) mm. The overall mean correlation model error was 1.03 (0.37) mm in the radial direction. The overall mean spine rotations were 0.27° (0.31), 0.25° (0.22), and 0.23° (0.26) for roll, pitch, and yaw, respectively. The treatment time was moderately associated with the correlation model errors and weakly related to spine rotation in the roll and yaw planes.

Conclusions: More caution and an additional safety margins are required when tracking a single fiducial marker.
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http://dx.doi.org/10.1016/j.rpor.2019.06.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6595081PMC
June 2019

Dose response and stability of water equivalent PRESAGE dosimeters for synchrotron radiation therapy dosimetry.

Phys Med Biol 2018 Dec 6;63(23):235027. Epub 2018 Dec 6.

Alfred Health Radiation Oncology, The Alfred, Melbourne, Victoria 3004, Australia. School of Health and Biomedical Sciences, RMIT University, Bundoora, Victoria 3083, Australia. Author to whom any correspondence should be addressed.

This research investigated the dose response and post-irradiation stability of water-equivalent PRESAGE dosimeters exposed to synchrotron radiation. Water-equivalent PRESAGE dosimeters were irradiated up to 1000 Gy in a synchrotron x-ray beam with a mean energy of 95.3 keV. The change in optical density was measured using UV/visible spectrophotometry pre- and post-irradiation using a wavelength of 630 nm. Dose response was found to be approximately linear from 0-200 Gy with saturation occurring above 300 Gy. The post-irradiation stability was determined by measuring the change in optical density at 10, 30, 60, 180, 420 min and 7, 21 and 33 d post-irradiation for three groups of dosimeters stored at different temperatures. Each group had two dosimeters irradiated at 50, 100, 200 and 300 Gy and each group was stored at a different temperature following irradiation: room temperature (22 °C), 4 °C and  -18 °C. The optimal time for readout of the dosimeters varied with the post-irradiation storage temperature. The room temperature group had an optimal time-to-readout of 10 min for maximum signal before fading, while the 4 °C group was reasonably stable from 90 min to 1 week. The  -18 °C group showed the least amount of ongoing post-irradiation development and fading with an optimal readout window from 30 min to 21 d. The intra-batch variation between the mean of each temperature control group was 4.2% at 10 min post-irradiation.
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http://dx.doi.org/10.1088/1361-6560/aaf1f5DOI Listing
December 2018

Effect of scanning parameters on dose-response of radiochromic films irradiated with photon and electron beams.

Heliyon 2018 Oct 17;4(10):e00864. Epub 2018 Oct 17.

Medical Radiation Programme, School of Health Sciences, Universiti Sains Malaysia (Health Campus), Kelantan, Malaysia.

Proper dosimetry settings are crucial in radiotherapy to ensure accurate radiation dose delivery. This work evaluated scanning parameters as affecting factors in reading the dose-response of EBT2 and EBT3 radiochromic films (RCFs) irradiated with clinical photon and electron beams. The RCFs were digitised using Epson Expression 10000XL flatbed scanner and image analyses of net optical density () were conducted using five scanning parameters i.e. film type, resolution, image bit depth, colour to grayscale transformation and image inversion. The results showed that increasing spatial resolution and deepening colour depth did not improve film sensitivity, while grayscale scanning caused sensitivity reduction below than that detected in the Red-channel. It is also evident that invert and colour negative film type selection negated values, hence unsuitable for scanning RCFs. In conclusion, choosing appropriate scanning parameters are important to maintain preciseness and reproducibility in films dosimetry.
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http://dx.doi.org/10.1016/j.heliyon.2018.e00864DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6197593PMC
October 2018

Determination of dose enhancement caused by AuNPs with Xoft Axxent Electronic (eBx™) and conventional brachytherapy: in vitro study.

Int J Nanomedicine 2018 25;13:5733-5741. Epub 2018 Sep 25.

Discipline of Medical Radiation, School of Health and Biomedical Sciences, RMIT University, Bundoora, VIC, Australia,

Purpose: The purpose of this study was to determine dose enhancement (DE) and the possible clinical benefits associated with the inclusion of gold nanoparticles (AuNPs) in cancer cells irradiated by either an Ir brachytherapy source or a Xoft Axxent Electronic (eBx™) Brachytherapy.

Patients And Methods: Brachytherapy DE caused by AuNPs is investigated using two methods, namely Ir and eBx™ Brachytherapy. The second method, which was recently introduced clinically, operates at ~50 kV, which is also the optimal beam energy for DE. In this in vitro study, two cancer cell lines, lung (A549) and prostate (DU145), were used. Cells were incubated with 1 mM (2% w/w) concentration of AuNPs of ~15 nm in size. The control groups were exposed to a range of doses from 0 (control) to 6 Gy, with eBx™ and Ir sources separately. A clonogenic assay was conducted to determine cell survival curves.

Results: High dose enhancement factor (DEF) values were achieved in treated groups with low concentration of AuNPs with the 50 kV energy associated with the eBx™. The DE levels in eBx™ for Du145 and A549 cells were found to be 2.90 and 2.06, respectively. The results showed DEFs measured for the same cell lines using Ir brachytherapy to be 1.67 and 1.54 for Du145 and A549 cancer cells, respectively. This clearly indicates that much higher DE values are obtained in the case of eBx™ X-ray brachytherapy compared to Ir gamma brachytherapy.

Conclusion: The higher DE values obtained with eBx™ compared to Ir brachytherapy can be attributed to the lower average energy of the former and being closer to the optimal energy for DE. This could potentially be utilized by medical practitioners and clinicians to achieve the same tumor control with a significantly lower dose from the eBx™ compared to the Ir brachytherapy treatment, thus bringing huge benefits to the brachytherapy-treated patients.
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http://dx.doi.org/10.2147/IJN.S174624DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6165788PMC
November 2018

Application of the 'Spiking' method to the measurement of low dose radiation (≤ 1Gy) using alanine dosimeters.

Appl Radiat Isot 2018 Mar 10;133:111-116. Epub 2018 Jan 10.

School of Health and Biomedical Sciences, RMIT University, Victoria 3083, Australia. Electronic address:

Alanine dosimeters are limited in radiotherapy by poor sensitivity at low doses (< 5Gy). A set of alanine dosimeters were 'spiked' with a large dose of radiation, (~30Gy, 6MV X-rays) and additional doses ranging between 0.5 and 10Gy. The radical yield was measured by Electron Paramagnetic Resonance (EPR) spectroscopy, and after subtraction of the contribution from the "spike" dose, a linear correlation between the radiation dose and the area of the central EPR signal was obtained for doses between 0.5 and 10Gy (regression value of 0.9890), and for the central peak's amplitude (regression value of 0.9895). Overall, this method is easy to perform, requires no complex EPR signal analysis, and offers much potential to extend the current usage of alanine dosimeters in radiotherapy.
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http://dx.doi.org/10.1016/j.apradiso.2018.01.003DOI Listing
March 2018

Water equivalent PRESAGE for synchrotron radiation therapy dosimetry.

Med Phys 2018 Mar 20;45(3):1255-1265. Epub 2018 Jan 20.

School of Health and Biomedical Sciences, RMIT University, Bundoora, Vic, 3083, Australia.

Purpose: Synchrotron Radiation Therapy techniques are currently being trialed and commissioned at synchrotrons around the world. The patient treatment planning systems (TPS) developed for these treatments use simulated data of the synchrotron x-ray beam to produce the dosimetry in the treatment plan. The purpose of this study was to investigate a water equivalent PRESAGE dosimeter capable of 3D dosimetry over an energy range suitable for synchrotron x-ray beams.

Methods: Water equivalent PRESAGE dosimeters were fabricated with a radiological effective atomic number similar to water over an energy range of 10 keV to 10 MeV. The dosimeters were irradiated at various energies, scanned using optical CT (OCT) scanning and compared to ion chamber measurements. Percentage depth dose and beam profiles of the synchrotron beam were compared to Monte Carlo (MC) model simulations.

Results: The PDD profiles of the water equivalent PRESAGE agreed with ion chamber measurements and MC calculations within 2% for all keV energies investigated. The PRESAGE also showed good agreement to the MC model for depths below 5 mm of the synchrotron beam where ion chamber data do not exist. The spatial resolution of the OCT was not sufficient to accurately measure the penumbra of the synchrotron beams compared to MC calculations or EBT3 film; however, the water equivalent PRESAGE was able to verify dose profile characteristics of the MC model.

Conclusions: The radiological response of a water equivalent PRESAGE dosimeter has been validated for synchrotron x-ray beam energies along with the ability to independently verify dose distributions of a MC model.
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http://dx.doi.org/10.1002/mp.12745DOI Listing
March 2018

Evaluation and Performance of ArcCheck and Film using Gamma Criteria in Pre-treatment Quality Assurance of Stereotactic Ablative Radiotherapy.

J Med Phys 2017 Oct-Dec;42(4):251-257

Medical Radiation Discipline, School of Health and Biomedical Science, RMIT University, Bundoora, Victoria, Australia.

Aim: The aim of this study is to assess the use of ArcCHECK (AC) as an alternative method to replace film dosimetry for pre-treatment quality assurance (QA) of three-dimensional conformal radiation therapy, intensity-modulated radiation therapy (IMRT), and volumetric-modulated arc therapy (VMAT) stereotactic ablative radiotherapy (SABR) treatment plans.

Materials And Methods: Twenty-five patients with a varied diagnosis of lung, spine, sacrum, sternum, ribs, scapula, and femur undergoing SABR were selected for this study. Pre-treatment QA was performed for all the patients using ionization chamber and film dosimetry. Measurements were also carried out on an AC phantom. The planned and measured doses from the AC device and EBT3 films were compared using four different gamma criteria: 2%/2 mm, 3%/2 mm, 3%/1 mm, and 3%/3 mm.

Results: The mean gamma passing rates at 3%/3 mm for all non-spine SABR cases were 98.79 ± 0.96 and 99.27 ± 1.03 with AC and films, respectively. The mean passing rates at 3%/2 mm for AC and films were 98.76 ± 0.42 and 99.43 ± 0.27 respectively for spine VMAT SABR, and 87.15 ± 2.45 and 99.79 ± 0.14 respectively for spine IMRT SABR. In the case of spine tumors, the gamma criterion was tightened due to the proximity of spinal cord to the planning target volume. Our results show that AC provides good results for all VMAT SABR plans.

Conclusion: The AC results at 3%/3 mm were in good agreement with film dosimetry for most cases. We observed a significant reduction in QA time on using AC for SABR QA. This study showed that AC results are comparable to film dosimetry for all studied sites except for spine IMRT SABR.
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http://dx.doi.org/10.4103/jmp.JMP_132_16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5744454PMC
January 2018

Titanium Dioxide Nanoparticles as Radiosensitisers: An and Phantom-Based Study.

Int J Med Sci 2017 15;14(6):602-614. Epub 2017 May 15.

Discipline of Medical Radiations, School of Health and Biomedical Sciences, RMIT University, Bundoora, Victoria, Australia.

Radiosensitisation caused by titanium dioxide nanoparticles (TiO-NPs) is investigated using phantoms (PRESAGE dosimeters) and using two types of cell lines, cultured human keratinocyte (HaCaT) and prostate cancer (DU145) cells. Anatase TiO-NPs were synthesised, characterised and functionalised to allow dispersion in culture-medium for studies and halocarbons (PRESAGE chemical compositions). PRESAGE dosimeters were scanned with spectrophotometer to determine the radiation dose enhancement. Clonogenic and cell viability assays were employed to determine cells survival curves from which the dose enhancement levels "radiosensitisation" are deduced. Comparable levels of radiosensitisation were observed in both phantoms and cells at kilovoltage ranges of x-ray energies (slightly higher . Significant radiosensitisation (~67 %) of control was also noted in cells at megavoltage energies (commonly used in radiotherapy), compared to negligible levels detected by phantoms. This difference is attributed to biochemical effects, specifically the generation of reactive oxygen species (ROS) such as hydroxyl radicals (OH), which are only manifested in aqueous environments of cells and are non-existent in case of phantoms. This research shows that TiO-NPs improve the efficiency of dose delivery, which has implications for future radiotherapy treatments. Literature shows that TiO-NPs can be used as imaging agents hence with these findings renders these NPs as theranostic agents.
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http://dx.doi.org/10.7150/ijms.19058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5479130PMC
March 2018

Information Loss Via Visual Assessment of Radiologic Images Using Modified Version of the Low-Contrast Detailed Phantom at Direct DR System.

J Med Imaging Radiat Sci 2017 Jun 14;48(2):137-143. Epub 2017 Jul 14.

Faculty of Medicine, Department of Radiology, Dammam University, Dammam, Saudi Arabia.

Introduction: Quality in radiology images can be assessed by determining the levels of information retained or lost in an image. Information loss in images has been recently assessed via a method based on information theory and the employment of a contrast-detail (CD) phantom. In this study, the traditional CD phantom (air-Perspex) and a modified CD phantom were used.

Methods: Using the Agfa DX-D 600 digital flat panel system, six phantom radiographs were acquired at 70 kVp and 20 mAs. Three x-ray images were acquired for each phantom.

Results: Our results demonstrate that the material within the CD phantom influences total information loss (TIL) and image quality figure (IQF) measurements. The modified CD phantom provides a more realistic account of TIL and IQF for soft tissue radiology imaging.

Conclusion: It is recommended that a low inherent subject contrast phantom, such as this modified CD phantom, be added to the image quality assessment processes of radiology departments. In addition, use of both IQF and TIL to assess image quality will provide radiology departments with greater evidence on which to base decisions.
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http://dx.doi.org/10.1016/j.jmir.2017.02.069DOI Listing
June 2017

Quantitative 3D Determination of Radiosensitization by Bismuth-Based Nanoparticles.

J Biomed Nanotechnol 2016 Mar;12(3):464-71

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 (< 15%) than with kilovoltage energy.
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http://dx.doi.org/10.1166/jbn.2016.2183DOI Listing
March 2016

Rectal complication probability from composite volumes derived from daily cone beam computed tomography in prostate cancer radiotherapy.

J Cancer Res Ther 2016 Jan-Mar;12(1):374-8

Department of Physical Sciences, Peter MacCallum Cancer Centre, St. Andrew Place, East Melboure, Vic 3002; Bendigo Radiotherapy Centre, Peter MacCallum Cancer Centre, Stewart Street, Vic 3550; School of Med Sciences, RMIT University, Bundoora Campus, Bundoora, Vic 3083, Australia.

Aim: The aim of this study is to investigate the rectal complication probabilities for various rectum volumes with intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) in patients undergoing prostate cancer radiotherapy.

Materials And Methods: Thirteen patients undergoing prostate cancer radiotherapy were consecutively selected for this study. All patients were treated with IMRT to a dose of 78 Gy in 39 fractions. Three different rectum volumes: (i) planned rectum (plan-rectum) (ii) Boolean sum of rectum volume based on the cone-beam computed tomography (CBCT) for first five fractions (planning organ at risk volumes [PRV]-CBCT-5), (iii) Boolean sum of rectum volume from all the CBCTs (PRV-CBCT-All) in addition to an average rectal complication (PRV-CBCT-AV) were used for computing the probabilities of rectal complications. To assess the rectal complications with 3D-CRT, a five-field plan was generated for comparison with IMRT. The Lyman-Kutcher-Burman (LKB) normal tissue complication probability (NTCP) model was used to assess the rectal complications for all of the defined rectal volumes.

Results: The NTCPs for rectum as assessed from plan-rectum, PRV-CBCT-5, PRV-CBCT-All, and PRV-CBCT-AV with IMRT were 9.71% ±4.69%, 16.34% ±9.51%, 19.39% ±9.71%, and 12.81% ±7.22%, respectively. Similarly, with 3D-CRT, the NTCPs were 17.41% ±10.44%, 19.61% ±11.08%, 21.03% ±11.06%, and 17.72% ±10.29%, respectively.

Conclusion: Our results showed that the rectal complications are reduced significantly with IMRT as compared to 3D-CRT. As such, the analyses of NTCP with various defined composite rectum volumes indicate that IMRT requires image-guided adaptive radiotherapy as opposed to 3D-CRT.
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http://dx.doi.org/10.4103/0973-1482.174529DOI Listing
December 2016

Low-Contrast Detail Phantom: Proof of Concept.

J Med Imaging Radiat Sci 2016 Mar 28;47(1):60-65. Epub 2015 Dec 28.

Faculty of Medicine, Department of Radiology, King Abdul-Aziz University Hospital, Jeddah, Saudi Arabia.

Purpose: To investigate the concept of filling the air gaps of the conventional contrast detail phantom (CDP) with various concentrations of contrast media, and to develop a variable level of attenuation-level differential phantoms that could be more appropriate for contrast measurements in some radiology cases.

Methods: Images were acquired using the digital radiography system of the traditional CDP (Perspex/air hole phantom) and the novel form of CDP where the air holes were replaced with attenuating material. In this study, two different attenuating materials were introduced, water and a 30% concentration of iodine-based contrast medium. Image quality was assessed using automated processing to calculate the image quality factor (IQF).

Results And Discussion: Phantom studies indicate that lower contrast levels are obtained when CDP holes are filled with water and a 30% concentration of iodine contrast media than those observed for air/Perspex or traditional CDP. As an example, when a 5-mAs beam is used the IQF values are 5.32 in the case of air filling the holes; however, when these holes are filled with water under the same conditions, the value of the IQF drops to 2.55, and to 2.83 when 30% of contrast media is used. Other concentrations were also tested. These results indicate that it is possible to extend the contrast scale in these phantoms to include ranges that are more realistic for a patient's body than just air and tissue-equivalent material.

Conclusions: These findings indicate that the proposed extension of the contrast scales allows smaller changes in contrast to be discerned. This is due to the small attenuation differences of the subject materials (e.g, 30% contrast liquid and wax) from the traditional form of CDP (material/air). This suggests that the low form of the CDP may have a useful role in assessing image quality in planar radiology as an evaluation tool to better represent low-subject contrast imaging requirements.
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http://dx.doi.org/10.1016/j.jmir.2015.11.001DOI Listing
March 2016

High resolution 3D imaging of synchrotron generated microbeams.

Med Phys 2015 Dec;42(12):6973-86

School of Medical Sciences, RMIT University, Bundoora, Victoria 3083, Australia.

Purpose: Microbeam radiation therapy (MRT) techniques are under investigation at synchrotrons worldwide. Favourable outcomes from animal and cell culture studies have proven the efficacy of MRT. The aim of MRT researchers currently is to progress to human clinical trials in the near future. The purpose of this study was to demonstrate the high resolution and 3D imaging of synchrotron generated microbeams in PRESAGE® dosimeters using laser fluorescence confocal microscopy.

Methods: Water equivalent PRESAGE® dosimeters were fabricated and irradiated with microbeams on the Imaging and Medical Beamline at the Australian Synchrotron. Microbeam arrays comprised of microbeams 25-50 μm wide with 200 or 400 μm peak-to-peak spacing were delivered as single, cross-fire, multidirectional, and interspersed arrays. Imaging of the dosimeters was performed using a nikon a1 laser fluorescence confocal microscope.

Results: The spatial fractionation of the MRT beams was clearly visible in 2D and up to 9 mm in depth. Individual microbeams were easily resolved with the full width at half maximum of microbeams measured on images with resolutions of as low as 0.09 μm/pixel. Profiles obtained demonstrated the change of the peak-to-valley dose ratio for interspersed MRT microbeam arrays and subtle variations in the sample positioning by the sample stage goniometer were measured.

Conclusions: Laser fluorescence confocal microscopy of MRT irradiated PRESAGE® dosimeters has been validated in this study as a high resolution imaging tool for the independent spatial and geometrical verification of MRT beam delivery.
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http://dx.doi.org/10.1118/1.4935410DOI Listing
December 2015

Dose variations caused by setup errors in intracranial stereotactic radiotherapy: a PRESAGE study.

Med Dosim 2014 6;39(4):292-9. Epub 2014 Jun 6.

School of Medical Sciences, RMIT University, Melbourne, Australia. Electronic address:

Stereotactic radiotherapy (SRT) requires tight margins around the tumor, thus producing a steep dose gradient between the tumor and the surrounding healthy tissue. Any setup errors might become clinically significant. To date, no study has been performed to evaluate the dosimetric variations caused by setup errors with a 3-dimensional dosimeter, the PRESAGE. This research aimed to evaluate the potential effect that setup errors have on the dose distribution of intracranial SRT. Computed tomography (CT) simulation of a CIRS radiosurgery head phantom was performed with 1.25-mm slice thickness. An ideal treatment plan was generated using Brainlab iPlan. A PRESAGE was made for every treatment with and without errors. A prescan using the optical CT scanner was carried out. Before treatment, the phantom was imaged using Brainlab ExacTrac. Actual radiotherapy treatments with and without errors were carried out with the Novalis treatment machine. Postscan was performed with an optical CT scanner to analyze the dose irradiation. The dose variation between treatments with and without errors was determined using a 3-dimensional gamma analysis. Errors are clinically insignificant when the passing ratio of the gamma analysis is 95% and above. Errors were clinically significant when the setup errors exceeded a 0.7-mm translation and a 0.5° rotation. The results showed that a 3-mm translation shift in the superior-inferior (SI), right-left (RL), and anterior-posterior (AP) directions and 2° couch rotation produced a passing ratio of 53.1%. Translational and rotational errors of 1.5mm and 1°, respectively, generated a passing ratio of 62.2%. Translation shift of 0.7mm in the directions of SI, RL, and AP and a 0.5° couch rotation produced a passing ratio of 96.2%. Preventing the occurrences of setup errors in intracranial SRT treatment is extremely important as errors greater than 0.7mm and 0.5° alter the dose distribution. The geometrical displacements affect dose delivery to the tumor and the surrounding normal tissues.
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http://dx.doi.org/10.1016/j.meddos.2014.04.005DOI Listing
August 2015

Optimal energy for cell radiosensitivity enhancement by gold nanoparticles using synchrotron-based monoenergetic photon beams.

Int J Nanomedicine 2014 19;9:2459-67. Epub 2014 May 19.

Division of Medical Radiation, School of Medical Sciences, Royal Melbourne Institute of Technology, Bundoora, VIC, NSW, Australia.

Gold nanoparticles have been shown to enhance radiation doses delivered to biological targets due to the high absorption coefficient of gold atoms, stemming from their high atomic number (Z) and physical density. These properties significantly increase the likelihood of photoelectric effects and Compton scattering interactions. Gold nanoparticles are a novel radiosensitizing agent that can potentially be used to increase the effectiveness of current radiation therapy techniques and improve the diagnosis and treatment of cancer. However, the optimum radiosensitization effect of gold nanoparticles is strongly dependent on photon energy, which theoretically is predicted to occur in the kilovoltage range of energy. In this research, synchrotron-generated monoenergetic X-rays in the 30-100 keV range were used to investigate the energy dependence of radiosensitization by gold nanoparticles and also to determine the photon energy that produces optimum effects. This investigation was conducted using cells in culture to measure dose enhancement. Bovine aortic endothelial cells with and without gold nanoparticles were irradiated with X-rays at energies of 30, 40, 50, 60, 70, 81, and 100 keV. Trypan blue exclusion assays were performed after irradiation to determine cell viability. Cell radiosensitivity enhancement was indicated by the dose enhancement factor which was found to be maximum at 40 keV with a value of 3.47. The dose enhancement factor obtained at other energy levels followed the same direction as the theoretical calculations based on the ratio of the mass energy absorption coefficients of gold and water. This experimental evidence shows that the radiosensitization effect of gold nanoparticles varies with photon energy as predicted from theoretical calculations. However, prediction based on theoretical assumptions is sometimes difficult due to the complexity of biological systems, so further study at the cellular level is required to fully characterize the effects of gold nanoparticles with ionizing radiation.
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http://dx.doi.org/10.2147/IJN.S59471DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4038454PMC
December 2014

A study on planning organ at risk volume for the rectum using cone beam computed tomography in the treatment of prostate cancer.

Med Dosim 2014 8;39(1):38-43. Epub 2014 Jan 8.

Radiation Therapy Services, Peter MacCallum Cancer Centre, Melbourne, Australia.

In this study, we analyzed planning organ at risk volume (PRV) for the rectum using a series of cone beam computed tomographies (CBCTs) acquired during the treatment of prostate cancer and evaluated the dosimetric effect of different PRV definitions. Overall, 21 patients with prostate cancer were treated radically with 78Gy in 39 fractions had in total 418 CBCTs, each acquired at the end of the first 5 fractions and then every alternate fraction. The PRV was generated from the Boolean sum volume of the rectum obtained from first 5 fractions (PRV-CBCT-5) and from all CBCTs (PRV-CBCT-All). The PRV margin was compared at the superior, middle, and inferior slices of the contoured rectum to compare PRV-CBCT-5 and PRV-CBCT-All. We also compared the dose received by the planned rectum (Rectum-computed tomography [CT]), PRV-CBCT-5, PRV-CBCT-All, and average rectum (CBCT-AV-dose-volume histogram [DVH]) at critical dose levels. The average measured rectal volume for all 21 patients for Rectum-CT, PRV-CBCT-5, and PRV-CBCT-All was 44.3 ± 15.0, 92.8 ± 40.40, and 121.5 ± 36.7cm(3), respectively. For PRV-CBCT-All, the mean ± standard deviation displacement in the anterior, posterior, right, and left lateral directions in centimeters was 2.1 ± 1.1, 0.9 ± 0.5, 0.9 ± 0.8, and 1.1 ± 0.7 for the superior rectum; 0.8 ± 0.5, 1.1 ± 0.5, 1.0 ± 0.5, and 1.0 ± 0.5 for the middle rectum; and 0.3 ± 0.3; 0.9 ± 0.5; 0.4 ± 0.2, and 0.5 ± 0.3 for the inferior rectum, respectively. The first 5 CBCTs did not predict the PRV for individual patients. Our study shows that the PRV margin is different for superior, middle, and the inferior parts of the rectum, it is wider superiorly and narrower inferiorly. A uniform PRV margin does not represent the actual rectal variations during treatment for all treatment fractions. The large variation in interpatient rectal size implies a potential role for adaptive radiotherapy for prostate cancer.
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http://dx.doi.org/10.1016/j.meddos.2013.09.003DOI Listing
September 2014

Nanoparticle augmented radiation treatment decreases cancer cell proliferation.

Authors:
Moshi Geso

Nanomedicine 2013 Feb 4;9(2):302-3. Epub 2012 Dec 4.

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http://dx.doi.org/10.1016/j.nano.2012.11.003DOI Listing
February 2013

A dose comparison survey in CT departments of dedicated paediatric hospitals in Australia and Saudi Arabia.

World J Radiol 2012 Oct;4(10):431-8

Hussain Al Mohiy, Jenny Sim, Nathan Annabell, Moshi Geso, Giovanni Mandarano, Rob Davidson, Discipline of Medical Radiations, School of Medical Sciences, RMIT University, Bundoora 3083, Australia.

Aim: To measure and compare computed tomography (CT) radiation doses delivered to patients in public paediatric hospitals in Australia and Saudi Arabia.

Methods: Doses were measured for routine CT scans of the head, chest and abdomen/pelvis for children aged 3-6 years in all dedicated public paediatric hospitals in Australia and Saudi Arabia using a CT phantom measurement cylinder.

Results: CT doses, using the departments' protocols for 3-6 year old, varied considerably between hospitals. Measured head doses varied from 137.6 to 528.0 mGy(·)cm, chest doses from 21.9 to 92.5 mGy(·)cm, and abdomen/pelvis doses from 24.9 to 118.0 mGy(·)cm. Mean head and abdomen/pelvis doses delivered in Saudi Arabian paediatric CT departments were significantly higher than those in their Australian equivalents.

Conclusion: CT dose varies substantially across Australian and Saudi Arabian paediatric hospitals. Therefore, diagnostic reference levels should be established for major anatomical regions to standardise dose.
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http://dx.doi.org/10.4329/wjr.v4.i10.431DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3495990PMC
October 2012

Polymer gels impregnated with gold nanoparticles implemented for measurements of radiation dose enhancement in synchrotron and conventional radiotherapy type beams.

Australas Phys Eng Sci Med 2012 Sep 15;35(3):301-9. Epub 2012 Aug 15.

Division of Medical Radiation, School of Medical Sciences, RMIT University, Bundoora, VIC, Australia.

Normoxic type polyacrylamide gel (nPAG) dosimeters are established for dose quantification in three-dimensions for radiotherapy and hence represent an adequate dosimeter for quantification of the dose variation due to the existence of the gold nanoparticles (AuNPs) in the target during irradiation. This work compared the degree of polymerisation in gel doped with nanoparticles (nPAG-AuNP) with control gel samples when irradiated by various sources. Samples were irradiated with a synchrotron radiation source of mean energy 125 keV, 80 kV X-ray beams from superficial therapy machine (SXRT), 6 MV X-rays and 6 MeV electron beams from linear accelerator. Analysis of the dose-response relation was used to determine a dose enhancement factor (DEF) of 1.76 ± 0.34 and 1.64 ± 0.44 obtained for samples irradiated with kilovoltage X-rays energy from synchrotron source and SXRT respectively. Similarly, including AuNPs in gel results in a DEF of approximately 1.37 ± 0.35 when irradiated by an electron beam and 1.14 ± 0.28 for high energy X-ray beams. The results demonstrate the use of AuNPs embedded in polymer gels for measuring the enhancement of radiation caused by metallic nanoparticles.
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http://dx.doi.org/10.1007/s13246-012-0157-xDOI Listing
September 2012

Novel multicompartment 3-dimensional radiochromic radiation dosimeters for nanoparticle-enhanced radiation therapy dosimetry.

Int J Radiat Oncol Biol Phys 2012 Nov 3;84(4):e549-55. Epub 2012 Jul 3.

Discipline of Medical Radiations, The Royal Melbourne Institute of Technology University, Victoria, Australia.

Purpose: 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.

Methods And Materials: 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.

Results: 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.

Conclusions: 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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http://dx.doi.org/10.1016/j.ijrobp.2012.05.029DOI Listing
November 2012

Imaging characteristics of extrapulmonary tuberculosis lesions on dual time point imaging (DTPI) of FDG PET/CT.

J Med Imaging Radiat Oncol 2011 Dec;55(6):556-62

Discipline of Medical Radiations, School of Medical Sciences, Bundoora West Campus, RMIT University, Victoria, Australia.

Introduction: This study aimed to evaluate the diagnostic value of dual time point imaging (DTPI) of 18F-fluorodeoxyglucose (FDG) positron emission tomography/CT (PET/CT) for detecting the infective lesions in patients with extrapulmonary tuberculosis (EPTB).

Methods: Eleven patients were consecutively recruited and evaluated. After the intravenous injection of 369 ± 153 MBq of FDG, all patients underwent FDG PET/CT imaging at two different time points: early scan at 57 ± 23 min and delayed scan at 136 ± 42 min. The maximum standardized uptake values (SUVmax) were recorded for both time points (early scan: SUVmax1 and delayed scan: SUVmax2).

Results: In total, 30 lesions were detected. The SUVmax2 in 22 of the lesions in confirmed EPTB patients were significantly higher than the SUVmax1 (7.9 ± 3.2 vs. 6.8 ± 2.5; P = 0.001). The SUVmax for another eight non-EPTB lesions also showed a significant increasing pattern of change (6.2 ± 2.6 vs. 6.5 ± 2.8; P = 0.044). However, there was insignificant difference between the mean percentage difference of SUVmax (%ΔSUVmax) of EPTB and non-EPTB lesions (P = 0.06).

Conclusion: Our study demonstrates that early whole body PET/CT imaging may be sufficient for the detection of the EPTB lesions and DTPI of PET/CT may also not be a useful technique in differentiating between EPTB and non-EPTB lesions. However, our findings are based on a limited number of patients, and therefore, further investigations in larger series of patients are warranted.
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http://dx.doi.org/10.1111/j.1754-9485.2011.02309.xDOI Listing
December 2011

Quantifying the effects of iodine contrast media on standardised uptake values of FDG PET/CT images: an anthropomorphic phantom study.

Australas Phys Eng Sci Med 2011 Sep 23;34(3):367-74. Epub 2011 Jul 23.

Discipline of Medical Radiations, School of Medical Sciences, Bundoora West Campus, RMIT University, VIC 3083, Australia.

This study aimed to quantify the amount of change in Standardised Uptake Values (SUVs) of PET/CT images by simulating the set-up as closely as possible to the actual patient scanning. The experiments were conducted using an anthropomorphic phantom, which contained an amount of radioactivity in the form of Fluorodeoxyglucose (FDG) in a primary plastic test tube and one litre saline bags, including the insertion of bony structures and another two test tubes containing different concentrations of iodine contrast media. Standard scanning protocols were employed for the PET/CT image acquisition. The highest absolute differences in the SUVmax and SUVmean values of the saline bags were found to be about 0.2 and 0.4, respectively. The primary test tube showed the largest change of 1.5 in both SUVs; SUV max and SUVmean. However, none of these changes were found to be statistically significant. The clinical literature also contains no evidence to suggest that the changes of this magnitude would change the final diagnosis. Based on these preliminary data, we propose that iodine contrast media can be used during the CT scan of PET/CT imaging, without significantly affecting the diagnostic quality of this integrated imaging modality.
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http://dx.doi.org/10.1007/s13246-011-0088-yDOI Listing
September 2011

Evaluation of the effects of gold nanoparticle shape and size on contrast enhancement in radiological imaging.

Australas Phys Eng Sci Med 2011 Jun 5;34(2):243-9. Epub 2011 Apr 5.

School of Medical Sciences, RMIT University, Bundoora, Melbourne, VIC, Australia.

There has been increasing interest in the use of a nanoparticle-based media as a contrast-enhancement agent in medical imaging, particularly with gold Nanoparticles in radiography. Particularly attractive, is the prospect of modifying the surface of these materials with monoclonal antibodies to preferentially bind the nanoparticles to tumour sites. These materials differ from conventional molecular agents in their ability to be modified with cell specificity, or tailored for size and shape for maximum uptake. We investigated the consideration that quantum confinement electronic effects in nanometre-sized metals might have an effect on the integrated photon attenuation of gold atoms; in the same manner as these materials affect X-ray absorption and scattering as seen in X-ray absorption spectroscopy. This experiment has been designed to identify any effect on contrast enhancement that might result from employing gold nanoparticles with a variety of sizes. Spherical particles and nanorods were synthesised for this application. Image contrast enhancement was quantified by contrast-to-noise ratio in computed radiography. Results are consistent with existing measurements of gold nanoparticle contrast enhancement in radiography. No significant variation in attenuation depending on particle size was observed. Findings indicate that nanoparticle-based contrast agents in the size range 4-30 nm-can be synthesised for maximum stability or cell specificity (directed cellular uptake) without consideration of effect of size on contrast enhancement.
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http://dx.doi.org/10.1007/s13246-011-0071-7DOI Listing
June 2011

Enhancement of radiation effects by gold nanoparticles for superficial radiation therapy.

Nanomedicine 2009 Jun;5(2):136-42

Medical Radiation Discipline, School Medical Sciences, RMIT University, Bundoora, Victoria, Australia.

Iodinated contrast agents, which are routinely used to improve contrast in x-ray diagnostic radiography, have been successfully proven to enhance radiation effects in kilovoltage x-ray radiation therapy beams. The studies determined the influence of iodine on the level of radiation biotoxicity to cells as an indicator of the radiation dose enhancement. The use of other high-atomic-number materials such as gold nanoparticles (AuNPs) may also provide advantages in terms of radiation dose enhancement. In this work AuNPs have been used for the enhancement of radiation effects on bovine aortic endothelial cells of superficial x-ray radiation therapy and megavoltage electron radiation therapy beams. Results reveal an increase of cell damage with increasing concentration of AuNPs. At 1 mM concentration of AuNPs, enhancement of radiation peaked at 25 times for a kilovoltage x-ray beam. AuNPs showed similar effects on electron beams but to a lesser extent. This study showed that AuNPs can be used to enhance the effect of radiation doses from kilovoltage x-ray radiation therapy and megavoltage electron radiation therapy beams. In the prevailing clinical circumstances, wherein radiation therapy dose is constrained by normal tissue tolerance, this enhancement could in the future be used to improve local control in superficial x-ray treatments, megavoltage electron beam radiation therapy, microbeam radiation therapy, and intraoperative irradiation using kilovoltage x-rays or megavoltage electron beams. Moreover, the value of this work also stems from the fact that the damage to the endothelial cells lining the highly vasculature structure of tumors deprives tumors of their oxygen and nutrients supply and enhances the efficiency of radiation therapy treatment, where it has been proven that more of the AuNPs injected into animals ends up into the blood than in the tumor.
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http://dx.doi.org/10.1016/j.nano.2009.01.014DOI Listing
June 2009
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