Causes of Ultrasound Doppler Twinkling Artifact

Brisbane W., Bailey M.R., Sorensen M.D.

Imaging is an important diagnostic tool and initial step in deciding which therapeutic options to use for the management of kidney stones and guidelines differ regarding the optimal initial imaging modality. In this Review, Brisbane and colleagues discuss the advantages and disadvantages of CT, ultrasonography, MRI and kidney, ureter, bladder (KUB) plain film radiography for stone imaging and propose an algorithm for imaging patients with acute stones. Kidney stone imaging is an important diagnostic tool and initial step in deciding which therapeutic options to use for the management of kidney stones. Guidelines provided by the American College of Radiology, American Urological Association, and European Association of Urology differ regarding the optimal initial imaging modality to use to evaluate patients with suspected obstructive nephrolithiasis. Noncontrast CT of the abdomen and pelvis consistently provides the most accurate diagnosis but also exposes patients to ionizing radiation. Traditionally, ultrasonography has a lower sensitivity and specificity than CT, but does not require use of radiation. However, when these imaging modalities were compared in a randomized controlled trial they were found to have equivalent diagnostic accuracy within the emergency department. Both modalities have advantages and disadvantages. Kidney, ureter, bladder (KUB) plain film radiography is most helpful in evaluating for interval stone growth in patients with known stone disease, and is less useful in the setting of acute stones. MRI provides the possibility of 3D imaging without exposure to radiation, but it is costly and currently stones are difficult to visualize. Further developments are expected to enhance each imaging modality for the evaluation and treatment of kidney stones in the near future. A proposed algorithm for imaging patients with acute stones in light of the current guidelines and a randomized controlled trial could aid clinicians.

Nikolaeva A.V., Tsysar S.A., Sapozhnikov O.A.

The paper considers the problem of precise measurement of the acoustic radiation force of an ultrasonic beam on targets in the form of solid spherical scatterers. Using known analytic relations, a numerical model is developed to perform calculations for different sizes of spherical scatterers and arbitrary frequencies of the incident acoustic wave. A novel method is proposed for measuring the radiation force, which is based on the principle of acoustic echolocation. The radiation force is measured experimentally in a wide range of incident wave intensities using two chosen methods differing in the way the location of the target is controlled.

Rahmouni A., Bargoin R., Herment A., Bargoin N., Vasile N.

PURPOSE To investigate a new color Doppler ultrasound (US) artifact that manifested as a rapidly changing mixture of red and blue behind a strongly reflecting structure. MATERIALS AND METHODS In 140 consecutive patients with parenchymal calcifications seen at US, the presence of color signal was assessed in calcified areas relative to adjacent noncalcified tissue. The artifact, called the twinkling color artifact, was stimulated with various strongly reflecting structures immersed in still water. RESULTS The artifact was found in 42 parenchymal calcifications. In vitro experiments showed that the twinkling artifact was present in granular structures, whereas no color signal was noted in smooth surfaces. The "twinkling sign" appeared to be generated by a strongly reflecting medium composed of individual reflectors. CONCLUSION The presence of a color signal close to calcifications should be interpreted with caution, and a flow spectrum should always be recorded to eliminate the twinkling artifact.

Ahmad S.K., Abdallah M.M.

Jamzad A., Setarehdan S.K.

The twinkling artifact is an undesired phenomenon within color Doppler sonograms that usually appears at the site of internal calcifications. Since the appearance of the twinkling artifact is correlated with the roughness of the calculi, noninvasive roughness estimation of the internal stones may be considered as a potential twinkling artifact application. This article proposes a novel quantitative approach for measurement and analysis of twinkling artifact data for roughness estimation.A phantom was developed with 7 quantified levels of roughness. The Doppler system was initially calibrated by the proposed procedure to facilitate the analysis. A total of 1050 twinkling artifact images were acquired from the phantom, and 32 novel numerical measures were introduced and computed for each image. The measures were then ranked on the basis of roughness quantification ability using different methods. The performance of the proposed twinkling artifact-based surface roughness quantification method was finally investigated for different combinations of features and classifiers.Eleven features were shown to be the most efficient numerical twinkling artifact measures in roughness characterization. The linear classifier outperformed other methods for twinkling artifact classification. The pixel count measures produced better results among the other categories. The sequential selection method showed higher accuracy than other individual rankings. The best roughness recognition average accuracy of 98.33% was obtained by the first 5 principle components and the linear classifier.The proposed twinkling artifact analysis method could recognize the phantom surface roughness with average accuracy of 98.33%. This method may also be applicable for noninvasive calculi characterization in treatment management.

Lu W., Sapozhnikov O.A., Bailey M.R., Kaczkowski P.J., Crum L.A.

The mechanism of the twinkling artifact (TA) that occurs during Doppler ultrasound imaging of kidney stones was investigated. The TA expresses itself in Doppler images as time-varying color. To define the TA quantitatively, beam-forming and Doppler processing were performed on raw per channel radio-frequency data collected when imaging human kidney stones in vitro. Suppression of twinkling by an ensemble of computer-generated replicas of a single radio frequency signal demonstrated that the TA arises from variability among the acoustic signals and not from electronic signal capture or processing. This variability was found to be random, and its suppression by elevated static pressure and return when the pressure was released suggest that the presence of bubbles on the stone surface is the mechanism that gives rise to the TA.

Kamaya A., Tuthill T., M. Rubin J.

The objective of our study was to evaluate the color Doppler sonographic effect known as twinkling artifact.Struvite (ammonium magnesium phosphate) stone fragments, wire mesh, and a flat surface were scanned in a water bath with a sonography scanner using a high-frequency linear array probe fixed in a ring clamp. Pulse repetition frequency, color-write priority, gray-scale gain, and spectral Doppler gain were varied. Color and spectral Doppler modes were used.Twinkling artifact and spectral broadening were seen most intensely behind struvite stone fragments, and both were seen more strongly behind wire mesh with greater surface roughness than behind wire mesh with less surface roughness or a flat surface. The appearance of the twinkling artifact is highly dependent on machine settings. System noise measured on a flat surface generates a band-limited Doppler shift on spectral displays with a mean frequency shift of 0 Hz and a mean (+/- SD) absolute fluctuation of 86 +/- 10 Hz over a pulse repetition frequency range of 1250-10,000 Hz. Rough surfaces increase the spectral bandwidth.The appearance of the twinkling artifact is highly dependent on machine settings and is likely generated by a narrow-band, intrinsic machine noise called phase (or clock) jitter. Surface roughness secondarily broadens the noise spectrum. With a strongly reflecting, rough surface such as a renal stone, the high amplitude, broadband signal appears as random motion in color Doppler sonography. Understanding of the twinkling artifact may result in better use of its clinical appearance.

Sorensen M.D., Harper J.D., Hsi R.S., Shah A.R., Dighe M.K., Carter S.J., Moshiri M., Paun M., Lu W., Bailey M.R.

To compare color Doppler twinkling artifact and B-mode ultrasonography in detecting kidney stones.Nine patients with recent CT scans prospectively underwent B-mode and twinkling artifact color Doppler ultrasonography on a commercial ultrasound machine. Video segments of the upper pole, interpolar area, and lower pole were created, randomized, and independently reviewed by three radiologists. Receiver operator characteristics were determined.There were 32 stones in 18 kidneys with a mean stone size of 8.9±7.5 mm. B-mode ultrasonography had 71% sensitivity, 48% specificity, 52% positive predictive value, and 68% negative predictive value, while twinkling artifact Doppler ultrasonography had 56% sensitivity, 74% specificity, 62% positive predictive value, and 68% negative predictive value.When used alone, B-mode is more sensitive, but twinkling artifact is more specific in detecting kidney stones. This information may help users employ twinkling and B-mode to identify stones and developers to improve signal processing to harness the fundamental acoustic differences to ultimately improve stone detection.

Wang M., Li J., Xiao J., Shi D., Zhang K.

Objectives The purpose of this study was to analyze factors related to display of the twinkling artifact by a phantom. Methods An in vitro phantom made of sandpaper was designed to mimic rough physiologic surfaces prone to generating the twinkling artifact. Sandpaper strips embedded in a plastic box were scanned through a water path under different machine settings with only 1 parameter varied each time. After choosing the best settings for displaying the twinkling artifact, 4 types of sandpaper with different roughness were scanned. The resulting images were recorded at random, and the number of color pixels in the color box of each image was calculated by a custom-designed program developed using commercially available software. All data were then evaluated by regression analysis, a paired 2-tailed Student t test, and single-factor analysis of variance. Results The highest color write priority and color gain, which were just below the threshold for color noise, a focus depth setting below the sandpaper, a maximum wall filter under a higher pulse repetition frequency, and a color box adjusted properly in the fundamental imaging mode (P < .001) were found to most readily improve the twinkling artifact intensity. The roughness of the sandpaper was shown to be highly correlated with the twinkling artifact intensity (R2 = 0.832; P < .001). Conclusions The twinkling artifact was influenced by some machine parameters and the roughness of the sandpaper. By adjusting some ultrasound machine parameters, a better image reflecting the twinkling artifact can be shown in clinical practice and research.

Hirsch S M., Palavecino B T., León R B.

Yu A., Lovstakken L.

Proper suppression of tissue clutter is a prerequisite for visualizing flow accurately in ultrasound color flow imaging. Among various clutter suppression methods, the eigen- based filter has shown potential because it can theoretically adapt its stopband to the actual clutter characteristics even when tissue motion is present. This paper presents a formative review on how eigen-based filters should be designed to improve their practical efficacy in adaptively suppressing clutter without affecting the blood flow echoes. Our review is centered around a comparative assessment of two eigen-filter design considerations: 1) eigen-component estimation approach (single-ensemble vs. multi-ensemble formulations), and 2) filter order selection mechanism (eigenvalue-based vs. frequencybased algorithms). To evaluate the practical efficacy of existing eigen-filter designs, we analyzed their clutter suppression level in two in vivo scenarios with substantial tissue motion (intra-operative coronary imaging and thyroid imaging). Our analysis shows that, as compared with polynomial regression filters (with or without instantaneous clutter downmixing), eigen-filters that use a frequency-based algorithm for filter order selection generally give Doppler power images with better contrast between blood and tissue regions. Results also suggest that both multi-ensemble and single-ensemble eigen-estimation approaches have their own advantages and weaknesses in different imaging scenarios. It may be beneficial to develop an algorithmic way of defining the eigen-filter formulation so that its performance advantages can be better realized.

Lo M., Hu K., Liu Y., Peng C.-., Novak V.

Quantification of nonlinear interactions between two nonstationary signals presents a computational challenge in different research fields, especially for assessments of physiological systems. Traditional approaches that are based on theories of stationary signals cannot resolve nonstationarity-related issues and, thus, cannot reliably assess nonlinear interactions in physiological systems. In this review we discuss a new technique called multimodal pressure flow (MMPF) method that utilizes Hilbert-Huang transformation to quantify interaction between nonstationary cerebral blood flow velocity (BFV) and blood pressure (BP) for the assessment of dynamic cerebral autoregulation (CA). CA is an important mechanism responsible for controlling cerebral blood flow in responses to fluctuations in systemic BP within a few heart-beats. The MMPF analysis decomposes BP and BFV signals into multiple empirical modes adaptively so that the fluctuations caused by a specific physiologic process can be represented in a corresponding empirical mode. Using this technique, we showed that dynamic CA can be characterized by specific phase delays between the decomposed BP and BFV oscillations, and that the phase shifts are significantly reduced in hypertensive, diabetics and stroke subjects with impaired CA. Additionally, the new technique can reliably assess CA using both induced BP/BFV oscillations during clinical tests and spontaneous BP/BFV fluctuations during resting conditions.

Yu A.C., Cobbold R.S.

Because of their adaptability to the slow-time signal contents, eigen-based filters have shown potential in improving the flow detection performance of color flow images. This paper proposes a new eigen-based filter called the Hankel-SVD filter that is intended to process each slow- time ensemble individually. The new filter is derived using the notion of principal Hankel component analysis, and it achieves clutter suppression by retaining only the principal components whose order is greater than the clutter eigen- space dimension estimated from a frequency-based analysis algorithm. To assess its efficacy, the Hankel-SVD filter was first applied to synthetic slow-time data (ensemble size: 10) simulated from two different sets of flow parameters that model: (1) arterial imaging (blood velocity: 0 to 38.5 cm/s, tissue motion: up to 2 mm/s, transmit frequency: 5 MHz, pulse repetition period: 0.4 ms) and 2) deep vessel imaging (blood velocity: 0 to 19.2 cm/s, tissue motion: up to 2 cm/s, transmit frequency: 2 MHz, pulse repetition period: 2.0 ms). In the simulation analysis, the post-filter clutter- to-blood signal ratio (CBR) was computed as a function of blood velocity. Results show that for the same effective stopband size (50 Hz), the Hankel-SVD filter has a narrower transition region in the post-filter CBR curve than that of another type of adaptive filter called the clutter- downmixing filter. The practical efficacy of the proposed filter was tested by application to in vivo color flow data obtained from the human carotid arteries (transmit frequency: 4 MHz, pulse repetition period: 0.333 ms, ensemble size: 10). The resulting power images show that the Hankel-SVD filter can better distinguish between blood and moving- tissue regions (about 9 dB separation in power) than the clutter-downmixing filter and a fixed-rank multi-ensemble- based eigen-filter (which showed a 2 to 3 dB separation).

Weinstein S.P., Seghal C., Conant E.F., Patton J.A.

Calcium carbonate particles embedded in gelatin and turkey breast tissues were visualized with acoustic resonance imaging and power Doppler ultrasonography. Sonography revealed that the region of color level detection corresponded to the location of the calcium carbonate particles. Correlation between color level detection and the location of the particles was confirmed on radiographs of the specimens obtained at core needle biopsy performed through the region of color level detection.

Wang P., Shen Y., Feng N.

In ultrasound color flow imaging systems, it is important to suppress the clutter signals originated from stationary and slowly moving tissue sufficiently. Without sufficient clutter rejection, the estimation of the blood flow velocity will be inaccurate, and the imaging quality will be poor. In this paper we present a new clutter rejection scheme involving first down-mixing the clutter signals to zero frequency and then cancelling the stationary echo by subtracting the signals from two consecutive pulses. This stationary echo cancelling scheme is easy to be realized with small computational power, and is adaptive to the clutter signals. Theoretical analysis and simulation using RF data prove that it's an efficient and practical clutter rejection scheme for color flow imaging.

Leonov D.V.

Ultrasound imaging is routinely used to diagnose and monitor the progression of kidney disease. It supports evaluation of the presence of abnormal formations such as stones, cysts, and tumors, and also the performance of various manipulations under ultrasound guidance. However, the effectiveness of an investigation depends largely on the qualifications of the sonologist. Training using phantoms increases qualifications. This article discusses the creation of a kidney phantom which can be used as a standalone training tool or as part of a more complex phantom, such as a torso model. This phantom is made of a durable material which is not susceptible to drying out or bacteria. It consists of models of the pelvis with Malpighian pyramids and cortex and contains kidney stones and focal formations. The acoustic characteristics of the phantom tissue are in the range of values characteristic of human tissues, namely, the speed of sound and the attenuation coefficient in the cortical layer model are 1530 m/sec and 0.35 dB/cm/MHz. The phantom supports development of skills in assessing the size, shape, and structure of the kidney and those of diagnosing stones and focal formations, and will be useful in advanced training courses for ultrasound diagnostic doctors.

Gromov A.I., Sapozhnikov O.A., Kaprin A.D.

The twinkling artifact has been known to specialists in ultrasound diagnostics since 1996. However, until now there is no understanding of the reasons for its appearance, and the place of its application in diagnostics.Material and methods. Electronic databases (PubMed, E-library, Web of Science) were searched studies using the keyword – “twinkling artifact”. The scientific publications on the Doppler twinkling artifact from the moment of the first reports about its existence is systematized and analyzed. The authors' own developments on this topic are presented. Modern views on this phenomenon and its place in ultrasound diagnostics are described. An explanation of the physical mechanisms of this phenomenon is given.Results. Recommendations are formulated for practitioners on changing the settings of an ultrasound scanner in order to increase twinkling artifact detectability. The directions of using the artifact to obtain additional diagnostic signs of pathological changes, which currently include the diagnosis of nephro-, uretero- and choledocholithiasis, are determined.Conclusions. The high efficiency of the use of the twinkling artifact for the diagnosis of small kidney stones, comparable with the capabilities of computed tomography, has been shown.  

Egoshina V.D., Gongalsky M.B., Tsurikova U.A., Sviridov A.P., Osminkina L.A., Andreev V.G.

Kang J., Han K., Song I., Kim K., Jang W.S., Kim M.J., Yoo Y.

Detecting microcalcifications (MCs) in real time is important in the guidance of many breast biopsies. Due to its capability in visualizing biopsy needles without radiation hazards, ultrasound imaging is preferred over X-ray mammography, but it suffers from low sensitivity in detecting MCs. Here, we present a new nonionizing method based on real-time multifocus twinkling artifact (MF-TA) imaging for reliably detecting MCs. Our approach exploits time-varying TAs arising from acoustic random scattering on MCs with rough or irregular surfaces. To obtain the increased intensity of the TAs from MCs, in MF-TA, acoustic transmit parameters, such as the transmit frequency, the number of focuses and f-number, were optimized by investigating acoustical characteristics of MCs. A real-time MF-TA imaging sequence was developed and implemented on a programmable ultrasound research system, and it was controlled with a graphical user interface during real-time scanning. From an in-house 3D phantom and ex vivo breast specimen studies, the MF-TA method showed outstanding visibility and high-sensitivity detection for MCs regardless of their distribution or the background tissue. These results demonstrated that this nonionizing, noninvasive imaging technique has the potential to be one of effective image-guidance methods for breast biopsy procedures.

Leonov D., Kodenko M., Leichenco D., Nasibullina A., Kulberg N.

Commercial medical ultrasound phantoms are highly specific as they simulate particular clinical scenarios. This makes them expensive to use in multi-target research and training. General approaches to human tissue and organ modeling are described in the manufacturing methodology, access to which is restricted by the manufacturer's trade secret. Our aim is to propose a reproducible methodology to design a head phantom for transcranial ultrasound training and research from widely available materials and to validate its applicability. To create an anthropomorphic phantom, we used data from real patients obtained by CT and MRI scans. We combined FDM and LCD 3D printing to achieve the desired acoustic performance and ergonomics of the phantom. We fabricated the phantom using polyvinyl chloride plastisol, photopolymer, and PLA to simulate brain tissue, temporal acoustic windows, and acoustically opaque parts of the skull, respectively. Notably, the phantom fabrication method uses only readily available materials and is easy to reproduce. We developed a basic one and anatomical one versions of the head phantom. The basic version contains a simplified brain: tissue-mimicking material is poured into the skull with needles inserted, which specific pattern is easy to recognize in B-mode images. The anatomical version has an anatomically correct brain dummy extracted from MRI data and contains multiple randomly distributed small metal, plastic, and bony objects ranging in size from 1 to 3 mm each. The proposed methodology allows producing head phantoms for transcranial ultrasound training and research. The anatomical accuracy of the model is proved by ultrasonography and CT studies. Both versions of the phantom comprise the skull and the brain and are intended for ultrasound imaging through the temporal bone acoustic window. Needles and small objects serve as navigation targets during the training procedure. The basic version helps learning basic navigation skills, while the anatomical one provides a realistic setting to perform the diagnostic procedure.

Leonov D.V., Reshetnikov R.V., Kulberg N.S., Nasibullina A.A., Gromov A.I.

BACKGROUND: Doppler twinkling artifact is a rapid change of colors seen in CFI-mode in the presence of kidney stones and calculi. Therefore, numerous researchers use the twinkling artifact as a diagnostic sign. However, this phenomenon is under-researched, because most assumptions concerning its causes are made based on pure visual observations of the scanners screen leaving the important steps of signal transformation hidden behind the black box curtains of ultrasound machines. MATERIALS AND METHODS: Raw radiofrequency ultrasound signals were recorded in the phantom studies. The recorded echoes were received from objects that create the Doppler twinkling artifact and artificial blood vessels and soft tissues imitators. The data were collected between June 2016 and March 2021. Sonomed-500 with the 7.5 L38 and 3.4 C60 probes served as the research machine for the signal capture. Data records: We present the database containing raw radiofrequency ultrasound signals from the beam former output of the research ultrasound machine. The dataset consists of CFI and B-mode echoes recorded from twinkling objects. Therefore, this database can be useful for those who test, develop and study ultrasound signal processing algorithms. Furthermore, the database is freely available online. The 10.5 GB database consists of echoes received from five phantoms. Raw radiofrequency signals were stored in the binary files; scanning parameters were stored in text files. The database is available at: https://mosmed.ai/datasets/ultrasound_doppler_twinkling_artifact. Code availability: The public can visualize the database content with the specially written program TwinklingDatasetDisplay available at: https://github.com/Center-of-Diagnostics-and-Telemedicine/TwinklingDatasetDisplay.git. Usage notes: The database can be used to test and develop signal-processing algorithms, such as wall filtration, velocity estimation, feature extraction, speckle reduction, etc. Furthermore, the public is free to share (copy, distribute, and transmit) and remix (adapt and do derivative works) the dataset considering appropriate credit is given.

Wiener P.C., Friend E.J., Pressman G.S., Bhargav R., Radhakrishnan K., Kadem L.

We write in response to the letter by Allievi et al.1 regarding our paper “Color Doppler Splay: A Clue to the Presence of Significant Mitral Regurgitation.”2 We initially determined that the splay signal likely originates as a side-lobe artifact at the point where a mitral regurgitant jet emerges into the left atrium and observed that it can be a clue to the presence of clinically significant regurgitation. In their letter, Allievi et al. point out that color Doppler splay can be present with other valvular lesions.

Kang J., Han K., Kim K., Jang W.S., Kim M.J., Yoo Y.

Purpose Mammography is the only method that has been proven to detect breast microcalcifications (MCs), but the sensitivity of mammography varies according to breast density. This paper proposes an ultrasound (US) color Doppler twinkling artifact (CDTA) method with optimized transmit conditions to identify breast MCs without ionizing radiation. Methods The transmit conditions for US color Doppler imaging (CDI) were optimized to enhance the sensitivity of the twinkling artifact (TA) that arises from random scattering on rough surfaces of breast MCs. To validate the proposed breast MC detection method, a chicken breast phantom with MC particles (groups of particles μ m and μ m ) was fabricated and scanned by a digital mammography system and an US research platform by an L11-5v linear array probe with a three-dimensional (3D) motion tracking system. Results From the phantom experiment, the proposed 3D CDTA imaging method with optimized transmit conditions (i.e., a center frequency of 5.0 MHz, an f-number of 1.3, and a peak negative pressure of 1.83 MPa) successfully detected all 16 MC particles, comparable to detection with mammography. For a human breast surgical specimen in the ex vivo study, all 10 MC clusters, marked by a radiologist on the mammogram, were identified with the proposed 3D CDTA imaging method. Conclusions In the phantom and ex vivo breast specimen studies, the proposed 3D CDTA imaging method successfully detected MCs, and the spatial localization was highly correlated with the mammogram results. These results indicate that the proposed 3D CDTA imaging method has great potential for the detection of MCs without ionizing radiation.

Leonov D.V., Kulberg N.S., Gromov A.I., Morozov S.P.

We analyzed the possibility to detect microcalcifications using a novel ultrasound diagnostic mode based on advanced analysis of the color Doppler twinkling artifact. The special mode was tested with two phantoms: a commercially available polyurethane mammographic breast phantom with dense inclusions simulating microcalcifications and a phantom developed in our laboratory and containing chemically grown CaSO4 microcrystals less than 200 μm in size. The mineral inclusions in the first phantom were visible in B-mode and correctly detected with the novel mode. The presence of inclusions in the second phantom was not obvious when imaged in B-mode; however, it was reliably detected with the special mode. The special mode used two colors to distinguish between the physical processes behind the color Doppler twinkling artifact — elastic vibration and microcavitation. This research demonstrated the applicability and usefulness of the special diagnostic mode for the detection of microcalcifications in phantoms.

Osipov L.V., Kulberg N.S., Leonov D.V., Morozov S.P.

This article continues a previously published review, “3D ultrasound: Current state, emerging trends and technologies,” which was the first part in a cycle addressing 3D/4D ultrasound technologies. The first part explained the basic mechanisms for obtaining three-dimensional ultrasound images and considered the physical basis, advantages, and drawbacks associated with the use of transducers and the main methods of volumetric scanning. The present article describes the capabilities of the state-of-the-art diagnostic ultrasound scanners to visualize 3D/4D data.

Leonov D.V., Kulberg N.S., Fin V.A., Podmoskovnaya V.A., Ivanova L.S., Shipaeva A.S., Vladzimirskiy A.V., Morozov S.P.

The article considers filtering techniques used to suppress clutter signals from moving tissues and to improve reliability of blood flow estimation. It compares polynomial and adaptive bases such as the result of empirical mode decomposition and singular vectors obtained through Karhunen−Loève transform. Filtering techniques are examined using a computer-simulated model, Doppler flow phantom and in vivo data. Filters are compared in terms of computational complexity, ability to retrieve flow profile without errors and through ROC curve analysis. Polynomial regression filters with tissue phase shift compensation were found to be the best fit for clutter suppression in terms of computational demands and accuracy of velocity estimation.

Osipov L.V., Kulberg N.S., Leonov D.V., Morozov S.P.

3D/4D ultrasound technology continues to penetrate ever deeper into medical practice. Effective use of this technology requires an understanding of how 3D images are formed. This article explains the principles of the construction of 3D images in medical ultrasound and discloses the physical basis, advantages and drawbacks of 3D scanning methods.

Leonov D.V., Kulberg N.S., Gromov A.I., Morozov S.P., Vladzimirskiy A.V.

The proposed ultrasound imaging mode allows detection of objects, which essentially differ in their scattering properties from the surrounding tissues and liquids. The objects in question are primarily microcalcifications, renal and urinary stones. Our previous study has shown that the Doppler signals from these objects have two components common for echoes from solid mineral inclusions. They can be in superposition with the blood and noise signals. One of these two mineral-related components is characterized by cavitation, the other – by elastic vibrations of the object presumably caused by acoustic radiation force. According to statistical and energy parameters, these components differ from each other, as well as from noise and blood echoes. The article proposes a practical method for identifying signals with mineral-related components. This method is the base for the novel diagnostic visualization mode specifically designed for the mineral inclusions detection with ultrasound.