Gamma radiation shielding properties for polymer composites reinforced with bismuth tungstate in different proportions.

In this study, inorganic compound (Bi2(WO4)3) was added into the composite to improve the radiation shielding properties of polymer composite. A polymer matrix was prepared by combining unsaturated polyester resin with methyl ethyl ketone peroxide and cobalt octoate (6%), and Bi2(WO4)3 was added to this polymer matrix at different ratios as filling material. In order to investigate the gamma radiation attenuation properties of the obtained polymer composites, mass attenuation coefficients, radiation shielding efficiencies, radiation transmission factors, linear attenuation coefficients, half values layer, tenth values layer, mean free path values, effective atomic numbers and effective electron densities parameters were obtained. Experimental studies were carried out with the help of HPGe detector at 22 different energies emitted from 22Na, 54Mn, 57Co, 60Co, 133Ba, 137Cs, 152Eu and 241Am radioactive sources in the photon energy range of 59.5-1408.0 keV. Each obtained experimental result was compared with the theoretical results. It was observed that the sample encoded with BiWO20 is the best radiation shielding material among all studied composites (except 59.5 keV).

A detailed investigation of gamma and neutron shielding capabilities of ternary composites doped with polyacrylonitrile and gadolinium (III) sulfate.

The shielding efficiencies of gamma and neutron radiations for ternary composites containing polyester resin, polyacrylonitrile and gadolinium (III) sulfate at different ratios were investigated in the present study. In order to investigate the gamma radiation shielding capacity of the produced ternary composites, linear and mass attenuation coefficients, half value layer, effective atomic number and radiation protection efficiency parameters were determined experimentally, theoretically and using the GEANT4 simulation code. The gamma shielding capabilities of the composites were studied in the photon energy range of 59.5-1332.5 keV. In order to investigate the neutron shielding abilities of composites, inelastic, elastic, capture and transport numbers, total macroscopic cross section and mean free path parameters were determined with the help of GEANT4 simulation code. In addition, the number of transmitted neutrons at different sample thicknesses and neutron energies were also determined. It was observed that gamma radiation shielding properties were improved due to the increasing amount of gadolinium (III) sulfate and neutron shielding properties were improved due to the increasing amount of polyacrylonitrile. While the composite coded P0Gd50 exhibits a better gamma radiation shielding ability than the others, the neutron shielding of the sample coded P50Gd0 is also more favorable than the others.

A comparative neutron and gamma-ray radiation shielding investigation of molybdenum and boron filled polymer composites.

This work presents a detailed radiation shielding study for polymer composites filled with Boron and Molybdenum additives. The chosen novel polymer composites were produced at different percentages of the additive materials to provide a proper evaluation of their neutron and gamma-ray attenuation abilities. The effect of additive particle size on the shielding characteristics was further investigated. On the gamma-ray side, simulation, theoretical and experimental evaluations were performed in a wide range of photon energies varying from 59.5 keV to 1332.5 keV with help of MC simulations (GEANT4 and FLUKA), WinXCOM code, a High Purity Germanium Detector, respectively. A remarkable consistency was reported between them. On the neutron shielding side, the prepared samples produced with nano and micron particle size additives were additionally examined by providing fast neutron removal cross-section (ΣR) and the simulated neutron transmissions through the prepared samples. The samples filled with nano sized particles show better shielding capability than the one filled with micron sized particles. In other words, a new polymer shielding material that does not contain toxic content is introduced: the sample codded N-B0Mo50 exhibits superior radiation attenuation.

Comparison of Monte Carlo simulations and theoretical calculations of nuclear shielding characteristics of various borate glasses including Bi, V, Fe, and Cd.

The aim of this study is to evaluate both buildup factors and photon attenuation effectiveness of some borate glasses doped by Cd, Fe, V, and Bi. The mass attenuation coefficients (µm) of these glass systems have been calculated via MCNP6 and GEANT4 computer simulation codes over 0.02-10 MeV energy range and compared with the theoretical results of WinXCOM program. And then, half-value layer, (HVL), mean free path (MFP), and effective atomic number (Zeff) for the different content based glasses have been determined. Through G-P fitting process, exposure buildup factors (EBF) have been found in the energy range of 0.015-15 MeV up to 40 mfp. It can be concluded that SrBiO20 glass is alternative material in terms of photon attenuation, respectively.

Novel Cu/Zn Reinforced Polymer Composites: Experimental Characterization for Radiation Protection Efficiency (RPE) and Shielding Properties for Alpha, Proton, Neutron, and Gamma Radiations.

In this study, brass (Cu/Zn) reinforced polymer composites with different proportions of brass powders were fabricated. Different types of nuclear shielding parameters such as mass and linear attenuation coefficients, radiation protection efficiency, half and tenth value layers, and effective atomic number values were determined experimentally and theoretically in the energy range of 0.060-1.408 MeV in terms of gamma-ray shielding capabilities of fabricated polymer composites. A high Purity Germanium detector (HPGe) in conjunction with a Multi-Channel Analyzer (MCA) and twenty-two characteristic gamma-ray energies have been used in the experimental phase. In addition, the exposure and energy absorption buildup factors of reinforced Cu/Zn composites were calculated, and relative dose distribution values were computed to verify them. Proton mass stopping power (ΨP), proton projected range (ΦP), alpha mass stopping power (ΨA), and alpha projected range (ΦA) parameters, which indicate the interactions of the produced composites with charged particle radiation, were investigated. Fast neutron removal cross-section (ΣR) results were determined to give an idea in terms of neutron shielding. According to the obtained results, it is reported that the CuZn20 coded sample's ability to attenuate gamma-ray and charged particle radiation is more efficient than that of other prepared composites. A CuZn05 coded sample was found to be more suitable for neutron shielding capability.

Shielding features, to non-ionizing and ionizing photons, of FeCr-based composites.

This paper has been focused on the a detail study on non-ionizing and ionizing electromagnetic (EM) shielding features and build-up factors of reinforced with ferrochrome (FeCr) composites. The non-inozing electromagnetic shielding performance quantities of composites have been determined in the frequency range between 12.4 and 18.0 GHz. Also, the experimental mass attenuation coefficients (MAC) have been estimated using gamma spectrometer and various radioactive point, and compared to those of theoretical and simulation (MCNPX) results. With help of the obtained linear attenuation coefficients, several attenuation quantities, i.e., effective atomic number (Zeff), half value layer (HVL), and mean free path (MFP) have been discussed. In addition, buildup factors (EBF and EABF) values have been estimated utilizing the G-P fitting method. The results showed that composite encoded FeCr(15%) is superior shielding attenuation properties among the investigated samples.

Determination of Kα,ß excitation factors in thin target for selected elements from Y to Te at 59.54 keV excitation energy.

The paper presents the first measurements of the Kα and Kß excitation factors for some selected elements from Y to Te. To determine the Kα and Kß excitation factors, the experimental values of K shell X-ray production cross sections and total absorption photoelectric cross sections were used. The measurements were performed using a Si(Li) detector coupled with 2048 multichannel analyzer and an Am-241 annular radioisotope source which is emitted 59.54 keV γ-photons. It is observed that the Kα excitation factors are 5-6 times larger than the Kß excitation factors. The measured excitation factors were compared only with theoretical calculated ones since there are no other experimental reports for the present elements in the literature. The present experimental values of Kα and Kß excitation factors are in satisfactory agreement with the theoretical results.

Studies on effective atomic numbers, electron densities from mass attenuation coefficients near the K edge in some samarium compounds.

The effective atomic numbers and electron densities of some samarium compounds were determined using the experimental total mass attenuation coefficient values near the K edge in the X-ray energy range from 36.847 up to 57.142 keV. The measurements, in the region from 36.847 to 57.142 keV, were done in a transmission geometry utilizing the Kα2, Kα1, Kß1 and Kß2 X-rays from different secondary source targets excited by the 59.54 keV gamma-photons from an Am-241 annular source. This paper presents the first measurement of the effective atomic numbers and electron densities for some samarium compounds near the K edge. The results of the study showed that the measured values were in good agreement with the theoretically calculated ones.

Determination of L X-ray fluorescence parameters for Ho, Lu, W, Hg and Bi.

In this work, L X-ray fluorescence cross sections, L sub-shell fluorescence yields and level widths and radiative vacancy transfer probabilities of L sub-shells to Mi, Ni and Oi sub-shells were measured for the elements Ho, Lu, W, Hg and Bi. Energy dispersive X-ray fluorescence (EDXRF) technique was used to measure L X-ray photons. To obtain related parameters, we used 59.54 keV gamma photons of (241)Am radioactive point source. Emitted L X-ray photons from targets were collected by means of a Si(Li) detector with resolution of 180 eV at 5.9 keV. The present results are generally in a good agreement with theoretical calculations and the other results obtained in the literature, within their range considering experimental uncertainty.

The effect of sirolimus in the development of chronic allograft nephropathy.

PURPOSE: The effect of sirolimus (SRL) in renal function was studied in renal transplant recipients. PATIENTS AND METHODS: We studied 20 patients who underwent live related kidney transplantation 1 to 2 years prior under cyclosporine (CsA) treatment and displayed serum creatinine values between 2 and 3 mg/dL. The patients were randomized into 2 groups prospectively. The calcineurin inhibitors (CNI) group continued taking CsA; the SRL group underwent a switch from CsA to SRL. Biopsies were performed to assess chronic allograft nephropathy (CAN) findings and TGFbeta1 in the transplanted kidneys at the beginning and the end of the study. Creatinine clearance, serum creatinine, and proteinuria values were detected in the beginning as well as at 1, 3, 6, and 12 months later. RESULTS: At the beginning of the study, the creatinine clearance and serum creatinine levels were 52.21 mL/min and 2.05 mg/dL in the CNI group and 47.76 mL/min and 2.13 mg/dL in the SRL group, respectively. At 12 months, these values were 48.11 mL/min and 2.57 mg/dL in the CNI group and 50.45 mL/min and 2.12 mg/dL in the SRL group, respectively. Creatinine clearance values between the 2 groups at 12 months were statistically different. Although it was not significant, there was a tendency toward decreases inflammatory infiltration and TGFbeta1 levels in the SRL group compared with the CNI group on the second biopsies. CONCLUSION: Pathologic findings of CAN development, serum creatinine, and creatinine clearance values were ameliorated in the SRL group. We concluded that SRL positively affected long-term graft survival.

Open versus laparoscopic donor nephrectomy in live related renal transplantation.

BACKGROUND: This analysis sought to evaluate the efficiency and safety of laparoscopic nephrectomy (LDN) for the donor, the recipient, and the graft. LDN seems to have advantages over the open donor nephrectomy (ODN) in length of hospital stay, postoperative comfort, and pain control. METHODS: The results of 40 patients who underwent LDN between October 2000 and September 2003 were compared to those of 40 ODN patients just preceding the LDN patients. Eight laparoscopy patients required conversion to an open procedure due to bleeding (4; two major and two minor), technical problems with the instrument (n = 1) and difficulty in the dissection (n = 3). RESULTS: The demographic data, percentages of right and left nephrectomy, number of vessels, rates of acute rejection episodes, as well as the rates of urologic and vascular complications were similar between the two groups. The time of hospital stay was shorter, and the duration of the operation and of the warm ischemia time were significantly longer for the LDN group. The postoperative decline in serum creatinine levels were similar for the two groups. Graft survival rates were 91.7% at both the first and third years in the LDN group; 92.5% and 87.0% for the ODN group, a difference that was not statistically significant. CONCLUSION: LDN is as efficient and safe as ODN for donors, recipients, and grafts.

Accelerated radiotherapy in locally advanced head-neck carcinomas: are concomitant boost and chemotherapy feasible in the routine outpatient-based radiotherapy clinic?

PURPOSE: Accelerated radiotherapy and concurrent chemoradiotherapy is an effective treatment modality in locally advanced head and neck carcinomas. In this study, we examined the efficacy and feasibility of concomitant boost radiotherapy and chemotherapy in the routine outpatient- based radiotherapy clinic. PATIENTS AND METHODS: Between January 1993 and December 2000, only 51 out of 127 eligible patients were deemed suitable to receive concomitant boost radiotherapy and/or chemotherapy. Their median age was 60 years (range 17-83 years). The histological diagnosis was squamous-cell carcinoma in 38 (75%) patients, undifferentiated nasopharyngeal carcinomas (WHO type III) in 10 (20%) patients and other histology in 3 (5%) patients. The concomitant boost regimen consisted of 70 Gy in 6 weeks (1.8 Gy/fraction/day, 5 days/week, to the clinical target volume (CTV), and 1.6 Gy/fraction/day to the gross tumor volume (GTV) as a second-daily treatment for the last 2 weeks). The concomitant chemotherapy regimen consisted of cisplatin 100 mg/m(2) given every 3 weeks for 3 courses, and the neoadjuvant regimen of cisplatin 100 mg/m(2) plus epirubicin 100mg/m(2), every 3 weeks for 3 courses. RESULTS: Only 55% of patients completed the treatment exactly as planned, with 82% completing treatment within acceptable limits. The median radiotherapy duration was 45 days (40-95 days). In univariate analysis, patients with better performance status (p=0.002) or nasopharyngeal carcinomas (p=0.043) had a significantly better compliance to treatment. In multivariate analysis only nasopharyngeal site was a significant predictor of compliance (p=0.019). The maximum acute reaction was grade 3 mucositis in 24 (49%) patients. No grade 4 acute or late reactions were seen. Complete and overall response rates were 51% and 75.5%, respectively. Patients with nasopharyngeal cancer and good treatment compliance had a better response rate (p=0.009 and 0.01, respectively). The median follow-up period of surviving patients was 28 months (range 6-58 months). The 3-year progression-free survival rate was 39%. CONCLUSION: In the routine outpatient-based setting we found that this intensive treatment schedule can only be given to a limited and highly selected group of patients.

A rare tumor of craniofacial bones in children: a pediatric chondroblastic osteosarcoma case with diagnostic and therapeutic problems.

Osteosarcoma of the cranial facial region is uncommon and only rarely involves the ethmoid or sphenoid bones. The authors report on an unusual case of a 17-year-old male presenting with chondroblastic osteosarcoma of the maxillary, ethmoid, and sphenoid sinuses who remains well and disease-free at 46 months. He was treated with anterior craniofacial resection followed by postoperative radiotherapy to the sight of the primary tumor. He did not receive chemotherapy because of emerging hepatitis-B infection and vasculitis. The literature on extragnathic craniofacial osteosarcomas is reviewed with particular emphasis on treatment options of this rare tumor.

Prognostic factors in lung cancer with brain metastasis.

BACKGROUND AND PURPOSE: Metastasis to the brain develops in 25% of all patients with lung cancer. Although the outcome is usually poor, there seems to be a subset of patients with favorable prognostic factors who may live longer. Prognostic factors were analyzed retrospectively in 103 patients with brain metastases from lung carcinoma to identify patients who would benefit from more intensive treatment strategies. MATERIALS AND METHODS: Between October 1991 and December 1994, 103 patients with brain metastasis from lung cancer were irradiated with palliative intent. Palliation was defined as 50% or more regression of neurological signs and symptoms 2 weeks after the completion of cranial radiotherapy. Local (related to the lung tumor) symptom status at the time of brain metastasis, the presence of metastases other than brain, multiplicity of brain metastases on CT scan and time of occurrence of brain metastasis were the factors which were evaluated with multivariate analysis. RESULTS: Palliation was accomplished in 85% of cases. Palliation duration ranged from 0.5 to 54 months (median 3 months). The overall median survival was 5 months. Only one patient is under follow-up without any symptoms related to the brain metastasis. According to the multivariate analysis survival was significantly decreased in the presence of symptoms related to the primary tumor (P = 0.001). CONCLUSION: The presence of symptoms related to the primary tumor at the time of brain metastasis is one of the factors that can be used to distinguish patients with a favorable outcome. In patients with favorable prognostic factors and thus longer survival probability, the role of boost dose after whole brain radiotherapy or surgical resection in suitable cases needs to be investigated.