Comparison between MCNP5, Geant4 and experimental data for gamma rays attenuation of PbO-BaO-B2O3 glasses.

Monte Carlo simulations, MCNP5 and Geant4 codes were developed to investigate radiation shielding properties of xPbO-(50-x) BaO-50B2O3 (where 5 ≤ x ≤ 45 mol%) consider to be glass systems. The mass attenuation coefficients were evaluated for different PbO concentration in the glass samples for varies photon energies of 0.356, 0.662, 1.173 and 1.332 MeV. The obtained mass attenuation coefficient values used to calculate half-value layer, effective atomic number, and electron density. The simulation parameters were compared with experimental data. Results show that the simulation results of mass attenuation coefficients for all PbO concentrations were generally in good agreement with experimental results, however, mass attenuation coefficient values calculated using Geant4 were slightly lower than MCNP5 and experimental data on the low energy of 0.356 MeV. The results obtained from MCNP5 and Geant4 codes might be able to assessment mass attenuation for different glass systems. Furthermore, gamma ray, fast neutron and charged particle interaction for the glass systems were studied using buildup factors, fast neutron removal cross sections and ranges respectively.

Radiation interaction parameters of dosimetric importance for some commonly used compensators in IMRT using Monte Carlo simulation code.

Radiotherapy is one of the commonly used treatments for cancer. A compensator is a device used in intensity modulated radiotherapy (IMRT) treatments to compensate for the irregularities of the body. One can provide a more uniform distribution of dose for the treatment of tumors using compensators in IMRT to obtain a better therapeutic outcome. A variety of compensators are used in IMRT. One high Z (cerrobend), two medium Z (brass and steel) and one low Z (lucite) compensators are selected for the present study. The mass attenuation coefficients have been computed in an energy range of 15 keV to 15 MeV using XCOM program and the Monte Carlo N-particle-5 (MCNP5) code. The percentage deviation between the values indicates that the mass attenuation coefficients obtained using both the methods are in good agreement. These values are further used to calculate the linear attenuation coefficients, mass energy absorption coefficients, effective atomic numbers, electron densities, equivalent atomic numbers and energy absorption and exposure buildup factors. All these parameters have been calculated in the energy range of 0.015-15.0 MeV. The variation of parameters has been studied with incident photon energies, chemical composition and penetration depth of the various compensators. It is observed that up to 3 MeV and 14 mean free path (mfp): compensator with lowest values of the effective atomic numbers has the highest value of the buildup factor. Cerrobend has a particularly high value of the buildup factor near 100 keV. Above 3 MeV and 14 mfp: compensator with lowest values of the effective atomic numbers has the lowest value of the buildup factor. Thus a complete reversal in trend is observed at 3 MeV and 14 mfp. All these observation have been explained due to the dominance of the different interaction processes in different energy regions.

Multifocal central nervous system hemangioblastoma: a case report and review of the literature.

An effective therapy for multifocal central nervous system hemangioblastoma (CNS HB) is needed. Here, we report a case of multifocal CNS HB. A 43-year-old man was diagnosed with CNS HB by enhanced computed tomography and magnetic resonance imaging. Six solid tumors and one cystic nodule were detected in his cerebellum. The patient underwent three surgeries followed by knife radiosurgery and had regular visits after the operation. In addition, histological observation with hematoxylin and eosin staining and immunohistochemistry for α-inhibin, Ki67, and vascular endothelial growth factor further provided evidence of cerebral HB. The symptoms of the patient were prominently improved after each operation, suggesting that multiple surgeries and radiation therapy are needed to prevent the proliferation and relapse of multifocal CNS HB. In addition, long-term, regular hospital visits were useful. Furthermore, genetic diagnosis and gene-targeted therapy might be a promising strategy against familial CNS HB in the future.

[Expression of left ventricular ANF-gene in rat with cardiac hypertrophy].

Plasma concentration of ANF and expression of left ventricular ANF-gene in rats with cardiac hypertrophy induced by abdominal aortic partial ligation were analyzed by RIA and Northern blot respectively. Results showed that plasma concentration of ANF and level of left ventricular ANF-mRNA in cardiac hypertrophic rats increased markedly, indicating that the cardiac load may induce transcription and expression of left ventricular ANF-gene. This effect could be potentiated by intracellular calcium modulator taurine and inhibited by vasodilator hydralazine.