B. C. De Simone

Rotating-frame spin-echo imaging in solids☆

Abstract Two-dimensional 1H images of a solid obtained by magic-angle rotating-frame echoes are presented. The images have been reconstructed by processing the rotating-frame echo signals of a solid sample under the action of static and rotating field gradients. The echo signals were directly detected in the rotating frame after 90°—r—180° “audio” pulse excitation.

Direct excitation and detection of NMR narrowed rotating frame spin echo in solids

Abstract A NMR rotating frame spin-echo was produced directly with “audio” frequency pulses excitation. Under magic angle narrowing condition, the echo allows the observation of fine and hyperfine interactions in solids.

Solid state nuclear spin mapping by rotary saturation

Abstract A new solid state NMR Imaging method is presented. The method is based on the Redfield-Lee-Goldburg rotary saturation. The spatially encoded rotary line is observed step by step in the laboratory frame with a valuable signal to noise ratio and spatial resolution. The experimental set-up and the excitation timing scheme are particularly simple.

Lee-Goldburg solid-state imaging

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.

Role of 3D imaging in small scale NMR tomography

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.

NMR imaging of systems with slow dynamics

Abstract Solid-state NMR imaging methods that are sensitive to slow or ultraslow molecular motion are reviewed in order to demonstrate their potential utilization for imaging of high-density macromolecular aggregates to which the low-frequency dynamics range is peculiar. The methods are based on Redfields rotating frame saturation theory of solids, which allows information to be obtained on a time-scale given by the evolution of magnetization in an effective magnetic field of a few gauss, with the “magic” possibility of damping the static spin coupling.

Hybrid rf coil for nuclear magnetic resonance imaging

Abstract A new rf coil for nuclear magnetic resonance imaging is presented. Its geometry is a hybrid between the saddle-shaped and the crossed-ellipse coil. The hybrid coil has a distributed capacitance and a proximity effect smaller than the saddle coil with the same number of turns and an equivalent rf field distribution and current-field efficiency.

Proton-NMR of Nuclei, Cell and Intact Tissue in Normal and Abnormal States: Significance of Relaxation Times as Correlated with Other Non-Invasive Biophysical Probes

In vivo Proton NMR imaging is becoming an increasingly popular tool in diagnostic medicine for its non-invasive nature and for its high resolution (1,2). In most clinical applications the 3-D reconstructed human images are based on local measurements of T1 and T2 proton relaxation times. Increases in these relaxation times in tumors (3) have been attributed to a change in the water concentration at the cytoplasmic and/or extracellular level (4) or to a change in the physical state of water (3,5). Similarly, during the cell cycle the variations in T1, i.e., its shortening during the Gl-S transcription (6), have been correlated with cellular changes in water concentration (7). More importantly, it has been found (7) that prior to mitosis an increase in relaxation times of water protons preceeds by 4 hours the increase in water concentration, suggesting that a change in the physical state of water may preceed cell division.

Signal-to-noise improvement in NMR imaging byB1 homogeneity optimization

SummaryThe role of the RF magnetic-field homogeneity for the quality of the signal-to-noise ratio is here discussed. Its effects on the e.m.f. generated by the nuclear magnetization is analysed as well. We also report here some results of a modified coil which improves the RF field homogeneity and thus the signal to noise.RiassuntoIl ruolo dell’omogeneità del campo di eccitazione a radio frequenza (RF) nel rapporto segnale-rumore (S/N) è discusso sulla base del principio di reciprocità. I risultati ottenuti mostrano che l’aumento dell’omogeneità del campo a RF produce un aumento del rapporto S/N. Su queste indicazioni à stata realizzata una nuova bobina RF con migliore omogeneità, che conferma sperimentalmente l’incremento del rapporto S/N.РезюмеВ этой статье обсуждается роль однородности высокочастотного магнитного поля для улучшения отношения сигнала к шуму. Также анализируется влияние однородности высокочастотного магнитного поля на электродвижущую силу, образованную ядерным намагничиванием. Приводятся также некоторые результаты для видонзмененной катушки, которая улучшает однородность высокочастотного поля и, следовательно, отношение сигнала к шуму.

Imaging of Solids by Audio Frequency Excitation in the Rotating Frame

Recentely, we implemented a new class of experiments in the Rotating Frame 1), with which we obtain narrowed spectra of solid samples.