Enhancing electrostatic charge stability of corona charged Teflon electret films for radiation dosimetry by optimizing metal electrode backing material.

Metal electrode backing (MEB) material was found to have a significant role on the electrostatic surface charge stability of Teflon polytetrafluoroethylene (PTFE) electret films. PTFE films of different thicknesses were positively and negatively charged by using our home-made modified point-to-plane corona poling rotating systems. Different MEB materials and thicknesses; aluminum, copper, stainless steel, zinc, silver, and gold were applied. The electrostatic surface charge stability of charged PTFE films was monitored for 200 h at similar storage conditions. Proper MEB material enhances the electrostatic surface charge stability of electret films due to the work function of the metal electrodes and high potential barrier formation at the interface of MEB material and electret film. The studies show that thinner MEB materials provide higher electrostatic surface charge stability in PTFE films. Therefore, thinner MEB material with higher work function is an effective compromise for producing electret films with higher electrostatic surface charge stability. The findings are extremely important for the applications of highly stable electret films for different applications in particular for radiation dosimetry with special regards to radon monitoring.

Classification of radioxenon spectra with deep learning algorithm.

In this study, we propose for the first time a model of classification for Beta-Gamma coincidence radioxenon spectra using a deep learning approach through the convolution neural network (CNN) technique. We utilize the entire spectrum of actual data from a noble gas system in Charlottesville (USX75 station) between 2012 and 2019. This study shows that the deep learning categorization can be done as an important pre-screening method without directly involving critical limits and abnormal thresholds. Our results demonstrate that the proposed approach of combining nuclear engineering and deep learning is a promising tool for assisting experts in accelerating and optimizing the review process of clean background and CTBT-relevant samples with high classification average accuracies of 92% and 98%, respectively.

Optimized Production and Biological Evaluation of 68Ga-PDTMP as a New Agent for PET Bone Scanning.

INTRODUCTION: In this study, 68Ga-PDTMP was introduced as a novel agent for PET bone scanning. METHODS: 68Ga-PDTMP was prepared with radiochemical purity of higher than 98% at the optimized conditions. RESULTS: Stability tests showed no decrease in radiochemical purity, even after 120 min. The capacity binding of 76.3% ± 0.7% after 10 min incubation for 68Ga-PDTMP was observed. CONCLUSION: Biological studies in normal mice demonstrated that most of the remained activity is transmitted from blood into bones. The results show that 68Ga-PDTMP can be considered as a potential radiolabelled complex for PET bone scanning.

Study on a new design of Tehran Research Reactor for radionuclide production based on fast neutrons using MCNPX code.

The aim of this work is to increase the magnitude of the fast neutron flux inside the flux trap where radionuclides are produced. For this purpose, three new designs of the flux trap are proposed and the obtained fast and thermal neutron fluxes compared with each other. The first and second proposed designs were a sealed cube contained air and D2O, respectively. The results of calculated production yield all indicated the superiority of the latter by a factor of 55% in comparison to the first proposed design. The third proposed design was based on changing the surrounding of the sealed cube by locating two fuel plates near that. In this case, the production yield increased up to 70%.

Absorbed doses in humans from 188Re-Rituximab in the free form and bound to superparamagnetic iron oxide nanoparticles: Biodistribution study in mice.

Absorbed doses to human organs from 188Re-Rituximab in the free form and bound to superparamagnetic iron oxide nanoparticles were predicted from results of the radiopharmaceutical biodistribution studies in mice by the RADAR method. Overall, equivalent and effective doses to human organs from the radiopharmaceutical on the nanoparticles were higher because of the enhanced permeability and retention effect. Liver, spleen and kidneys received higher equivalent doses than other organs (5.29, 3.70 and 3.06mSv/MBq, respectively, for the free radiopharmaceutical and 6.12, 3.96 and 3.93mSv/MBq for the drug on the nanoparticles).

Preparation and evaluation of APTES-PEG coated iron oxide nanoparticles conjugated to rhenium-188 labeled rituximab.

Radioimmuno-conjugated (Rhenium-188 labeled Rituximab), 3-aminopropyltriethoxysilane (APTES)-polyethylene glycol (PEG) coated iron oxide nanoparticles were synthesized and then characterized. Therapeutic effect and targeting efficacy of complex were evaluated in CD20 express B cell lines and tumor bearing Balb/c mice respectively. To reach these purposes, superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized using coprecipitation method and then their surface was treated with APTES for increasing retention time of SPIONs in blood circulation and amine group creation. In the next step, N-hydroxysuccinimide (NHS) ester of polyethylene glycol maleimide (NHS-PEG-Mal) was conjugated to the APTES-treated SPIONs. After radiolabeling of Rituximab antibody with Rhenium-188 (T1/2=16.9h) using synthesized N2S4 chelator, it was attached to the APTES-PEG-MAL-SPIONs surface through thiol-maleimide coupling reaction. In vitro evaluation of the 188ReN2S4-Rituximab-SPION-complex thus obtained revealed that at 24 and 48h post-treatment effective cancer cell killing had been achieved. Bio-distribution study in tumor bearing mice showed capability of this complex for targeted cancer therapy. Active and passive tumor targeting strategies were applied through incorporated anti-CD20 (Rituximab) antibody and also enhanced permeability and retention (EPR) effect of solid tumors for nanoparticles respectively.

Triple Therapy of HER2+ Cancer Using Radiolabeled Multifunctional Iron Oxide Nanoparticles and Alternating Magnetic Field.

By using radio-labeled multifunctional superparamagnetic iron oxide nanoparticles (SPIONs) and an alternating magnetic field (AMF), we carried out targeted hyperthermia, drug delivery, radio-immunotherapy (RIT), and controlled chemotherapy of cancer tumors. We synthesized and characterized Indium-111-labeled, Trastuzumab and Doxorubicin (DOX)-conjugated APTES-PEG-coated SPIONs in our previous work. Then, we evaluated their capability in SPECT/MRI (single photon emission computed tomography/magnetic resonance imaging) dual modal molecular imaging, targeting, and controlled release. In this research, AMF was introduced to evaluate therapeutic effects of magnetic hyperthermia on radionuclide-chemo therapy of HER2+ cells and tumor (HER2+)-bearing mice. In vitro and in vivo experiments using synthesized complex were repeated under an AMF (f: 100 KHz, H: 280 Gs). Instead of an intra-tumor injection in most hyperthermia experiments, SPIONs were injected to the tail vein, based on our delivery strategies. For magnetic delivery, we held a permanent Nd-B-Fe magnet near the tumor region. The results showed that simultaneous magnetic hyperthermia enhanced SKBR3 cancer cells, killing by 24%, 28%, 33%, and 80% at 48 hours post-treatment for treated cells with (1) bare SPIONs; (2) antibody-conjugated, DOX-free, surface-modified SPIONs; (3) 111In-labeled, antibody-conjugated surface-modified SPIONs; and (4) 111In-labeled, antibody- and DOX-conjugated surface-modified SPIONs, respectively. Moreover, tumor volume inhibitory rate was 85% after a 28 day period of treatment. By using this method, multimodal imaging-guided, targeted hyperthermia, RIT, and controlled chemotherapy could be achievable in the near future.

Development of an electrochemical 188W/188Re generator as a technique for separation and purification of 188Re in radiopharmaceutical applications.

In this study, a simple electrochemical procedure adaptable for using low specific activity 188W for separation and purification of 188Re from 188W to obtain no carrier added (NCA) 188Re is developed. The electrochemical parameters were optimized to maximize the 188Re electrodeposition yield with minimal 188W contamination. Two cycle electrolysis procedure was developed. The first electrochemical cell was used for separation of 188Re and in the second electrochemical cell, separation and purification of 188Re with >90% deposition yield of 188Re and minimal contamination of 188W (<10-4%) was achieved. The overall electrodeposition yield of 188Re was >90% with >99% radionuclidic purity and >99% radiochemical purity suitable for radiopharmaceutical applications. Furthermore, the performance of the generator remained consistent during a period of 69 days, one half-life of 188W, when the electrochemical separation procedure was performed frequently, at least once in 5 days.

Estimation of human absorbed dose for (166)Ho-PAM: comparison with (166)Ho-DOTMP and (166)Ho-TTHMP.

OBJECTIVE: In this study, the human absorbed dose of holmium-166 ((166)Ho)-pamidronate (PAM) as a potential agent for the management of multiple myeloma was estimated. METHODS: (166)Ho-PAM complex was prepared at optimized conditions and injected into the rats. The equivalent and effective absorbed doses to human organs after injection of the complex were estimated by radiation-absorbed dose assessment resource and methods proposed by Sparks et al based on rat data. The red marrow to other organ absorbed dose ratios were compared with these data for (166)Ho-DOTMP, as the only clinically used (166)Ho bone marrow ablative agent, and (166)Ho-TTHMP. RESULTS: The highest absorbed dose amounts are observed in the bone surface and bone marrow with 1.11 and 0.903 mGy MBq(-1), respectively. Most other organs would receive approximately insignificant absorbed dose. While (166)Ho-PAM demonstrated a higher red marrow to total body absorbed dose ratio than (166)Ho-1,4,7,10-tetraazacyclo dodecane-1,4,7,10 tetra ethylene phosphonic acid (DOTMP) and (166)Ho-triethylene tetramine hexa (methylene phosphonic acid) (TTHMP), the red marrow to most organ absorbed dose ratios for (166)Ho-TTHMP and (166)Ho-PAM are much higher than the ratios for (166)Ho-DOTMP. CONCLUSION: The result showed that (166)Ho-PAM has significant characteristics than (166)Ho-DOTMP and therefore, this complex can be considered as a good agent for bone marrow ablative therapy. ADVANCES IN KNOWLEDGE: In this work, two separate points have been investigated: (1) human absorbed dose of (166)Ho-PAM, as a potential bone marrow ablative agent, has been estimated; and (2) the complex has been compared with (166)Ho-DOTMP, as the only clinically used bone marrow ablative radiopharmaceutical, showing significant characteristics.

Human absorbed dose estimation for a new (175)Yb-phosphonate based on rats data: Comparison with similar bone pain palliation agents.

In this work, the absorbed dose to human organs for (175)Yb-BPAMD was evaluated based on the biodistribution studies in rats. The results showed that the bone surface would receive the highest absorbed dose after injection of (175)Yb-BPAMD with 13.32mGy/MBq, while the other organs receive insignificant absorbed dose. Also, the comparison of (175)Yb-BPAMD with other therapeutic phosphonate complexes demonstrated noticeable characteristics for this new agent. Generally, based on the obtained results, (175)Yb-BPAMD can be considered as a promising agent for bone pain palliative therapy in near future.

Estimation of photoneutron yield in linear accelerator with different collimation systems by Geant4 and MCNPX simulation codes.

At present, the bremsstrahlung photon beams produced by linear accelerators are the most commonly employed method of radiotherapy for tumor treatments. A photoneutron source based on three different energies (6, 10 and 15 MeV) of a linac electron beam was designed by means of Geant4 and Monte Carlo N-Particle eXtended (MCNPX) simulation codes. To obtain maximum neutron yield, two arrangements for the photo neutron convertor were studied: (a) without a collimator, and (b) placement of the convertor after the collimator. The maximum photon intensities in tungsten were 0.73, 1.24 and 2.07 photon/e at 6, 10 and 15 MeV, respectively. There was no considerable increase in the photon fluence spectra from 6 to 15 MeV at the optimum thickness between 0.8 mm and 2 mm of tungsten. The optimum dimensions of the collimator were determined to be a length of 140 mm with an aperture of 5 mm × 70 mm for iron in a slit shape. According to the neutron yield, the best thickness obtained for the studied materials was 30 mm. The number of neutrons generated in BeO achieved the maximum value at 6 MeV, unlike that in Be, where the highest number of neutrons was observed at 15 MeV. Statistical uncertainty in all simulations was less than 0.3% and 0.05% for MCNPX and the standard electromagnetic (EM) physics packages of Geant4, respectively. Differences among spectra in various regions are due to various cross-section and stopping power data and different simulations of the physics processes.

The effect of Mg, Cu and P impurities on dose response of LiF:Mg,Cu,P phosphors: simulation versus experiments.

In this research, the effect of magnesium (Mg), copper (Cu) and phosphorus (P) impurities on dosimetry response of LiF:Mg,Cu,P phosphors is studied experimentally and by the simulation procedure. In the experimental procedure, LiF:Mg,Cu,P phosphors in the powder form were synthesised by chemical co-precipitation method. After annealing at 250°C for 10 min, known amounts of powder were exposed to gamma doses from 0.2 to 1 Gy. The activation energy of the electronic traps for the dosimetric peak at 150°C in LiF:Mg,Cu,P crystalline lattice obtained was 0.69 eV. In the simulation study, the role of stated dopants on electronic and structural properties of LiF crystalline lattice is investigated with the WIEN2 K Code. The activation energies of the electronic and hole traps for the dosimetric peak at the same temperature in LiF:Mg,Cu,P crystalline lattice obtained are 0.75 and 3.1 eV, respectively. It is shown that the experimental results are in agreement with simulation results.

Study of Bone Surface Absorbed Dose in Treatment of Bone Metastases via Selected Radiopharmaceuticals: Using MCNP4C Code and Available Experimental Data.

Bone metastases are major clinical concern that can cause severe problems for patients. Currently, various beta emitters are used for bone pain palliation. This study, describes the process for absorbed dose prediction of selected bone surface and volume-seeking beta emitter radiopharmaceuticals such as (32)P, (89)SrCl2,(90)Y-EDTMP,(153)Sm-EDTMP, (166)Ho-DOTMP, (177)Lu-EDTMP,(186)Re-HEDP, and (188)Re-HEDP in human bone, using MCNP code. Three coaxial sub-cylinders 5 cm in height and 1.2, 2.6, and 7.6 cm in diameter were used for bone marrow, bone, and muscle simulation respectively. The *F8 tally was employed to calculate absorbed dose in the MCNP4C simulations. Results show that with injection of 1 MBq of these radiopharmaceuticals given to a 70 kg adult man, (32)P, (89)SrCl2, and (90)Y-EDTMP radiopharmaceuticals will have the highest amount of bone surface absorbed dose, where beta particles will have the greatest proportion in absorbed dose of bone surface in comparison with gamma radiation. These results demonstrate moderate agreement with available experimental data.

Synthesis, characterization and theranostic evaluation of Indium-111 labeled multifunctional superparamagnetic iron oxide nanoparticles.

Indium-111 labeled, Trastuzumab-Doxorubicin Conjugated, and APTES-PEG coated magnetic nanoparticles were designed for tumor targeting, drug delivery, controlled drug release, and dual-modal tumor imaging. Superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized by thermal decomposition method to obtain narrow size particles. To increase SPIONs circulation time in blood and decrease its cytotoxicity in healthy tissues, SPIONs surface was modified with 3-Aminopropyltriethoxy Silane (APTES) and then were functionalized with N-Hydroxysuccinimide (NHS) ester of Polyethylene Glycol Maleimide (NHS-PEG-Mal) to conjugate with thiolated 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid (PCTA) bifunctional chelator (BFC) and Trastuzumab antibody. In order to tumor SPECT/MR imaging, SPIONs were labeled with Indium-111 (T1/2=2.80d). NHS ester of monoethyl malonate (MEM-NHS) was used for conjugation of Doxorubicin (DOX) chemotherapeutic agent onto SPIONs surface. Mono-Ethyl Malonate allows DOX molecules to be attached to SPIONs via pH-sensitive hydrazone bonds which lead to controlled drug release in tumor region. Active and passive tumor targeting were achieved through incorporated anti-HER2 (Trastuzumab) antibody and EPR effect of solid tumors for nanoparticles respectively. In addition to in vitro assessments of modified SPIONs in SKBR3 cell lines, their theranostic effects were evaluated in HER2 + breast tumor bearing BALB/c mice via biodistribution study, dual-modal molecular imaging and tumor diameter measurements.

In vivo SPECT imaging of tumors by 198,199Au-labeled graphene oxide nanostructures.

Graphene oxide (GO) sheets functionalized by aminopropylsilyl groups (8.0 wt.%) were labeled by (198,199)Au nanoparticle radioisotopes (obtained through reduction of HAuCl4 in sodium citrate solution followed by thermal neutron irradiation) for fast in vivo targeting and SPECT imaging (high purity germanium-spectrometry) of tumors. Using instant thin layer chromatography method, the physicochemical properties of the amino-functionalized GO sheets labeled by (198,199)Au NPs ((198,199)Au@AF-GO) were found to be highly stable enough in organic phases, e.g. a human serum, to be reliably used in bioapplications. In vivo biodistribution of the (198,199)Au@AF-GO composite was investigated in rats bearing fibrosarcoma tumor after various post-injection periods of time. The (198,199)Au@AF-GO nanostructure exhibited a rapid as well as high tumor uptake (with uptake ratio of tumor to muscle of 167 after 4h intravenous injection) that resulted in an efficient tumor targeting/imaging. Meantime, the low lipophilicity of the (198,199)Au@AF-GO caused to its fast excretion (~24 h) throughout the body by the kidneys (as also confirmed by the urinary tract). Because of the short half-life of (198,199)Au radioisotopes, the (198,199)Au@AF-GO with an excellent tumor targeting/imaging and fast washing out from the body can be suggested as one of the most effective and promising nanomaterials in nanotechnology-based cancer diagnosis and therapy.

Prediction of 94mTc production for positron emission tomography studies using the Monte Carlo code MCNPX-2.6.

In this study, a Monte Carlo code was used to simulate a proton beam flux to calculate the (94m)Tc production yield from the (94)Mo(p,n)(94m)Tc reaction. An experimental yield of 3.465 GBq/µAh was measured for 48 min of irradiation at 1µA. An estimated value of 3.048 GBq/µAh was calculated for the yield produced based on the MCNPX proton flux in the same situation. These results demonstrate the usefulness and precision of MCNPX as a tool to design targets for the production of PET radionuclides. The yield of isotopic impurities from the (94)Mo(p,xn)(94g, 93m, 93g)Tc reactions was also calculated by the MCNPX code.

Production, Quality Control and Biological Evaluation of (166)Ho-PDTMP as a Possible Bone Palliation Agent.

OBJECTIVE(S): In this study, (166)Ho-1,2-propylene di-amino tetra(methy1enephosphonicAcid) ((166)Ho-PDTMP) complex was prepared as a bone palliation agent. MATERIALS AND METHODS: The complex was successfully prepared using an in-house synthesized EDTMP ligand and (166)HoCl3. Ho-166 chloride was obtained by thermal neutron irradiation (1 × 1013 n.cm-2.s-1) of natural Ho(NO3)3 samples followed by radiolabeling and stability studies. Biodistribution in wild type rats was also peformed. RESULTS: The complex was prepared with the specific activity of 278 GBq/mg and high radiochemical purity (>99%, checked by ITLC). (166)Ho-PDTMP complex was stabilized in the final preparation and in the presence of human serum (>90%) up to 72 hr. The biodistribution of (166)Ho-PDTMP in wild-type rats demonstrated significant bone uptake was up to 48 hr compared to (166)HoCl3. CONCLUSION: The produced (166)Ho-PDTMP properties suggest a possible new bone palliative therapeutic to overcome the metastatic bone pains.

Influence of ridge filter material on the beam efficiency and secondary neutron production in a proton therapy system.

In this work, the 3D proton dose profile is calculated in a homogenous water phantom using a Monte Carlo application developed with the Geant4 toolkit. The effect of the ridge filter material (for SOBP widths of 6, 9 and 12cm) on the homogeneity of the dose distribution, secondary neutron production and beam efficiency are investigated in a single ring wobbling irradiation system. The energy spectrum of secondary neutrons per primary proton at various locations around the phantom surface is calculated. The simulation revealed that most of the produced neutrons are released at slight angles which enable them to reach the patient and consequently to be hazardous. Also, the homogeneity of the dose distribution at the proximal edge of spread out Bragg peak (SOBP) field is deteriorated due to the scattering of protons in the ridge filter. It is found that for reducing the above mentioned destructive effects, usage of a PMMA ridge filter is better than Al one. For a similar value of 9cm water equivalent thickness, beam widening radius of Al at isocenter is twice of PMMA. Furthermore, for uniform irradiation of the target, the beam efficiency of the system for Al is less than of PMMA and also regarding to the secondary neutron production PMMA is a better choice.

Optimal per cent by weight of elements in diagnostic quality radiation shielding materials.

By increasing the usage of radiation in all aspects of lives, the human body is becoming more exposed to ionising radiation. The purpose of this study is to find the optimal radiation shielding materials to protect humans from the radiation hazards of radiation. Some elements and compounds such as Ag, Bi, Pb, W, BaSO(4) were chosen on the basis of their attenuation coefficients and other characteristics to produce optimised radiation shielding compounds. Multi-objective non-dominated sorting genetic algorithm-II was used to optimise the weight fraction of the elements in compounds based on the dose equivalent rate, shield weight and cost. Consequently, sets of suitable compounds were obtained depending on various applications for energy 0.06 and 0.15 MeV. In addition, optimised lead free compounds were obtained. The results presented in a series of graphs should enable radiation shield designers to choose an appropriate combination according to their requirements.

Proton beam dosimetry: a comparison between a plastic scintillator, ionization chamber and Faraday cup.

In this study, a comparison was made between a plastic scintillator (BC400), a Faraday Cup (FC) and an ionization chamber (IC) used for routine proton dosimetry. Thin scintillators can be applied to proton dosimetry and consequently to proton therapy as relative dosimeters because of their water-equivalent nature, high energy-light conversion efficiency, low dimensions and good proportionality to the absorbed dose at low stopping powers. To employ such scintillators as relative dosimeters in proton therapy, the corrective factors must be applied to correct the quenching luminescence at the Bragg peak. A fine linear proportionality between the luminescence light yield Y and the proton flux in a thin (0.5 mm) scintillator for the 20 and 30 MeV proton beams were observed. The experimental peak/plateau ratios of Bragg Curve for 2, 1 and 0.5 mm scintillators with an accuracy of 0.5% were obtained to be 1.87, 1.91 and 2.30, respectively. With combination of the Markus chamber and the CR-39 detector, the peak/plateau ratio was improved to 3.26. The obtained data of the luminescence yield as a function of the specific energy loss is in agreement with the Craun-Birk's theory. Results show that the FC and Markus ionization chamber are in agreement within 4%, while the FC gives a lower dose evaluation. For a defined beam, the data for the fluence measurements are reproducible within a good accuracy.