Comparative dosimetry in intracavitary balloon catheter brachytherapy with I-125 and in Cf-252 brachytherapy combined with BNCT for brain tumors

Objective Comparative analysis of dosimetry in intracavitary balloon catheter brachytherapy with I-125 and in Cf-252 brachytherapy combined with BNCT for treatment of brain tumors. Materials and Methods Simulations of intracavitary balloon catheter brachytherapy with I-125 and in Cf-252 brachytherapy combined with BNCT were performed with the MCNP5 code, modeling the treatment of a brain tumor on a voxel computational phantom representing a human head. Absorbed dose rates were converted into biologically weighted dose rates. Results Intracavitary balloon catheter brachytherapy with I-125 produced biologically weighted mean dose rates of 3.2E-11, 1.3E-10, 1.9E-11 and 6.9E-13 RBE.Gy.h-1.p-1.s, respectively, on the healthy tissue, on the balloon periphery and on the I 1 and I 2 tumor infiltration zones. On the other hand, Cf-252 brachytherapy combined with BNCT produced a biologically weighted mean dose rate of 5.2E-09, 2.3E-07, 8.7E-09 and 2.4E-09 RBE.Gy.h-1.p-1.s, respectively on the healthy tissue, on the target tumor and on the I 1 and I 2 infiltration zones. Conclusion Cf-252 brachytherapy combined with BNCT delivered a selective irradiation to the target tumor and to infiltration zones, while intracavitary balloon catheter brachytherapy with I-125 delivered negligible doses on the tumor infiltration zones.

Selective On-Resonance N.M.R. Irradiation of a Dipolar Double.

Raman magnetic resonance where double-quantum transitions are observed without the need for multidimensional n.m.r. spectroscopy has been investigated further. Theoretical analysis of the on-resonance case where weak continuous-wave irradiation was applied at the frequency of a single-quantum transition was performed and guidelines for a consistent perturbation treatment were devised. Theoretical results agree well with experimental data obtained for a system of two dipolar coupled nuclei of spin oriented by a liquid crystal. The same approach is applicable to near-resonance experiments which are shown to be the optimal experimental scheme for Raman n.m.r. By using weak selective irradiation, a symmetric excitation–detection scheme can be realized for multiple-quantum n.m.r. experiments. Near- or on-resonance selective irradiation provides an efficient transfer of multiquantum coherence into observable coherences and could be used to study multiquantum relaxation processes.