Biomedical subjects

S Capuani

Publications and source records attributed to S Capuani.

13 recordsLinked to original sources

PubMed2005

Diffusion tensor imaging to study anisotropy in a particular porous system: the trabecular bone network.

During the last decade, considerable effort has been invested into the development of diffusion tensor imaging (DTI) mainly used to investigate cerebral morphology. The aim of this paper is to review and to discuss our recent results about high magnetic field DTI application to study spongy bone tissue. Due to its peculiar properties, spongy bone represents a particular porous system sample. Strategies to perform DTI on porous systems and issues linked to DTI outcome interpretation are presented on the basis of our results concerning trabecular bone network characterization.

Animals↗

PubMed2004

New openings for porous systems research from intermolecular double-quantum NMR.

It has been recently recognized that residual intermolecular double-quantum coherences (iDQcs) provide a novel contrast mechanism to study heterogeneity in liquid systems. This is of much interest in the field of the physics of matter and biomedicine. Nowadays, literature concerning the behaviour of the iDQc signal originated by highly heterogeneous systems such as fluids in porous media is scarce. In this paper, we report and discuss our principal results about iDQc signal behaviour in confined liquid systems (trabecular bone, travertine, porous standard systems) and also some new results obtained on doped water in glass capillary pipes.

Adsorption↗

PubMed2003

Intermolecular double quantum coherences (iDQc) and diffusion-weighted imaging (DWI) imaging of the human brain at 1.5 T.

To study the sensitivity of intermolecular double quantum coherences (iDQc) imaging contrast to brain microstructure and brain anisotropy, we investigated the iDQC contrast between differently structured areas of the brain according to the strength and the direction of the applied correlation gradient. Thus diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) maps have been obtained. This procedure, which consists of analyzing both iDQc and DWI images at different gradient strength and gradient direction, could be a promising tool for clinical brain investigations performed with higher than 1.5 T magnetic fields.

Anisotropy↗

PubMed2003

NMR applications to low porosity carbonate stones.

The purpose of this paper is to investigate NMR applications to porous materials widely employed in artistic and historical monuments and largely studied in the Cultural Heritage conservation field. Carrara marble, Candoglia marble and travertine samples were studied and data from relaxation times measurements were compared. Very interesting results from treated samples are reported and explained under the structure related spin lattice relaxation time point of view. Images of Carrara marble aged sample (XIX century), coming from the Florence Cathedral obtained for short absorption time of water by capillary rise and for relatively small thickness slices together show the fluid's spatial distribution within the stone. Comparative images showing untreated sample with the treated ones were obtained suggesting very useful applications for the determination of treatment effectiveness.

Carbonates↗

PubMed2002

Multiple spin echoes in heterogeneous systems: physical origins of the observed dips.

Dipolar interactions in liquids have recently offered a new challenge to investigate porous media by exploiting intermolecular quantum coherences, which are obtained through a simple two-pulse sequence (90 degrees -tau-120 degrees ). This sequence, in the presence of an external gradient (G), refocuses a train of echoes at multiple integer values of time tau. The first and second echo amplitudes are acquired for heterogeneous systems such as porous media at different time values (tau). In our first experiments on bovine bone samples we have observed unpredicted dips on the second echo time behavior. We argue that a strict relation occurs between the average pore dimensions and the dips time position through the correlation distance d=pi/(gamma G tau) (defined as half a cycle of the magnetization helix, which originates in the presence of an external gradient). Although the experimental results have revealed an exceptional connection between the porous structure and the correlation distance, no physical explanation was so far provided. In this paper we propose a possible physical cause of the observed phenomenon. In addition we report an accurate analysis of new experiments performed on glass beads phantoms, which confirms our conclusions.

Magnetic Resonance Spectroscopy↗

PubMed2002

Multiple spin echoes for the evaluation of trabecular bone quality.

We report a simple and efficient MR method for the evaluation of trabecular bone quality. This technique is based on detection and imaging of Multiple Spin-Echoes (MSE), a manifestation of the dipolar field generated by residual intermolecular dipolar couplings in liquids. In the particular implementation we have used, originally proposed by Bowtell [J. Magn. Reson. 100 (1992) 1; J. Magn. Reson. 88 (1990) 643; Phys. Rev. Lett. 76 (1996) 4971], multiple spin echoes (MSE) are refocused in a two-pulse experiment in the presence of a correlation linear magnetic field gradient G(c). This gradient generates a magnetisation helix and results in the spatial modulation of the sample magnetisation. In heterogeneous systems, the amplitude of the MSE signal depends on sample heterogeneity over a distance d=pi/(gammaG(c)tau) which is half a cycle of the magnetisation helix, thus providing a novel contrast mechanism that can be tuned to a specific length scale. We have exploited this mechanism to study young bovine trabecular bone samples ex-vivo. We show that MSE images present a different contrast from conventional MR images, and that, by varying the experimental parameters, the image contrast can be related to specific trabecular pore sizes. The potential of this technique for the early diagnosis of osteoporotic diseases is discussed.

Animals↗

PubMed2002

In vivo multiple spin echoes imaging of trabecular bone on a clinical 1.5 T MR scanner.

In vivo multiple spin echoes (MSE) images of bone marrow in trabecular bone were obtained for the first time on a clinical 1.5 T scanner. Despite of a reduced sensitivity of the MSE trabecular bone images with respect to the cerebral matter ones, it is possible to observe some features in the MSE trabecular bone images that may be useful in the diagnosis of osteopenic states. Two different CRAZED-type MSE imaging sequences based on spin-echo and EPI imaging modalities were applied in phantom and in vivo. Preliminary experimental results indicate that EPI imaging readout seems to conceal the MSE contrast correlated with pore dimension in porous media. However it is still possible to detect anisotropy effects related to the bone structure in MSE-EPI images. Some strategies are suggested to optimize the quality of MSE trabecular bone images.

Adult↗

PubMed2001

Characterization of trabecular bone by dipolar demagnetizing field MRI.

A multiple spin-echo (MSE) sequence has been applied for the first time to study trabecular bone ex vivo. The second echo generated by the demagnetizing field presents discrete drops in signal intensity for certain values of the pitch of the magnetization helix created by the correlation gradient. These dips may reflect characteristic pore sizes in the trabecular bone specimens. This hypothesis is supported by similar experiments performed on a phantom with uniform pore size distribution. Trabecular bone images weighted in the MSE contrast mechanism are reported.

Animals↗

PubMed2001

Effects of higher rank multipoles on relaxation of an I = 3 spin system.

Magnetic multipoles of rank higher than one become active in spin systems with I > 1/2 and their contribution to relaxation depends on dynamics. The appearance of multipole terms complicates the relaxation description and supports the multiexponential behavior of relaxation. In this paper the effects of high-rank multipoles on lineshape and longitudinal relaxation of I = 3 spin systems are presented. Results obtained from both numerical simulation and experimental data show that longitudinal and transverse relaxation are strongly influenced by these multipole terms, especially at lower temperature where, due to lower molecular mobility, the extreme narrowing condition is not fulfilled.

Journal Article↗

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↗

PubMedDate not supplied

Characterization of porous media structure by non linear NMR methods.

In this paper we discuss the possibility of modifying the multiple spin echoes existing theory, developed for a homogeneous system, to describe also an inhomogeneous system such as a porous medium. We report here the first experimental application of MSE methods to materials like travertine. The ratio A(2)/A(1) from water in travertine presents minima for characteristic values of the delay time tau, like what was previously observed in the trabecular bone. By a judicious choice of the delay time tau and of the G gradient strength, the MSE sequence can be made sensitive to a specific length-scale of the sample heterogeneity. Furthermore the MSE image shows a particular new contrast that makes the non linear NMR method very attractive for the assessment of variations of the porous structure in porous systems.

Calcium Carbonate↗

PubMedDate not supplied

Intermolecular double-quantum NMR techniques to probe microstructures on porous media.

In heterogeneous systems the amplitude of the intermolecular double-quantum (DQ) signal depends on sample heterogeneity over a correlation distance dc=pi/(gammaGct). In this paper two different CRAZED-type sequences were applied in a porous medium phantom. One of these sequences gives rise to a DQ-T2 weighted signal, while the other one gives rise to a DQ-T2* weighted signal. Experimental results indicate that tuning of the correlation distance dc in a porous medium can alter the DQ signal in a manner which depends on the microstructure. This is evident only using the CRAZED-type sequence which gives rise to a DQ-T2* weighted signal.

Magnetic Resonance Spectroscopy↗

PubMedDate not supplied

NMR study on the early stages of hydration of a porous carbonate stone.

Nuclear Magnetic Resonance was employed to obtain information on the pore filling during the absorption process. A porous carbonate stone, largely employed for buildings and mainly outdoor decorations was studied during water absorption by capillary rise, and filled pores radii were evaluated by comparison between experimental and theoretical parametric magnetization decay curves. Non mono-exponential T2 allowed spin populations to be split among the associated different relaxation times.

Absorption↗