Optimal dose calibration in radiotherapy

In this paper, the tools provided by the theory of Optimal Experimental Design are applied to a nonlinear calibration model. This is motivated by the need of estimating radiation doses using radiochromic films for radiotherapy purposes. The calibration model is in this case nonlinear and the explanatory variable cannot be worked out explicitly from the model. In this case an experimental design has to be found on the dependent variable. For that, the inverse function theorem will be used to obtain an information matrix to be optimized. Optimal designs on the response variable are computed from two different perspectives, first for fitting the model and estimating each of the parameters and then for predicting the proper dose. While the first is a common point of view in a general context of the Optimal Experimental Design, the latter is actually the main objective of the calibration problem for the practitioners and algorithms for computing these optimal designs are also provided. The optimal designs obtained have just three different points in their support, but practitioners usually demand for more support points. Thus, a methodology for computing space-filling designs is also provided when the support points are forced to follow some mathematical rule, such as arithmetic or geometric sequences. Cross efficiencies of all these designs are computed in order to show their ability for different goals

New Indices for Refining Multiple Choice Questions

Multiple choice questions (MCQs) are one of the most popular tools to evaluate learning and knowledge in higher education. Nowadays, there are a few indices to measure reliability and validity of these questions, for instance, to check the difficulty of a particular question (item) or the ability to discriminate from less to more knowledge. In this work two new indices have been constructed: (i) the no answer index measures the relationship between the number of errors and the number of no answers; (ii) the homogeneity index measures homogeneity of the wrong responses (distractors). The indices are based on the lack-of-fit statistic, whose distribution is approximated by a chi-square distribution for a large number of errors. An algorithm combining several traditional and new indices has been developed to refine continuously a database of MCQs. The final objective of this work is the classification of MCQs from a large database of items in order to produce an automated-supervised system of generating tests with specific characteristics, such as more or less difficulty or capacity of discriminating knowledge of the topic

Optimal dose calibration in radiotherapy

In this paper, the tools provided by the theory of Optimal Experimental Design are applied to a nonlinear calibration model. This is motivated by the need of estimating radiation doses using radiochromic films for radiotherapy purposes. The calibration model is in this case nonlinear and the explanatory variable cannot be worked out explicitly from the model. In this case an experimental design has to be found on the dependent variable. For that, the inverse function theorem will be used to obtain an information matrix to be optimized. Optimal designs on the response variable are computed from two different perspectives, first for fitting the model and estimating each of the parameters and then for predicting the proper dose. While the first is a common point of view in a general context of the Optimal Experimental Design, the latter is actually the main objective of the calibration problem for the practitioners and algorithms for computing these optimal designs are also provided. The optimal designs obtained have just three different points in their support, but practitioners usually demand for more support points. Thus, a methodology for computing space-filling designs is also provided when the support points are forced to follow some mathematical rule, such as arithmetic or geometric sequences. Cross efficiencies of all these designs are computed in order to show their ability for different goals

X Jornadas de estadística pública

Este peque˜no volumen contiene una buena cantidad de res´umenes de ponencias y posters que se presentarán en el XXXVI Congreso de la SEIO. Hemos avanzado mucho en la investigación en Estadística e InvestigaciónOperativa en todos estos años en los que se viene celebrando este congreso organizado por nuestra sociedad. Las más de 200 comunicaciones orales y los casi 60 posters contienen un buen porcentaje trabajos que han sido o ser´an publicados en revistas de alto impacto. Esto nos hace sentirnos orgullosos, a la vez que alentados a seguir en esta l´ınea que tiene un nombre propio en la comunidad internacional

Estimación y contrastes en modelos de retención de partículas radiactivas

A partir de nuevos modelos de retención de partículas radiactivas en el cuerpo humano se calcularán diseños óptimos para la estimación de los parámetros principales, así como contrastes sobre los mismos

Experimental Designs for Autoregessive Models Applied to Industrial Maintenance

Experimental Designs for Autoregessive Models Applied to Industrial Maintenanc

Optimal Experimental Designs in the Flow Rate of Particles

<p>This paper focuses on analysing the process of jam formation during the discharge by gravity of granular material stored in a 2D silo. The aim of the paper is twofold. Firstly, optimal experimental designs are computed, in which four approaches are considered: D–optimality, a combination of D–optimality and a cost/gain function, Bayesian D–optimality and sequential designing. These results reveal that the efficiency of the design used by the experimenters can be improved dramatically. A sensitivity analysis with respect to the most important parameter is also performed. Secondly, estimation of the unknown parameters is done using least squares, i.e. assuming normality, and also via maximum likelihood assuming the exponential distribution. Simulations for the designs considered in this paper show that the variance, the mean square error and the bias of the estimators using maximum likelihood are in most cases lower than those using least squares.</p

Too good to go? Neanderthal subsistence strategies at Prado Vargas Cave (Burgos, Spain)

Understanding the relationship between Neanderthal groups and their environment and they it is essential to comprehending their ways of life. In this article, we use both zooarchaeology and taphonomy to study the fauna assemblages found in Level 4 of Prado Vargas Cave (Cornejo, Burgos, Spain). The results point to a site in which the main accumulating agent was Neanderthal groups, who transported small- and medium-sized animal carcasses—with deer as the dominant taxon—according to their general utility to systematically and intensely exploit the major muscle bundles, bone marrow, skin, and tendons. According to dental microwear analysis, reiterated and prolonged occupations occurred in diverse moments, suggesting that the site was used most often as a long-term campsite. We detected a minimal amount of carnivore activity, who accessed the cave during periods of human absence and modified some of the remains left by the Neanderthals. Together, this information indicates that Prado Vargas is a key site to understand the dynamics of the Neanderthals in the linking area between the Castillan Plateau and the Cantabrian Range.We are grateful for the financial support received from the Junta de Castilla y León, through the Consejería de Cultura y Turismo, Dirección General de Patrimonio Cultural, which funded the project “Intervención arqueológica en la Cueva de Prado Vargas, in Cornejo” (Merindad de Sotoscueva, Burgos) (SUBV-22/011-BU). We also want to thank Beni and the mayors of La Merindad de Sotoscueva and Cornejo for their support and collaboration. The same goes for all of those who participated and participate in excavation campaigns, without whom we would not have been able to do this work. Finally, a special thanks to the Prehistory Laboratory of the UBU partners, Marta Santamaría and Pedro Alonso, for their immeasurable and indispensable support

Analytical performance validation of aPROMISE platform for prostate tumor burden, index and dominant tumor assessment with 18F-DCFPyL PET/CT. A pilot study

Abstract To validate the performance of automated Prostate Cancer Molecular Imaging Standardized Evaluation (aPROMISE) in quantifying total prostate disease burden with 18F-DCFPyL PET/CT and to evaluate the interobserver and histopathologic concordance in the establishment of dominant and index tumor. Patients with a recent diagnosis of intermediate/high-risk prostate cancer underwent 18F-DCFPyL-PET/CT for staging purpose. In positive-18F-DCFPyL-PET/CT scans, automated prostate tumor segmentation was performed using aPROMISE software and compared to an in-house semiautomatic-manual guided segmentation procedure. SUV and volume related variables were obtained with two softwares. A blinded evaluation of dominant tumor (DT) and index tumor (IT) location was assessed by both groups of observers. In histopathological analysis, Gleason, International Society of Urological Pathology (ISUP) group, DT and IT location were obtained. We compared all the obtained variables by both software packages using intraclass correlation coefficient (ICC) and Cohen’s kappa coefficient (k) for the concordance analysis. Fifty-four patients with a positive 18F-DCFPyL PET/CT were evaluated. The ICC for the SUVmax, SUVpeak, SUVmean, tumor volume (TV) and total lesion activity (TLA) was: 1, 0.833, 0.615, 0.494 and 0.950, respectively (p < 0.001 in all cases). For DT and IT detection, a high agreement was observed between both softwares (k = 0.733; p < 0.001 and k = 0.812; p < 0.001, respectively) although the concordances with histopathology were moderate (p < 0001). The analytical validation of aPROMISE showed a good performance for the SUVmax, TLA, DT and IT definition in comparison to our in-house method, although the concordance was moderate with histopathology for DT and IT