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Showing 24 results for Chi
A.r. Jalilian, B. Fateh, M. Ghergherehchi, A. Karimian, M. Matlloobi,
Volume 1, Issue 1 (6-2003)
Abstract
Backgrounds: Bleomycin (BLM) has been labeled with radioisotopes and widely used in therapy and diagnosis. In this study BLM was labeled with [62Zn] zinc chloride for oncologic PET studies. Materials and methods: The complex was obtained at the pH=2 in normal saline at 90 ° C in 60 min. Radio-TLC showed an overall radiochemical yield of 95-97% (radiochemical purity > 97%). Stability of complex was checked in vitro in mice and human plasma/urine. Results: Preliminary in vivo studies performed to determine complex stability and distribution of [62Zn] BLM in normal and fibrosarcoma-bearing mice. [62Zn] BLM accumulated significantly in induced fibrosarcoma tumors in mice according to bio-distribution/imaging studies. Conclusion: [62Zn] BLM can be used in PET oncology studies due to its suitable physico-chemical properties as a diagnostic complex in vitro and in vivo. Further studies should be performed for evaluation of the complex behavior in higher animals. Iran . J. Radiat. Res., 2003 1(1): 37 - 44.
M. Ghergherehchi, H. Afarideh, M. Ghanadi, A. Mohammadzadeh, M. Esmaeilnezhad,
Volume 6, Issue 3 (12-2008)
Abstract
Background: High and intermediate energy protons are not able to form a track in a solid state nuclear track detector (SSNTD) directly. However, such tracks can be formed through secondary particles created during primary radiation nuclear reactions in a SSNTD. Materials and Methods: The protons with primary energies of 9.6 and 30 MeV available at the cyclotron accelerator with corresponding low LETs of 5.87 and 2.40 keV/μm were taken into consideration. The nuclear tracks etch rate ratio V in CR-39 were measured and transformed into LET spectra for the absorbed and equivalent dose measurements. Results: The optimum etching condition of 6 N NaOH solutions at 65 to 70 ºC over a 6-hour period for the CR-39 were found initially. The corresponding bulk etching rate reached a steady rate of about 0.62 to 1.3 um/h after nine hours for an optimum etching condition. Although the LET was low, but the energy range seemed sufficient enough to create secondary particles with much higher LET through the nuclear reactions in CR-39. The relative absorbed dose contribution of the created secondary particles to the primary particles for the 9.6 and 30 MeV protons in CR-39 at 1 Gy entrance dose were 7.5 and 29.6%, respectively. Conclusion: The contribution of the secondary particle increased relatively with the proton energy decrease. This phenomenon could modify the characteristics of the energy transfer process due to secondary particles when such particles are used for radiobiological studies and/or for radiotherapy. Iran. J. Radiat. Res., 2008 6 (3): 113-120
M. Shourian, Dr. H. Ghourchian,
Volume 12, Issue 4 (10-2014)
Abstract
Background: Hydrogen peroxide (H2O2), produced by gamma ray irradiation to watery solution, was used as an analytical parameter for dosimetry of cobalt-60 (60Co) radiation. Materials and Methods: Detection of the produced H2O2 was carried out using two methods: an amperometric biosensor fabricated by immobilization of anthraquinone 2-carboxylic acid modified horseradish peroxidase on glassy carbon electrode, and chemiluminescence technique using luminol as a fluorophore and diperiodatocuprate as a catalyst. Results: In the first method, at the applied potential of -550 mV (vs. Ag/AgCl) the biosensor showed the sensitivity of 74.46 nA/Gray and detection limit of 0.061 Gray (R.S.D=3.67% for N=3) towards H2O2 produced by 60Co. In the second method, the sensitivity and detection limit for 60Co gamma ray was determined to be 2.34 (luminescence intensity/Gray) and 0.069 Gray (R.S.D=4.16% for N=3), respectively. Conclusion: The obtained results revealed that both proposed techniques, with leaner range from 0.25 to 5 Grays are applicable for detection and dosimetry of gamma ray from 60Co.
Dr. A. Chaparian, H. Karimi Zarchi,
Volume 16, Issue 1 (1-2018)
Abstract
Background: Computed tomography angiography (CTA) scan is a suitable imaging technique to evaluate the blood vessels. However, one major disadvantage is the potential risk of cancer related to ionizing radiation exposure during the procedures. The aim of this investigation was to estimate the risk of exposure induced cancer death (REID) values for some common computed tomography angiography (CTA) scans. Materials and Methods: The scan parameters and patient gender and age were collected for a total of 251 patients undergoing CTA scans of the head (51), carotid (50), abdomen (50), thoracic (50) and the lower extremities (50). The effective diameter, scan length, effective tube current and the dose-length product (DLP) values were obtained for each patient. The organ doses and the effective dose were calculated by the ImpactDose program. The REID values were estimated for the different CTA scans by the calculated organ doses and corresponding age- and sex- specific risk factors. Results: The REID values for the CTA scans of head were 17±4 and 20±3 per million, carotid were 35±9 and 67±14 per million, the lower extremities were 60±26 and 64±24 per million, thoracic were 97±28 and 204±72 per million, and for abdomen were 101±25 and 194±72 per million, for males and females, respectively. Conclusion: The results of this investigation showed that CTA scans are associated with non-negligible risk of exposure induced cancer. A variation in radiation cancer risk as a function of age and gender of the patients was demonstrated and found that the younger female patients were at the highest risk.
Dr. H. Kaizu, M. Hata, S. Takano, T. Kasuya, G. Nishimura, I. Koike, T. Taguchi, N. Oridate,
Volume 16, Issue 3 (7-2018)
Abstract
Background: Using high energy X-rays (>10 MV) as a radiotherapy boost in treating oropharyngeal cancers (OPC) to reduce mandible radiation exposure may result in deterioration of disease control rates due to re-build-up of X-rays at the tumor surface. Therefore, we retrospectively compared the treatment outcomes and toxicities in OPC patients treated with radiotherapy using 15 MV and/or 4–6 MV X-rays as a boost. Materials and Methods: Between 2008 and 2014, 63 OPC patients received definitive 3-dimensional conformal radiotherapy. The median total dose was 70.2 (range, 46.8–75.6) Gy. The median follow-up period for surviving patients was 48 (range, 9–88) months. Twenty-one patients (33.3%) received a boost employing 15 MV X-ray in at least one beam during treatment, and 42 patients (66.7%) received only 4–6 MV X-rays. Local control (LC), locoregional control (LRC), disease-free survival (DFS), overall survival (OS) rates and the incidence of osteoradionecrosis (ORN) in the mandible for the two cohorts were estimated using the Kaplan-Meier method and compared using the log-rank test. Results: There were no statistically significant differences between the two cohorts in either treatment outcomes (3-year LC, 81% versus 75% [p=0.742]; 3-year LRC, 71% versus 71% [p=0.925]; 3-year DFS, 66% versus 66% [p=0.934]; 3-year OS, 65% versus 78% [p=0.321]) or incidence of grade >2 ORN in the mandible (9.5% versus 11.9% [p=0.883]). Conclusion: Employing 15 MV X-rays in a boost may provide comparable treatment outcomes to 4–6 MV X-rays. However, reduction in the incidence of ORN in the mandible was not demonstrated.
Dr M. Ito, T. Kawamura, Y. Mori, T. Mori, A. Takeuchi, Y. Oshima, K. Nakamura, T. Aoyama, N. Kaneda, T. Ishiguchi, S. Mizumatsu,
Volume 16, Issue 4 (10-2018)
Abstract
Background: Several high-precision stereotactic radiation therapy modalities are currently used in clinical settings. We aimed to evaluate whether the CyberKnife (CK) or TrueBeam (TB) radiation treatment systems were more appropriate for treating targets of various morphologies according to the physical properties of each device. Materials and Methods: Spheres (diameter = 5–50 mm), as well as triangular prisms and cubes (length of a side = 10–50 mm), were used as virtual targets for each treatment delivery system. A phantom with dosimetry film was irradiated to evaluate the flatness and gradient of the radiation treatment from each modality. Results: The homogeneity index (HI) for the spherical targets was significantly higher (dose distribution was more homogeneous) using the TB than when using the CK (1.9 vs. 1.4; p = 0.002). There were no significant differences between treatment modalities in the HI for more complex shapes. The HI increased monotonically as the virtual target diameter increased for the CK (p = 0.048). The flatness parameter was lower for the TB than for the CK (1.4 vs. 1.1; p < 0.001). Conclusion: The CK is particularly robust for delivering therapeutic radiation to small targets, while the TB is more suitable for targets with a simple shape or when the HI is a critical treatment factor.
Ph.d K. Yamauchi, Y. Tsutsumi, K. Ichinohe, M. Yoneya, J.i. Komura, T. Ono, K. Tanaka,
Volume 17, Issue 1 (1-2019)
Abstract
Background: The development of methods to alleviate radiation-induced health effects is important for the practical use of radiation therapy and for understanding the molecular mechanisms mediating these effects. Here, we examined the protective capability of N-acetylcysteine (NAC) on life-shortening effects induced by continuous low dose-rate gamma-ray exposure in mice. Materials and Methods: Female B6C3F1 mice were exposed to gamma-rays for 400 days at a dose rate of 20 mGy/day beginning at 8 weeks of age. Control unexposed mice and exposed mice were divided into two groups; the first was provided with regular water, and the second was administered 40 mM NAC during the exposure period. Results: Although NAC administration did not affect the life span of non-irradiated mice (p = 0.232), a 59-days life extension was observed in the exposed group (p = 0.0177). Moreover, radiation exposure and NAC treatment affected body weight. The reduction of body weight observed in NAC treated mice was associated with a reduction in water intake. Conclusion: Our data demonstrated that the life-shortening effects of chronic low dose-rate radiation exposure in mice were alleviated by NAC administration.
P. Haddad, F. Hadjilooei, H.a. Nedaei, Dr. B. Kalaghchi, F. Amouzgar Hashemi, F. Farhan, M. Babaei, M. Esfahani, Sh. Shahriarian,
Volume 17, Issue 1 (1-2019)
Abstract
Background: Breast-conserving surgery (BCS) followed by radiotherapy (RT) is the standard of care for women with breast cancer. Evidence shows that RT dose to the heart can result in ischemic heart disease. In this study we compared 3 different RT techniques were for heart, left anterior descending coronary artery (LAD) and lung doses in left breast cancer patients after breast-conserving surgery. Materials and Methods: Three different plans were designed for each patient using conventional tangential fields, 6+18 MV combination beams, and field-in-field (FIF) technique. These were compared in terms of doses to the planning target volume (PTV), ipsilateral lung, heart and LAD. Results: Forty left breast cancer patients were included in this study. Mean PTV V95% was 95.74% for conventional, 90.45% for FIF and 87.89% for 6+18 MV combination beams (p<0.05). Mean left lung dose was 11.22 Gy for FIF, 12.25 Gy for 6+18 MV and 12.95 Gy for conventional technique (p<0.05). Mean heart dose was 4.52 Gy for FIF, 4.85 Gy for 6+18 MV and 5.13 Gy for conventional technique (p<0.05), and mean D2% for LAD was 40.06, 43.43 and 45.25 Gy (p<0.01) in FIF, 6+18 MV and conventional techniques, respectively.
Conclusion: These results indicated that FIF and 6+18 MV combination techniques significantly reduced the doses received by the heart, LAD and left lung compared to conventional tangential fields, while FIF was superior to 6+18 MV considering the above-mentioned variables. The lower doses to the organs at risk were achieved with a small but statistically significant loss in PTV coverage.
R.h. Zhang, J. Fleckenstein, Y.l. Gao, M.c. Miao, Z.f. Chi, Ph.d. W.w. Bai,
Volume 17, Issue 2 (4-2019)
Abstract
Background: As the volumetric modulated arc therapy (VMAT) becoming a main role of treatment ways, the effect of couch top becomes more significant. It is imperative to re-evaluate the couches that previously may have been considered of no importance during early treatment techniques. The impact of couch top on radiation delivery was explored and the couch model was tested with the aim of reducing the couch absorption influences. Materials and Methods: Attenuation measurements were performed in a cylindrical phantom with an ionization chamber positioned at the isocenter. Couch model was obtained by importing its actual CT scan, and the accuracy was evaluated by comparing percentage deviation at 2 and 5 mm voxel grid size. Effects on surface dose were measured using EBT3 film with the constant SSD at different depths and beam energies at the gantry angle 180° and 0°, respectively. Results: Couch top increases surface dose from 45.9 % to 95.8 % , from 35.0 % to 87.9 % and from 29.2% to 73.9 % for 10 cm ×10 cm field at 6 ,10 and 18 MV, respectively. Due to the couch absorption the case of vertebral metastasis VMAT plan D50 of the PTV changed from 30 Gy to 29.3 Gy. Couch model with uniform electron density of 0.18g/cm3 demonstrated an excellent agreement between measured and TPS computed dose. Conclusion: The treatment couch presence between the patient and beam source significantly alters dose in the patient. Modelling the couch in the Monaco TPS can adequately predict the altered dose distribution.
Phd., B. Rawaa, S. Al Tarabichi ,
Volume 17, Issue 4 (10-2019)
Abstract
Background: Ondo Estimating the health effect of 222Rn progeny deposited on inner surfaces of airways regions is of great interest because 222Rn progeny are considered the major contributors in imparted energy to lung structures. Materials and Methods: In this study, (CT) scan of a healthy, non-smoking Syrian volunteer male, 3D-Slicer 4.7.0 medical image processing software, Solidworks mechanical design software and MCNPX 2.5.B code were used to create the geometry and to evaluate the absorbed fraction and specific energy due to alpha particles emitted by inhaled radon progeny in nuclei and layers of sensitive cells in the epithelium of human trachea-bronchial tree. Absorbed fraction (AF) and specific energy were determined using Micro-dosimetry approach and airway tube wall as proposed by ICRP (1994), and NRC (1991). Results: Absorbed fractions (AFs) and specific energy of alpha particles were calculated for each generation from 1st to 15th. Comparison of average AFs values in sensitive layers was carried out with ICRP66 airway model where some significant differences were found due to dimensions differences between both models. Furthermore, AFs of cell nuclei had the same trend of those for layers, where the highest values were for 7.69 MeV alpha particles in BB region and the opposite in bb region. Conclusion: Interactions of alpha particles with secretory and basal cells show significant differences which can influence dose weightings. Comparisons with ICRP66 data reveal the influence of geometry and target cells distribution on absorbed fraction and specific energy values.
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