ABSTRACT
The hands of nuclear medicine (NM) personnel involved in radiopharmaceutical preparation and administration can receive significant radiation doses. The dose distribution across the hand is nonuniform and the Hp(0.07) doses obtained by an individual passive ring dosimeter do not always present a real situation. The aim of this study was to assess the extremity exposure of NM workers working with99mTc-labelled radiopharmaceuticals and with an automatic IRIDE (COMECER, Italy)18F-FDG injection system. Hp(0.07) doses were measured using calibrated thermoluminescent dosimeters-100 (TLD-100) and were read by a RIALTO TLD (NE Technology) reader. It was found that the most exposed parts of the hand during work with18F and99mTc radionuclides are the fingertips of the thumb, index finger and middle finger. The maximum fingertip doses were 1.3-2.4 times higher compared with the doses from the typical monitoring position (base of the middle finger of the dominant hand). When working with99mTc, the average hand doses were relatively high, i.e. 0.17 ± 0.04 and 0.37 ± 0.13 mSv Gbq-1for the left and the right hand, respectively, during preparation, and 58 ± 20 and 53 ± 13µSv GBq-1for the left and the right hand, respectively, during administration of99mTc labelled radiopharmaceuticals. Meanwhile, the lowest doses were found for hands during administration of18F-FDG (average hand dose 28 ± 13µSv GBq-1for the left hand and 28 ± 7µSv GBq-1for the right hand), which shows the advantages of automated injection/infusion systems, thus implementation of automatic infusion/injection in hospitals could be an expedient way to optimize Hp(0.07) doses to NM workers.
Subject(s)
Occupational Exposure , Radiopharmaceuticals , Fluorodeoxyglucose F18 , Hand , Humans , Occupational Exposure/analysis , Radiation DosageABSTRACT
The essential component of modern radiation therapy is the application of steep dose gradients during patient treatment in order to maximize the radiation dose to the target volume and protect neighboring heathy tissues. However, volumetric dose distribution in an irradiated target is still a bottleneck of dose verification in modern radiotherapy. Dose gels are almost the only known dosimetry tool which allows for the evaluation of dose distribution in the irradiated volume due to gel's polymerization upon irradiation. The accuracy of dose gel dosimetry has its own obstacle, which is related to the continuation of the gel's polymerization after the radiation treatment procedure is finished. In this article, a method to monitor the polymerization dynamics of dose gels in real-time is proposed using a modified optical spectrometry system. Using the proposed method, the changes of the optical characteristics of irradiated nMAG dose gels in situ were assessed. The investigation revealed that the detectable polymerization in dose gel proceeds up to 6 h after irradiation. This time is significantly shorter compared with a commonly recommended 24 h waiting time allocated for polymer gel to settle. It was also found that dose rate significantly influences the temporal response of the nMAG dosimeter. By increasing the irradiation dose rate by a factor of 2, the time needed for the polymerization process to settle was increased by 22%. Identification of the gel's post-irradiation polymerization time interval and its dependence on irradiation parameters will contribute to more accurate dose verification using dose gel dosimetry.
ABSTRACT
Polymer gels and films, due to their near equivalence to biological tissue, are amongst the most promising future dosimetry tools for medical applications. The application of polymer dose gels is limited by the sensitivity of dose readout methods and dose gel properties. It is a challenge to find suitable dosimeters for registration of doses delivered to the target by orthovoltage therapy units. The application of metal-particle-enriched polymer composites for dose registration in X-ray therapy might be an elegant solution, especially if recent dose-reading technologies exploring advantages of different physical phenomena are involved. In this work, X-rays from the orthovoltage therapy range were used for the irradiation of experimental samples. In addition, radiation-induced processes of formation of silver nanoparticles in AgNO3-PVA gels and in free standing AgNO3PVA films, also containing some additional solvents, namely glycerol, ethanol, and isopropanol, have been investigated, with the aim to apply the developed composites for medical dosimetry purposes. A simple and environmentally friendly method for the formation of free-standing AgPVA films at room temperature was proposed and realized for preparing AgPVA films for investigation. Radiation-induced synthesis of silver nanoparticles in AgPVA composites was investigated, analyzing LPSR-based UV-VIS spectral changes to the irradiated films with respect to irradiation doses, and dose-related tendencies were also evaluated. It was shown that AgPVA films were more sensitive for detection of doses from the interval 0-1.0 Gy, thus indicating potential application of AgPVA films for dosimetry purposes.
ABSTRACT
The rapid development of micro- and nanostructures containing silver nanoparticles is based on their unique physical properties. Despite the new applications of silver nanoparticles in nanomedicine are under heavy discussions, silver nanoparticles could be used in liquid radiation detectors thanks to the irradiation-induced surface plasmon resonance (SPR) phenomena observed in the colloidal solutions. Silver nitrate (1 mM AgNO(3)) and sodium citrate (1 wt% and 5 wt% C(6)H(5)O(7)Na(3)) were used as precursors for the fabrication of colloidal solutions. Prepared solutions were exposed to gamma-rays from a (60)Co gamma therapy unit 'Rokus-M' to varying absorbed doses, from 2 to 250 Gy. A UV/VIS/NIR spectrometer (Avantes-2048) was used for the measurement of the optical properties (absorbance) of the silver solutions. It was found that an initial absorbed dose of 2 Gy induced the formation of spherical silver nanoparticles as it was indicated in the absorbance spectrum of the solution, which had a well-pronounced absorption maximum at the wavelength of 410 nm. There is a potential to measure absorbed doses down to around 20 mGy. The SPR peaks at the wavelengths of 500-700 nm were found at the highest investigated doses >100 Gy, indicating the presence of silver nanorods. The colour of colloidal solutions ranged from pale yellow to green and was dependent on the absorbed dose. The investigation has shown that density, size and shape of synthesised silver nanoparticles are dependent on the absorbed dose and that shape transformations of the particles due to irradiation are possible. Application of colloidal solutions containing silver nanoparticles for dosimetric purposes is discussed on the basis of the obtained results.
