New Publications are available for Sonic and ultrasonic radiation (biomedical imaging/measurement)
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New Publications are available now online for this publication.
Please follow the links to view the publication.Unsupervised textural segmentation of SonoElastographic breast images
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0462
Breast Cancer, the most common malignancy in women and the second leading cause of death for women all over the world. By earlier detection of cancer, the better treatment can be provided. SonoElastography, a new medical imaging technique reduces un necessary biopsies compared to mammography and conventional ultrasonography. The diagnosis and treatment of the cancer rely on segmentation of SonoElastographic images. Texture features are widely used in classification problems, i. e. mainly for diagnostic purposes where the Region Of Interest (ROI) is delineated manual ly. It has not yet been considered for SonoElastographic segmenta tion. SonoElastographic images of 15 patients taken using Siemens Acuson Antares are considered for experimentation. The images contain both benign and malignant tumors. From the experimental procedure it is proposed that the combination of texture features, Local Binary Pattern (LBP), Contrast and Variance are best suited for segmentation of SonoElastographic breast images. The images are first enhanced using sticks filter to remove noise, to improve contrast, and emphasize tumor boundary. Then extract the features to segment the breast image. The resultant images undergo some post-processing steps to remove the spurious spots. The segmented image is thinned to mark the tumor boundary. The results are then quantified with the help of an expert radiologist. The proposed work can be used for further diagnostic process, to decide if the segmented tumor is benign or malignant.Research on image filtering method to combine mathematics morphology with adaptive median filter
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1152
As a imaging technology of no-traditional lamp-house irradiation ,ultrasound medical imaging with its many advantages, such as no harm to the human body, real-time, cheap and easy to use, is widely used in clinic. But the ultrasonic imaging speckle noise make it difficulties to distinguish between normal tissue and pathological tissue. According to the character of noise in the medical ultrasonic image , an new method of the medical ultrasonic imaging filter based on mathematics morphology and adaptive filtering is proposed after analysis of speckle noise and general filter, and an experiment is made to validate. The experimental method is as follows : Firstly the Rayleigh noise is imposed on the original image , and then the median filter and the adaptive median filter are used on the contaminated image. Secondly the morphological filter is used to improve image quality and enhance the contrast , after the adaptive median filter is used on the image, to retain more necessary details. Finally the three noise filtering methods are compared from the images denoise and evaluation . And the results indicate that the new method is superior to other ones.Estimation of tissue elasticity by image processing of simulated B-mode ultrasound images
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1682
Elastography and strain imaging often use ultrasound to measure mechanical properties of soft tissues. These techniques generally examine radiofrequency signals from an ultrasound scanner. This study investigates the feasibility of strain estimation directly from an ultrasound B-mode image, using segmentation and shape analysis. Several thousand computer generated tissue mimicking phantoms with stiff inclusions were produced and analysed, evaluating the change in shape when the phantom is subjected to 1-D compression in order to estimate strain. The resulting stiffness measurements are accurate to within 8% of the actual values. (6 pages)Blind source separation to extract foetal heart sounds from noisy abdominal phonograms: a single channel method
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080431
A method for extracting foetal heart sounds (FHS) from noisy single channel abdominal phonograms is proposed. First, an appropriate matrix of delays is constructed; then multiple independent components are calculated using FastICA; finally, components are projected back onto the measurement space and those associated to FHS are subjectively selected. Three single channel phonograms, obtained from different subjects were analysed. Preliminary results are promising and showed successfully extractions of FHS (S1, S2). Future work will increase the number of subjects, evaluate the extraction quality, look for more information about foetal well-being, find an objective way to select FHS, and explore ICA implementations that utilise temporal structure such as Temporal Decorrelation source SEParation (TDSEP). (4 pages)Effective ultrasound data processing - a seismic exploration perspective
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080440
Many similarities exist between the seismic exploration technique and diagnostic medical ultrasound. The data processing associated with seismic exploration typically involves the application of numerous advanced algorithms, many of which may be utilised effectively in ultrasound. This paper briefly reviews the seismic exploration technique and investigates application of some typical seismic processing algorithms to medical ultrasound data. In particular, ensemble averaging, time-variant spectral whitening, predictive deconvolution and image reconstruction algorithms are considered, and shown to be very effective in enhancing the ultrasound image. (4 pages)Spectral analysis of backscattered ultrasound field from hydroxyapatite granules
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080469
Microcalcifications (MCs) are of great importance in breast cancer early diagnosis and sometimes they do represent the unique evidence of cancer disease (up to 47%). Their visualization in ultrasound (US) is limited by a number of factors the most important of which are speckle and system limited spatial resolution. MCs are modelled as hydroxyapatite (HA) microgranules and sound scattering from HA microgranules can be solved by mean of Faran model. Agar based phantoms have been manufactured to simulate human soft tissues with cylindrical shape and a commercial echo-scanner (Technos Mpx di ESAOTE s.r.l., Genova, Italia) has been used to perform the scan of the phantom. This work concerns with phantoms and the analysis of US data for the visualization of HA microgranules under multiple angle scan. A reconstruction method was hence used to get a 2D map of reflectivity from the target and further Fourier analysis was applied to radio frequency (RF) data. (4 pages)Motion compensated complementary coding for medical ultrasound
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080646
Ultrasonic imaging using complementary coded pulses offers the SNR improvements of signal coding without the filter side-lobes introduced by single transmit codes. The effects of the transducer and motion in the medium, however, can introduce mismatch artefacts and high side-lobes due to misalignment. A method for filtering and motion compensation of complementary coded signals appropriate for use in medical imaging scenarios is presented in this paper. The method has been shown by simulation to reduce side-lobes to levels that compare favourably to systems using FM-coded signals of similar length and bandwidth while increasing coding gain and range resolution.Restoration of medical ultrasound images via modified homomorphic deconvolution
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080366
Compared with other medical imaging devices, ultrasound imaging suffers from its poor resolution. Therefore, in order to obtain the important diagnostic image detail, restoration procedure need to be performed. The paper describes a modified homomorphic deconvolution which is used to improve the quality of medical ultrasound image. The proposed deconvolution performs the homomorphic filtering based on the estimation of the point-spread function (PSF). Especially, the application of a non-local means (NL-means) algorithm makes PSF estimation more precise for rejecting the white-Gaussian noise (WGN) effectively. We validate our method for different radio-frequency (RF) images with resolution improvement.A fast algorithm for automated independent process separation from single channel biomedical signal recordings: fastIPA
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080430
Independent component analysis (ICA) has found many uses in source separation in biomedical signals. We highlight a methodology and put forward an algorithm which allows single channel ICA to be performed on single channel biomedical signal recordings. The algorithm uses a fast, deflationary approach to efficiently extract independent processes underlying the single channel recordings. We show that for processes which are reasonably spectrally disjoint the algorithm can separate out individual sources. We show examples of this using brain signal recordings and abdominal foetal recordings. (4 pages)An anisotropic diffusion filter for ultrasonic speckle reduction
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080332
Anisotropic diffusion has been widely used to reduce speckle noise from ultrasound images. However, in traditional anisotropic diffusion methods, usually four directions neighborhood are used, which have many disadvantages, such as the sensitivity to the noise, the loss of image details and false contours. In this paper, we modify the standard SRAD (speckle reducing anisotropic diffusion) algorithm in the discrete domain by considering larger neighborhoods in its computation; then we adopt a confine term to keep the closest equivalence between the filtered image and the original image. Experimental results show that, in the presence of speckle nose, this proposed method could effectively preserve edges and detailed structures while suppressing speckle noise These preliminary results indicate that the proposed speckle reduction method could improve image quality and the visibility of small structures and fine details in the medical ultrasound images.Wavelet energy based compression of phonocardiogram (PCG) signal for telecardiology
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070692
This paper presents a novel phonocardiogram (PCG) signal compression method based on Wavelet transform. The proposed compression method uses energy based thresholding for retaining significant coefficients, uniform scalar zero zone quantizer (USZZQ) for quantizing the amplitudes of the significant coefficients and differencing coder for integer significance map (ISM). This method is tested using the PCG records taken from qdheart and eGeneralMedical databases. The performance of the compression method is assessed in terms of compression ratio (CR), percentage root mean square difference (PRD), Wavelet energy based diagnostic distortion (WEDD) measure and mean opinion score (MOS). The compression method is evaluated with PCG signals of more than 100 records with normal sounds, murmurs, stenosis, noise and other pathologies. High compression ratios with lower distortions are achieved with the proposed method.Patient compatibility of devices
http://dl-live.theiet.org/content/conferences/10.1049/ic_20060300
This paper discusses the patient compatibility of medical devices. A device is said to be patient compatible if it meets the regulatory requirements of safety, functionality and is according to the Annex 1 of the European Medical Device Directive. As it is accepted that medical devices constitute a risk, the benefits of the device should outweight the risks. The risk should be minimised hence a risk management programme must be undertaken. The relevance of device encapsulation is also discussed. If some materials are not biocompatible, they must be covered or encapsulated. A case study on an intravascular ultrasound (IVUS) coronary catheter is presented.Resonant acoustic profiling
http://dl-live.theiet.org/content/conferences/10.1049/ic_20060429
The article consists of a Powerpoint presentation on resonant acoustic profiling technology. The areas discussed include: components of RAP technology; antibody specificity; mouse IgG concentration analysis; IL-1β detection and interaction; serum detection; cell expression media; multi-protein complex formation; drug-enzyme profiling; kinetics of drug binding; bacteria detection; inflammatory marker; etc.Occlusal sound analysis revisited
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060392
We present a review of the gnathosonics technique, several improvements and a revision of concepts. Then, we present a method of nonlinear signal processing and heuristic features extraction. (4 pages)Estimating boundaries of primary heart sounds for diagnosing heart valve disorders
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060354
Estimation of the boundaries of primary heart sounds (S1 & S2) aids the characterization of murmurs present in the heart sound cycle for diagnosing heart valve disorders. The work presents an effective boundary estimation algorithm. Extensive incorporation of biomedical domain features facilitates the development of a computationally efficient algorithm using fundamental time-domain signal analysis techniques. The accuracy of algorithm is established over complex heart sound patterns pertaining to various heart valve disorders. (4 pages)Ultrasound image segmentation using watersheds and region merging
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060512
This paper presents an efficient hybrid image segmentation scheme for biomedical ultrasound images based on watershed transformation and region merging. It consists of four major stages. These stages are pre-processing, multiscale morphological gradient, watershed segmentation and finally region merging. The proposed scheme is tested using a set of medical ultrasound images. Experimental results show that our proposed method is capable of producing accurate contours in medical ultrasound images.Improved assessment of pulsatile blood flow during resuscitation using Doppler ultrasound
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060357
Early defibrillation is critical for successful resuscitation of a sudden cardiac arrest patient. Defibrillators currently do not assess the patient's heartbeat or blood circulation and the responder has to manually check for the pulse, a procedure known to be very inaccurate. Previously we had developed an ultrasound Doppler based approach to determine the presence of blood flow in the context of resuscitation. Here we extend our earlier work to develop a generalized pulsation index based on a spectral analysis of the Doppler signal. This new method has the advantage to better distinguish between states of pulse and pulselessness, since it aims at capturing the essentially non-sinusoidal behaviour of cardiac activity. In turn, this leads to better sensitivity and specificity for pulsatile flow assessment. The method was demonstrated on data from pigs undergoing cardiac arrest and defibrillation. (4 pages)Eigenhearts for diagnosis of congestive heart failure (CHF)
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060390
Common cardiac diseases such as cardiomyopathy, coronary artery diseases, and valve diseases, result in abnormal myocardial movement, which could eventually lead to heart failure, also called congestive heart failure (CHF). CHF is a disease in which the heart's ability to pump blood efficiently is lost. Possible presence of this disease and location of the abnormal activity can be diagnosed from patient's scan images, by determining the wall motion abnormalities. In this paper, a new principal component analysis (PCA) technique, Eigenhearts, is presented to diagnose the abnormal contractility of heart wall. Experiments were carried out using a preliminary set of simulated scan data and the results are discussed. (4 pages)Improved detection of embolic signals using multi scale wavelet filtering, AR and ANN, for TCD ultrasound
http://dl-live.theiet.org/content/conferences/10.1049/ic_20050332
Transcranial Doppler ultrasound can be used to detect emboli in blood flow in the brain. The presence of emboli is an indication of high risk of stroke. Embolic signals have characteristic transient chirps suitable for wavelet analysis. We have implemented an on-line intelligent wavelet pre-filter combined with a new frequency based neural network classification system (NFS) to produce a new online detection system. Initial results show an improvement in accuracy compared with the widely used FS-1 system. Our system makes, use of multi-scale wavelet denoising using an adaptive coefficient threshold. The pre-filtering system is combined with a detection system which uses a two layer neural classifier and a new auto-regressive event detector. For conditions such as carotid stenosis an improvement of 20% in detection accuracy was obtained. Our online (real time) intelligent wavelet amplifier and its matrix optimised form uses the matched filter properties of multiple coefficients from multiple wavelets to significantly enhance embolic signals and improve classification performance.A reduced forward operator for acoustic scattering problems
http://dl-live.theiet.org/content/conferences/10.1049/cp_20050327
This paper describes the development of a reduced forward operator for solving acoustic scattering problems that arise in ultrasonic imaging applications. The reduction, inspired by the contrast source inversion technique, is obtained by decoupling the interaction between locations in the computational domain at which contrast is present and those positions at which there is a zero contrast. The decoupling is achieved by multiplication by a diagonal matrix whose entries reflect the presence or absence of contrast at the associated point. Numerical results confirm that the reduced operator produces convergent results in less iterations.Frequency domain blind source separation
http://dl-live.theiet.org/content/conferences/10.1049/ic_20040612
Blind source separation (BSS) has attracted dramatic research interests in the past decade due to its potential applications in signal processing, telecommunications, and medical imaging. Among the open issues in BSS is how to recover the source signals from the linear convolutive mixtures which are observed by an array of sensors, and this remains a challenging problem. An effective solution is to transform the convolutive model into the frequency domain so that a series of complex-valued instantaneous BSS can be applied independently to each frequency bin. This has simplified the separation problem with a better convergence performance. However, a crucial problem, called the permutation problem, should be solved before gaining a good separation performance. This talk gives an outline of our approach to the frequency domain BSS with emphasis on the solutions to the permutation problem. Some recent results, together with a comparative discussion of the state-of-the-art approaches will be presented. (14 pages)Performance analysis of a compact robotic tele-echography E-health system over terrestrial and mobile communication links
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040647
In this work, we present a comparative performance analysis of an end-to-end robotic tele-echography system using two means of communication links; satellite and mobile (GPRS and UMTS) links. The functional modalities of the system in terms of the delay, total throughput and the jitter has been investigated, showing the capabilities and limitations of each communication link. The effect of concurrent and asynchronous system data transmission have been studied. The transmission of still and stream of ultrasound images investigated under different network conditions, has been simulated and studied on a real network. The limitation of the GPRS network with respect to the other communication links options, has been verified and analysed. The outcome of the study shows that the UMTS network is a promising communication link for the OTELO system.An ultrasonic-based enuresis treatment device
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040588
Primary nocturnal enuresis is characterised by an involuntary discharge of urine which happens unconsciously during the night. Enuresis can be treated by means of a conditioning device that wakens the wearer once the bladder volume has reached a preestablished threshold of capacity. Existing research using this preemptive technique indicates good results. However, deep sleep and inability to waken limits its effectiveness. The paper describes an intelligent ultrasonic-based bladder volume monitor and alarm system which enables investigation of multiple complex wakening sounds and stimuli. The proposed system also accurately logs all events for support of on-going research.PhiSAS: a low-cost medical system for the observation of respiratory dysfunction
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020042
Respiratory illness is recognised internationally as one of the commonest medical disorders affecting the world's populous, and is especially a major problem that affects the third world. The World Health Organisation (WHO) pursues an extensive health program that is aimed at reducing the plight of respiratory disorders by treatment and education. As with the majority of third-world health care programs, the effectiveness is limited by the availability of resources and finance. PhiSAS (Physiological Signal Analysis System) is a novel system developed for the observation of lung sounds. The system consists of a Personal Computer (PC) supported with dedicated software and hardware. Lung sounds can be recorded via chest microphones into the computer system for storage in digital form. This data can then be retrieved for post-processing using an array of software-based Digital Signal Processing (DSP) techniques that can mathematically manipulate lung sounds to extract important features. Data and results can be presented audibly by sound playback, or graphically by using spectrographs. The spectrograph is a representation of lung sound spectral energy with respect to time and frequency. PhiSAS has the ability to present three types of analysis based on conventional and novel mathematical techniques: Fourier, Wavelet and Time-Frequency Analysis. The purpose of the PhiSAS system is to provide objective analysis of lung sounds. The practice of auscultation (the art of listening to body sounds) has been practiced by physicians since the days of Hippocratic medicine. However, many physicians believe that respiratory auscultation performed with a stethoscope offers little scientific value due to the way it is practiced. For example, observations can be subjective depending on the physicians hearing ability and experience. Moreover, descriptions of lung sounds are described using onomatopoeic references that are ambiguous. By exploiting advances in low-cost PC technology and techniques in signal analysis, the physician can express sound observations in a more precise scientific manner. (5 pages)Heart sound segmentation by hidden Markov models
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020297
The segmentation of phonocardiogram (PCG) signals is the first step in the automatic diagnosis based on heart sounds. The majority of attempts to segment PCG signals depend on a reference provided by simultaneous electrocardiogram recordings. The algorithm proposed in this paper is based on the analysis of the PCG signal only and does not require an ECG reference signal. In this paper we propose the tracking of the log spectral components that vary slowly with frequency (the low-time components). That is Cepstral analysis is used to provide the features selected to represent the heart sounds. The algorithm utilises a hidden Markov Model to identify the S1 and S2 components of the heart sound, which delimit the systolic and diastolic cycles. The parameters of a simple hidden Markov model with single Gaussian distribution for continuous observations are learned from a training set of heart sounds. Once the parameters of the model are obtained PCG signals from different sets are used to test the segmentation procedure. (4 pages)Speckle reduction techniques in B-mode ultrasound images
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020288
The traditional 1D spilt spectrum processing (SSP) method suffers from a relatively high-resolution loss limitation, inherent to the method. There is a trade-off between speckle reduction and resolution loss. On the other hand, the new 2D SSP with directive filters perform well. In this method, the filters are chosen to have a bandwidth larger than that of the ultrasound pulse and this helps to maintain image resolution. Even though SSP is a single-image method, it tackles the speckle reduction problem in a similar way to frequency compounding (a multi-image method), where a set of images from the same structure is acquired by using ultrasound pulses with different frequencies for each image. Likewise, the use of directive filters in the (single image) 2D SSP method has a similarity with angle compounding method (a multi-image method), where a number of images are acquired from different scanning angles in order to decorrelate the speckle. However, practical difficulties with the use of angle compounding methods in a medical context are overcome by the new 2D SSP with directive filters, which requires only a single image. The zero adjustment processing (ZAP) is a very powerful method, and is the only technique that can recover the apparent energy loss suffered in destructive interference, and promises well for further development. The hybrid method was used to demonstrate the synergy between different techniques, and the concept certainly looks ripe for further development. (6 pages)A novel approach for non-stationary medical signal analysis using Hilbert spectrum
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020292
This paper discusses a novel method to study the nonlinear and non-stationary processes and to investigate the time-varying frequency of the practical medical signals. The aim of this contribution is to explore the role that both empirical mode decomposition and Hilbert transform can be used to play in such medical signals. A Hilbert transform is applied to each intrinsic mode function to obtain the global time-frequency distribution of the underlying signal with a point of view of instantaneous frequency. Two kinds of clinical phonocardiogram signals with normal and abnormal cardiac functions were analyzed by using the proposed method. The instantaneous frequency distributions of the PCG signals were also compared with the results by using the wavelet transform. Both simulation and experimental results were presented and discussed to demonstrate the power and effectiveness of the proposed new approach. (6 pages)Comparison of transformation methods to determine frequency specific cochlear hearing loss based on TEOAE
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020294
In this paper, we aim to determine frequency-specific cochlear hearing loss (HL) by means of transient evoked otoacoustic emissions (TEOAE). Exemplarily, the differentiation of three groups of frequency-specific HL is performed by parametrisation of the time-domain TEOAE responses based on three transforms, namely discrete wavelet transformation, wavelet packets and Gabor frames. Using an SNR-like criterion, the various transforms are tested for their ability to differentiate between the three groups of hearing ability. This differentiation is evaluated on a large group of data from patients. The separability results for each transform method are checked against the data of a second control group. (6 pages)Fuzzy, Weighted-Offset, Multiscale Edge Detection for automatic echocardiographic LV boundary extraction
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020289
This paper describes a new Fuzzy, Weighted-Offset, Multiscale Edge Detection algorithm for cardiac left ventricular (LV) epicardial and endocardial boundary detection on short axis (SA) echocardiographic images. The proposed method uses the `centre-based' approach, previously described in S.K. Setarehdan and J.J. Soraghan, 1999, IEEE Transaction on Biomedical Engineering. Vol. 46, No. 11, 1364 - 1378. The Edge-detection stage uses a new Fuzzy Weighted Offset Multiscale Edge Detection (FWOMED) technique in order to identify a single moving point for each one of the epicardial and endocardial boundaries over the N radii in an echocardiographic frame. This technique achieves optimal edge detection through non-decimated wavelet decomposition of the original signal followed by a fuzzy based decision technique, which is applied across the scales. Finally, a uniform cubic B-spline approximation is used to define the closed LV boundaries. The performance of this technique is compared to Mallat's (S. Mallat and S. Zhong, 1992, IEEE Trans. PAMI, Vol. 14, No. 7, 710-723.) multiscale edge detection technique, for a range of test data sets comprising different synthetic noisy signals. (6 pages)Long-term objective cough recognition and quantification
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020298
The application of advanced digital signal processing (DSP) and spectral estimation techniques to the analysis of cough has produced many benefits in recent years. The ability to recognise the characteristic features of a signal defined to be a cough and to distinguish these from the features of other signals such as speech and background noise have allowed accurate cough identification, counting and frequency determination to be carried out in increasingly natural every-day environments. This work requires an algorithm that identifies cough sounds from patients over extended periods of time and produces a series of statistical measurements for comparing the effectiveness of different anti-tussive drug treatments. To achieve the required specificity and sensitivity, the properties of sounds characteristic of different conditions: asthma, cystic fibrosis, cryptogenic fibrosing alveolitis, and chronic obstructive pulmonary disease were analysed and used to adapt the algorithm to detect sound characteristic of coughs. The accuracy of the detector has been assessed. A sensitivity of 80.8% and specificity of 99.3% were achieved for overnight recordings. (4 pages)Nonlinear analysis of carotid artery echographic images
http://dl-live.theiet.org/content/conferences/10.1049/cp_20000334
Deals with the application of nonlinear analysis to the identification of spatially complex patterns in echographic images of normal and pathological carotid arteries. Complexity measures and indices are evaluated in normal and atherosclerotic plaques, related to the slow space-temporal evolution of biological patterns. In particular, we have found that the correlation dimension index lets one differentiate normal from pathological groups, allowing one to infer the complex interaction mechanism which is responsible for the plaque formation process.Bone fracture imaging study with an acoustic technique
http://dl-live.theiet.org/content/conferences/10.1049/cp_20000341
Imaging studies of bones are important for orthopaedic doctors to know the physical condition of the bones, to enable them to decide about the treatment of a particular abnormality. Generally, the X-ray technique is used by clinicians to assess the condition of the bone, but this method is cumbersome and has diagnostic limitations, particularly in the case of minor fractures. In order to overcome this problem, an acoustic stress wave technique is developed for the study of bone imaging. This technique is quick, less expensive and reliable for evaluating the inner structure of the bone, layer by layer, non-destructively and non-invasively. This paper describes a comparative study of imaging patterns in normal and fractured bones.Wavelet analysis of quadrature Doppler ultrasound signals
http://dl-live.theiet.org/content/conferences/10.1049/cp_20000346
Most Doppler ultrasound systems employ quadrature demodulation techniques at the detection stage. The information concerning flow direction encoded in the phase relationship between in-phase and quadrature-phase channels is not obvious at this stage. Complex FFT can be used to obtain directional information in the frequency domain as well as time-frequency analysis of Doppler signals. However it has an inherent time-frequency resolution limitation. The wavelet transform allows the time-frequency resolution compromise to be optimized. Mapping directional information in scale domain is also desirable. A method based on the utilisation of complex wavelets and negative scales is described. It eliminates the intermediate processing stages for obtaining directional Doppler signals for time-scale analysis.Introducing transmission line matrix (TLM) modeling and its application in medical ultrasound
http://dl-live.theiet.org/content/conferences/10.1049/cp_20000340
Transmission line matrix (TLM) modeling is a numerical technique for modeling wave propagation. It was used originally for modeling electromagnetic waves. P.P.M. So et al. (1991) introduced the inverse TLM, which is TLM in time reversal. In this paper, we introduce TLM modeling and inverse TLM modeling and explain how it would be used for modeling ultrasound waves. Some applications of TLM modeling in medical ultrasound systems are also proposed.An efficient algorithm for 3-D image reconstruction over parallel and distributed architectures
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990324
We have designed an efficient parallel algorithm for performing 3D image reconstruction. In this framework, we have considered 3-D image to be reconstructed from a series of 2-D images, produced using ultrasonography, computer tomography, etc. The paper discusses a general parallel algorithm for 3D image reconstruction over CRCW, CREW and EREW PRAM models. We have developed efficient implementations of this algorithm over a vector machines, a distributed system comprising of a cluster of workstations and various interconnection network like a mesh network and a reconfigurable bus network. The performance of the above algorithms are tested using simulation experiments performed for 3D image reconstruction of the vitreous region of the eye using ophthalmic ultrasonograms. A novel approximation scheme has also been proposed for a drastic improvement in performance for specific kinds of image. The results indicate the time complexities of the algorithms are in resonance with the expected theoretical values and image obtained has a uncompromising level of accuracy.Fetal echocardiographic image segmentation using neural networks
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990374
This paper discusses supervised and unsupervised neural network approaches to fetal echocardiographic image segmentation. The obtained results were compared with images segmented by a known unsupervised clustering technique (i.e. k-means). The visual aspect of the segmented images was evaluated with respect to its visual quality by an expert. A subset of the segmented images showed sufficient detail of the internal heart anatomy to allow medical diagnosis. The visual observation was matched closely by our unsupervised image segmentation approach, using the modified Hubert index.Speckle reduction with edges preservation for ultrasound images: using function spaces approach
http://dl-live.theiet.org/content/journals/10.1049/iet-ipr.2011.0366
In this study, a novel speckle reduction method is proposed for ultrasound images. This denoising method is designed to preserve both the edges and structural details of the image. Speckle noise is suppressed, without smearing the edges, by extending the smoothness of the image in the wavelet-based Hölder spaces. A comparison of smoothing speckles with the other well-known methods is provided via the size of Besov norm. The authors validate the proposed method using synthetic data, simulated and real ultrasound images. Experiments demonstrate the performance improvement of the proposed method over other state-of-the-art methods in terms of image quality and edge preservation indices.Wavelet domain Bayesian processor for speckle removal in medical ultrasound images
http://dl-live.theiet.org/content/journals/10.1049/iet-ipr.2009.0110
Speckle reduction is a prerequisite for many ultrasound image processing tasks. In this study, the authors introduce a novel speckle suppression method for ultrasound images, based on statistical modelling of wavelet coefficients. First, the authors demonstrate that the wavelet coefficients of log-transformed ultrasound images have significantly non-Gaussian statistics and a two-dimensional heteroscedasticity exists in them. Previously, they described the overall multiscale wavelet transform of the log-transformed ultrasound images using two-dimensional generalised autoregressive conditional heteroscedastic (2D GARCH) model. In this study, they introduce a new heteroscedastic model, that is, 2D-GARCH generalised Gaussian (2D-GARCH-GG) as an extension of 2D-GARCH model. This new model can capture heavy-tailed marginal distribution and the intrascale dependencies of wavelet coefficients. Also, 2D-GARCH-GG model introduces additional flexibility in the model formulation in comparison with 2D-GARCH model, which results in better characterisation of ultrasound images subbands and improved restoration in noisy environments. In consequence, the authors introduce maximum a-posteriori estimator, based on GARCH-GG modelling to estimate the clean wavelet coefficients. In order to evaluate the performance of the proposed method in speckle suppression, they compare it with other denoising methods applied on some artificially speckled and actual ultrasound images and we verify the performance improvement in utilising the new strategies.Ultrasonic image fusion using compressed sensing
http://dl-live.theiet.org/content/journals/10.1049/el.2012.2282
Presented is a new approach to fuse the fundamental ultrasonic image and second-harmonic ultrasonic image using compressed sensing. First, source image compressed measurements are obtained by star-shaped sampling mode in the 2D Fourier plane. The measurements are fused into fused measurements by the adaptive weighted average fusion scheme. The fused image is then reconstructed from the fused measurements by total variation optimisation. Experimental results show that the proposed method has better performance over wavelets and principal component fusion methods in improving the quality of the fused image.Locally adaptive wavelet domain Bayesian processor for denoising medical ultrasound images using Speckle modelling based on Rayleigh distribution
http://dl-live.theiet.org/content/journals/10.1049/ip-vis_20050975
The authors present a statistical approach to speckle reduction in medical ultrasound B-scan images based on maximum <i xmlns="http://pub2web.metastore.ingenta.com/ns/">a posteriori</i> (MAP) estimation in the wavelet domain. In this framework, a new class of statistical model for speckle noise is proposed to obtain a simple and tractable solution in a closed analytical form. The proposed method uses the Rayleigh distribution for speckle noise and a Gaussian distribution for modelling the statistics of wavelet coefficients in a logarithmically transformed ultrasound image. The method combines the MAP estimation with the assumption that speckle is spatially correlated within a small window and designs a locally adaptive Bayesian processor whose parameters are computed from the neighboring coefficients. Further, the locally adaptive estimator is extended to the redundant wavelet representation, which yields better results than the decimated wavelet transform. The experimental results show that the proposed method clearly outperforms the state-of-the-art medical image denoising algorithm of Pizurica <i xmlns="http://pub2web.metastore.ingenta.com/ns/">et al.</i>, spatially adaptive single-resolution methods and band-adaptive multi-scale soft-thresholding techniques in terms of quantitative performance as well as in terms of visual quality of the images. The main advantage of the new method over the existing techniques is that it suppresses speckle noise well, while retaining the structure of the image, particularly the thin bright streaks, which tend to occur along boundaries between tissue layers.Adaptive compression of medical ultrasound images
http://dl-live.theiet.org/content/journals/10.1049/ip-vis_20045168
An adaptive image-coding algorithm for compression of medical ultrasound (US) images in the wavelet domain is presented. First, it is shown that the histograms of wavelet coefficients of the subbands in the US images are heavy-tailed and can be better modelled by using the generalised Student's <i xmlns="http://pub2web.metastore.ingenta.com/ns/">t</i>-distribution. Then, by exploiting these statistics, an adaptive image coder named JTQVS-WV is designed, which unifies the two approaches to image-adaptive coding: rate–distortion (R–D) optimised quantiser selection and R–D optimal thresholding, and is based on the varying-slope quantisation strategy. The use of varying-slope quantisation strategy (instead of fixed R–D slope) allows coding of the wavelet coefficients across various scales according to their importance for the quality of reconstructed image. The experimental results show that the varying-slope quantisation strategy leads to a significant improvement in the compression performance of the JTQVS-WV over the best state-of-the-art image coder, SPIHT, JPEG2000 and the fixed-slope variant of JTQVS-WV named JTQ-WV. For example, the coding of US images at 0.5 bpp yields a peak signal-to-noise ratio gain of >0.6, 3.86 and 0.3 dB over the benchmark, SPIHT, JPEG2000 and JTQ-WV, respectively.Inertial snake for contour detection in ultrasonography images
http://dl-live.theiet.org/content/journals/10.1049/ip-vis_20040310
Snakes, or active contour models are used extensively for image segmentation in varied fields. However, some major challenges restrict their use in many fields. The authors propose a new inertial snake model, that introduces an inertial effect of the control points into the snake framework. The proposed inertial force along with the first- and second-order continuity forces controls the spline motion through the concavities and also against weak edge forces. This smart force field, added to the inertial energy framework, posses the ability to adaptively reduce its effect near the true edges, so that the energy minimising spline converges into the edges. A greedy snake has been used for computation of the energy minimising spline. The algorithm has been tested on phantoms and ultrasound images as well. It is shown in the results that the proposed algorithm classifies the object from the background class in most of the images perfectly. Ultrasound images of a lower limb artery of an adult woman have been tested with this algorithm, and also extended for motion tracking.Compressive sensing photoacoustic imaging based on multi-view error gradient fusion
http://dl-live.theiet.org/content/journals/10.1049/iet-opt.2011.0055
Compressive sensing photoacoustic imaging (PAI) is an emerging method for photoacoustic signal sampling and image reconstruction. Based on the method, the high-imaging rate and low-system cost can be achieved. Unfortunately, artefacts exist in the reconstructed images and appear heavier if the measurement is fewer. The artefacts appear at different pixels when images are observed from different angles, and can be rejected by the fusion of multi-view images. In this study, a multi-view image fusion method based on error gradient is proposed. The theory of compressive sensing PAI is introduced firstly. Then a feasible measurement scheme based on the digital micromirror device is constructed. Subsequently, error gradient of the reconstructed image is defined and the fusion rule based on error gradient is made. Finally, the proposed method is testified by the simulations, in which images observed from 0 and 90° are used to take the fusion. Simulation results demonstrate that the image artefacts can be reduced effectively by the proposed method.Nonlinear dynamic analysis of speech from pathological subjects
http://dl-live.theiet.org/content/journals/10.1049/el_20020198
Nonlinear dynamic methods are employed to describe the complexity of speech from healthy and pathological subjects with vocal polyps. The analysis demonstrates the low-dimensional dynamic characteristics of normal and pathological voices as well as their statistically significant differences. The potential clinical application of nonlinear dynamics in speech signal processing of pathological voices is suggested.Microfluidic-assisted formation of multifunctional monodisperse microbubbles for diagnostics and therapeutics
http://dl-live.theiet.org/content/journals/10.1049/mnl.2011.0141
Microbubbles (MBs) coated by surfactant or polymer have been shown to be the most effective contrast agents for diagnostic ultrasound contrast imaging and targeted molecular imaging. With the development of both diagnostic and therapeutic applications of ultrasound contrast agents (UCAs), there is a demand for new preparation technologies to provide a high degree of control over MB size, composition, stability and uniformity in response. MBs produced by traditional methods, such as sonication or mechanical agitation, have poor control over MBs' size and uniformity. A polydisperse size distribution may have the inherent limitation of low acoustic backscattering efficiency and uncontrollable safety concern if used <i xmlns="http://pub2web.metastore.ingenta.com/ns/">in vivo</i>. This study presents successful production of five kinds of monodisperse MBs by flow-focusing method based on four flow-focusing units integrated microfluidic devices. These MBs act as a vehicle to carry fluorescent probe 6-coumarin, tumour-targeted peptide (LyP-1), paclitaxel, superparamagnetic iron oxide Fe<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">4</sub> nanoparticles and CdTe/ZnS quantum dots in the lipid shells, respectively. The sizes of MBs are controlled on the order of 2–7 µm by adjusting gas pressure and liquid flow velocity. These functional MBs have the potential applications in emerging areas, such as drug delivery, ultrasound molecular imaging and dual-modality imaging.Segmentation and identification of some pathological phonocardiogram signals using time-frequency analysis
http://dl-live.theiet.org/content/journals/10.1049/iet-spr.2010.0013
Heart sounds that are multicomponent non-stationary signals characterise the normal phonocardiogram (PCG) signals and the pathological PCG signals. The time-frequency analysis is a powerful tool in the analysis of non-stationary signals especially for PCG signals. It permits detecting and characterising abnormal murmurs in the diagnosis of heart disease. In this study, the authors introduce a novel method based on time‐frequency analysis in conjunction with a threshold evaluated on Rényi entropy for the segmentation and the analysis of PCG signals. The method was applied to different sets of PCG signals: early aortic stenosis, late systolic aortic stenosis, pulmonary stenosis and mitral regurgitation. The analysis has been conducted on real biomedical data. Tests performed proved the ability of the method for segmentation between the main components and the pathological murmurs of the PCG signal. Also, the method permits elucidating and extracting useful features for diagnosis and pathological recognition.Robust non-homomorphic approach for speckle reduction in medical ultrasound images
http://dl-live.theiet.org/content/journals/10.1049/mbec_20053980
Most existing wavelet-based image denoising techniques are developed for additive white Gaussian noise. In applications to speckle reduction in medical ultrasound (US) images, the traditional approach is first to perform the logarithmic transform (homomorphic processing) to convert the multiplicative speckle noise model to an additive one, and then the wavelet filtering is performed on the log-transformed image, followed by an exponential operation. However, this non-linear operation leads to biased estimation of the signal and increases the computational complexity of the filtering method. To overcome these drawbacks, an efficient, non-homomorphic technique for speckle reduction in medical US images is proposed. The method relies on the true characterisation of the marginal statistics of the signal and speckle wavelet coefficients. The speckle component was modelled using the generalised Nakagami distribution, which is versatile enough to model the speckle statistics under various scattering conditions of interest in medical US images. By combining this speckle model with the generalised Gaussian signal first, the Bayesian shrinkage functions were derived using the maximum a posteriori (MAP) criterion. The resulting Bayesian processor used the local image statistics to achieve soft-adaptation from homogeneous to highly heterogeneous areas. Finally, the results showed that the proposed method, named GNDShrink, yielded a signal-to-noise ratio (SNR) gain of 0.42 dB over the best state-of-the-art despeckling method reported in the literature, 1.73 dB over the Lee filter and 1.31 dB over the Kaun filter at an input SNR of 12.0 dB, when tested on a US image. Further, the visual comparison of despeckled US images indicated that the new method suppressed the speckle noise well, while preserving the texture and organ surfaces.Analysis of the O-wave in acute right ventricular apex impedance measurements with a standard pacing lead in animals
http://dl-live.theiet.org/content/journals/10.1049/mbec_20023709
Modern pacemakers (implantable devices used for maintaining an appropriate heart rate in patients) can use an intracardiac ventricular impedance signal for physiological cardiac stimulation control. Intracardiac ventricular impedance from nine animal subjects is analysed and presented (seven sheep: 49.0±6.5 kg, sinus rhythm 100.3±16.5 beats min<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>, average impedance 629.8±72.6 Ω; and two dogs: 30 kg each, sinus rhythm 86.0 beats min<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>, 862.1 Ω and 134.0 beats min<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>, 1114.6 Ω, respectively). The averaged curve and standard deviation curve of the impedance in sinus rhythm were analysed in MATLAB to clarify and study consistent impedance shape over one heart cycle. In eight of nine (89%) animal subjects, a consistent impedance slope change (notch) was observed in the early stage of the cardiac filling phase. This result was reproduced in an additional subject with simultaneous echocardiographical measurements of mitral valve blood flow. The notch occured soon after rapid early filling (E-wave in mitral flow) but prior to ventricular filling caused by atrial contraction, indicating that the impedance notch was caused by rapid ventricular filling and that it might be a sensed feature of diagnostic value. The intracardiac impedance notch in the present study had similar features to the non-invasive transthoracic impedance O-wave reported by others, and it is shown here that an O-wave is found in intracardiac impedance signals, strongly suggesting that the non-invasive O-wave is caused by cardiac events.Accuracy evaluation in ultrasonic-based measurement of microscopic change in thickness
http://dl-live.theiet.org/content/journals/10.1049/el_19990669
For the diagnosis of atherosclerosis, one acoustical method involves measuring the change in thickness of the arterial wall during one cardiac cycle and then noninvasively evaluating the elastic properties of the arterial wall. An alternative method for obtaining such a diagnosis is proposed, the phased tracking method, which can be used to accurately measure the instantaneous displacement signals on the intima and adventitia of the arterial wall from the skin surface using pulsive ultrasonic waves. A minute change in the thickness of the arterial wall of several micrometres is obtained by integrating the difference between two instantaneous displacement signals. Using a rubber plate in a water tank, the accuracy of the proposed method is evaluated by measuring such microscopic changes in thickness.Indentation test of soft tissues with curved substrates: A finite element study
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043899
Indentation is a commonly used approach to measure the mechanical properties of soft tissues, such as articular cartilage and limb tissues. The Young's modulus of tissue can be calculated from the indentation test using a mechanical model, where the soft tissue is normally assumed to have a flat substrate. In this study, a series of 2D finite element models were established to investigate the effects of bones with various curvatures embedded in the soft tissues during an indentation test. For each curvature of the hard substrate, the errors in the calculation of the Young's modulus were estimated for different indentation depths (0–10%) and aspect ratios <i xmlns="http://pub2web.metastore.ingenta.com/ns/">a</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">h</i> of the indentor diameter and the tissue thickness (0.2–2 in seven steps). The radius ratio <i xmlns="http://pub2web.metastore.ingenta.com/ns/">a</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">R</i> of the indentor and the curved substrate ranged from 0 to 0.38 in nine steps. Results showed that the error in calculation of the Young's modulus increased by 21.2% when the curvature <i xmlns="http://pub2web.metastore.ingenta.com/ns/">a</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">R</i> of the bone increased from 0 to 0.38 (under the condition of <i xmlns="http://pub2web.metastore.ingenta.com/ns/">a</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">h</i>=1.0, Poisson's ratio ν=0.45). The error increased from 6.0 to 18.2% when the tissue thickness increased from 0.2 to 2 (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">a</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">R</i>=0.18, ν=0.45). It was found that the error in the Young's modulus calculation caused by the curved hard substrates could be corrected by a single factor for different indentation depths. This factor depends on the Poisson's ratio, the aspect ratio <i xmlns="http://pub2web.metastore.ingenta.com/ns/">a</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">h</i> and the radius ratio <i xmlns="http://pub2web.metastore.ingenta.com/ns/">a</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">R</i>.