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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Nanomedicine Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: Dose Enhancement, Radiation Therapy, Radiosensitization, Nanoparticle,Nano-Cluster
- چکیده:
- چکیده انگلیسی: Objective(s): One major difficulty of conventional radiotherapy is the lack of selectivity between the tumor and the organs at risk. In nanoparticle aided radiotherapy, heavy elements are present at higher concentrations in the tumor than normal tissues. This study aimed to model the characteristics of secondary electrons generated from the interaction of clusters comprised of five different nanoparticles including Gold, Gadolinium, Iridium, Bismuth, and Hafnium atoms with low energy x-rays (similar to brachytherapy sources in terms of energy) as a function of nanoparticle size and beam energy.
Materials and Methods: To better evaluate the contributions of secondary electrons in energy deposition, and also to develop a framework in analyzing further measurements in the future, we attempted to enhance and promote existing mathematical models for energy deposition in endothelial cells by nanoparticle-enhanced radiotherapy. Also, the MCNPX Monte Carlo code was used to model the identical geometry and the dose enhancement factor was calculated for all types of simulated nano-clusters.
Results: Our results showed that for our model consist of a nano-cluster and an endothelial cell the DEF significantly depends on the energy of photons and L- and K-edge binding energy of the atoms inside the nano-cluster. However, for Gd at the energy 60 keV, a higher dose enhancement factor was seen.
Conclusion: It can be concluded that the mathematical model considers the DEF variation with photon energy and the effect of NP type is considered in DEF calculations. However, the MC method has indicated very high sensitivity to photon energy, and NP type compared to the mathematical method.- انتشار مقاله: 15-07-1399
- نویسندگان: Elham Mansouri,Asghar Mesbahi,Parivar Yazdani
- مشاهده
- جایگاه : پژوهشی
- مجله: Nanomedicine Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: Nanoparticles,Nanocomposite,Nuclear Medicine,radiation shielding
- چکیده:
- چکیده انگلیسی: Objective(s): The present study aimed to design new nanoparticle-based shielding materials for photons used in single-photon emission computed tomography and positron emission tomography facilities.
Materials and Methods: Initially, the mass attenuation coefficients and half value layer (HVL) of the composites were comprehensively investigated based on a silicon rubber containing various ratios of micro- and nano-barium sulfate (BaSO4), lead oxide (PbO), and tungsten oxide (WO3) particles at 60, 80, 100, 150, 200, 300, 400, 500, and 600 keV photon energies using the MCNP-X6 Monte Carlo (MC) code and WinXCOM software. In the second stage, the composites composed of 10 wt% and 20 wt% WO3 and PbO particles were constructed in a liquid silicone rubber-based matrix. The mass attenuation coefficients and HVL of the designed shields were experimentally assessed using Cs-137 and Am-241 radioactive sources.
Results: The particles sizes of PbO and WO3 were within the range of 50-200 nanometers. The MC and measurement results indicated that the linear attenuation coefficients of the composites were augmented with the addition of all the studied nano- and micro-particles. However, the PbO composites had more significant shielding properties compared to the BaSO4 and WO3 composites.
Conclusion: According to the results, the nanocomposites had better ability to shield γ-rays at both energies compared to the micro-composites.- انتشار مقاله: 19-03-1399
- نویسندگان: Reza Malekzadeh,Vahid Sadeghi Zali,Okhtay Jahanbakhsh,Murat Okutan,Asghar Mesbahi
- مشاهده
- جایگاه : پژوهشی
- مجله: Nanomedicine Journal
- نوع مقاله: Journal Article
- کلمات کلیدی: CT,MRI,Biomedical applications,Bimodal Imaging,Nanoprobe
- چکیده:
- چکیده انگلیسی: Bimodal imaging combines two imaging modalities in order to benefit from their advantages and compensate the limitations of each modality. This technique could accurately detect diseases for diagnostic purposes. Nanoparticles simultaneously offer diagnostic data via various imaging modalities owing to their unique properties. Moreover, bimodal nanoprobes could be incorporated into theranostic systems for the design of multifunctional agents. Magnetic resonance imaging (MRI) and computed tomography (CT) are frequently used as noninvasive imaging modalities. These powerful, noninvasive diagnostic techniques used for the imaging of soft and hard tissues, respectively. However, MRI has low sensitivity and is not suitable for the imaging of bony structures. On the other hand, low soft tissue contrast is a major limitation of CT. Therefore, the development of various contrast agents that are proper for bimodal MRI/CT nanoprobes could largely influence modern medicine. This review aimed to specifically focus on the imaging properties of bimodal MRI/CT nanoprobes and their biomedical applications.
- انتشار مقاله: 15-05-1398
- نویسندگان: Fatemeh Bakhtiari-Asl,Baharak Divband,Asghar Mesbahi,Nahideh Gharehaghaji
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Medicinal and Chemical Sciences
- نوع مقاله: Journal Article
- کلمات کلیدی: Electromagnetic Field,Female infertility,Nonionizing radiation
- چکیده:
- چکیده انگلیسی: This article presents a review of the published scientific studies on the potential adverse effects of power frequency electromagnetic field (50-60 Hz) from domestic and occupational sources and electric transmission lines on female reproduction system and pregnancy outcome. In this review, publications in English were searched in the ISI Web of Knowledge, PubMed databases and GoogleScholar from January 2000 to December 2017 articles. For ascertaining the reliability of study, data were extracted independently and in duplicate by two investigators. According to some of the conducted studies, environmental exposure to power frequency EMF (electromagnetic field) exposure was found to adversely affect sex hormones, female genital system, embryonic development, pregnancy outcome and fetal and offspring development, while other studies reported no significant effect of power frequency EMF exposure on reproductive parameters and embryonic and fetal development. Overall, the results were not convergent and there was controversy regarding the findings. However, it can be concluded that a part of controversy can be attributed to differences in field strength and exposure time, the experiment condition in terms of in vivo and in vitro which had a significant impact on the observed results.
- انتشار مقاله: 26-09-1397
- نویسندگان: Elham Mansuori,Alireza Alihemmati,Asghar Mesbahi
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Medical Physics
- نوع مقاله: Journal Article
- کلمات کلیدی: modeling,Radiation Therapy,Complications,Acute Esophagitis,Concurrent Chemotherapy
- چکیده:
- چکیده انگلیسی: Introduction: The current study aimed to compare the performance of radiobiological models in predicting acute esophagitis (AE) complications after three-dimensional conformal radiation therapy (3D-CRT).
Material and Methods: Out of a total of 100 patients, 50 patients with concurrent chemotherapy and 50 patients without such therapy were treated with different total doses and a daily dose range of 1.8-2.4 Gy on the basis of 5 days a week for 3 months. Predictions of AE were based on Lyman–Kutcher–Burman (LKB) and equivalent uniform dose (EUD)-based radiobiological models. Consequently, 3 months of follow-upwere performed to monitor the complication incidence among the studied patients. Receiver operating characteristic (ROC) and univariable logistic regression analyses were carried out to determine the effect of mean dose, volume percentage, and weight loss percentage on the probability of AE grade ³ 2.
Results: The EUD-basedmodel showed a better concordance with the clinical data for all patients (area under the curve [AUC]=0.919) and the concurrent chemoradiotherapy (CCRT) group (AUC=0.986). For the radiation therapy group, the LKB model had a better performance than the EUD-based model (AUC=0.921). Grade ³ 2 esophagitis occurred 37.94±4.0 and 68.39±7.1 days after the initiation of radiation therapy in the chemoradiation and radiation therapy groups, respectively.
Conclusion: The EUD-basedmodel showed a higher agreement with the follow-up data. The incidence time of grade ³ 2 AE in the CCRT was approximately two times shorter than that in the non-CCRT group.- انتشار مقاله: 30-02-1398
- نویسندگان: Mostafa Alizade-harakiyan,Amir Ghasemi Jangjoo,Behnam Nasiri,Tohid Jafari-Koshki,Murat Okutan,Asghar Mesbahi
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Medical Physics
- نوع مقاله: Journal Article
- کلمات کلیدی: nanoparticle,Radiation,Attenuation Coefficient Concrete
- چکیده:
- چکیده انگلیسی: Introduction: The present study aimed to evaluate the impact of PbO nano and micro-sized fillers on ordinary and heavy concretes for different photon energies. Material and Methods: The MCNPX Monte Carlo code (version 2.6.0) was used for all simulations in the present study. A model of narrow-beam geometry was validated and utilized to calculate the linear attenuation of samples. Three concentrations of PbO, including the weight of 23%, 37.5%, and 50% were simulated. The nano- and microparticle-loaded concretes were simulated using the Lattice and Universe properties of MCNPX code. Finally, the mass attenuation coefficients of studied concretes were analyzed and compared in this study. Results: Among all the studied concretes, the highest increase of 11% in attenuation coefficient was seen for concretes doped with PbO nanoparticles. The particle size effect was not observed for 18 MeV photon beam, and maximum difference between nano-fillers and micro-fillers was observed for photon energies around 1 MeV. Conclusion: The difference between nano-fillers and micro-fillers was not significant for heavy concretes in comparison to that for ordinary concrete. It is recommended to apply PbO nanoparticles as effective filler in the ordinary concrete composition for providing higher shielding performance.
- انتشار مقاله: 24-02-1398
- نویسندگان: Khatibeh Verdipoor,Asghar Mesbahi
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Medical Physics
- نوع مقاله: Journal Article
- کلمات کلیدی: cancer,Intensity modulated Radiotherapy,Nasopharyngeal,Radiobiology
- چکیده:
- چکیده انگلیسی: Introduction: Radiobiological modeling of radiotherapy plans are used for treatment plan comparisons. The current study aimed to compare the three-dimensional conformal radiation therapy (3DCRT) and intensity-modulated radiation therapy (IMRT) plans for nasopharyngeal cancer using radiobiological modeling.
Materials and Methods: This study was conducted on 10 patients with nasopharyngeal carcinoma, who were planned for 3DCRT and IMRT treatments by using the TiGRT treatment planning system. The planning target volume (PTV) doses of 70 and 72 Gy were administered for the 3DCRT and IMRT plans, respectively. The BIOLPLAN software and the Niemierko’s equivalent uniform dose (EUD) model were utilized for the estimation of tumor control probability (TCP) and normal tissue complication probability (NTCP). The NTCPs of the spinal cord, brain stem, parotid glands, middle ears, temporomandibular joints (TMJ), mandible, and thyroid were calculated by using two radiobiological models.
Results: According to the results, the mean TCPs for 3DCRT and IMRT plans were 89.92%±8.92 and 94.9%±3.86, respectively, showing no statistically significant difference (P=0.08). The NTCPs of the parotid glands, thyroid gland, spinal cord, TMJ, and mandible were considerably lower in the IMRT plans, compared to those in the 3DCRT plans. On the other hand, the calculated NTCPs for the middle ears and brain stem increased for the IMRT plans, which were not statistically significant. On average, the NTCPs of the critical organs were lower based on the EUD model than the Lyman-Kutcher-Burman model.
Conclusion: From the radiobiological point of view, the IMRT plans were significantly advantageous over the 3DCRT plans with some small variations in each patient. On average, the two radiobiological models generated different NTCPs depending on the studied organs. Consequently, more studies are needed for the optimization of radiobiological models for the prediction of the treatment outcomes in radiation therapy.- انتشار مقاله: 21-12-1395
- نویسندگان: Asghar Mesbahi,Naser Rasuli,Behnam Nasiri,Mohammad Mohammadzadeh
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Medical Physics
- نوع مقاله: Journal Article
- کلمات کلیدی: Prostate cancer,image guided radiation therapy,Cone beam computed tomography,volumetric modulated arc therapy
- چکیده:
- چکیده انگلیسی: Introduction: The aim of this retrospective study was to evaluate the variations in delivered dose to the bladder, rectum, and femoral heads of prostate cancer patients during a course of treatment by image-guided radiation therapy (IGRT).
Materials and Methods: Overall, 15 patients with prostate cancer were selected and. Each week, for each patient five consecutive cone beam computed tomography (CBCT) images were taken after bony anatomy alignment by using two orthogonal radiographic images, as well as CBCT images. Dose distributions and dose volume histograms (DVH) for all the original and CBCT plans were obtained. Maximum, as well as mean doses and volumes of the bladder, rectum, and both femoral heads were recorded for each CBCT plan and compared with the original CT plan. For all the studied body parts, the differences in DVH between CBCT plans and original CT plan were calculated and compared.
Results: Considering all the 75 CBCT images for the 15 patients, average of changes in mean doses and volumes were 17.8%, 41.8%, 7.1%, and 36.8% for the bladder and rectum, respectively. There was a significant (P<0.05) negative correlation between mean bladder dose and volume, while a weak and positive correlation was found between mean dose and volume of rectum in our patients.
Conclusion: Our results showed that changes in volumes of the bladder and rectum alter their received inter-factional mean doses. Further attention to the volume variations of the bladder and rectum during a radiotherapy course is recommended for more accurate IGRT treatment.- انتشار مقاله: 14-07-1395
- نویسندگان: Asghar Mesbahi,Dogukan Akcay,Ismail Volkan Tekcan,Zumre Arican Alikus
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Medical Physics
- نوع مقاله: Journal Article
- کلمات کلیدی: Attenuation Coefficient,Monte Carlo method,High-density concrete,radiation shielding
- چکیده:
- چکیده انگلیسی: Introduction: Globally, the need for radiotherapy as a part of cancer management increases every year. Thus, the shielding for megavoltage radiotherapy rooms is of great importance.
Materials and Methods:
In the present study, 14 types of developed high-density concrete with densities ranging from 2.45 to 5.11 were simulated by using Monte Carlo method. The linear attenuation coefficient and the tenth value layer were also calculated. These dosimetric parameters were investigated for megavoltage photon beam spectra for various energies (4, 6, 10, 15, and 18 MeV) of the Varian linac and 60Co gamma rays. The results of simulation were compared with the available published results.
Results:
The results showed that the attenuation of high-energy photons is primarily administered by the atomic number and density of the concrete. Moreover, the variation of attenuation coefficient with density was not completely linear.
Conclusion: It was concluded that the attenuation of high-energy photons not only depends on the density of concrete, but also on the atomic number of its composing elements.
dependent on density of concrete but also on atomic number of composing elements.- انتشار مقاله: 04-07-1395
- نویسندگان: Rezvan Khaldari,Asghar Mesbahi,Umit Kara
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Medical Physics
- نوع مقاله: Journal Article
- کلمات کلیدی: Radiation Therapy,Monte Carlo,Treatment Planning,Convolution,Mall Beamlet
- چکیده:
- چکیده انگلیسی: Introduction
Radiotherapy with small fields is used widely in newly developed techniques. Additionally, dose calculation accuracy of treatment planning systems in small fields plays a crucial role in treatment outcome. In the present study, dose calculation accuracy of two commercial treatment planning systems was evaluated against Monte Carlo method.
Materials and Methods
Siemens Once or linear accelerator was simulated, using MCNPX Monte Carlo code, according to manufacturer’s instructions. Three analytical algorithms for dose calculation including full scatter convolution (FSC) in TiGRT, along with convolution and superposition in XiO system were evaluated for a small solid liver tumor. This solid tumor with a diameter of 1.8 cm was evaluated in a thorax phantom, and calculations were performed for different field sizes (1×1, 2×2, 3×3 and4×4 cm2). The results obtained in these treatment planning systems were compared with calculations by MC method (regarded as the most reliable method).
Results
For FSC and convolution algorithm, comparison with MC calculations indicated dose overestimations of up to 120%and 25% inside the lung and tumor, respectively in 1×1 cm2field size, using an 18 MV photon beam. Regarding superposition, a close agreement was seen with MC simulation in all studied field sizes.
Conclusion
The obtained results showed that FSC and convolution algorithm significantly overestimated doses of the lung and solid tumor; therefore, significant errors could arise in treatment plans of lung region, thus affecting the treatment outcomes. Therefore, use of MC-based methods and super position is recommended for lung treatments, using small fields and beamlets.- انتشار مقاله: 26-11-1393
- نویسندگان: Asghar Mesbahi,Ismail Zergoug
- مشاهده