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Multi-resolution parallel integral projection for fast localization of a straight electrode in 3D ultrasound images
Uherčík, Marián; Kybic, Jan; Liebgott, Hervé; Cachard, Christian
2008 -
We address the problem of fast and accurate localization of miniature surgical instruments like needles or electrodes using 3D ultrasound (US). An algorithm based on maximizing a parallel integral transform (PIP) can automatically localize line-shaped objects in 3D US images with accuracy on the order of hundreds of micrometers. Here we propose to use a multi-resolution to accelerate the algorithm significantly. We use a maximum function for downsampling to preserve the high intensity voxels of a thin electrode. We integrate the multi-resolution pyramid into a hierarchical mesh-grid search of PIP. The experiments with a tissue mimicking phantom and breast biopsy data show that proposed method works well on real US images. The speed-up is threefold compared to original PIP method with the same accuracy 0.4 mm. A further speed-up up to 16 times is reached by an early stopping of the optimization, at the expense of some loss of accuracy.
Keywords:
3D ultrasound; electrode; localization; parallel integral projection; multi-resolution
Available in digital repository of ČVUT.
Multi-resolution parallel integral projection for fast localization of a straight electrode in 3D ultrasound images
We address the problem of fast and accurate localization of miniature surgical instruments like needles or electrodes using 3D ultrasound (US). An algorithm based on maximizing a parallel integral ...
Microstructure Analysis and Measurement of Nonlinearity of Vapour Phase Reflowed Solder Joints
Pietriková, A.; Mach, P.; Livovský, Ľ.; Urbančík, J.
2008 -
The goal of the study is to compare quality of lead-free vapour phase reflowed solder joints soldered on different printed circuit board (PCB) surface finishes. The solder joints quality comparison is based on evaluation of microstructure development of the solder, solder/PCB pad interface and on the measurement of the solder joints nonlinearity of the current-voltage (C-V) characteristics. The microstructure is evaluated before and after accelerated ageing.
Available in digital repository of ČVUT.
Microstructure Analysis and Measurement of Nonlinearity of Vapour Phase Reflowed Solder Joints
The goal of the study is to compare quality of lead-free vapour phase reflowed solder joints soldered on different printed circuit board (PCB) surface finishes. The solder joints quality comparison is ...
Electrical Connection Network Within an Electrically Conductive Adhesive
Bušek, D.; Mach, P.
2008 -
This paper deals with the connection network in isotropically conductive adhesives (ICAs). The reader will learn about conductive network creation, tunneling effect, possible ways of modeling the conductive network and differences between failures within soldered joints and electrically conductive adhesive joints. This article compares theoretical models with real measurement and properties of the electrically conductive adhesive. The inner structure of the adhesive that is either formed by micro-sized particles, or micro-sized particles mixed with nano-sized particles, is described.
Available in digital repository of ČVUT.
Electrical Connection Network Within an Electrically Conductive Adhesive
This paper deals with the connection network in isotropically conductive adhesives (ICAs). The reader will learn about conductive network creation, tunneling effect, possible ways of modeling the ...
Fast no ground truth image registration accuracy evaluation: Comparison of bootstrap and Hessian approaches
Kybic, Jan
2008 -
Image registration algorithms provide a displacement field between two images. We consider the problem of estimating accuracy of the calculated displacement field from the input images only and without assuming any specific model for the deformation. We compare two algorithms: the first is based on bootstrap resampling, the second, new method, uses an estimate of the criterion Hessian matrix. We also present a block matching strategy using multiple window sizes where the final result is obtained by fusion of partial results controlled by the accuracy estimates for the blocks involved. Both accuracy estimation methods and the new registration strategy are experimentally compared on synthetic as well as real medical ultrasound data.
Keywords:
image registration; accuracy estimation; bootstrap
Available in digital repository of ČVUT.
Fast no ground truth image registration accuracy evaluation: Comparison of bootstrap and Hessian approaches
Image registration algorithms provide a displacement field between two images. We consider the problem of estimating accuracy of the calculated displacement field from the input images only and ...
Reducing false positive responses in lung nodule detector system by asymmetric adaboost
Dolejší, Martin; Kybic, Jan; Tůma, Stanislav; Polovinčák, Michal
2008 -
We are developing a complex computer aided diagnosis (CAD) system to detect small pulmonary nodules from helical CT scans. Here we present a classifier to reduce the number of false positive responses of the primary detector. Our approach is based on an asymmetric Adaboost which enables us to give different weights to missed nodules (false negatives, FNs) and incorrectly detected structures (false positives, FPs). This is useful because there are noticeably more negative examples in the nodule candidate set than real nodules-true positives (TPs). The whole system is meant as a second opinion for a human radiologist to speed up reading the examination. That is why we should detect as many true nodules as possible, while a certain number of FPs is acceptable. The system was tested on 147 cases (36559 slices) containing 357 nodules marked by an expert radiologist. The new classifier significantly reduced the number of false positives, while only a few nodules were incorrectly omitted.
Keywords:
computer aided diagnostic; nodule detection; CT; asymmetric Adaboost
Available in digital repository of ČVUT.
Reducing false positive responses in lung nodule detector system by asymmetric adaboost
We are developing a complex computer aided diagnosis (CAD) system to detect small pulmonary nodules from helical CT scans. Here we present a classifier to reduce the number of false positive responses ...
Analysis and Prediction of Electrical Contact Resistance for Anisotropic Conductive Adhesives
Duraj, Aleš; Mach, Pavel
2008 -
Anisotropic conductive adhesives (ACAs) and anisotropic conductive films (ACFs) are promising solder alternatives. These materials are preferable for fine pitch and ultra-fine pitch connections in electronics assembly. Quality of these interconnections is usually evaluated with measurement of electrical resistance. This paper describes few simple models for prediction of electrical contact resistance in ACAs interconnects. Nevertheless in these models is usually neglected effect of thin insulating layer between conductive particles and conductive tracks on substrate. Therefore two different methods for evaluation of electron tunneling resistance are analyzed and implement into models for prediction of electrical contact resistance of ACAs/ACFs. Extended models are directly compared with experimental results. Also effect of bonding pressure and different materials of conductive tracks is analyzed.
Available in digital repository of ČVUT.
Analysis and Prediction of Electrical Contact Resistance for Anisotropic Conductive Adhesives
Anisotropic conductive adhesives (ACAs) and anisotropic conductive films (ACFs) are promising solder alternatives. These materials are preferable for fine pitch and ultra-fine pitch connections in ...
Evaluation and Correction of Cable Phase Stability in High Frequency Near-Field Measurement
Vancl, Jan; Černý, Petr; Škvor, Zbyněk; Mazánek, Miloš
2008 -
In case of the near-field measurement, the radiated field by the measured antenna is received by two- dimensional scanner in defined points. During the process of the field scanning, the cable between the VNA and the scanner antenna is moved and its parameters are changed. This paper deals with the evaluation of the cable parameters changes. The dominant change is represented by the phase deviation of the cable transmission coefficient. The paper also proposes the method of the cable errors correction and evaluation of the correction method efficiency. The correction can be based on the full calibration at the reference plane of the scanner antenna feeding in all points of scanned field. The aforementioned approach is more time consuming than the proposed method, where the full calibration is performed in one selected point, while the correction of the cable parameters is based on the estimation based on the input impedance of the cable loaded by the scanner antenna.
Keywords:
near-filed; radiation pattern; cable phase stability; VNA; 2D plane scanner; error two-port
Available in digital repository of ČVUT.
Evaluation and Correction of Cable Phase Stability in High Frequency Near-Field Measurement
In case of the near-field measurement, the radiated field by the measured antenna is received by two- dimensional scanner in defined points. During the process of the field scanning, the cable between ...
Stable affine frames on isophotes
Perd’och, Michal; Matas, Jiří; Obdržálek, Štěpán
2007 -
We propose a new affine-covariant feature, the stable affine frame (SAF). SAFs lie on the boundary of extremal regions, i.e. on isophotes. Instead of requiring the whole isophote to be stable with respect to intensity perturbation as in maximally stable extremal regions (MSERs), stability is required only locally, for the primitives constituting the three-point frames. The primitives are extracted by an affine invariant process that exploits properties of bitangents and algebraic moments. Thus, instead of using closed stable isophotes, i.e. MSERs, and detecting affine frames on them, SAFs are sought even on some unstable extremal regions. We show experimentally on standard datasets that SAFs have repeatability comparable to the best affine covariant detectors tested in the state-of-the-art report (Mikolajczyk et al., 2005) and consistently produce a significantly higher number of features per image. Moreover, the features cover images more evenly than MSERs, which facilitates robustness to occlusion.
Available in digital repository of ČVUT.
Stable affine frames on isophotes
We propose a new affine-covariant feature, the stable affine frame (SAF). SAFs lie on the boundary of extremal regions, i.e. on isophotes. Instead of requiring the whole isophote to be stable with ...
Adaptive Parameter Optimization for Real-time Tracking
Zimmermann, Karel; Svoboda, Tomáš; Matas, Jiří
2007 -
Adaptation of a tracking procedure combined in a common way with a Kalman filter is formulated as an constrained optimization problem, where a trade-off between precision and loss-of-lock probability is explicitly taken into account. While the tracker is learned in order to minimize computational complexity during a learning stage, in a tracking stage the precision is maximized online under a constraint imposed by the loss-of-lock probability resulting in an optimal setting of the tracking procedure. We experimentally show that the proposed method converges to a steady solution in all variables. In contrast to a common Kalman filter based tracking, we achieve a significantly lower state covariance matrix. We also show, that if the covariance matrix is continuously updated, the method is able to adapt to a different situations. If a dynamic model is precise enough the tracker is allowed to spend a longer time with a fine motion estimation, however, if the motion gets saccadic, i.e. unpredictable by the dynamic model, the method automatically gives up the precision in order to avoid loss-of-lock.
Available in digital repository of ČVUT.
Adaptive Parameter Optimization for Real-time Tracking
Adaptation of a tracking procedure combined in a common way with a Kalman filter is formulated as an constrained optimization problem, where a trade-off between precision and loss-of-lock probability ...
Novel Entire Top Surface Planar Leaky Wave Antenna
Zehentner, Ján; Macháč, Jan; Zabloudil, Pavel
2007 -
This paper presents the application of a flat waveguide with a longitudinal slot in the middle of its wider wall for the design of a leaky wave antenna. The antenna is fed from a coaxial connector on its bottom, and provides a totally flat top surface and a radiation pattern with better suppression of side lobes than in the case of an antenna fed via a CPW patch. The antenna radiates into one relatively narrow main beam. The antenna characteristics and radiation aspects are discussed here. Its measured characteristics are in accord with those predicted by simulation.
Available in digital repository of ČVUT.
Novel Entire Top Surface Planar Leaky Wave Antenna
This paper presents the application of a flat waveguide with a longitudinal slot in the middle of its wider wall for the design of a leaky wave antenna. The antenna is fed from a coaxial connector on ...
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