Optical images of dose distributions in Gel-Fricke: dosimetric performances of the gel.

The purpose of this work was to examine the dosimetric performances of the radiochromic Fricke-Agarose-Xylenol Orange gel by optical measurements in order to perform dose reconstructions, in view of a future development for 3-D maps. Optical images and dose-response curves of the gel were obtained by a CCD-based device, originally designed for reading radiochromic films, that was modified to meet the optical properties of the dosemeter. With a resolution of 0.18 x 0.18 mm the optimum range of doses in which per cent uncertainty is lower than 2% was 3-10 Gy. The minimum detectable dose, estimated as the absorbed dose corresponding to 3 SD above background, was 0.1 Gy. With a resolution of 1.98 x 1.98 mm the optimum range of doses in which per cent uncertainty is lower than 2% was 0.3-10 Gy. The minimum detectable dose, estimated as the absorbed dose corresponding to 3 SD above background, was 0.015 Gy. The comparison with alanine dosemeters in the dose range 7-10 Gy showed agreement within a few per cent and the same agreement was observed for the comparison with TLD in the range 1-3 Gy.

Optical imaging of dose distributions in Fricke gels.

Ferrous-sulphate infused gels, or 'Fricke gels', encounter great interest in the field of radiation dosimetry, due to their potential for 3D radiation dose mapping. Typically, magnetic resonance (MR) relaxation rates are determined in these systems in order to derive the absorbed dose. However, when large concentration gradients are present, diffusion effects before and during the MR imaging may not be negligible. In these cases, optical techniques may represent a viable alternative. This paper describes research aimed at measuring 3D dose distributions in a Fricke-xylenol orange gel by measuring optical density with a CCD camera. This method is inexpensive and fast. A series of early experiments is described, in which optical density profiles were measured with a commercial microdensitometer for film dosimetry. The light box of the device was modified to work at 567 nm, close to the maximum absorbance of the ferric ion-xylenol orange complex. Under these conditions, the gel shows linearity with dose and high sensitivity.

[Examples of intervention in cases of electromagnetic pollution in research laboratories]. / Esempi di intervento in casi di inquinamento elettromagnetico in laboratori di ricerca.

Two examples of technical measures taken to reduce levels of radiofrequency electromagnetic radiation in research laboratories are reported. The first intervention was aimed at avoiding undue exposure of operators. The case is of interest because of the special exposure conditions, which are not as well characterized as in industrial applications, and require ad hoc analyses, measurements, and mitigation actions. As shown by the second example, such actions also allow effective screening of experimental apparatuses, which is of special importance when high sensitivities are required.

[An experimental device for measuring the characteristics of echographic emissions]. / Un apparato sperimentale per la determinazione delle caratteristiche di emissione di ecografi.

An experimental system for the evaluation of the parameters characterizing the acoustic power emission of echographs is described. The apparatus is based on a commercial device, which has been modified to allow the analysis of different echographic probes, particularly used for diagnosis. The modified instrument is quite versatile in use and is suitable for the examination of virtually any kind of probe.