Renato Toffanin

Publications

• Fast MRI Methods for the Clinical Evaluation of Skeletal Disorders

  Renato Toffanin, Giuseppe Guglielmi, Maria A. Cova

  12/2011;

  ISBN: 978-953-307-774-1
• 1.45

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  3 T magnetic resonance imaging of the musculoskeletal system.

  G Guglielmi, N Biccari, F Mangano, R Toffanin

  La Radiologia medica. 02/2010; 115(4):571-84.

  The increasing distribution of high-field (3 T) magnetic resonance (MR) systems for clinical use has been accompanied by the need to fully understand the advantages and disadvantages that the increase in signal quality confers. Continuous development of the coils is required to fully express the pot... [more] The increasing distribution of high-field (3 T) magnetic resonance (MR) systems for clinical use has been accompanied by the need to fully understand the advantages and disadvantages that the increase in signal quality confers. Continuous development of the coils is required to fully express the potential of these systems, especially given the synergy between parallel imaging and the recent multichannel phased-array coils, which are able to improve image quality, spatial resolution and diagnostic accuracy in musculoskeletal imaging. The increase in signal offered by the high field makes possible improved visualisation of bone, cartilage, tendons and ligaments. This advantage, together with increased spatial resolution, is particularly useful when studying joints or some of their components, the evaluation of which has produced suboptimal results in non arthrographic examinations such as the glenoid labrum of the shoulder and the articular cartilage of the knee. Thanks to the greater signal-to-noise ratio and improved spatial resolution, MR imaging at 3 T is able to notably increase diagnostic performance in the musculoskeletal setting, with a consequent improvement in patient treatment and management.
• 1.57

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  Fast T2 mapping of the patellar articular cartilage with gradient and spin-echo magnetic resonance imaging at 1.5 T: validation and initial clinical experience in patients with osteoarthritis.

  Emilio Quaia, Renato Toffanin, Giuseppe Guglielmi, Maja Ukmar, Alexia Rossi, Bruno Martinelli, Maria Cova

  Skeletal radiology. 04/2008;

  OBJECTIVE: To evaluate the T2 mapping of patellar articular cartilage in patients with osteoarthritis using gradient and spin-echo (GRASE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: After the imaging of a phantom consisting of two sealed 50-ml test objects with different concentrations ... [more] OBJECTIVE: To evaluate the T2 mapping of patellar articular cartilage in patients with osteoarthritis using gradient and spin-echo (GRASE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: After the imaging of a phantom consisting of two sealed 50-ml test objects with different concentrations (30% and 90% weight/volume) of copper sulphate, the T2 mapping of patellar articular cartilage was performed in 35 patients (21 male and 14 female; mean age +/- SD 42 +/- 17 years) with moderate degree of patellar osteoarthritis. Turbo-spin-echo (TSE) (TR milliseconds/minimum-maximum TE milliseconds 3,000/15-120; total acquisition time 5 min 52 s) and GRASE (TR milliseconds/minimum-maximum TE milliseconds 3,000/15-120; total acquisition time 1 min 51 s) were employed. In each patient patellar cartilage was segmented at nine locations (three superior, three central, and three inferior) by manually defined regions of interest. T2 relaxation times were calculated using a linear fit applied to the logarithm of signal intensity decay. RESULTS: In the phantom the T2 values measured by GRASE were similar to those measured by MR spectroscopy (test object 1: 48.1 ms vs 51 ms; test object 2: 66.8 ms vs 71 ms; P > 0.05, Wilcoxon test). In patients GRASE and TSE-derived T2 values demonstrated good agreement (mean difference +/- SD, 1.81 +/- 3.63 ms). The within-patient coefficient of variation was 22% for TSE and 23% for GRASE. CONCLUSION: Fast T2 mapping of the patellar articular cartilage can be performed with GRASE within a third of the time of that of standard sequences.
• 2.82

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  Mechanical and diffusive properties of homogeneous alginate gels in form of particles and cylinders.

  E Pasut, R Toffanin, D Voinovich, C Pedersini, E Murano, M Grassi

  Journal of biomedical materials research. Part A. 02/2008;

  In this study, alginate polymers are used to get homogeneous cylindrical or spherical gels. MRI techniques are employed to study homogeneity of these gels. Four different alginates are used and, for each one, five different concentrations for mechanical tests and three different concentrations for r... [more] In this study, alginate polymers are used to get homogeneous cylindrical or spherical gels. MRI techniques are employed to study homogeneity of these gels. Four different alginates are used and, for each one, five different concentrations for mechanical tests and three different concentrations for release tests are studied. Mechanical tests are performed to get gels' linear viscoelasticity region and then to evaluate their crosslink density in relation to polymer concentration. Afterwards, three model molecules (theophylline, vitamin B(12), and myoglobin) are loaded within gels to study the release kinetics in water from both cylindrical and spherical gels. Diffusion coefficients calculated from these experiments are then used to estimate the polymeric network mesh wideness. This work shows how crosslink density increases with polymer concentration regardless of the alginate type considered. In addition, while vitamin B(12) diffusion coefficient is inversely proportional to crosslink density, myoglobin is too large to diffuse through the polymeric network, whatever the alginate type and polymer concentration. At the same time, theophylline is too small to be sensibly affected by increasing the polymeric network crosslink density. Finally, MRI analysis and vitamin B(12) diffusion coefficient values prove that, structurally speaking, cylinders and spheres are similar and homogeneous. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008.
• 2.82

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  Chondrocyte-alginate bioconstructs: a nuclear magnetic resonance relaxation study.

  Paola Fantazzini, Carla Garavaglia, Santiago Gomez, Renato Toffanin, Franco Vittur

  Journal of biomedical materials research. Part A. 12/2007; 83(2):345-53.

  Proton nuclear magnetic resonance (NMR) relaxometry can give informations about hydrogel scaffold properties. As these properties can be modified with culture time and conditions according to scaffold biodegradability and new tissue biosynthesis, the aim of this research was to test the efficiency o... [more] Proton nuclear magnetic resonance (NMR) relaxometry can give informations about hydrogel scaffold properties. As these properties can be modified with culture time and conditions according to scaffold biodegradability and new tissue biosynthesis, the aim of this research was to test the efficiency of this noninvasive NMR technique in the follow-up of 3D cultures for tissue engineering. The distributions of proton relaxation times T1 and T2 have been measured on cylindrical gel samples of different types of alginate, in the presence or absence of hyaluronate, in gels or bioconstructs with encapsulated chondrocytes cultured for 30 days in normal or reduced weight conditions. It was found that T2 increases with the mannuronate/guluronate ratio in alginate samples and with the presence of hyaluronate. The distributions of both T1 and T2 result wider for bioconstructs cultured in normal gravity than for those cultured in reduced weight conditions. Neither cell growing nor collagen production but only GAG neosynthesis have been demonstrated in our experimental conditions. In conclusion, T2 is sensitive to the gel properties (possibly to the rigidity of macromolecular components). The homogeneity of bioconstructs can be monitored by the distribution of T1 and T2. We propose that nonspatially resolved NMR relaxometry can efficiently be used in monitoring tissue development in a biodegradable scaffold for tissue engineering.
• 2.03

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  Structure of the exopolysaccharide produced by Enterobacter amnigenus.

  Paola Cescutti, Anne Kallioinen, Giuseppe Impallomeni, Renato Toffanin, Piero Pollesello, Matti Leisola, Tero Eerikäinen

  Carbohydrate research. 03/2005; 340(3):439-47.

  The bacterial species Enterobacter amnigenus was isolated from sugar beets harvested in Finland. It produced an exopolysaccharide rich in l-fucose, which gave viscous water solutions. Its primary structure was determined mainly by NMR spectroscopy and ESIMS of oligosaccharides and a polysaccharide w... [more] The bacterial species Enterobacter amnigenus was isolated from sugar beets harvested in Finland. It produced an exopolysaccharide rich in l-fucose, which gave viscous water solutions. Its primary structure was determined mainly by NMR spectroscopy and ESIMS of oligosaccharides and a polysaccharide with decreased molecular weight, obtained by Smith degradation of the O-deacetylated native polymer [carbohydrate structure: see text]
• 2.62

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  Degenerative changes of porcine intervertebral disc induced by vertebral endplate injuries.

  Gianluca Cinotti, Carlo Della Rocca, Salvatore Romeo, Franco Vittur, Renato Toffanin, Guido Trasimeni

  Spine. 02/2005; 30(2):174-80.

  STUDY DESIGN: Graded endplate injuries were performed in porcine lumbar discs. The effects of such injuries were compared to control animals in which a sham operation was performed. OBJECTIVES: To investigate the effects of endplate injuries on disc tissue. SUMMARY OF BACKGROUND DATA: Studies have s... [more] STUDY DESIGN: Graded endplate injuries were performed in porcine lumbar discs. The effects of such injuries were compared to control animals in which a sham operation was performed. OBJECTIVES: To investigate the effects of endplate injuries on disc tissue. SUMMARY OF BACKGROUND DATA: Studies have shown that injuries of vertebral endplates are frequently found at autopsy. However, little is known on the effects of acute injuries of vertebral endplates in vivo. METHODS: Ten domestic pigs were included in the study group. Under general anesthesia, the lower three discs of the lumbar spine were exposed and randomly submitted to multiple endplate injuries, isolated endplate injury, and no treatment. A sham operation was performed in 5 pigs used as control group. Animals were killed 7 months after surgery and the harvested lumbar spine submitted to MRI investigations, histologic, and biochemical analysis. RESULTS: MRI showed that all but one discs treated with multiple endplate injuries were markedly degenerated while, of the discs treated with an isolated injury, one was markedly degenerated, five slightly degenerated and two were normal (P = 0.01). Histologic analysis showed severe changes in discs treated with multiple injuries. In those who had an isolated injury, changes were less severe and essentially limited to the posterior anulus or the inner anterior anulus. Biochemical analysis showed an inverse correlation between uronate content in the nucleus pulposus and severity of endplate injuries. CONCLUSIONS: Injuries of vertebral endplates in porcine discs were found to cause degenerative changes in the disc tissue on MRI, histologic, and biochemical investigations. The severity of such degenerative changes was related to the severity of endplate injuries. Injuries of vertebral endplate may be one of the pathomechanisms leading to early changes in the disc matrix and eventually to abnormal biomechanical behavior of the whole disc. The present animal model seems to be a suitable experimental model for disc degeneration.
• 2.53

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  Transverse relaxation mechanisms in articular cartilage.

  V Mlynárik, P Szomolányi, R Toffanin, F Vittur, S Trattnig

  Journal of magnetic resonance (San Diego, Calif. : 1997). 09/2004; 169(2):300-7.

  Relaxation rates in the rotating frame (R1rho) and spin-spin relaxation rates (R2) were measured in articular cartilage at various orientations of cartilage layer to the static magnetic field (B0), at various spin locking field strengths and at two different static magnetic field strengths. It was f... [more] Relaxation rates in the rotating frame (R1rho) and spin-spin relaxation rates (R2) were measured in articular cartilage at various orientations of cartilage layer to the static magnetic field (B0), at various spin locking field strengths and at two different static magnetic field strengths. It was found that R1rho in the deep radial zone depended on the orientation of specimens in the magnet and decreased with increasing the spin locking field strength. In contrast, R1rho values in the transitional zone were nearly independent of the specimen orientation and the spin locking field strength. Measurements of the same specimens at 2.95 and 7.05 T showed an increase of R1rho and most R2 values with increasing B0. The inverse B0 dependence of some R2 values was probably due to a multicomponent character of the transverse magnetization decay. The experiments revealed that the dominant T1rho and T2 relaxation mechanism at B0 < or = 3 T is a dipolar interaction due to slow anisotropic motion of water molecules in the collagen matrix. On average, the contribution of scalar relaxation due to rapid proton exchange in femoral head cartilage at 2.95 T is about 6% or less of the total R1rho at the spin locking field of 1000 Hz.

• Numerical simulation of trabecular bone magnetic resonance imaging.

  I Strolka, R Toffanin, A. Accardo, D Dreossi, I Frollo, F Vittur

  Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference. 02/2004; 2:1088-91.

  A numerical simulation of trabecular bone structure MR imaging is described. The input of the model is derived from synchrotron 3D muCT trabecular bone images with a resolution of 14mummu14mumx14mum. The static magnetic field perturbation in the bone sample induced by the differences in magnetic sus... [more] A numerical simulation of trabecular bone structure MR imaging is described. The input of the model is derived from synchrotron 3D muCT trabecular bone images with a resolution of 14mummu14mumx14mum. The static magnetic field perturbation in the bone sample induced by the differences in magnetic susceptibility values between mineralized bone and bone marrow is computed and the MRI experiment for a selected imaging sequence is modeled.
• 2.15

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  Ex vivo assessment of trabecular bone structure from three-dimensional projection reconstruction MR micro-images

  A. Accardo, G. Candido, V. Jellus, R. Toffanin, F. Vittur

  Biomedical Engineering, IEEE Transactions on. 09/2003;

  Magnetic resonance (MR) imaging has recently been proposed for assessing osteoporosis and predicting fracture risks. However, accurate acquisition techniques and image analysis protocols for the determination of the trabecular bone structure are yet to be defined. The aim of this study was to assess... [more] Magnetic resonance (MR) imaging has recently been proposed for assessing osteoporosis and predicting fracture risks. However, accurate acquisition techniques and image analysis protocols for the determination of the trabecular bone structure are yet to be defined. The aim of this study was to assess the potential of projection reconstruction (PR) MR microscopy in the analysis of the three-dimensional (3-D) architecture of trabecular bone and in the prediction of its biomechanical properties. High-resolution 3-D PR images (41 × 41 × 82 μm³ voxels) of 15 porcine trabecular bone explants were analyzed to determine the trabecular bone volume fraction (Vv), the mean trabecular thickness (Tb.Th), and the mean trabecular separation (Tb.Sp) using the method of directed secants. These parameters were then compared with those derived from 3-D conventional spin-echo microimages. In both cases, segmentation of the high-resolution images into bone and bone marrow was obtained using a spatial adaptive threshold. The contemporary inclusion of Vv, Tb.Th and 1/Tb.Sp in a multiple regression analysis significantly improved the prediction of Young's modulus (YM). The parameters derived from the PR spin-echo images were found to be stronger predictors of YM (R² = 0.94, p = 0.004) than those derived from conventional spin-echo images (R² = 0.79, p = 0.051). Our study indicates that projection reconstruction MR microscopy appears to be more accurate than the conventional Fourier transform method in the quantification of trabecular bone structure and in the prediction of its biomechanical properties. The proposed PR approach should be readily adaptable to the in vivo MRI studies of osteoporosis.
• 1.45

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  [Quantitative magnetic resonance of trabecular bone]

  Giuseppe Guglielmi, Renato Toffanin, Maria Cova, Mario Cammisa

  La Radiologia medica. 04/2003; 105(3 Suppl 1):34-40.

• Magnetic resonance microscopy for the quantitative analysis of trabecular bone architecture.

  Renato Toffanin, Agostino Accardo, Franco Vittur

  Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology. 08/2002; 9(1):P173-4.

  A major concern for long-term spaceflight is the effect of microgravity on bone structure and mass as a loss of cortical and trabecular bone volume and density, both of which can lead to decreased bone strength and an increased risk of bone fracture. Detailed analysis of the three-dimensional struct... [more] A major concern for long-term spaceflight is the effect of microgravity on bone structure and mass as a loss of cortical and trabecular bone volume and density, both of which can lead to decreased bone strength and an increased risk of bone fracture. Detailed analysis of the three-dimensional structure of trabecular bone, and its relation to bone strength has become feasible only recently using high-resolution 3D imaging techniques. In particular, magnetic resonance microscopy (MRM) has proved to be particularly useful for the ex vivo evaluation of the complex architecture of trabecular bone. In this study, we describe the use of two different MRM-based methods for the quantitative evaluation of the three-dimensional structure of trabecular bone explants and for the prediction of their biomechanical properties. The in vivo application of such methods is also discussed.
• 3.59

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  MR microscopy of hyaline cartilage: current status.

  Maria Cova, Renato Toffanin

  European radiology. 05/2002; 12(4):814-23.

  Cartilage degenerative diseases, such as osteoarthritis, affect million of people. Magnetic resonance imaging is presently the most accurate imaging modality in evaluating the state of hyaline cartilage; however, clinical MRI does not accurately reveal early degenerative alterations in cartilage, du... [more] Cartilage degenerative diseases, such as osteoarthritis, affect million of people. Magnetic resonance imaging is presently the most accurate imaging modality in evaluating the state of hyaline cartilage; however, clinical MRI does not accurately reveal early degenerative alterations in cartilage, due mainly to low spatial resolution. Magnetic resonance microscopy (MRM, or microMRI) appears exceptionally well suited to the in vitro or ex vivo study of this heterogeneous tissue, due to its high spatial resolution; however, despite this, further studies are necessary to evaluate the potential of MRM in the detection of early cartilage damage. Herein we briefly review the current applications of MRM in the study of hyaline cartilage. In particular, we review the MR appearance of hyaline cartilage on high-resolution images, the different MRM techniques used to image normal and enzymatically or chemically degraded cartilage and the potential use of contrast agents. The future directions and the relevance of MRM findings for a better understanding of cartilage physiology in health and disease are also discussed.
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  Structural investigations of cross-linked hyaluronan.

  Amelia Gamini, Sergio Paoletti, Renato Toffanin, Fulvio Micali, Luigi Michielin, Carla Bevilacqua

  Biomaterials. 03/2002; 23(4):1161-7.

  Structural properties of several cross-linked hyaluronan derivatives, obtained by scanning electron microscopy, monodimensional NMR microscopy and small angle X-ray scattering of synchrotron radiation, are presented and compared with those observed for non-modified hyaluronic acid, used as a referen... [more] Structural properties of several cross-linked hyaluronan derivatives, obtained by scanning electron microscopy, monodimensional NMR microscopy and small angle X-ray scattering of synchrotron radiation, are presented and compared with those observed for non-modified hyaluronic acid, used as a reference material. The experimental results, obtained in different media, showed a consistent picture of the synthesized matrices. In particular, the presence of zones of denser polymeric material observed by electron microscopy resulted in a higher transversal relaxation rate of the bulk water protons as well as in a decrease of the diffusion coefficient obtained by NMR microscopy. Moreover, the presence of polymer junction zones gave rise to the appearance of a well-defined correlation peak in the pattern of intensity of the scattered X-radiation.

• Quantification of trabecular bone structure from three-dimensionalμMR images

  A. Accardo, G. Candido, R Toffanin, F Vittur, V. Jellus

  Image Processing, 2001. Proceedings. 2001 International Conference on; 11/2001

  Magnetic resonance imaging (MRI) has recently been applied to the study of osteoporosis. Accurate acquisition techniques and image analysis protocols for the determination of trabecular bone structure are yet to be defined. Two different approaches for three-dimensional acquisition and reconstructio... [more] Magnetic resonance imaging (MRI) has recently been applied to the study of osteoporosis. Accurate acquisition techniques and image analysis protocols for the determination of trabecular bone structure are yet to be defined. Two different approaches for three-dimensional acquisition and reconstruction are exploited to derive the structural parameters of trabecular bone explants. In particular, MR microscopy (μMRI) is used to obtain conventional (FT) and projection reconstruction (PR) spin-echo images (41×41×41 μm³/voxel). Segmentation of the high-resolution images into bone and bone marrow is obtained by using a suitable threshold. The main bone structural parameters are then derived by using a 3D version of the directed secant algorithm applied to a series of contiguous sections. The efficiency of the two methods in the assessment of trabecular bone architecture is discussed
• 3.05

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  Proteoglycan depletion and magnetic resonance parameters of articular cartilage.

  R Toffanin, V Mlynárik, S Russo, P Szomolányi, A Piras, F Vittur

  Archives of biochemistry and biophysics. 07/2001; 390(2):235-42.

  Calcium ions and various amounts of proteoglycans were removed from porcine articular cartilage explants using ethylenediaminetetraacetic acid or guanidinium chloride solutions. The water proton magnetic parameters such as T(1) and T(2) relaxation times, diffusion (D), and magnetization transfer (M(... [more] Calcium ions and various amounts of proteoglycans were removed from porcine articular cartilage explants using ethylenediaminetetraacetic acid or guanidinium chloride solutions. The water proton magnetic parameters such as T(1) and T(2) relaxation times, diffusion (D), and magnetization transfer (M(S)/M(0)) were then measured by 1D MR microscopy on native specimens, after incubation in the extracting solutions and after final reconditioning in a physiological saline. While the replacement of the interstitial fluid by the treating solutions strongly affected the various MR parameters, calcium depletion did not show any influence on the MRI appearance of the chondral tissue. Interestingly, only the longitudinal relaxation time T(1) and the diffusion coefficient D were seen to be sensitive to an extensive proteoglycan depletion of the tissue. Our results indicate that a modest proteoglycan depletion, as it occurs in the early stage of a pathological cartilage degradation, has little relevance to the above MR parameters. Further MRI studies on the macromolecular components of cartilage are, therefore, necessary for a better understanding of the interaction mechanisms between water and extracellular matrix that might lead to the early diagnosis of the cartilage damage.

• Collagen fibrils are differently organized in weight-bearing and not-weight-bearing regions of pig articular cartilage.

  S Gomez, R Toffanin, S Bernstorff, M Romanello, H Amenitsch, M Rappolt, R Rizzo, F Vittur

  The Journal of experimental zoology. 11/2000; 287(5):346-52.

  The magnetic resonance (MR) appearance of the weight-bearing ("loaded") and not-weight-bearing ("unloaded") regions in T(2)-weighted images of pig articular cartilage is different. On the hypothesis that this difference may be ascribed, at least in part, to a different collagen f... [more] The magnetic resonance (MR) appearance of the weight-bearing ("loaded") and not-weight-bearing ("unloaded") regions in T(2)-weighted images of pig articular cartilage is different. On the hypothesis that this difference may be ascribed, at least in part, to a different collagen fibre organization in the two regions, this organization was studied using biochemical, histological, and X-ray diffraction methods. While the mean concentrations of collagen and of its cross-links were the same in the two regions, a regular small angle X-ray diffraction pattern was observed only for the habitually "loaded" tissue. It was also seen by light microscopy that the four typical functional zones were well displayed in the "loaded" cartilage whereas they were not clearly depicted in the "unloaded" tissue. Collagen presented a high concentration of fibrils forming an intricate and dense meshwork at the surface of both "loaded" and "unloaded" cartilage. A second zone of high collagen concentration was present at the upper layer of the deep zone of "loaded" cartilage. By contrast, this lamina of highly concentrated fibrils was lacking in "unloaded" cartilage and collagen fibrils appear thinner. Our study proves that the organization of collagen fibres is different for the "loaded" and "unloaded" regions of articular cartilage. It also suggests that this different organization may influence the MR appearance of the tissue. J. Exp. Zool. 287:346-352, 2000.
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  Articular cartilage repair in rabbits by using suspensions of allogenic chondrocytes in alginate.

  E Fragonas, M Valente, M Pozzi-Mucelli, R Toffanin, R Rizzo, F Silvestri, F Vittur

  Biomaterials. 05/2000; 21(8):795-801.

  The feasibility of allogenic implants of chondrocytes in alginate gels was tested for the reconstruction in vivo of artificially full-thickness-damaged articular rabbit cartilage. The suspensions of chondrocytes in alginate were gelled by the addition of calcium chloride solution directly into the d... [more] The feasibility of allogenic implants of chondrocytes in alginate gels was tested for the reconstruction in vivo of artificially full-thickness-damaged articular rabbit cartilage. The suspensions of chondrocytes in alginate were gelled by the addition of calcium chloride solution directly into the defects giving in situ a construct perfectly inserted and adherent to the subchondral bone and to the walls of intact cartilage. The tissue repair was controlled at 1, 2, 4 and 6 months after the implant by NMR microscopy, synchrotron radiation induced X-ray emission to map the sulfur of glycosaminoglycans and by histochemistry. Practically a complete repair of the defect was observed 4-6 months from the implant of the chondrocytes with the recovery of a normal tissue structure. Controls in which Ca-alginate alone was implanted developed only a fibrous cartilage.
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  Inhomogeneous alginate gel spheres: an assessment of the polymer gradients by synchrotron radiation-induced X-ray emission, magnetic resonance microimaging, and mathematical modeling.

  B Thu, O Gåserød, D Paus, A Mikkelsen, G Skjåk-Braek, R Toffanin, F Vittur, R Rizzo

  Biopolymers. 02/2000; 53(1):60-71.

  It has been previously demonstrated that calcium alginate gels prepared by dialysis often exhibit a concentration inhomogeneity being the polymer concentration considerably lower in the center of the gel than at the edges. Inhomogeneity may be a preferred structure in microcapsules due to low porosi... [more] It has been previously demonstrated that calcium alginate gels prepared by dialysis often exhibit a concentration inhomogeneity being the polymer concentration considerably lower in the center of the gel than at the edges. Inhomogeneity may be a preferred structure in microcapsules due to low porosity and higher stability so that it is interesting to evaluate the polymer gradient in spherically symmetrical small alginate beads (1.0-0.7 mm diameter) obtained in different conditions. In this paper, two complementary techniques have been used to investigate this aspect. The concentration gradient of alginate has been analyzed by measuring both the spatial distribution of calcium ions in sections of alginate gel spheres, by means of x-ray fluorescence spectroscopy, and the T2 relaxation behavior on intact gel beads using magnetic resonance microimaging. The experimentally determined gradients from three-dimensional gels provide data to reevaluate the parameter estimates in the recently reported mathematical model for alginate gel formation (A. Mikkaelsen and A. Elgsaeter, Biopolymers, 1995, Vol. 36, pp. 17-41). The model may account for the gels being less inhomogeneous when nongelling sodium or magnesium ions are added during gelation.
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  Short-TE projection reconstruction MR microscopy in the evaluation of articular cartilage thickness.

  M Cova, R Toffanin, P Szomolanyi, F Vittur, R S Pozzi-Mucelli, V Jellús, F Silvestri, L Dalla Palma

  European radiology. 02/2000; 10(8):1222-6.

  The aim of this study was to assess the potential of projection-reconstruction (PR) MR microscopy in the accurate measurement of cartilage thickness. Short-TE PR microimages were acquired at 7.05 T on bone-cartilage cylindrical plugs excised from four regions of two disarticulated femoral heads (i. ... [more] The aim of this study was to assess the potential of projection-reconstruction (PR) MR microscopy in the accurate measurement of cartilage thickness. Short-TE PR microimages were acquired at 7.05 T on bone-cartilage cylindrical plugs excised from four regions of two disarticulated femoral heads (i. e. superior, inferior, posterior and anterior), using an NMR instrument equipped with a microimaging accessory. The PR microimages were then correlated with conventional spin-echo (SE) microimages and with histology. On PR microimages, acquired with an echo time of 3.2 ms, the cartilage signal was increased, allowing an accurate delineation of the cartilage from the tidemark/cortical bone region. As a consequence, by the PR method a more precise measurement of cartilage thickness compared with that performed by the conventional SE approach was feasible. An excellent correlation between PR microimages and histology was also obtained (r = 0.90). By the proposed method it is possible to accurately determine the cartilage thickness better than with the conventional SE sequences.