Query: ultrasound b mode

title: The Delay Multiply and Sum Beamforming Algorithm in Ultrasound B Mode Medical Imaging
abstract: Most of ultrasound medical imaging systems currently on the market implement standard Delay and Sum (DAS) beamforming to form B mode images. However, image resolution and contrast achievable with DAS are limited by the aperture size and by the operating frequency. For this reason, different beamformers have been presented in the literature that are mainly based on adaptive algorithms, which allow achieving higher performance at the cost of an increased computational complexity. In this paper, we propose the use of an alternative nonlinear beamforming algorithm for medical ultrasound imaging, which is called Delay Multiply and Sum (DMAS) and that was originally conceived for a RADAR microwave system for breast cancer detection. We modify the DMAS beamformer and test its performance on both simulated and experimentally collected linear scan data, by comparing the Point Spread Functions, beampatterns, synthetic phantom and in vivo carotid artery images obtained with standard DAS and with the proposed algorithm. Results show that the DMAS beamformer outperforms DAS in both simulated and experimental trials and that the main improvement brought about by this new method is a significantly higher contrast resolution (i.e. narrower main lobe and lower side lobes) which turns out into an increased dynamic range and better quality of B mode images.

title: Speckle in ultrasound B mode scans
abstract: Ultrasound images obtained with a simple linear or sector scan show a granular appearance, called "speckle." This speckle is analyzed. The reduction in speckle that can be obtained with a compound scan with maximum amplitude writing is computed. The reduction in speckle is almost as large as can be obtained with averaging. It depends on the number of independent amplitude values that are measured. The condition for the independence of two amplitude values is derived, and thus a limit is given for the possible reduction in speckle.

title: Detection and Tracking of Multiple Microbubbles in Ultrasound B Mode Images
abstract: The imaging of microvessels and the quantification of their blood flow is of particular interest in the characterization of tumor vasculature. The imaging resolution (50 200 mm) of highfrequency ultrasound (US) (20 50 MHz) is not sufficient to image microvessels ~10 mm) and Doppler sensitivity is not high enough to measure capillary blood flow ~1 mm/s) For imaging of blood flow in microvessels, our approach is to detect single microbubbles (MBs) track them over several frames, and to estimate their velocity. First, positions of MBs will be detected by separating B mode frames in a moving foreground and a static background. For the crucial task of association of these positions to tracks, we implemented a modified Markov chain Monte Carlo data association (MCMCDA) algorithm, which can handle a high number of MBs. False alarms, the detection, initiation, and termination of MBs tracks are incorporated in the underlying model. To test the performance of algorithms, a US imaging simulation of a vessel tree with flowing MBs was set up (resolution 148 mm) The trajectories and flow velocity in the vessels with a lateral distance of 100 mm were reconstructed with super resolution. In a phantom experiment, a suspension of MBs was pumped through a tube (diameter 0.4 mm) at speeds of 2.2, 4.2, 6.3, and 10.5 mm/s and was imaged with a Vevo2100 system (Visualsonics) Estimated mean speeds of the MBs were 2.1, 4.7, 7, and 10.5 mm/s. To demonstrate the applicability for in vivo measurements, a tumor xenograft bearing mouse was imaged by this approach. The tumor vasculature was visualized with higher resolution than in a maximum intensity persistence image and the velocity values were in the expected range 0 1 mm/s.

title: A New Feature Enhanced Speckle Reduction Method Based on Multiscale Analysis for Ultrasound B Mode Imaging
abstract: Effective speckle reduction in ultrasound B mode imaging is important for enhancing the image quality and improving the accuracy in image analysis and interpretation. In this paper, a new feature enhanced speckle reduction (FESR) method based on multiscale analysis and feature enhancement filtering is proposed for ultrasound B mode imaging. In FESR, clinical features (e.g. boundaries and borders of lesions) are selectively emphasized by edge, coherence, and contrast enhancement filtering from fine to coarse scales while simultaneously suppressing speckle development via robust diffusion filtering. In the simulation study, the proposed FESR method showed statistically significant improvements in edge preservation, mean structure similarity, speckle signal to noise ratio, and contrast to noise ratio (CNR) compared with other speckle reduction methods, e.g. oriented speckle reducing anisotropic diffusion (OSRAD) nonlinear multiscale wavelet diffusion (NMWD) the Laplacian pyramid based nonlinear diffusion and shock filter (LPNDSF) and the Bayesian nonlocal means filter (OBNLM) Similarly, the FESR method outperformed the OSRAD, NMWD, LPNDSF, and OBNLM methods in terms of CNR, i.e. 10.70 0.06 versus 9.00 0.06, 9.78 0.06, 8.67 0.04, and 9.22 0.06 in the phantom study, respectively. Reconstructed B mode images that were developed using the five speckle reduction methods were reviewed by three radiologists for evaluation based on each radiologist's diagnostic preferences. All three radiologists showed a significant preference for the abdominal liver images obtained using the FESR methods in terms of conspicuity, margin sharpness, artificiality, and contrast, p<;0.0001. For the kidney and thyroid images, the FESR method showed similar improvement over other methods. However, the FESR method did not show statistically significant improvement compared with the OBNLM method in margin sharpness for the kidney and thyroid images. These results demonstrate that the proposed FESR method can improve the image quality of ultrasound B mode imaging by enhancing the visualization of lesion features while effectively suppressing speckle noise.

title: Ultrasound B mode imaging in observational studies of atherosclerotic progression.
abstract: Investigations of the progression of atherosclerosis in human arteries suggest that changes in the thickness of the arterial intima media complex, observable with B mode ultrasonography, may precede development of atherosclerotic lesions. For epidemiological studies and clinical trials, B mode ultrasound has the advantage that it is noninvasive, can be used in nonsymptomatic subjects, and can be carried out repeatedly, thus reducing the necessary sample size. In the Kuopio Ischaemic Heart Disease Risk Factor Study, we have assessed the reliability of B mode ultrasound through studying intraobserver and interobserver variability. We have also investigated its predictive value by associating ultrasound observations with clinical end points, risk factors for common carotid and femoral atherosclerosis, and predictors of progression of common carotid atherosclerosis.  The study of B mode ultrasound reliability was conducted in 10 middle aged men, with initial and two repeat scannings. The between observer coefficient of variation was 10.5% for the first assessments by four observers. The intraobserver variability, described as the mean of the absolute difference between the first and third observations, was 0.087 mm, or 8.3% of the mean intimal medial thickness (IMT) Ultrasonographic assessment of 1,257 men was compared with diagnostic information obtained from a prospective registry for acute myocardial infarction (AMI) The presence of any atherosclerotic findings was associated with a 3.0 fold risk of AMI. For each 0.1 mm of common carotid IMT, AMI risk increased by 11% (p 0.001) Common carotid artery and femoral artery atherosclerosis, as assessed by mean maximal IMT, had different risk factor profiles. Age, serum low density lipoprotein cholesterol, smoking, platelet aggregability, serum copper, serum selenium (inversely) and blood hemoglobin were the strongest predictors of 2 year increase of common carotid IMT.  On the basis of our experience and findings, the ultrasonographic assessment of common carotid atherosclerosis appears to be a feasible, reliable, valid, and cost effective method for both population studies and clinical trials of atherosclerosis progression and regression.

title: Postprocessing Approaches for the Improvement of Cardiac Ultrasound B Mode Images: A Review
abstract: The improvement in the quality and diagnostic value of ultrasound images has been an ongoing research theme for the last three decades. Cardiac ultrasound suffers from a wide range of artifacts such as acoustic noise, shadowing, and enhancement. Most artifacts are a consequence of the interaction of the transmitted ultrasound signals with anatomic structures of the examined body. Structures such as bone, lungs (air) and fat have a direct limiting effect on the quality of the acquired images. Furthermore, physical phenomena such as speckle introduce a granular pattern on the imaged tissue structures that can sometimes obscure fine anatomic detail. Over the years, numerous studies have attempted to address a range of artifacts in medical ultrasound, including cardiac ultrasound B mode images. This review provides extensive coverage of such attempts identifying their limitations as well as future research opportunities.

title: Stability evaluation of parameter estimation of multi Rayleigh model for ultrasound B mode image of liver fibrosis
abstract: A diagnosis of liver fibrosis using an ultrasound B mode image has the advantages of real time observation and noninvasive properties. In our previous study, a multi Rayleigh model was proposed to express a probability density function (PDF) of echo amplitudes from a fibrotic liver. From the multi Rayleigh model, fibrosis parameters, such as the amount of fibrotic tissue and its progressive ratio, can be extracted. To quantitatively evaluate liver fibrosis using the multi Rayleigh model, it is important to evaluate the stability of the estimation method of multi Rayleigh model parameters. In this study, a numerical simulation using random variables following the multi Rayleigh model was performed and the estimation stability of the parameters of the multi Rayleigh model with two components was examined. From the simulation results, it was found that estimation becomes unstable under a certain condition owing to statistical variations of moments, which are inputs in the estimation algorithm. The instability of estimated parameters could be evaluated by focusing on changes in moments upon changes in multi Rayleigh model parameters. It was indicated that we can evaluate the reliability of the estimated parameters of the multi Rayleigh model only from the estimated values.

title: A novel automatic algorithm for the segmentation of the lumen of the carotid artery in ultrasound B mode images
abstract: A novel algorithm is proposed for the segmentation of the lumen and bifurcation boundaries of the carotid artery in B mode ultrasound images. It uses the image contrast characteristics of the lumen and bifurcation of the carotid artery in relation to other tissues and structures for their identification. The relevant ultrasound data regarding the artery presented in the input image is identified using morphologic operators and processed by an anisotropic diffusion filter for speckle noise removal. The information obtained is then used to define two initial contours, one corresponding to the lumen and the other one regarding the bifurcation boundaries, for the application of the Chan Vese level set segmentation model. A set of longitudinal ultrasound B mode grayscale images of the common carotid artery was acquired using a GE Healthcare Vivid e ultrasound system. The results reveal that the new algorithm is effective and robust, and that its main advantage relies on the automatic identification of the carotid lumen, which overcomes the known limitations of the traditional algorithms.

title: Segmentation of the luminal border in intravascular ultrasound B mode images using a probabilistic approach
abstract: Intravascular ultrasound (IVUS) is a catheter based medical imaging technique that produces cross sectional images of blood vessels and is particularly useful for studying atherosclerosis. In this paper, we present a computational method for the delineation of the luminal border in IVUS B mode images. The method is based in the minimization of a probabilistic cost function (that deforms a parametric curve) which defines a probability field that is regularized with respect to the given likelihoods of the pixels belonging to blood and non blood. These likelihoods are obtained by a Support Vector Machine classifier trained using samples of the lumen and non lumen regions provided by the user in the first frame of the sequence to be segmented. In addition, an optimization strategy is introduced in which the direction of the steepest descent and Broyden Fletcher Goldfarb Shanno optimization methods are linearly combined to improve convergence. Our proposed method (MRK) is capable of segmenting IVUS B mode images from different systems and transducer frequencies without the need of any parameter tuning, and it is robust with respect to changes of the B mode reconstruction parameters which are subjectively adjusted by the interventionist. We validated the proposed method on six 20MHz and six 40MHz IVUS stationary sequences corresponding to regions with different degrees of stenosis, and evaluated its performance by comparing the segmentation results with manual segmentation by two observers. Furthermore, we compared our method with the segmentation results on the same sequences as provided by the authors of three other segmentation methods available in the literature. The performance of all methods was quantified using Dice and Jaccard similarity indexes, Hausdorff distance, linear regression and Bland Altman analysis. The results indicate the advantages of our method for the segmentation of the lumen contour.

title: Irreversible electroporation ablation of the liver can be detected with ultrasound B mode and elastography.
abstract: Irreversible electroporation (IRE) is a novel ablation technique that induces permanent membrane permeability and cell death. We are interested in ultrasound B mode and elastography to monitor IRE ablation in the liver.  Yorkshire pigs underwent IRE ablation of the liver and were imaged with ultrasound B mode and elastography. Histologic evaluation of cell death by triphenyltetrazolium chloride and hematoxylin and eosin staining was performed.  Elastography showed that liver ablated by IRE exhibited increased tissue stiffness with a peak strain ratio of 2.22. The IRE lesion had a discrete border without bubble artifact, and the lesion size significantly correlated with area of cell death on histology. IRE ablation was unaffected by presence of large blood vessels or bile ducts.  IRE ablation led to increased tissue stiffness that was detectable by elastography and indicative of cell death. Elastography may complement B mode ultrasonography to monitor IRE ablation of the liver.