74 research outputs found

    Support vector machine versus logistic regression modeling for prediction of hospital mortality in critically ill patients with haematological malignancies

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    Background: Several models for mortality prediction have been constructed for critically ill patients with haematological malignancies in recent years. These models have proven to be equally or more accurate in predicting hospital mortality in patients with haematological malignancies than ICU severity of illness scores such as the APACHE II or SAPS II [1]. The objective of this study is to compare the accuracy of predicting hospital mortality in patients with haematological malignancies admitted to the ICU between models based on multiple logistic regression (MLR) and support vector machine (SVM) based models. Methods: 352 patients with haematological malignancies admitted to the ICU between 1997 and 2006 for a life-threatening complication were included. 252 patient records were used for training of the models and 100 were used for validation. In a first model 12 input variables were included for comparison between MLR and SVM. In a second more complex model 17 input variables were used. MLR and SVM analysis were performed independently from each other. Discrimination was evaluated using the area under the receiver operating characteristic (ROC) curves (+/- SE). Results: The area under ROC curve for the MLR and SVM in the validation data set were 0.768 (+/- 0.04) vs. 0.802 (+/- 0.04) in the first model (p = 0.19) and 0.781 (+/- 0.05) vs. 0.808 (+/- 0.04) in the second more complex model (p = 0.44). SVM needed only 4 variables to make its prediction in both models, whereas MLR needed 7 and 8 variables in the first and second model respectively. Conclusion: The discriminative power of both the MLR and SVM models was good. No statistically significant differences were found in discriminative power between MLR and SVM for prediction of hospital mortality in critically ill patients with haematological malignancies

    Stretchable circuits with polyimide supported thin-film metal meanders

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    Recently we have presented stretchable circuits, based on printed circuit board technology [1]. These circuits are not very well suited for applications where a high degree of biocompatibility is required (e.g. for implantation purposes), because they use standard Cu as the electrical interconnection material. Moreover fine interconnection pitches (smaller than 100 micrometer) cannot be achieved because patterning resolution is limited by the Cu thickness which usually is 17”m or 35”m in PCB technology. Therefore thin-film versions of the PCB technology based technology for elastic circuits have been developed and will be presented in this contribution. They use sputter deposited TiW/Au thin-film metal layers as metal interconnects. TiW (typically 50nm thick) is used as an adhesion layer, while Au (typical thickness 250nm) is a biocompatible metal with low resistivity. This biocompatible thin-film metal stack is supported by polyimide which is a flexible polymer material. The metal layer, as well as its polyimide support are patterned as meanders, which after embedding in biocompatible elastic PDMS (poly-dimethyl siloxane, silicone rubber) material, allows in plane deformation (stretching) of the meander without loss of its electrical interconnection functionality. The polyimide starting material can either be a spin-on material (e.g. HD Microsystems 2611), or a sheet, as used in standard flexible circuits (e.g. Dupont KaptonÂź). The metal meanders are formed by lithography and wet etching, for the polyimide meanders dry etching with a hard metal mask is used for patterning. Metal meandering lines with widths as low as 20 micrometer were successfully patterned in this way. Supporting the thin-film metal meanders with a flexible polyimide drastically increases the mechanical reliability, compared to non-supported meanders. Measurements for HD2611 supported TiW/Au meanders, embedded in Dow Corning SilasticÂź MDX4-4210 PDMS show a minimum lifetime of 500’000 cycles at a strain of 10%, without any measurable change in meander resistance. Moreover, in the case of use of the spin-on polyimide we have demonstrated for the first time the possibility to integrate an ultra-thin chip package (UTCP, [2]) together with thin-film stretchable interconnections in the same soft PDMS substrate. The chip is thinned down to a thickness of 20 to 30 micron. It is embedded in HD2611 spin-on polymide, which simultaneously serves as the support for the stretchable interconnects. The TiW/Au metal layer is used, not only as stretchable interconnection metallization, but also as contact material to the chip pads, and fan-out to the stretchable interconnects. In this contribution we will describe the different fabrication processes in further detail and show examples of fabricated devices, using these technologies. [1] J. Vanfleteren et al., MRS-B, Vol.37, pp.254-260 , 2012. [2] W. Christiaens et al., IEEE Trans. Comp. Pack. Techn., 33 (4): pp. 754-760, 2010

    Lammerdries 25, B 2250 OLEN (Belgium) Presented at MRS 1997 Fall Meeting in Boston

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    ABSTRACT The new generation of elementary particle and nuclear physics experiments demand instrumentation with a more precise spatial resolution and a better and faster energy response. Nuclear physics and space experiments need position sensitive pad detectors having very thin entrance windows while high energy physics and medical applications use fast microstrip or drift detectors. Silicon pixel detectors can be improved by implementing integrated electronics on it. They allow a better X-ray energy resolution and are also used in hybrid photocathode tubes for faster timing and larger dynamic range. INTRODUCTION Passivated implanted planar silicon (PIPS) detectors [1] can be designed as position sensitive devices giving a position information in one or two directions. The position resolution is virtually possible in the range 25 ” to 20 mm but depends on the particle energy, timing features and number of preamplifiers. There is always an optimum solution for each requirement because of the limitations of the different designs. Furthermore, active area and depletion thickness play an important role because leakage current and diode capacitance have a large contribution to the electronic noise and will give important limitations in position and energy resolution
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