Barcelona, Spain
Barcelona, Spain

Time filter

Source Type

Negredo E.,Autonomous University of Barcelona | Bonjoch A.,Autonomous University of Barcelona | Gomez-Mateu M.,Polytechnic University of Catalonia | Estany C.,Autonomous University of Barcelona | And 9 more authors.
PLoS ONE | Year: 2012

Background: Algorithms for bone mineral density (BMD) management in HIV-infected patients are lacking. Our objective was to assess how often a dual-energy x-ray absorptiometry (DXA) scan should be performed by assessing time of progression to osteopenia/osteoporosis. Methods: All DXA scans performed between 2000 and 2009 from HIV-infected patients with at least two DXA were included. Time to an event (osteopenia and osteoporosis) was assessed using the Kaplan-Meier method. Strata (tertiles) were defined using baseline minimum T scores. Differences between strata in time to an event were compared with the log-rank test. Results: Of 391 patients (1,639 DXAs), 49.6% had osteopenia and 21.7% osteoporosis at their first DXA scan. Of the 112 (28.6%) with normal BMD, 35.7% progressed to osteopenia; median progression time was 6.7 years. These patients were stratified: "low-risk" (baseline minimum T score >-0.2 SD), "middle-risk" (between -0.2 and -0.6 SD), and "high-risk" (from -0.6 to -1 SD); median progression time to osteopenia was 8.7, >7.2, and 1.7 years, respectively (p<0.0001). Of patients with osteopenia, 23.7% progressed to osteoporosis; median progression time was >8.5 years. Progression time was >8.2 years in "low-risk" tertile (T score between -1.1 and -1.6 SD), >8.5 years in "middle-risk" (between -1.6 and -2), and 3.2 years in "high-risk" (from -2 to -2.4) (p<0.0001). Conclusions: Our results may help to define the BMD testing interval. The lowest T score tertiles would suggest recommending a subsequent DXA in 1-2 years; in the highest tertiles, ≥6 years. Early intervention in patients with bone demineralization could reduce fracture-related morbidity/mortality. © 2012 Negredo et al.


Negredo E.,Foundation University | Negredo E.,Autonomous University of Barcelona | Negredo E.,University of Vic | Bonjoch A.,Foundation University | And 20 more authors.
HIV Medicine | Year: 2015

Objectives: Given the need for easily managed treatment of osteoporosis in HIV-infected patients, we evaluated the efficacy and tolerability of two doses of zoledronate, by comparing three groups of patients: those with annual administration, those with biennial administration (one dose in 2 years) and a control group with no administration of zoledronate. Methods: We randomized (2:1) 31 patients on antiretroviral therapy with low bone mineral density (BMD) to zoledronate (5mg administered intravenously; 21 patients) plus diet counselling and to a control group (diet counselling; 10 patients). At week 48, patients treated with zoledronate were randomized again to receive a second dose (two-dose group; n=12) or to continue with diet counselling only (single-dose group; n=9). Changes in lumbar spine and hip BMD and bone turnover markers were compared. Results: The median percentage change from baseline to week 96 in L1-L4 BMD was -1.74% [interquartile range (IQR) -2.56, 3.60%], 7.90% (IQR 4.20, 16.57%) and 5.22% (IQR 2.02, 7.28%) in the control, two-dose and single-dose groups, respectively (P<0.01, control vs. two doses; P=0.02, control vs. single dose; P=0.18, two doses vs. single dose). Hip BMD changed by a median of 2.12% (IQR -0.12, 3.08%), 5.16% (IQR 3.06, 6.74%) and 4.47% (IQR 1, 5.58%), respectively (P=0.04, control vs. two doses; P=0.34, two doses vs. single dose). No differences between the two-dose and single-dose groups were detected in bone markers at week 96. Conclusions: The benefits for BMD of a single dose of zoledronate in 2 years may be comparable to those obtained with two doses of the drug after 96 weeks, although this study is insufficiently powered to exclude a real difference. Future studies should explore whether biennial administration of zoledronate is a useful alternative in the treatment of osteoporosis in HIV-infected patients. © 2015 British HIV Association.


Castro I.,University Pompeu Fabra | Castro I.,CIBER ISCIII | Humbert L.,University Pompeu Fabra | Humbert L.,CIBER ISCIII | And 7 more authors.
Proceedings - International Symposium on Biomedical Imaging | Year: 2012

Low back pain is a current and increasing problem closely related to intervertebral disc degeneration, which is responsible for over 90% of spinal surgical procedures. In clinical routine, clinicians base their diagnosis of disc degeneration on 2D analysis of Magnetic Resonance (MR) images. In this work, an automatic 3D segmentation method, based on active shape models, is presented for both degenerated and normal intervertebral discs. A database of 25 intervertebral discs was used to semi-automatically build a shape statistical model and intensity models. Then, a 3D reconstruction was achieved by using those models to deform an initial shape. The method was evaluated using the 25 intervertebral discs and a leave-one-out cross validation, resulting in a mean shape accuracy of 1.6mm and a mean dice similarity index of 83.6%. This automatic and accurate 3D reconstruction method opens the way for an improved diagnosis of disc degeneration. © 2012 IEEE.


Guanabens N.,University of Barcelona | Guanabens N.,CIBER ISCIII | Monegal A.,University of Barcelona | Muxi A.,University of Barcelona | And 10 more authors.
Osteoporosis International | Year: 2012

Summary The effect of ascites on bone densitometry has been assessed in 25 patients with advanced cirrhosis, and it was concluded that ascites over 4 l causes inaccuracy of BMD measurements, particularly at the lumbar spine. This fact must be considered when assessing bone mass in patients with decompensated cirrhosis. Introduction Bone mineral density (BMD) measured by dual-energy x-ray absorptiometry (DXA) is the best procedure for assessment of osteoporosis and fracture risk, but BMD values at the central skeleton may be influenced by changes in soft tissues. Therefore, we have studied the effect of ascites on BMD. Methods BMD was measured by DXA at the lumbar spine, femoral neck and total hip, just before and shortly after therapeutic paracentesis in 25 patients with advanced liver cirrhosis. Changes in BMD, lean and fat mass, abdominal diameter and weight, as well as the amount of removed ascites were measured. Results The amount of drained ascites was 6.6±0.5 l (range: 3.0 to 12.7 l). After paracentesis, BMD increased at the lumbar spine (from 0.944±0.035 to 0.997±0.038 g/cm2, p<0.001) and at the total hip (from 0.913±0.036 to 0.926±0.036 g/cm2, p<0.01). Patients with a volume of drained ascites higher than 4 l showed a significant increase in lumbar BMD (7.0%), compared with patients with a lower amount (1.5%) (p<0.03). The decrease in total soft tissue mass correlated with the amount of removed ascites (r=0.951, p<0.001). Diagnosis of osteoporosis or osteopenia changed after paracentesis in 12% of patients. Conclusion Ascites over 4 l causes inaccuracy of BMD measurements, particularly at the lumbar spine. This fact must be considered when assessing bone mass in patients with advanced cirrhosis. © The Author(s) 2011.


Whitmarsh T.,University Pompeu Fabra | Fritscher K.D.,UMIT University for Health Sciences, Medical Informatics and Technology | Humbert L.,University Pompeu Fabra | Del Rio Barquero L.M.,Center Medic | And 5 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

This work presents a statistical model of both the shape and Bone Mineral Density (BMD) distribution of the proximal femur for fracture risk assessment. The shape and density model was built from a dataset of Quantitative Computed Tomography scans of fracture patients and a control group. Principal Component Analysis and Horn's parallel analysis were used to reduce the dimensionality of the shape and density model to the main modes of variation. The input data was then used to analyze the model parameters for the optimal separation between the fracture and control group. Feature selection using the Fisher criterion determined the parameters with the best class separation, which were used in Fisher Linear Discriminant Analysis to find the direction in the parameter space that best separates the fracture and control group. This resulted in a Fisher criterion value of 6.70, while analyzing the Dual-energy X-ray Absorptiometry derived femur neck areal BMD of the same subjects resulted in a Fisher criterion value of 0.98. This indicates that a fracture risk estimation approach based on the presented model might improve upon the current standard clinical practice. © 2011 Springer-Verlag.


Valverde E.,University of Barcelona | Galvez-Lopez E.,University of Barcelona | Alba-Fernandez C.,University of Barcelona | Del Rio L.,Center Medic | Casinos A.,University of Barcelona
American Journal of Human Biology | Year: 2010

To detect and differentiate between possible heterochronic processes in the ontogenetic growth pattern of the human lumbar region, in relationship with sexual dimorphism. We measured the growth trajectories of average length and width, length/width ratio, posterior projected surface area, and bone mineral density using dual energy X-ray absorptiometry, in a sample group of 1718 modern humans. These growth patterns were analyzed using the Gompertz model. In adult lumbar region, only surface area and width were significantly higher in men. Regarding the ontogenetic growth pattern leading to the dimorphic states, all values obtained for women were significantly higher than those obtained for men. Maximum initial growth rates occurred for surface area and density in women. Width scaled faster than length in both sexes. The lumbar region followed patterns similar to those of other skeletal elements when compared with a previous classification of growth patterns in the human skeleton; however, in this study, the growth rate was slower. With regard to the effect of dimorphism, sexual differences in growth rate accounted for only a small proportion of the variation in lumbar length, mineral density, and surface area. Nevertheless, these sexual differences played an important role in the increase of the length/width ratio, which was reflected in the ages at which sexual dimorphism developed. The sexual dimorphism found in the lumbar region of human adults is not caused by any heterochronic process. The lower values of bone mineral density in adult women could explain the origin of some pathologies related. © 2010 Wiley-Liss, Inc.


Whitmarsh T.,University Pompeu Fabra | Whitmarsh T.,Networking Biomedical Research Center | Fritscher K.D.,Institute for Biomedical Image Analysis | Humbert L.,University Pompeu Fabra | And 9 more authors.
Bone | Year: 2012

Although the areal Bone Mineral Density (BMD) measurements from dual-energy X-ray absorptiometry (DXA) are able to discriminate between hip fracture cases and controls, the femoral strength is largely determined by the 3D bone structure. In a previous work a statistical model was presented which parameterizes the 3D shape and BMD distribution of the proximal femur. In this study the parameter values resulting from the registration of the model onto DXA images are evaluated for their hip fracture discrimination ability with respect to regular DXA derived areal BMD measurements. The statistical model was constructed from a large database of QCT scans of females with an average age of 67.8 ± 17.0. years. This model was subsequently registered onto the DXA images of a fracture and control group. The fracture group consisted of 175 female patients with an average age of 66.4 ± 9.9. years who suffered a fracture on the contra lateral femur. The control group consisted of 175 female subjects with an average age of 65.3 ± 10.0. years and no fracture history. The discrimination ability of the resulting model parameter values, as well as the areal BMD measurements extracted from the DXA images were evaluated using a logistic regression analysis. The area under the receiver operating curve (AUC) of the combined model parameters and areal BMD values was 0.840 (95% CI 0.799-0.881), whilst using only the areal BMD values resulted in an AUC of 0.802 (95% CI 0.757-0.848). These results indicate that the discrimination ability of the areal BMD values is improved by supplementing them with the model parameter values, which give a more complete representation of the subject specific shape and internal bone distribution. Thus, the presented method potentially allows for an improved hip fracture risk estimation whilst maintaining DXA as the current standard modality. © 2012 Elsevier Inc.


Humbert L.,Galgo Medical | Hazrati Marangalou J.,TU Eindhoven | Del Rio Barquero L.M.,Center Medic | Van Lenthe G.H.,Catholic University of Leuven | Van Rietbergen B.,TU Eindhoven
Medical Physics | Year: 2016

Purpose: Cortical thickness and density are critical components in determining the strength of bony structures. Computed tomography (CT) is one possible modality for analyzing the cortex in 3D. In this paper, a model-based approach for measuring the cortical bone thickness and density from clinical CT images is proposed. Methods: Density variations across the cortex were modeled as a function of the cortical thickness and density, location of the cortex, density of surrounding tissues, and imaging blur. High resolution micro-CT data of cadaver proximal femurs were analyzed to determine a relationship between cortical thickness and density. This thickness-density relationship was used as prior information to be incorporated in the model to obtain accurate measurements of cortical thickness and density from clinical CT volumes. The method was validated using micro-CT scans of 23 cadaver proximal femurs. Simulated clinical CT images with different voxel sizes were generated from the micro-CT data. Cortical thickness and density were estimated from the simulated images using the proposed method and compared with measurements obtained using the micro-CT images to evaluate the effect of voxel size on the accuracy of the method. Then, 19 of the 23 specimens were imaged using a clinical CT scanner. Cortical thickness and density were estimated from the clinical CT images using the proposed method and compared with the micro-CT measurements. Finally, a case-control study including 20 patients with osteoporosis and 20 age-matched controls with normal bone density was performed to evaluate the proposed method in a clinical context. Results: Cortical thickness (density) estimation errors were 0.07 ± 0.19 mm (-18 ± 92 mg/cm3) using the simulated clinical CT volumes with the smallest voxel size (0.33 × 0.33 × 0.5 mm3), and 0.10 ± 0.24 mm (-10 ± 115 mg/cm3) using the volumes with the largest voxel size (1.0 × 1.0 × 3.0 mm3). A trend for the cortical thickness and density estimation errors to increase with voxel size was observed and was more pronounced for thin cortices. Using clinical CT data for 19 of the 23 samples, mean errors of 0.18 ± 0.24 mm for the cortical thickness and 15 ± 106 mg/cm3 for the density were found. The case-control study showed that osteoporotic patients had a thinner cortex and a lower cortical density, with average differences of -0.8 mm and -58.6 mg/cm3 at the proximal femur in comparison with age-matched controls (p-value < 0.001). Conclusions: This method might be a promising approach for the quantification of cortical bone thickness and density using clinical routine imaging techniques. Future work will concentrate on investigating how this approach can improve the estimation of mechanical strength of bony structures, the prevention of fracture, and the management of osteoporosis. © 2016 American Association of Physicists in Medicine.


Whitmarsh T.,University Pompeu Fabra | Whitmarsh T.,Networking Biomedical Research Center Bioengineering | Whitmarsh T.,University of Sheffield | Humbert L.,University Pompeu Fabra | And 8 more authors.
Medical Image Analysis | Year: 2013

Current vertebral fracture prevention measures use Dual-energy X-ray Absorptiometry (DXA) to quantify the density of the vertebrae and subsequently determine the risk of fracture. This modality however only provides information about the projected Bone Mineral Density (BMD) while the shape and spatial distribution of the bone determines the strength of the vertebrae. Quantitative Computed Tomography (QCT) allows for the measurement of the vertebral dimensions and volumetric densities, which have been shown to be able to determine the fracture risk more reliably than DXA. However, for the high cost and high radiation dose, QCT is not used in clinical routine for fracture risk assessment. In this work, we therefore propose a method to reconstruct the 3D shape and density volume of lumbar vertebrae from an anteroposterior (AP) and lateral DXA image used in clinical routine. The method is evaluated for the L2, L3 and L4 vertebra. Of these vertebrae a statistical model of the vertebral shape and density distribution is first constructed from a large dataset of QCT scans. All three models are then simultaneously registered onto both AP and lateral DXA image. The shape and volumetric BMD at several regions of the reconstructed vertebrae is then evaluated with respect to the ground truth QCT volumes. For the L2, L3 and L4 vertebrae respectively the shape was reconstructed with a mean (2RMS) point-to-surface distance of 1.00 (2.64). mm, 0.93(2.52). mm and 1.34(3.72). mm and a strong correlation (r>0.82) was found between the trabecular volumetric BMD extracted from the reconstructions and from the same subject QCT scans. These results indicate that the proposed method is able to accurately reconstruct the 3D shape and density volume of the lumbar vertebrae from AP and lateral DXA, which can potentially improve the fracture risk estimation accuracy with respect to the currently used DXA derived areal BMD measurements. © 2013 Elsevier B.V.


PubMed | Center Medic, Catholic University of Leuven, Galgo Medical and TU Eindhoven
Type: Journal Article | Journal: Medical physics | Year: 2016

Cortical thickness and density are critical components in determining the strength of bony structures. Computed tomography (CT) is one possible modality for analyzing the cortex in 3D. In this paper, a model-based approach for measuring the cortical bone thickness and density from clinical CT images is proposed.Density variations across the cortex were modeled as a function of the cortical thickness and density, location of the cortex, density of surrounding tissues, and imaging blur. High resolution micro-CT data of cadaver proximal femurs were analyzed to determine a relationship between cortical thickness and density. This thickness-density relationship was used as prior information to be incorporated in the model to obtain accurate measurements of cortical thickness and density from clinical CT volumes. The method was validated using micro-CT scans of 23 cadaver proximal femurs. Simulated clinical CT images with different voxel sizes were generated from the micro-CT data. Cortical thickness and density were estimated from the simulated images using the proposed method and compared with measurements obtained using the micro-CT images to evaluate the effect of voxel size on the accuracy of the method. Then, 19 of the 23 specimens were imaged using a clinical CT scanner. Cortical thickness and density were estimated from the clinical CT images using the proposed method and compared with the micro-CT measurements. Finally, a case-control study including 20 patients with osteoporosis and 20 age-matched controls with normal bone density was performed to evaluate the proposed method in a clinical context.Cortical thickness (density) estimation errors were 0.07 0.19 mm (-18 92 mg/cm(3)) using the simulated clinical CT volumes with the smallest voxel size (0.33 0.33 0.5 mm(3)), and 0.10 0.24 mm (-10 115 mg/cm(3)) using the volumes with the largest voxel size (1.0 1.0 3.0 mm(3)). A trend for the cortical thickness and density estimation errors to increase with voxel size was observed and was more pronounced for thin cortices. Using clinical CT data for 19 of the 23 samples, mean errors of 0.18 0.24 mm for the cortical thickness and 15 106 mg/cm(3) for the density were found. The case-control study showed that osteoporotic patients had a thinner cortex and a lower cortical density, with average differences of -0.8 mm and -58.6 mg/cm(3) at the proximal femur in comparison with age-matched controls (p-value < 0.001).This method might be a promising approach for the quantification of cortical bone thickness and density using clinical routine imaging techniques. Future work will concentrate on investigating how this approach can improve the estimation of mechanical strength of bony structures, the prevention of fracture, and the management of osteoporosis.

Loading Center Medic collaborators
Loading Center Medic collaborators