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ABSTRACT: Diffuse liver diseases have a definitive radiological importance due to the ability of MR imaging to demonstrate abnormalities before the patient is symptomatic or the liver damage is advanced. Biopsy procedures are invasive, may lead to complications and have a sample bias. Imaging biomarkers target to fat, water, and iron tissue concentrations may be considered as hepatic virtual biopsies. There is a need to identify a rapid and practicable method to accurately quantify liver steatosis, differentiate steatohepatitis from simple steatosis, grade the necroinflammatory activity, calculate the liver iron burden and monitor overload progression. MR is used in the evaluation of diffuse liver disorders with accurate approaches such as the use of chemical shift, Dixon vector analysis, turbo spin echo fat suppression, and T2* gradient echo techniques. These methods are influenced by some factors like proportional ambiguity, T1 and T2* effects on signal decay, adding a significant bias in the combined fat-water-iron quantification. A GRE multi-echo chemical shift sequence was configured to independently calculate fat, water, and iron parametric liver images. It is now necessary to conduct a pilot project in order to validate this method in a group of subjects without and with different grades of fat, water, and iron liver changes.
Abdominal Imaging 06/2011; 37(2):180-7. · 1.73 Impact Factor
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Elies Fuster-Garcia,
Clara Navarro,
Javier Vicente,
Salvador Tortajada,
Juan M García-Gómez,
Carlos Sáez,
Jorge Calvar,
John Griffiths,
Margarida Julià-Sapé,
Franklyn A Howe, [......],
Wolfhard Semmler,
Jaume Capellades,
Carles Majós, Angel Alberich-Bayarri,
Antoni Capdevila,
Daniel Monleón,
Luis Martí-Bonmatí,
Carles Arús,
Bernardo Celda,
Montserrat Robles
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ABSTRACT: This study demonstrates that 3T SV-MRS data can be used with the currently available automatic brain tumour diagnostic classifiers which were trained on databases of 1.5T spectra. This will allow the existing large databases of 1.5T MRS data to be used for diagnostic classification of 3T spectra, and perhaps also the combination of 1.5T and 3T databases.
Brain tumour classifiers trained with 154 1.5T spectra to discriminate among high grade malignant tumours and common grade II glial tumours were evaluated with a subsequently-acquired set of 155 1.5T and 37 3T spectra. A similarity study between spectra and main brain tumour metabolite ratios for both field strengths (1.5T and 3T) was also performed.
Our results showed that classifiers trained with 1.5T samples had similar accuracy for both test datasets (0.87 ± 0.03 for 1.5T and 0.88 ± 0.03 for 3.0T). Moreover, non-significant differences were observed with most metabolite ratios and spectral patterns.
These results encourage the use of existing classifiers based on 1.5T datasets for diagnosis with 3T (1)H SV-MRS. The large 1.5T databases compiled throughout many years and the prediction models based on 1.5T acquisitions can therefore continue to be used with data from the new 3T instruments.
MAGMA Magnetic Resonance Materials in Physics Biology and Medicine 02/2011; 24(1):35-42. · 1.88 Impact Factor
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ABSTRACT: In vivo two-dimensional (2D) fractal dimension (D2D) analysis of the cancellous bone at 1.5 T has been related to bone structural complexity and shown to be a potential imaging-based biomarker for osteoporosis. The objectives of this study were to assess at 3 T the in vivo feasibility of three-dimensional (3D) bone fractal dimension (D3D) analysis, analyze the relationship of D2D and D3D with osteoporosis, and investigate the relationship of D3D with spinal bone mineral density (BMD).
A total of 24 female subjects (67 +/- 7 yr old, mean +/- SD) was included in this study. The cohort consisted of 12 healthy volunteers and 12 patients with osteoporosis. MR image acquisitions were performed in the nondominant metaphysis of the distal radius with a 3 T MR scanner and an isotropic resolution of 180 microm. After segmentation and structural reconstruction, 2D and 3D box-counting algorithms were applied to calculate the fractal complexity of the cancellous bone. D2D and D3D values were compared between patients with osteoporosis and healthy subjects, and their relationship with radius BV/TV and spinal BMD was also assessed.
Significant differences between healthy subjects and patients with osteoporosis were obtained for D3D (p < 0.001), with less differentiation for D2D (p = 0.04). The relationship between fractal dimension and BMD was not significant (r = 0.43, p = 0.16 and r = 0.23, p = 0.48, for D2D and D3D, respectively).
The feasibility of trabecular bone D3D calculations at 3 T and the relationship of both D2D and D3D parameters with osteoporosis were demonstrated, with a better differentiation for the 3D method. Furthermore, the D3D parameter has probably a different nature of information regarding the trabecular bone status not directly explained by BMD alone. Future studies with subjects with osteopenia and larger sample sizes are warranted to further establish the potential of D2D and D3D in the study of osteoporosis.
Medical Physics 09/2010; 37(9):4930-7. · 2.83 Impact Factor
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ABSTRACT: During the last decades, treatment of bone defects has been directed to the research in polymer scaffolds of different architectures. Scaffolds play a key role in bone regeneration and the design of their 3D architecture is crucial to develop their function. The use of high spatial resolution acquisitions from µCT scanners in combination with advanced image processing methods represent a powerful tool to develop a structural and mechanical characterization of the synthesized polymer scaffolds and evaluate the achievement of the desired properties at the manufacture stage. The algorithms employed for the image analysis and fast meshing processes allows for the detailed numerical simulations of the mechanical properties at a micro scale level, also called µFE. These simulations suppose a high computational burden that can be optimized by proper µFE model definition. µFE results obtained for the apparent Young’s modulus are highly close to the experimental results. All the simulations performed in the synthesized scaffolds using the µFE method have been done in the linear behaviour domain. However, in future it would be of high interest to improve in the knowledge of the non-linear behaviour of the scaffolds when strong compressive conditions are considered and buckling processes begin. Also, the analysis of the scaffolds using µCT combined with µFE before and after cell seeding would help to evaluate the non-invasive method proposed as a reliable way to quantify the levels of new tissue deposition in the scaffold.
08/2010; , ISBN: 978-953-307-123-7
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ABSTRACT: Although further evaluation is needed about the usefulness of these methods in osteoporosis, it seems clear that computational generated 3D models of the cancellous bone from high resolution 3 Tesla MRI can be used to characterize bone in vivo, analyzing different mechanical conditions of the cancellous microstructure. The FE analysis could be performed in a more complex philosophy, if bone anisotropy is considered for bulk material properties definition (Hellmich et al., 2008), and also if not only the part with linear behaviour of the stress–strain curve is considered, but also the curve region showing plasticity or non-recoverable deformation. These studies should add more information to the mechanisms involved in bone fracture, like buckling phenomena, just before the breaking point arrives. Patients are classified nowadays using the World Health Organization (WHO) criteria, depending on the amount of bone loss, in osteopenic or osteoporotic patient. These are the clinical references used for new biomarkers evaluation. However, multivariate studies may provide different groups or classification patterns for the patient populations. Results of the mechanical simulations among a large population should provide knowledge for the establishment of new biomarkers of disease. New clinical trials and studies should help to analyze the sensitivity of these parameters to the treatment.
08/2010; , ISBN: 978-953-307-123-7
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ABSTRACT: The most important advantage of 3.0-T magnetic resonance (MR) imaging systems is their increased signal-to-noise ratio (SNR) compared with 1.5-T systems. The higher SNR can be used to shorten acquisition time, achieve higher spatial resolution, or a combination of the two, thereby improving image quality and clinical diagnosis. In fact, 3.0-T MR imaging systems have already proved superior to 1.5-T systems in neuroradiologic and musculoskeletal applications. In the abdomen, 3.0-T MR imaging is uniquely beneficial for techniques such as enhanced and nonenhanced hepatic imaging, diffusion-weighted imaging, angiography, MR pancreatography, and colonography. Admittedly, 3.0-T abdominal imaging has important technical limitations, such as standing wave artifact, chemical shift artifact, susceptibility artifact, and safety issues such as increased energy deposition within the patient's body. Furthermore, 3.0-T abdominal MR imaging is still in the early stages of development and requires substantial modifications of the pulse sequences and hardware components used for 1.5-T imaging. Nevertheless, the ability to obtain physiologic and functional information within reasonably short acquisition times with 3.0-T abdominal MR imaging bodies well for the future of this imaging technique.
Radiographics 10/2009; 29(6):1547-63. · 2.85 Impact Factor
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Angel Alberich-Bayarri,
David Moratal,
Jorge L Escobar Ivirico,
José C Rodríguez Hernández,
Ana Vallés-Lluch,
Luis Martí-Bonmatí,
Jorge Más Estellés,
Joao F Mano,
Manuel Monleón Pradas,
José L Gómez Ribelles,
Manuel Salmerón-Sánchez
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ABSTRACT: Detailed knowledge of the porous architecture of synthetic scaffolds for tissue engineering, their mechanical properties, and their interrelationship was obtained in a nondestructive manner. Image analysis of microcomputed tomography (microCT) sections of different scaffolds was done. The three-dimensional (3D) reconstruction of the scaffold allows one to quantify scaffold porosity, including pore size, pore distribution, and struts' thickness. The porous morphology and porosity as calculated from microCT by image analysis agrees with that obtained experimentally by scanning electron microscopy and physically measured porosity, respectively. Furthermore, the mechanical properties of the scaffold were evaluated by making use of finite element modeling (FEM) in which the compression stress-strain test is simulated on the 3D structure reconstructed from the microCT sections. Elastic modulus as calculated from FEM is in agreement with those obtained from the stress-strain experimental test. The method was applied on qualitatively different porous structures (interconnected channels and spheres) with different chemical compositions (that lead to different elastic modulus of the base material) suitable for tissue regeneration. The elastic properties of the constructs are explained on the basis of the FEM model that supports the main mechanical conclusion of the experimental results: the elastic modulus does not depend on the geometric characteristics of the pore (pore size, interconnection throat size) but only on the total porosity of the scaffold.
Journal of Biomedical Materials Research Part B Applied Biomaterials 06/2009; 91(1):191-202. · 2.15 Impact Factor
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ABSTRACT: Normal and degenerated cartilages have different magnetic resonance (MR) capillary permeability (K(trans)) and interstitial interchangeable volume (v(e)). Our hypothesis was that glucosamine sulfate treatment modifies these neovascularity abnormalities in osteoarthritis. Sixteen patients with patella degeneration, randomly distributed into glucosamine or control groups, underwent two 1.5-Tesla dynamic contrast-enhanced MR imaging studies (treatment initiation and after 6 months). The pain visual analog scale (VAS) and American Knee Society (AKS) score were used. A two-compartment pharmacokinetic model was used. Percentages of variations (postreatment-pretreatment/pretreatment) were compared (t-test for independent data). In the glucosamine group, pain and functional outcomes statistically improved (VAS: 7.3 +/- 1.1 to 3.6 +/- 1.3, p < 0.001; AKS: 18.6 +/- 6.9 to 42.9 +/- 2.7, p < 0.01). Glucosamine significantly increased K(trans) at 6 months (-54.4 +/- 21.2% vs 126.7 +/- 56.9%, p < 0.001, control vs glucosamine). In conclusion, glucosamine sulfate decreases pain while improving functional outcome in patients with cartilage degeneration. Glucosamine sulfate increases K(trans), allowing its proposal as a surrogate imaging biomarker after 6 months of treatment.
European Radiology 02/2009; 19(6):1512-8. · 3.22 Impact Factor
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ABSTRACT: The purpose of this study was to investigate the in vivo morphologic and elastic parameters of trabecular bone with high-resolution 3-T MRI in a healthy reference population.
A series of wrist MR images were acquired with high-spatial-resolution (180 mum) isotropic voxels from 40 subjects without reported bone disease. After image postprocessing, the bone volume-to-total volume ratio, trabecular thickness, trabecular separation, and trabecular number were calculated in the morphologic analysis. Trabecular bone was mechanically simulated using the finite-element method to calculate the apparent elastic modulus parameter. The relationship between morphologic and mechanical parameters was studied. The influence of the analyzed bone volume was also investigated.
Statistically significant sex influences were found on the bone volume-to-total volume ratio (p = 0.003), trabecular thickness (p = 0.02), and apparent elastic modulus (p = 0.01); these parameters were lower in women. However, trends were found only on trabecular separation (p = 0.06) and trabecular number (p = 0.07). Age had no statistically significant influence in any morphologic (bone volume-to-total volume ratio, r = -0.24, p = 0.13; trabecular thickness, r = -0.03, p = 0.88; trabecular separation, r = 0.12, p = 0.47; and trabecular number, r = -0.23, p = 0.16) or elastic (apparent elastic modulus, r = -0.18, p = 0.26) parameter. A statistically significant relationship between apparent elastic modulus and the square of bone volume-to-total volume ratio was found (r = 0.968, p < 0.001). This association was not seen (r = 0.185, p = 0.25) and apparent elastic modulus results were considerably different (p < 0.001) if the volume of analyzed bone was reduced.
We found that bone volume-to-total volume ratio, trabecular thickness, and apparent elastic modulus are parameters significantly influenced by sex. Apparent elastic modulus results show a relationship with bone volume-to-total volume ratio. Trabecular bone volume should be maximized for an appropriate mechanical analysis.
American Journal of Roentgenology 10/2008; 191(3):721-6. · 2.78 Impact Factor
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ABSTRACT: To study if the pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance (DCE-MR) images of the patellar cartilage are influenced by the main magnetic field strength.
DCE-MR images of the knee were obtained from 16 normal male subjects (eight cases in each 1.5 and 3T magnets). Also, four volunteers were evaluated in both equipments within 1 week. Cartilage pharmacokinetic parameters of vascular permeability (K(trans)), extraction ratio (k(ep)), extravascular extracellular space volume fraction (v(e)) and intravascular space volume fraction (v(p)) were obtained.
Statistically significant differences were observed between the 1.5 and 3T groups for K(trans) (mean+/-S.D.; 5.44+/-2.27 vs. 1.01+/-0.41, respectively) and v(e) (3.37+/-2.32 vs. 0.81+/-0.80). A difference in K(trans) was also present when the same controls were evaluated in both equipments. There were no significant differences for k(ep) and v(p) values. Reproducibility of the pharmacokinetic calculations, assessed with the 24 acquisitions, showed a very low test-retest root mean square coefficient of variation (0.13, 0.10, 0.23 and 0.18 for K(trans), k(ep), v(e) and v(p), respectively).
Cartilage vascular permeability values are influenced by the MR field strength. This should be taken in consideration when analyzing this biomarker.
European Journal of Radiology 05/2008; 67(3):448-52. · 2.61 Impact Factor
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ABSTRACT: In order to help the assessment of trabecular bone diseases and complement Dual X-Ray Absorptiometry (DXA) in diagnosis process, it is needed an accurate mechanical characterization of trabecular bone structure to estimate the risk of fracture and evaluate micro-architecture deterioration. As Finite Element modeling has become a well-established method for analysis of complex structures, an algorithm has been developed to build a Finite Element mesh from three-dimensional reconstruction information in voxels. Generated mesh is loaded in a Finite Element analysis software in order to simulate micro-architecture mechanical behavior under compression conditions. Most part of related researches have been based on ex vivo micro-Computed Tomography (microCT) scans. This study uses three-dimensional trabecular bone reconstructions from high resolution Magnetic Resonance images acquired in vivo.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:1603-6.
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ABSTRACT: As Bone Mineral Density has been demonstrated to be insufficient to elaborate a correct diagnosis of bone diseases such as osteoporosis, a new software tool called EsTra has been developed in order to estimate the most significant structural parameters of trabecular bone microarchitecture. In EsTra, different techniques as automated segmentation, snakes, filtering, skeletonization, voxel classification and three-dimensional reconstruction are applied to Magnetic Resonance images of distal radius and ulna. A microarchitectural study is also carried out from three different viewpoints involving morphological, topological and fractal analysis. Results can be exported to a database to help the research of the disease and a clinical report is elaborated containing the most significant parameters obtained from the analysis.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:2073-6.
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ABSTRACT: As Bone Mineral Density has been demonstrated to be insufficient to elaborate a correct diagnosis of bone diseases such as osteoporosis, a new software toot called EsTra has been developed in order to estimate the most significant structural parameters of trabecular bone microarchitecture. In EsTra, different techniques as automated segmentation, snakes, filtering, skeletonization, voxel classification and three-dimensional reconstruction are applied to Magnetic Resonance images of distal radius and ulna. A microarchitectural study is also carried out from three different viewpoints involving morphological, topological and fractal analysis. Results can be exported to a database to help the research of the disease and a clinical report is elaborated containing the most significant parameters obtained from the analysis.
2007 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-16, 345 E 47TH ST, NEW YORK, NY 10017 USA;
