Assessment of skyshine photon dose rates from 9 and 18 MV medical linear accelerators

Background: skyshine describes the radiation scattered by the atmosphere above a LINAC facility to a point on the ground. The aim of this study was to measure the skyshine photon dose rates from two different [9 MV and 18 MV] medical linear accelerators

Materials and Methods: the photon beam was directed upward [180 degree gantry position], with a maximum photon field size [40 × 40 cm2] at the isocenter. Measurements were obtained around the external points selected outside the room facilities at a horizontal distance from the target by the calibrated RDS-110 survey meter at four points around the isocenter

Results: the measured values of the skyshine photon exposure rates at four points for 9 MV and 18 MV were 0.6, 0.5, 0.5, and 0.4 microSv/h, and 0.6, 0.4, 0.4, and 0.5 micro Sv/h, respectively. All the measured skyshine photon exposure rates were lower than the values recommended by NCRP 147

Conclusion: there is a poor agreement between the measured and the calculated values; therefore it seems that caution is needed while using the equations available in NCRP 147 or 151

Three-dimensional gel dosimetry for dose volume histogram verification in compensator-based IMRT

Some tissues in human body are radiobiologically different from water and these inhomogeneity must be considered in dose calculation in order to achieve an accurate dose delivery. Dose verification in complex radiation therapy techniques, such as intensity-modulated radiation therapy [IMRT] calls for volumetric, tissue equivalent and energy independent dosimeter. The purpose of this study is to verify a compensator-based IMRT plan in anthropomorphic inhomogeneous phantom by Dose Volume Histograms [DVH] using polymer gel dosimetry. An anthropomorphic pelvic phantom was constructed with places for gel inserts. Two attached cubic inserts for prostate and bladder and a cylindrical insert for rectum. A prostate treatment case was simulated in the phantom and the treatment was delivered by a five field compensator-based IMRT. Gel dosimeters were scanned by a 1.5 Tesla magnetic resonance imaging [MRI]. Results were analyzed by DVH and difference of differential DVH. Results showed for 3D compensator-based IMRT treatment plan for prostate cancer, there was overall good agreement between calculated dose distributions and the corresponding gel measured especially in planning target volume [PTV] region. Our measurements showed that the used treatment plan configuration has had clinically acceptable accuracy and gel dosimetry can be considered as a useful tool for measuring DVH. It may also be used for quality assurance and compensator-based IMRT treatment verification

[Relationship between cyclosporine blood level and CMV infection during the first 3 months after kidney transplantation]

Organ transplantation is revolutionized since production of cyclosporine. Considering the increased incidence of cytomegalovirus [CMV] infection in patients with transplantation, this study is designed to evaluate the relationship between cyclosporine blood level in patients undergone kidney's transplantation and the rate of CMV infection. This retrospective descriptive study evaluated 511 kidny's transplanted patients for cyclosporine blood level and rate of CMV infection during 100 postoperative days in Labbafinejad hospital [2001-2003]. 57 [11%] out of 511 developed CMV infection. The minimum interval between surgery and infection was 20 days, the maximum interval was 99 days with a mean of 56 days. Mean blood cyclosporine levels in infected and non-infected patients were 383.3 and 310 ng/ml respectively. This difference was statistically significant [p<0.05]. We conclude that CMV infection is closely related to cyclosporine blood level. In order to obtain more efficacy and less cytomegalovirus infections, careful cyclosporine blood level monitoring [<300 ng/ml] is recommended

efficacy of oral ribavirin in the treatment of 81 proved of Crimean-Congo hemorrhagic fever [CCHF] in Iran [1999-2001]

Crimean-Congo Hemorrhagic Fever is a fatal viral disease that occurs in some parts of Africa, Asia, Eastern Europe and the Middle-East. Primarily it is a zoonosis but can be seen sporadically in humans. Recently outbreaks have been reported from Pakistan, Afghanistan, Saudi Arabia, United Arab Emirates and Iran. In this retrospective study, we evaluated the efficacy of oral Ribavirin in the treatment of CCHF cases, by comparing the outcome in two groups of treated and non-treated confirmed CCHF cases. 81 confirmed CCHF cases [by serology or viral culture] were evaluated for the incidence of outcome [death or recovery] in the form of an analytic case-control study. 61 out of 69 treated cases and 5 out of 12 non-treated cases survived. Oral Ribavirin with an efficacy of 91% can be an effective medical therapy for management of Crimean Congo Hemorrhagic Fever