Statistical models to analyze recurrent fragility fractures

Most studies on fragility fracture risk focus on the analysis of the first incident fracture. Our aim is to use the European Prospective Investigation into Cancer and Nutrition cohort to model recurrent fragility fractures using the stratified proportional hazards models proposed by Prentice-Williams-Peterson. All participants are at risk for the first stratum, but only those with an event in the previous stratum are at risk for the subsequent stratum. In order to deal with death as a competing event, the use of a multi-state model will also be evaluated

Sensores hiperespectrales aerotransportados: eliminación del efecto de deriva

En este artículo se explican los conceptos básicos de los sensores hiperespectrales rotacionales aerotransportados. Así mismo, se hace una revisión de las diferentes circunstancias causantes de los errores en la formación de las imágenes y se propone una metodología para corregirlas. A continuación, mostramos un ejemplo práctico en el que se observa cómo la consideración y eliminación del efecto de deriva permite georreferenciar con alta precisión imágenes hiperespectrales tomadas con sensores rotacionales

Accuracy analysis of a mobile mapping system for close range photogrammetric projects

[EN] Image-based mapping solutions require accurate exterior orientation parameters independently of the cameras used for a survey. This paper analyses the inclusion of up to two stereo-based geometric constraints in the form of baseline distance and convergence angle between camera axes to boost the integrated sensor orientation performance on outdoor close-range projects. A terrestrial low-cost mobile mapping GNSS/IMU multi-camera system is used to test the performance of the stereo-based geometric constraint on a weak geometric network in a stop-and-go survey. The influence of the number of control points (CPs) is analysed to confirm the performance and usability of the geometric constraints in real live terrestrial projects where far from ideal setups can exist across the survey. Improvements in image residuals up to 9 times and deviation errors better than 1 cm are expected when at least three CPs are incorporated into the adjustmentThe authors gratefully acknowledge the support from the Spanish Ministerio de Economia y Competitividad to the project HAR2014-59873-R. Contributions on direct georeferencing from professors Dr. David Hernandez-Lopez, Dr. Luis Garcia-Asenjo and D. Pascual Garrigues are highly appreciated.Navarro Tarin, S.; Lerma García, JL. (2016). Accuracy analysis of a mobile mapping system for close range photogrammetric projects. Measurement. 93:148-156. https://doi.org/10.1016/j.measurement.2016.07.0301481569

Spherical harmonics to quantify cranial asymmetry in deformational plagiocephaly

[EN] Cranial deformation and deformational plagiocephaly (DP) in particular affect an important percentage of infants. The assessment and diagnosis of the deformation are commonly carried by manual measurements that provide low interuser accuracy. Another approach is the use of three-dimensional (3D) models. Nevertheless, in most cases, deformation measurements are carried out manually on the 3D model. It is necessary to develop methodologies for the detection of DP that are automatic, accurate and take profit on the high quantity of information of the 3D models. Spherical harmonics are proposed as a new methodology to identify DP from head 3D models. The ideal fitted ellipsoid for each head is computed and the orthogonal distances between head and ellipsoid are obtained. Finally, the distances are modelled using spherical harmonics. Spherical harmonic coefficients of degree 2 and order - 2 are identified as the correct ones to represent the asymmetry characteristic of DP. The obtained coefficient is compared to other anthropometric deformation indexes, such as Asymmetry Index, Oblique Cranial Length Ratio, Posterior Asymmetry Index and Anterior Asymmetry Index. The coefficient of degree 2 and order - 2 with a maximum degree of 4 is found to provide better results than the commonly computed anthropometric indexes in the detection of DP.This article was funded by Instituto de Salud Carlos III and European Regional Development Fund (FEDER) (Grant no. PI18/00881).Grieb, J.; Barbero-García, I.; Lerma, JL. (2022). Spherical harmonics to quantify cranial asymmetry in deformational plagiocephaly. Scientific Reports. 12(1):1-10. https://doi.org/10.1038/s41598-021-04181-z11012

Monitoring crustal movements and sea level in Lanzarote

The Institute of Astronomy and Geodesy is measuring sea level variations in Lanzarote Island by two automated tide gauges of precision since 1993. In order to obtain "real" sea level variations a permanent GPS station has been installed near the tide gauges. The goal of this GPS station is to measurement vertical crustal movements in order to obtain absolute sea level variations removing these movements from tide gauge data. A vertical tie with high accuracy between the reference point of the pillar where the GPS antenna is installed and the tide gauges bench marks is absolutely necessary. We have carried out this altimetric link yearly since year 2000. Methods of repeated geometric and trigonometric levelling of very short tracts have been used due to the great level difference existent. The control of the local stability of the pillar where the GPS antenna has been established, is carried out by a micro-geodetic control network building around it. This network of 13 benchmarks has been regularly observed by classic and GPS geodetic techniques in years 2000, 2001, 2002, 2003 and 2004. The data of these campaigns have been processed by different types of adjustments in the same reference system. The precision of the measurements and the reliability of the networks have been calculated. In this work the results obtained, the evaluation of the altimetric links and levelling campaigns, and the comparison of the levels of different measurements are presented

Cadenas de Markov en genética poblacional

El estudio de la genética lleva evolucionando desde principios del siglo XX hasta el punto de haberse convertido en una rama de la biología de gran importancia. En la genética poblacional se pretende estudiar la presencia de los alelos de un locus a lo largo del tiempo, habiendo llegado a desarrollarse los modelos de Fisher-Wright y Moran, que plantean eventos de nacimiento y muerte de maneras distintas, permitiendo así realizar predicciones y estudiar la población a lo largo del tiempo. Mediante el uso de las cadenas de Markov vamos a estudiar ambos modelos, su comportamiento a largo plazo y lo que representa la manera en la que ocurren los acontecimientos de nacimiento y muerte. Además vamos a realizar comparaciones entre los modelos, entendiendo sus diferencias y la necesidad de ambos para un adecuado estudio de las poblaciones.Grado en Estadístic

Análisis de repetibilidad en videogrametría para la evaluación de la deformación craneal en niños

[EN] Cranial deformation affects a large number of infants. The methodologies commonly employed to measure the deformation include, among others, calliper measurements and visual assessment for mild cases and radiological imaging for severe cases, where surgical intervention is considered. Visual assessment and calliper measurements usually lack the required level of accuracy to evaluate the deformation. Radiological imaging, including Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), are costly and highly invasive. The use of smartphones to record videos that can be used for three-dimensional (3D) modelling of the head has emerged as a low-cost, noninvasive methodology to extract 3D information of the patient. To be able to analyse the deformation, a novel technique is employed: the obtained model is compared with an ideal head. In this study we have tested the repeatability of the process. For this purpose, several models of two patients have been obtained and the differences between them are evaluated. The results show that the differences in the ellipsoid semiaxis for the same patient are usually below 4 mm, although they increase up to 6.4 mm in some cases. The variability in the distances to the ideal head, which are the values used to evaluate deformity, reaches a maximum value of 2.7 mm. The errors obtained are comparable to those of classical measurement techniques and show the potential of the methodology in development.[ES] La deformación craneal afecta a un elevado porcentaje de lactantes, a pesar de esto, no existen estándares para su medición. Existen diversas metodologías empleadas para el análisis de este tipo de deformación, que van desde el análisis visual o la medición con calibre en casos leves, a pruebas radiológicas en casos más graves, en los que se plantea la posibilidad de una intervención quirúrgica. El análisis visual y la medición con calibre a menudo carecen de la precisión requerida para evaluar la deformación, mientras que las pruebas radiológicas (Tomografía Axial Computarizada, TAC, o Resonancia Magnética, RM) son altamente invasivas y tienen un alto coste. Otras soluciones como la fotografía tridimensional (3D) incluyen complejos sistemas de varias cámaras, lo que también supone un coste elevado. La posibilidad de utilizar videos tomados con teléfonos inteligentes para la creación de modelos 3D craneales se ha convertido en una posibilidad para obtener información 3D del paciente de forma precisa y con un coste bajo. Para analizar la deformación se ha planteado una metodología que consiste en calcular las distancias entre el modelo generado y una forma craneal ideal. En este estudio se ha llevado a cabo el análisis de la repetibilidad del proceso de obtención del modelo y de la cabeza ideal ajustada, para ello se han obtenido varios modelos 3D de dos pacientes y se han evaluado las diferencias entre ellos. Los resultados muestran unas diferencias en los semiejes de los elipsoides de aproximadamente 4 mm, aunque este error llega a incrementarse hasta 6.4 mm en algunos casos. La variabilidad en las distancias del modelo a la cabeza ideal, empleadas para medir la deformidad tienen un máximo de 2.7 mm. Las precisiones obtenidas con esta metodología son comparables a las obtenidas mediante técnicas de análisis tradicionales y muestran el potencial de la metodología en desarrollo.This work was supported by Subprogram C (No. C10) for the development of coordinated actions between the UPV and the IIS La Fe.Barbero García, I.; Lerma García, JL.; Marqués Mateu, Á.; Miranda, P. (2017). Analysis of repeatability on videogrammetry for infants' cranial deformation. En Primer Congreso en Ingeniería Geomática. Libro de actas. Editorial Universitat Politècnica de València. 15-19. https://doi.org/10.4995/CIGeo2017.2017.6604OCS151