Abstract-A statistical methodology is proposed to rank several estimation methods of a relevant clinical parameter when no gold standard is available. Based on a regression without truth method, the proposed approach was appliedtorankeightmethodswithout using any ap riori information regarding the reliability of each method and its degree of automation. It was only based on a prior concerning the statistical distribution of the parameter of interest in the database. The ranking of the methods relies on figures of merit derived from the regression and computed using a bootstrap process. The methodology was applied to the estimation of the left ventricular ejection fraction derived from cardiac magnetic resonance images segmented using eight approaches with different degrees of automation: three segmentations were entirely manually performed and the others were variously automated. The ranking of methods was consistent with the expected performance of the estimation methods: the most accurate estimates of the *J. Lebenberg is with the LIF, INSERM UMR_S 678, Université Pierre et Marie Curie, 75013 Paris, France, and also with the PRIAM, ESME-Sudria, 94200 Ivry-sur-Seine, France (e-mail: jessica.lebenberg@gmail.com).C. Constantinidès is with the LIF, INSERM UMR_S 678, Université Pierre et Marie Curie, 75013 Paris, France, and also with the PRIAM, ESME-Sudria, 94200 Ivry-sur-Seine, France.A
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The design and operation of a compact antenna array offering circularly polarized (CP) radiation for picosat and other small satellites for communication applications is presented. The proposed array combines folded-shorted patches (FSPs) and meandering for antenna miniaturization. Realization of CP is achieved by a compact and planar feed circuit consisting of a network of meander-shaped 90-and 180-degree hybrid couplers which can provide quadrature feeding of the FSP elements and can be integrated onto the backside of the antenna ground plane which is only 5 cm by 5 cm. Agreement in terms of the simulations and measurements is observed with realized gain values of more than 3 dBic at 1.065 GHz and with an antenna size of 0.17λ0 by 0.17λ0.
A fully automated segmentation method of the left ventricle from short-axis cardiac MR images is proposed and evaluated. The segmentation is based on morphological filtering and gradient vector flow snake for which an automatic setting of parameters has already been proposed. The present work focuses on the automatic detection of a region of interest (ROI) surrounding the left ventricle, prior to the segmentation step. The whole process was applied to the MICCAI 2009 Left Ventricle Challenge database containing 45 subjects (9 healthy subjects and 36 with pathology). The automatic detection of the ROI was judged accurate in 86% of the cases. It failed in 2% of the slices and provided an overestimation in 9% of the slices. Furthermore, the endocardial segmentation was accurate in 80% of the slices and the epicardial was judged satisfactory in 71% of the slices. This fully automated procedure can thus be used as a first step in a user controlled approach, in order to reduce the total number of interactions.
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