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Gadolinium as marker for in-vivo /sup 10/B imaging in BNCT

Measurements have been carried out for inquiring the feasibility of utilizing gadolinium for achieving 2D and 3D images of the spatial distribution of 10B in boron neutron capture therapy (BNCT). The spatial distribution of boron can be obtained by detecting gadolinium images, if gadolinium and boron are bound to the same carrier. The isotope 157Gd has a very high cross section (sigma=255,000b) for (n,gamma) reaction with thermal neutrons, and its presence in tissue exposed to thermal or epithermal neutron fields can rise the gamma dose in tissue and deplete thermal neutron flux. Dose and fluence images have been detected by means of gel-dosimeter layers. The sensitivity of neutron radiography has been tested, utilizing tissue-equivalent phantoms containing gadolinium (and sometimes also boron), but the results have shown that the needed amount of gadolinium would be very high, and the consequent dose in healthy tissue results to be not acceptable. On the opposite, quantitative imaging of the carrier distribution can be obtained with good reliability and reproducibility by means of magnetic resonance imaging (MRI), technique already utilizing gadolinium as marker. In this case, the needed concentration of gadolinium is very low, fully acceptable for what concerns dosimetry requirements