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C Casieri

Publications and source records attributed to C Casieri.

12 recordsLinked to original sources
PubMed2003

Self-diffusion coefficient by single-sided NMR.

It is presented a novel method for the measure of the self-diffusion coefficient. The method exploits the fixed gradient of an open magnet, as that used in single-sided NMR, and it does not use prior information on T(2). The approach presented in this paper can be practiced also on the fringe field of superconducting magnets and it is based on the construction of the ratios between echoes taken at different interpulses separation in a Carr-Purcell-Meiboom-Gill pulse sequence. The determination of the self-diffusion coefficient facilitates the estimate of T(2) because the transverse relaxation results almost influenced by the molecular diffusion effect, also at the shorter interpulses time, when it is measured in field strongly inhomogeneous.

Journal Article↗
PubMed2002

Spin interaction filter in solid-state NMR Imaging.

In the tilted rotating frame (TRF), the transverse relaxation time T(2rho) depends strongly on the orientation of TRF with respect to the usual rotating frame. In the spin space, the relative orientation of the two reference frames modifies the contribution of various spin interactions to T(2rho) relaxation. Since the orientation of the frames and, to some extent, the role of the spin Hamiltonians in TRF are controllable experimentally, the T(2rho) relaxation can be made sensitive to molecular mechanisms related to the selected spin interaction. In this paper, the realization of a contrast Hamiltonian-dependent in solid-state NMR Imaging is proved. The solid-state imaging approach is based on the magic angle in the rotating frame. Some results on simple solid polymers are presented.

Journal Article↗
PubMed2001

Proton MRI of (13)C distribution by J and chemical shift editing.

The sensitivity of (13)C NMR imaging can be considerably favored by detecting the (1)H nuclei bound to (13)C nuclei via scalar J-interaction (X-filter). However, the J-editing approaches have difficulty in discriminating between compounds with similar J-constant as, for example, different glucose metabolites. In such cases, it is almost impossible to get J-edited images of a single-compound distribution, since the various molecules are distinguishable only via their chemical shift. In a recent application of J-editing to high-resolution spectroscopy, it has been shown that a more efficient chemical selectivity could be obtained by utilizing the larger chemical shift range of (13)C. This has been made by introducing frequency-selective (13)C pulses that allow a great capability of indirect chemical separation. Here a double-resonance imaging approach is proposed, based on both J-editing and (13)C chemical shift editing, which achieves a powerful chemical selectivity and is able to produce full maps of specific chemical compounds. Results are presented on a multicompartments sample containing solutions of glucose and lactic and glutamic acid in water.

Journal Article↗
PubMed2001

In vivo detection of 13C-enriched glucose metabolites in mouse brain by T-SEDOR imaging.

Protons J-coupled to 13C were selectively detected in the mouse head by in vivo 1H NMR imaging based on Twin Spin Echo DOuble Resonance (T-SEDOR) excitation. This pulse sequence combines a good chemical specificity with high sensitivity, requires no solvent pre-saturation and is well adapted to the imaging modality. 1H T-SEDOR maps of the mouse head allowed detection of areas of preferential accumulation of 13C-enriched compounds, upon repeated injections of uniformly 13C-labelled glucose, which induced hyperglycemia. The results demonstrated the feasibility, both in time scale and metabolite concentration, of applying T-SEDOR MRI for in vivo mapping brain areas characterized by enhanced rates of glucose uptake and/or accumulation of its metabolites.

Animals↗
PubMed2000

Double-resonance J-edited (1)H-NMR detection of 6-(13)C-D-2-deoxyglucose uptake in glioma cells.

The C6 methylene protons were selectively detected in (1)H-NMR spectra of intact glioma cells incubated with 6-(13)C-D-2-deoxyglucose (6-(13)C-2dG), a (13)C-enriched glucose analog that is suitable for monitoring glucose utilization in brain tumors. Spectral editing via (1)H-(13)C scalar coupling was performed with twin spin-echo double resonance (T-SEDOR), a pulse sequence which combines chemical specificity and high sensitivity, requires no solvent pre-saturation, and can easily be adapted to imaging protocols. This work demonstrates the suitability of the pulse sequence for monitoring 6-(13)C-2dG uptake in living cells in vitro, in spite of line-broadening and the occurrence of other strong signals in the spectral region of interest (3.5-4.4 ppm).

Animals↗
PubMed1999

The spin coherence relaxation in the rotating frame as a microscopy parameter for strongly coupled spin systems.

The transverse relaxation time in the rotating frame T2rho is proposed as an effective parameter to get specific contrast in solid state imaging. Several peculiarities make T2rho an interesting candidate to map dynamics and structure in solids: the effect of the secular spin interaction can be controlled by the experimenter and therefore the relaxation associated with the nonsecular terms, which is particularly sensitive to very slow dynamics, can be observed. In this paper we present preliminary results obtained on polymers and prove the capability of the MARF Imaging, enhanced by a filter based on rotary echo refocusing, to produce images of solids contrasted by T2rho.

Magnetic Resonance Spectroscopy↗
PubMed1998

13C imaging by double resonance scalar-coupling editing.

The two-dimensional FT Imaging of 13C-glucose obtained with twin spin-echo double resonance sequence is presented. The images have been obtained by a doubly tuned surface coil on samples containing water and 13C-enriched glucose in water. It is shown, both theoretically and experimentally, that the whole editing capability of the twin spin-echo double resonance imaging sequence is also preserved in the presence of the radiofrequency field inhomogeneity produced by the surface coil. As in an efficient selective irradiation method, the enhancement in the signal-to-noise ratio with respect to the direct 13C detection, depends on the number of protons J-coupled to 13C.

Carbon Isotopes↗
PubMed1998

T1rho space dependence in rigid polymers by effective radio frequency gradient.

An extension of the solid-state nuclear magnetic resonance (NMR) imaging based on magic angle in the rotating frame (MARF) line narrowing approach is presented. The modified magic angle in the rotating frame imaging sequence is able to yield T1rho maps of large band polymers with remarkable contrast sensitivity and without contrast parameter alteration referable to the narrowing procedure. This last feature is examined closely in order to outline the actual effectiveness of the method. Further experimental details, especially regarding probe coil design, recently improved, are discussed and some new results are presented.

Image Processing, Computer-Assisted↗
PubMed1992

Spin-lattice relaxation in murine tumors after in vivo treatment with interferon alpha/beta or tumor necrosis factor alpha.

1H NMR spin-lattice relaxation times (T1) were measured in vitro and in vivo in Friend leukemia cell tumors during subcutaneous tumor growth in syngeneic mice and after in vivo administration of either purified murine interferon alpha/beta (IFN) or recombinant tumor necrosis factor alpha (TNF). Untreated tumors exhibited monoexponential T1 relaxation independently of tumor age at least until Day 16 after implantation. Histological examinations showed that under these conditions tumors were highly homogeneous and substantially free of necrotic areas. Peritumoral administrations of either IFN or TNF did not significantly alter the tumor relaxation properties at early stages of inhibition of tumor growth. The longitudinal relaxation decay became instead clearly biexponential at later stages (more than 7 days of IFN treatment or 2 days after TNF administration). While the T1 relaxation behavior could be unequivocally correlated with the presence of necrotic areas in these tumors, it could not be considered as an early marker of the altered growth capability, induced by administration of either IFN or TNF.

Animals↗
PubMed1992

Immiscible fluids permeability by T1 imaging.

Soil pollution by hydrocarbon compounds is an important part of the more general pollution problem. Some analogies with research problems encountered in studies of oil reservoirs in rocks suggested to us the opportunity to study the pollution dynamics by imaging the spatial distribution of the pollutant in a wet soil model by an NMR imaging technique. Some preliminary results using T1-weighted imaging are reported here.

Magnetic Resonance Spectroscopy↗
PubMed1986

Modified crossed-ellipse radiofrequency coil for MRI.

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.

Abdomen↗