The analysis of the carotid artery wall is crucial for the diagnosis of serious cardiovascular pathologies or for the assessment of a subject's cardiovascular risk. Several algorithms have been ...proposed for the segmentation of ultrasound carotid artery images, but almost all require a certain degree of user interaction. We recently developed a completely user-independent algorithm for the segmentation of the common-carotid-artery wall; specifically, the algorithm traces the contour of the interfaces between the lumen and the intima layer and between the media and adventitia layers. In this paper, we show the characterization of the algorithm in terms of segmentation error. Moreover, we compare the output of the algorithm with the segmentations manually traced by four experts, using the percent statistics test and testing the automatically generated segmentation against the average human segmentations. We show that our algorithm's segmentation is not statistically different from that of a trained operator and that the segmentation error is lower than 1 pixel for both the lumen-intima interface and for the media-adventitia interface.
Multicellular tumor spheroids are valuable experimental tools in cancer research. By introducing an intermediate model, we have been able to successfully relate mesoscopic and macroscopic ...descriptions of spheroid growth. Since these descriptions stem from completely different roots (cell dynamics, and energy conservation and scaling arguments, respectively), their consistency validates both approaches and allows us to establish a direct correspondence between parameters characterizing processes occurring at different scales. Our approach may find applications as an example of bridging the gap between models at different scale levels in other contexts.
Dynamic infrared imaging has been proposed in literature as an adjunctive technique to mammography in breast cancer diagnosis. It is based on the acquisition of hundreds of consecutive thermal images ...with a frame rate ranging from 50 to 200 frames/s, followed by the harmonic analysis of temperature time series at each image pixel. However, the temperature fluctuation due to blood perfusion, which is the signal of interest, is small compared to the signal fluctuation due to subject movements. Hence, before extracting the time series describing temperature fluctuations, it is fundamental to realign the thermal images to attenuate motion artifacts. In this paper, we describe a method for the quantitative evaluation of any kind of feature-based registration algorithm on thermal image sequences, provided that an estimation of local velocities of reference points on the skin is available. As an example of evaluation of a registration algorithm, we report the evaluation of the SNR improvement obtained by applying a nonrigid piecewise linear algorithm.
This book comes as a result of the research work developed in the framework of two large international projects: the European Science Foundation (ESF) supported program NATEMIS (Nonlinear Acoustic ...Techniques for Micro-Scale Damage Diagnostics) (of which Professor Delsanto was the European coordinator, 2000-2004) and a Los Almos-based newtork headed by Dr. P.A. Johnson. The main topic of both programs and of this book is the description of the phenomenology, theory and applications of nonclassical Nonlinearity (NCNL). In fact NCNL techniques have been found in recent years to be extremely powerful (up to more than 1000 times with respect to the corresponding linear techniques) in a wide range of applications, including Elasticity, Material Characterization, Ultrasonics, Geophysics to Maintenance and Restoration of artifacts (paintings, stone buildings, etc.). The book is divided into three parts: Part I -defines and describes the concept of NCNL and its universality and reviews several fields to which it may applpy, Part II - describes the phenomenology, theory, modelling and virtual experiments (simulations), Part III - discusses some of the most relevant experimental techniques and applications.
The presence of different kinds of artifacts has long been a problem in the analysis and interpretation of electroencephalographic recordings. Recently blind source separation by Independent ...Component Analysis (ICA) has been successfully employed for the detection and removal of artifactual components and new methods for the automatic identification of the artifactual components are being proposed. In this paper we focus on the automatic removal of eyeblink components from EEG data. First a model of the topographic maps associated to the ICA eyeblink component and a distance quantifying the resemblance to the model are defined. To further improve the reliability of the system, an eyeblink detector was designed which locates the individual eyeblinks within the component, thus confirming the nature of the activation.
Gaseous detectors are widely used in high-energy physics experiments, and in particular at the CERN Large Hadron Collider (LHC), to provide tracking and triggering over large volumes. It has been ...recently estimated that Resistive Plate Chambers (RPC), used for muon detection, have the highest contribution on the overall greenhouse gas (GHG) emissions at the LHC experiments. Gas mixtures for RPCs are mainly made of C\(_{2}\)H\(_{2}\)F\(_{4}\), which is a greenhouse gas with a high environmental impact in the atmosphere. C\(_{2}\)H\(_{2}\)F\(_{4}\) is already phasing out of production, due to recent European Union (EU) regulations, and its cost is expected to increase in the near future. Therefore, finding alternative gas mixtures made of gas components with a low Global Warming Potential (GWP) has become extremely important for limiting the GHG emissions as well as for economic reasons. The novel hydrofluoroolefins are likely appropriate candidates to replace C\(_{2}\)H\(_{2}\)F\(_{4}\) due to their similar chemical structures. This study is focused on the characterization of innovative gas mixtures with tetrafluoropropene HFO1234ze(E) (C\(_{3}\)H\(_{2}\)F\(_{4}\)) that is one of the most eco-friendly hydrofluoroolefins, thanks to its very low GWP. HFO1234ze(E)-based gas mixtures with the addition of Ar, N\(_{2}\), O\(_{2}\) and CO\(_{2}\) are extensively discussed in this paper as well as the role of i-C\(_{4}\)H\(_{10}\) and SF\(_{6}\) in such mixtures.
The muon identification system of the ALICE experiment at the CERN LHC is based on Resistive Plate Chamber (RPC) detectors. These RPCs are operated in the so-called maxi-avalanche mode with a gas ...mixture made of tetrafluoroethane (C\(_{2}\)H\(_{2}\)F\(_{4}\)), sulfur hexafluoride (SF\(_{6}\)) and isobutane (i-C\(_{4}\)H\(_{10}\)). All of these components are greenhouse gases: in particular, the first two gases are already phasing out of production, due to recent European Union regulations, and their cost is progressively increasing. Therefore, finding a new eco-friendly gas mixture has become extremely important in order to reduce the impact of the RPC operation on the environment, and for economic reasons. Due to the similar chemical structure, hydrofluoroolefins appear appropriate candidates to replace C\(_{2}\)H\(_{2}\)F\(_{4}\) thanks to their very low GWPs, especially tetrafluoropropene (C\(_{3}\)H\(_{2}\)F\(_{4}\)) with the trade name HFO1234ze. In order to identify an eco-friendly gas mixture fulfilling the requirements for operation in the ALICE environment in the coming years, a dedicated experimental set-up has been built to carry out R&D studies on promising gas mixtures. Measurements have been performed with a small-size RPC equipped with the front-end electronics, providing signal amplification, developed for ALICE operation at high luminosity after the LHC Long Shutdown 2. HFO1234ze-based mixtures with the addition of CO\(_{2}\) are discussed in this paper as well as the role of i-C\(_{4}\)H\(_{10}\) and SF\(_{6}\) as quenchers in such mixtures.
Resistive Plate Chambers (RPC) have shown stable operation at the Large Hadron Collider and satisfactory efficiency for the entire Run 1 (2010-2013) and Run 2 (2015-2018) with ...C\(_{2}\)H\(_{2}\)F\(_{4}\)-based gas mixtures and the addition of SF\(_{6}\) and i-C\(_{4}\)H\(_{10}\). Since its global warming potential (GWP) is high, C\(_{2}\)H\(_{2}\)F\(_{4}\) is phasing out of production due to recent European Union regulations and as a result its cost is progressively increasing. Therefore, finding a new RPC gas mixture with a low GWP has become extremely important. This contribution describes the simulation of the RPC efficiency with tetrafluoropropene C\(_{3}\)H\(_{2}\)F\(_{4}\) (HFO1234ze), a hydrofluoroolefin with very low GWP. Simulation results are systematically compared with measurements of RPC efficiency in C\(_{3}\)H\(_{2}\)F\(_{4}\)-based gas mixtures with the addition of different combinations of Ar, He, CO\(_{2}\), O\(_{2}\) and i-C\(_{4}\)H\(_{10}\) in various concentrations. This simulation allows the study of the interplay between C\(_{3}\)H\(_{2}\)F\(_{4}\) and the other gas components in the mixture as well as may allow the identification of the most promising environment-friendly gas mixtures with C\(_{3}\)H\(_{2}\)F\(_{4}\) for RPCs.
The analysis of the carotid wall is of paramount importance in clinical practice. In fact, the intima-media thickness is a risk index for some of the most severe acute cerebrovascular pathologies; ...hence, the need for an accurate segmentation of the different layers of the carotid artery. In the past ten years, a wide variety of algorithms for the carotid tunica segmentation have been proposed, but they require a certain degree of user interaction. In this paper we propose a novel approach to the completely user-independent segmentation of the carotid artery wall. Our algorithm has been designed for the extraction of the intima and media layers of the distal carotid wall, based on ultrasonic B-mode images. We evaluated the performance of the algorithm on a set of 63 images and compared the automatic segmentation to that traced by a trained operator. We obtained a mean error lower than 1.3 pixel both on the intima and media layers, which is comparable to that obtained by means of operator dependent techniques
Non-invasive plaque characterization of the carotid wall is crucial for the early assessment of pathology, as well as for the monitoring of the progression of a degenerative phenomenon. Specifically, ...in clinical practice the carotid wall status is assessed by means of B-Mode ultrasound scans. We recently implemented an algorithm for the segmentation of the common tract of the carotid wall using ultrasound relative to healthy subjects. This paper presents a superior strategy for plaque characterization, which accurately determines both echolucent-type II and echogenic plaques in pathologic subjects. We preserve both user-independence and pixel fuzziness in our approach, thereby designing an accurate intima-media thickness (IMT). Our database consists of 20 subjects comprising of normal, stable (echogenic) and unstable (echolucent) plaques. In this database of 45 images, we demonstrate our performance with respect to the gold standard tracings to an accuracy determined as normalized error to be about 8%. The results are very promising and this algorithm is being integrated into clinical setup for automatic pathologic carotid wall analysis
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