[en] Oligochitosans (OCT) were prepared from chitosan (CTS) by gamma irradiation technique. The parameters affecting to the chitosan degradation were studied. And then, OCT nanoparticles wereformed using the method of tripolyphosphate (TPP) cross-linking. Effect of concentration and molecular weight of OCT, concentration of TPP on particle size of the formed OCT nanoparticles were also studied. The formation of OCT nanoparticles was verified by Fourier transform infrared (FT-IR) spectrometer and differential scanning calorimeter (DSC), the morphology was observed using scanning electron microscope (SEM), and the characteristics (particle size and zeta potential) of OCT nanoparticles were also studied. The effect of OCT nanoparticles on strawberry presevation was carried out using the coating method. Results showed that an increase in radiation dose resulted in a decrease of chitosan molecular weight. The OCT with molecular weight of approximately 7.7 kDa was obtained by the synergistic effect of hydrogen peroxide (5%, v/v) and gamma ray at dose of 30 kGy. The smaller OCT nanoparticles was obtained with a lower molecular weight of OCT. The results of FTIR, DSC indicated the success in the formation of OCT nanoparticles with the particle size approximately 129.9 nm, with the spherical shape. The application of OCT nanoparticles on strawberry has prolonged the preservation times approximately 2.5 times higher compared to the control. (author)

[en] This letter to the editor discusses the definition of the unit of dose equivalent: the sievert

[en] To determine an equivalent dose (D_e), the initial signal of the CW-OSL decay curve, supposedly dominated by the fast component, is used. Previous studies suggest that the resulting D_e however, may be underestimated if thermally unstable medium or slow components are part of the initial decay curve. The D_e(t) plot has the potential to reveal the 'unclean' fast component. We have here studied quartz samples obtained from late Pleistocene floodplain deposits in the Lower Mississippi Valley (LMV), which show decreasing values of D_e with increasing stimulation time. The deconvolution analysis of CW-OSL signals from these samples confirm the interpretation of the D_e(t) plots. As a consequence, component-resolved values of D_e were determined to obtain an accurate estimation of D_e. Contrary to previous studies, our results indicate that the values of D_e obtained with the initial signal are not underestimated for our samples containing a thermally unstable medium component.

[en] The concepts of physical quantity and physical units of measurement are presented. The relations between quantities, the names and symbols for SI (International System) base units, derived units and special names of SI units are illustrated. From the definition of the radiation quantity dose equivalent, the SI unit for this quantity is shown to be dimensionally identical with the joule per kilogram. The sievert (Sv) is the special (restricted) name for the SI unit of the quantity dose equivalent, with 1 Sv=1 J/kg

[en] Intensity modulated radiation therapy (IMRT) has been introduced in our department for treatment of the head and neck region with the intention Of reducing complications without compromising treatment outcome. However, these new treatment modalities inevitably require a substantial increase in monitor units per target dose yielding an increased risk of secondary malignancies induced by the treatment. This study aims at assessing the increased risk by means of in vivo measurements of the whole-body equivalent dose of both the conventional and the IMRT treatment techniques for head and neck lesions. A conventional technique using parallel opposed wedged treatment fields has been compared with a slice-by-slice rotation technique for IMRT. Both techniques were used to treat head and neck lesions with a 6-MV photon beam. Thermoluminescent badges and neutron bubble detectors designed for personnel monitoring have been applied to obtain the estimated whole-body equivalent dose on three patients for each treatment technique. The nominal probability coefficient for a lifetime risk of excess fatal cancer, recommended by the ICRP 60 has been used for risk estimates based on the estimated dose values. An estimated whole-body equivalent dose per monitor unit equal to 1.2 x 10^-2 mSv/MU and 1.6 x 10^-2 MSv/MU have been obtained with the conventional and IMRT technique, respectively. Applying the average amount of MU necessary to realize a 70 Gy target the estimated whole-body equivalent dose for both treatment techniques becomes 242 mSv (conventional) and 1969 mSv (IMRT), yielding an increase in the risk for secondary malignancies with a factor 8. Historically the risk of secondary malignancies has been accepted to take advantage of the possible benefits of improved vocal control and treatment outcome. However, the introduction of new and sophisticated treatment techniques will also increase the risk of radiation induced malignancies. Therefore, these risk estimates become important to assess whether the benefits of the treatment technique outweigh the possible risks. (author.)

[en] Abstract only

[en] Full text: In many parts of the world, predominantly in Europe, small sized survey meters based on Geiger-Mueller or proportional counters are widely used for dose rate and dose equivalent rate measurements, while in other regions, especially in the U.S., ionisation chambers are preferred for this task. This paper tries to shed some light on the likely reasons for these two diverging instrumental inclinations. Their respective strengths and weaknesses is analyzed in respect to energy response, dose rate measuring range, size, weight and susceptibility to environmental influences. Furthermore the response and limitations regarding the measurement of pulsed radiation (medical X-ray and CT-devices, accelerators, non-destructive testing) is discussed. A newly developed pocket size instrument based on a pan-cake Geiger-Mueller tube is used as an example to explain the capability and flexibility of modern survey meters. The RadEye B20 is a compact multi-purpose dose rate meter and contamination meter for alpha, beta, gamma and X-ray radiation. By virtue of carefully designed multi-layer gamma energy filters, H*(10) (deep dose) or H'(0,07) (shallow dose) measurements from 17 - 1300 keV can be performed. The instrument can even be worn in a belt holster, so that the impact to the mobility of the user is minimized. For emergency response purposes alpha and beta contamination can be discriminated using another optional filter; a simple sample changer adapter can extend the scope of application. Immediate and reproducible counter measurements, e.g. of smear tests can be performed locally. (author)

[en] Philosophies and quantities for radiation protection have often been subjected to changes, and some of the developments are traced which ultimately led to recent proposals by ICRU. Development in the past has largely been towards clarification and generalisation of definitions. The present changes, however, reflect a more fundamental issue, the transition from the limitation system to the assessment system in radiation protection. The index quantities were suitable tools to ascertain compliance with the limitation system of radiation protection. The new quantities proposed by ICRU are suitable estimators for effective dose equivalent, which is an essential quantity in the assessment system of radiation protection. A synopsis of the definitions is given. (author)

[en] In 1990 ICRP made significant changes in its recommendations relative to radiation protection quantities and units. New system of quantities is not coherent with ICRU operational quantities, such as the ambient dose equivalent. Comments to the introduced changes are presented and an alternative approach is proposed to retain coherence of the system of quantities and units used in radiation protection. (author). 12 refs

No abstract available