ABSTRACT
The influence of halogen atom substitution (Br and I), in different amounts and positions in an aza-BODIPY skeleton, on the photophysical properties of some aza-BODIPY derivatives has been investigated by using density functional theory and its time-dependent extension. The heavy atom effect on excitation energies, singlet-triplet energy gaps and spin-orbit matrix elements has been considered. The maximum absorption within the therapeutic window has been confirmed for all the aza-BODIPY derivatives. The feasible intersystem spin crossing pathways for the population of the lowest triplet state, that will depend on the values of the spin-orbit matrix elements, the energy gap as well as the orbital composition of the involved states have been found to most likely involve the S1 and T1 or T2 states. The outcomes of computations support the potential therapeutic use of these compounds as photosensitizers in photodynamic therapy.
ABSTRACT
An approach to electrical impedance tomography (EIT) data acquisition inspired by NMR-filtered back-projection imaging with fan isochromat distribution is proposed. A current projection is generated by injecting current at a certain point of the sample and simultaneously collecting the current itself at different points on the half space opposite the point of current injection. After that, the injection is shifted to another point and collected as above and so on. A very simple algebra and software support the numerical simulations. This method is expected to be more sensitive than the traditional method based on potential measurements. A preliminary low resolution experiment is presented.
Subject(s)
Algorithms , Computer Simulation , Electric Impedance , Image Enhancement/methods , Plethysmography, Impedance/methods , Electrodes , Feasibility Studies , Models, Theoretical , Phantoms, Imaging , Plethysmography, Impedance/instrumentation , Scattering, RadiationABSTRACT
A new approach to solid-state imaging (SSI) is presented. The method relies on narrowing the resonance line using the Lee-Goldburg sequence. The technique is easy to implement in practice and may find widespread applications in materials science.
Subject(s)
Magnetic Resonance Spectroscopy , Magnetic Resonance Spectroscopy/methodsABSTRACT
A comparison between contrast and signal-to-noise ratio (SNR), as obtained by both maximum entropy (ME) and 2DFT reconstruction, is reported for NMR images. Our results show that in the ME elaboration the contrast and SNR are generally increased with respect to the 2DFT elaboration. The magnitude of such an increase depends on the ME statistical parameter and also, quite strongly, on the values of contrast and SNR of the 2DFT image.
Subject(s)
Magnetic Resonance Imaging/methodsABSTRACT
New coil geometries obtained by computer simulations from the crossed-ellipse rf coil are reported. These geometries with elliptical transverse section improve the signal-to-noise ratio with respect to the classic ellipse and saddle coils. The increase of signal-to-noise ratio is mainly due to the reduction of coil losses and to the better B1 efficiency and distribution.
Subject(s)
Magnetic Resonance Spectroscopy/instrumentation , Abdomen/pathology , Biometry , Biophysical Phenomena , Biophysics , Humans , Radio Waves , Thorax/pathologyABSTRACT
Some advantages of using 3D techniques in small scale NMR imaging are suggested. In particular the 3D methods are likely to be useful in slow dynamical processes occurring in vivo. Three-dimensional images obtained with our first home built prototype are also reported.
