Ultrasound Artifacts Research Articles

Ultrasound mirror-image artifacts during transversus abdominis plane blockade.

Ultrasound mirror-image artifacts during transversus abdominis plane blockade.

Use of lung ultrasound in the differential diagnosis of the causes of dyspnea

Background/Aim. The field of lung ultrasonography (US) is a fast-developing one, and it provides the medical community with numerous new diagnostic opportunities. The aim of this study was to examine the etiology of dyspnea on admission and assess the stage of heart failure (HF) according to the US examination of the heart and lungs. Methods. The cross-sectional study included a total of 110 patients treated for the symptoms of dyspnea. The study included all patients treated for any heart or pulmonary condition, as well as patients who reported the first episode of dyspnea with-out any previous illness. The most important diagnostic sign in the US of the lungs in patients with HF was the appearance of B-lines or ?comets? (ultrasound artifacts reminiscent of comet tails), which indicate the accumulation of fluid in the interstitium of the lungs. Results. The mean number of registered ?comets? in the total number of patients was 14.2 ? 7.4 (minimum 2, maximum 30). The mean number of ?comets? among patients with HF was 18.8 ? 5.9. The mean number of ?comets? among patients without HF was 8.0 ? 3.7 (p ? 0.001). Multivariate linear regression analyses showed the association between the number of ?comets? and HF (p ? 0.001). Conclusion. As the assessment of present ?comets? in pulmonary US examination is safe and non-invasive, it can easily be integrated into the daily clinical practice because it has been shown that the number of pulmonary ?comets? is significantly higher in patients with HF compared to those with dyspnea of other etiologies.

Numerical Modeling of Ultrasound Artifacts with Grid-Characteristic Method

Numerical Modeling of Ultrasound Artifacts with Grid-Characteristic Method

Lung ultrasound for evaluation of dyspnea: a pictorial review.

Lung ultrasound is based on the analysis of ultrasound artifacts generated by the pleura and air within the lungs. In recent years, lung ultrasound has emerged as an important alternative for quick evaluation of the patient at the bedside. Several techniques and protocols for performing lung ultrasound have been described in the literature, with the most popular one being the Bedside Lung Ultrasound in Emergency (BLUE) protocol which can be utilized to diagnose the cause of acute dyspnea at the bedside. We attempt to provide a simplified approach to understanding the physics behind the artifacts used in lung ultrasound, the imaging techniques, and the application of the BLUE protocol to diagnose the commonly presenting causes of acute dyspnea.

The Doppler ultrasound twinkling artifact on crevices etched in silicon wafers

The twinkling artifact, or rapid color shifts, are observed when imaging kidney stones and other mineralizations. The current theory is that scattering from bubbles in micron-sized crevices causes twinkling. Our objective is to investigate the effect of ultrasound frequency and crevice size and number on twinkling of silicon wafers. Ten or 100 randomly positioned cylindrical crevices with diameters of 1, 10, or 100 μm and depths of 10 μm were dry-etched on wafers. A research ultrasound system was used to image wafers at 5, 7.8, and 18.5 MHz; IQ data were post-processed to calculate twinkling or Doppler power. Twinkling for all crevice sizes and numbers followed the trend 5 MHz>7.8 MHz>18.5 MHz. For crevice size, at 5 and 7.8 MHz, twinkling was higher for 1- or 10-μm crevices compared to 100 μm; at 18.5 MHz, twinkling was only observed on 100-μm crevices. Increasing the number of crevices increased twinkling for 1 μm crevices at 5 and 7.8 MHz and 10 μm crevices at 7.8 MHz; no differences were noted at 18.5 MHz. These results support previous work showing twinkling is frequency-dependent and suggest that even 10, 1-μm crevices are sufficient to cause twinkling. [Work supported by SURIEA, NSF CAREER-1943937.]

Pediatric COVID-19 Follow-Up with Lung Ultrasound: A Prospective Cohort Study.

During the COVID-19 pandemic, lung ultrasound (LUS) was widely used to assess SARS-CoV-2 infection. To date, there are patients with persistence of symptoms after acute infection. Therefore, it may be useful to have an objective tool to follow these patients. The aim of our study was to evaluate the presence of LUS artifacts after SARS-CoV-2 infection in children and to analyze the associations between time elapsed since infection and symptomatology during acute infection. We conducted an observational study, enrolling 607 children infected with SARS-CoV-2 in the previous twelve months. All patients performed a LUS and medical history of demographic and clinical data. We observed irregular pleural lines in 27.5%, B-lines in 16.9%, and subpleural consolidations in 8.6% of the cases. These artifacts were more frequently observed in the lower lobe projections. We have observed that the frequency of artifacts decreases with increasing time since infection. In symptomatic patients during COVID infection, B-lines (p = 0.02) were more frequently found. In our sample, some children, even after months of acute infection, have ultrasound artifacts and showed an improvement with the passage of time from the acute episode. Our study provides additional evidence about LUS in children with previous COVID-19 as a support to follow these patients in the months following the infection.

Cinefluoroscopy for assessment of mechanical heart valves with suspected dysfunction.

BackgroundMechanical heart valves (MHVs) are preferred prosthesis types in many, especially younger patients who need surgical valve replacement. Although echocardiography is most frequently performed for prosthesis assessment during follow-up, ultrasound artifacts usually preclude a precise investigation of prosthesis function. Cinefluoroscopy (CF) is a simple and effective method to analyze and quantify opening and closing of prosthesis leaflets but requires careful visualization of the valve using optimal viewing angles. Here, we investigated the quality of CF studies in clinical routine and their suitability for quantitative analysis of prosthesis function.Methods and resultsWe retrospectively identified 94 patients with 118 cinefluoroscopies performed by 31 different investigators in one tertiary center from 2012 to 2021. Of 150 MHVs (98% bi-leaflet prostheses), 87 (58%) were aortic, 53 (34%) mitral, 7 (5%) tricuspid, and 5 (3%) pulmonary valve prostheses, respectively. CF studies were categorized by their suitability to quantitatively assess opening and closing angles. Visualization of valve function was “sufficient” in 23%, “suboptimal” in 46%, and “unsuitable” in 31% of the cases.ConclusionIn clinical routine, only one-fourth of CF studies allow for a complete assessment of leaflet motion of MHVs. Although this may be in part due to the varying experience of operators, the high number of unsuitable studies suggests that optimal viewing angles may not be achievable in all patients. Further research is required to investigate standard viewing angles and anatomy after MHV implantation to improve the quality of CF studies and reduce radiation exposure of patients and operators.

The effect of surface tension on the color Doppler ultrasound twinkling artifact

Imaging crystalline structures with Doppler ultrasound can produce a rapid color shift, termed the twinkling artifact, that can assist in diagnosing pathological mineralizations such as kidney stones, heterotopic ossification, gout, and breast microcalcifications. Twinkling is theorized to arise from scattering off surface crevice microbubbles, which are affected by the surface tension between the bubble and surrounding medium. In this study, we evaluated the effect of surface tension on twinkling in pure crystals. Cholesterol, calcium phosphate, and uric acid crystals were grown in vitro (n = 5 each) and imaged with a Philips/ATL L7-4 transducer and Vantage-128 research ultrasound system. Crystals were imaged in water while varying surfactant concentration (0%–4%) leading to surface tensions that ranged from 45–72 mN/m. Surface tension of the solution was determined by measuring the contact angle of 0.1-mL droplet on an acrylic sheet exposed to air. As the concentration of surfactant increased, twinkling was found to decrease by ∼20% for cholesterol and calcium phosphate and ∼10% for uric acid. These results continue to support the crevice bubble theory of twinkling and suggest the importance of surface tension when evaluating minerals with the twinkling artifact. [Work supported by NSF-CAREER-1943937 and NSF-GRFP-DGE1255832.]

Mechanistic analysis of B-line formation in lung ultrasound

The number and distribution of lung ultrasound (LUS) imaging artifacts—B-lines—is correlated with the presence of lung interstitial syndrome such as viral infection and pulmonary edema. The detection and quantification of B-lines is machine and operator dependent, and the mechanisms for B-line formation are not fully understood. The goals of this work were to collect RF data during LUS exams in patients with pulmonary edema and to compare to the signals and corresponding images simulated numerically to elucidate the B-line formation process. Verasonics ultrasound engine (VUE) with a phased array probe (4.5 MHz) was used to perform standard 10-zone LUS in ten patients with confirmed pulmonary edema. The RF data corresponding to each B-mode image and a series of 35 plane wave acquisitions were collected for off-line analyses. Finite element modeling of LUS pulse propagation was performed in COMSOL with fluid-filled inclusions of variable sizes and shapes in air-like medium simulating edematous lung areas. The B-mode image resulting from the simulated RF signals was reconstructed using VUE beamforming. The B-lines similar to those observed experimentally formed in simulated images only under specific conditions of sizes and shapes of water-filled areas relatively to LUS imaging wavelength. [Work supported by NIH R01EB023910.]

Investigating the link between intensity of lung ultrasound vertical artifacts and penetration depth of ultrasound waves, in silico study

Lung ultrasound (LUS) is nowadays widely applied for lung surface evaluation. In particular, LUS is often based on the analysis of vertical artifacts, which correlate with various pathologies but whose genesis is not fully comprehended yet. To better understand the phenomena causing these artifacts' appearance, numerical simulations can represent a powerful tool. Specifically, we present a simulation study (k-Wave MATLAB toolbox) that investigates whether a link exists between the intensity of these artifacts and the penetration depth of ultrasound waves through the lung parenchyma. The size of the simulated numerical domain is 4 cm × 2 cm, with the simulated lung surface located at a depth of 2 cm. Different alveolar structures were modeled by varying the alveolar diameter (from 40 to 800 μm), the inter-alveolar axial-spacing (from 40 to 790 μm) and inter-alveolar lateral-spacing (from 10 to 100 μm). For each configuration, Gaussian pulses (with bandwidth equal to 0.5 MHz at −6 dB) having different center frequencies (from 1 to 5 MHz) were transmitted without focusing (plane wave imaging). Results highlight how the artifacts' intensity seems to be independent from waves' penetration depth.

Investigating the color Doppler twinkling artifact as an early detector of cellular mineralization

Heterotopic ossification (HO) occurs when bone develops in areas where bone does not usually exist, often appearing after blast injuries or other musculoskeletal trauma. Current methods of diagnosis, such as three-phase bone scintigraphy, x-ray, or CT scans, take several weeks after the trauma before HO is visible. The color Doppler ultrasound twinkling artifact has been shown to detect the presence of kidney stones and other crystals. Twinkling could provide a more sensitive method of HO detection, which would allow for earlier diagnosis and treatment and limit HO severity. In our research, human bone marrow-derived stem cells (HBMSCs) were plated onto collagen scaffolds and cultured in osteogenic media to promote mineralization orgrowth media (controls). The cells were imaged every 3rd day from day 10 – day 25 using Phillips L7-4, L12-5, and Vermon L22-14v transducers and a Vantage-128 research ultrasound system; I/Q data were bulk saved for quantitative analysis. Samples with mineralization on 0.5% of their surface showed a 17% increase in Doppler magnitude compared to controls, suggesting that the twinkling artifact is a sensitive method for detection of mineralization in vitro. Further studies will investigate whether this method is effective in a murine model. [Work supported by DoD CDMRP PR201164.]

What Is COVID 19 Teaching Us about Pulmonary Ultrasound?

In lung ultrasound (LUS), the interactions between the acoustic pulse and the lung surface (including the pleura and a small subpleural layer of tissue) are crucial. Variations of the peripheral lung density and the subpleural alveolar shape and its configuration are typically connected to the presence of ultrasound artifacts and consolidations. COVID-19 pneumonia can give rise to a variety of pathological pulmonary changes ranging from mild diffuse alveolar damage (DAD) to severe acute respiratory distress syndrome (ARDS), characterized by peripheral bilateral patchy lung involvement. These findings are well described in CT imaging and in anatomopathological cases. Ultrasound artifacts and consolidations are therefore expected signs in COVID-19 pneumonia because edema, DAD, lung hemorrhage, interstitial thickening, hyaline membranes, and infiltrative lung diseases when they arise in a subpleural position, generate ultrasound findings. This review analyzes the structure of the ultrasound images in the normal and pathological lung given our current knowledge, and the role of LUS in the diagnosis and monitoring of patients with COVID-19 lung involvement.

Common and Uncommon Errors in Emergency Ultrasound

Errors in emergency ultrasound (US) have been representing an increasing problem in recent years thanks to several unique features related to both the inherent characteristics of the discipline and to the latest developments, which every medical operator should be aware of. Because of the subjective nature of the interpretation of emergency US findings, it is more prone to errors than other diagnostic imaging modalities. The misinterpretation of US images should therefore be considered as a serious risk in diagnosis. The etiology of error is multi-factorial: it depends on environmental factors, patients and the technical skills of the operator; it is influenced by intrinsic US artifacts, poor clinical correlation, US-setting errors and anatomical variants; and it is conditioned by the lack of a methodologically correct clinical approach and excessive diagnostic confidence too. In this review, we evaluate the common and uncommon sources of diagnostic errors in emergency US during clinical practice, showing how to recognize and avoid them.

The challenges facing deep learning–based catheter localization for ultrasound guided high‐dose‐rate prostate brachytherapy

Automated catheter localization for ultrasound guided high-dose-rate prostate brachytherapy faces challenges relating to imaging noise and artifacts. To date, catheter reconstruction during the clinical procedure is performed manually. Deep learning has been successfully applied to a wide variety of complex tasks and has the potential to tackle the unique challenges associated with multiple catheter localization on ultrasound. Such a task is well suited for automation, with the potential to improve productivity and reliability. We developed a deep learning model for automated catheter reconstruction and investigated potential factors influencing model performance. The model was designed to integrate into a clinical workflow, with a proposed reconstruction confidence metric to aid in planner verification. Datasets from 242 patients treated from 2016 to 2020 were collected retrospectively. The anonymized dataset comprises 31,000 transverse images reconstructed from 3D sagittal ultrasound acquisitions and 3500 implanted catheters manually localized by the planner. Each catheter was retrospectively ranked based on the severity of imaging artifacts affecting reconstruction difficulty. The U-NET deep learning architecture was trained to localize implanted catheters on transverse images. A fivefold cross-validation method was used, allowing for evaluation over the entire dataset. The postprocessing software combined the predictions with patient-specific implant information to reconstructed catheters in 3D space, uniquely matched to the implanted grid positions. A reconstruction confidence metric was calculated based on the number and probability of localized predictions per catheter. For each patient, deep learning prediction and postprocessing reconstruction were completed in under 2 min on a nonperformance PC. Overall, 80% of catheter reconstructions were accurate, within 2mm along 90% of the length. The catheter tip was often not detected and required extrapolation during reconstruction. The reconstruction accuracy was 89% for the easiest catheter ranking and decreased to 13% for the highest difficulty ranking, when the aid of live ultrasound would have been recommended. Even when limited to the easiest ranked catheters, the reconstruction accuracy decreased at distal grid positions, down to 50%. Individual implantation style was found to influence the frequency of severe artifacts, slightly impacting the model accuracy. A reconstruction confidence metric identified the difficult catheters, removed the observed individual variation, and increased the overall accuracy to 91% while excluding 27% of the reconstructions. The deep learning model localized implanted catheters over a large clinical dataset, with overall promising results. The model faced challenges due to ultrasound artifacts and image degradation distal to the probe, underlining the continued importance of maintaining image quality and minimizing artifacts. A potential workflow for integration into the clinical procedure was demonstrated, including the use of a confidence metric to predict low accuracy reconstructions. Comparison between models evaluated on different datasets should also consider underlying differences, such as the frequency and severity of imaging artifacts.

The Mechanisms Underlying Vertical Artifacts in Lung Ultrasound and Their Proper Utilization for the Evaluation of Cardiogenic Pulmonary Edema.

The recent advances in lung ultrasound for the diagnosis of cardiogenic pulmonary edema are outstanding; however, the mechanism of vertical artifacts known as B-lines used for the diagnosis has not yet been fully elucidated. The theory of “acoustic trap” is useful when considering the generation of vertical artifacts. Basic research in several studies supports the theory. Published studies with pilot experiments indicate that clarification of the relationship between the length and intensity of vertical artifacts and physical or acoustic composition of sources may be useful for differentiating cardiogenic pulmonary edema from lung diseases. There is no international consensus with regard to the optimal settings of ultrasound machines even though their contribution to the configuration of vertical artifacts is evident. In the clinical setting, the configuration is detrimentally affected by the use of spatial compound imaging, the placement of the focal point at a deep level, and the use of multiple focus. Simple educational materials using a glass microscope slide also show the non-negligible impact of the ultrasound machine settings on the morphology of vertical artifacts.

Ten Years of Pediatric Lung Ultrasound: A Narrative Review.

Lung diseases are the most common conditions in newborns, infants, and children and are also the primary cause of death in children younger than 5 years old. Traditionally, the lung was not thought to be a target for an ultrasound due to its inability to penetrate the gas-filled anatomical structures. With the deepening of knowledge on ultrasound in recent years, it is now known that the affected lung produces ultrasound artifacts resulting from the abnormal tissue/gas/tissue interface when ultrasound sound waves penetrate lung tissue. Over the years, the application of lung ultrasound (LUS) has changed and its main indications in the pediatric population have expanded. This review analyzed the studies on lung ultrasound in pediatrics, published from 2010 to 2020, with the aim of highlighting the usefulness of LUS in pediatrics. It also described the normal and abnormal appearances of the pediatric lung on ultrasound as well as the benefits, limitations, and possible future challenges of this modality.

Investigation Study of Ultrasound Practitioners' Awareness about Artefacts of Hepatobiliary Imaging in Almadinah Almunawwarah.

Objectives:To investigate the knowledge and awareness of ultrasound practitioners’ concerning ultrasound artefacts in evaluating the hepatobiliary system.Methods:This electronic questionnaire-based comparative study involved the ultrasound practitioners’ who work in the radiology departments in Almadinah Almunawwarah governmental hospitals during the period from 1 November 2020 to 30 April 2021. Spearman’s rho correlation test was used to correlate between knowledge and job, academic qualification, and years of experience. A T-test and cross tabulation test were done to compare the knowledge about artefacts among radiologists and radiologic technologists.Results:This study involved 94 participants distributed as 22 (23.4%) radiologists and 72 (76.6%) radiologic technologists. The results shows that 85%, 71%, 73%, 69%, 54% and 53% of the participants assigned the acoustic shadowing, acoustic enhancement, ring down, side lobe, reverberation and mirror artefacts, as artefacts respectively. However, 68%, 53%, 19%, 19%, 18%, and 40% of the participants gave correct final diagnosis of acoustic shadowing, acoustic enhancement, ring down, side lobes, reverberation, and mirror artifacts, respectively. Spearman’s rho correlation test shows significant correlation between participants with more than three years experience and knowledge related mirror artefacts (r=0.328, p=0.001). It shows significant correlation between radiologists with knowledge related mirror artefacts (r=0.367, p<0.001). A significant correlation was found between highly qualified participants and knowledge related mirror artefacts (r=0.336, p=0.001) and side lobe artefacts (r=0.237, p=0.008).Conclusion:The questionnaire-based comparative study of knowledge about artefacts of hepatobiliary ultrasound imaging reveals a high level of Ultrasound practitioners’ knowledge in differentiating artefacts from pathology with a high level of knowledge in identifying hepatobiliary acoustic shadowing and acoustic enhancement artefacts. However, insufficient knowledge was noted in identifying mirror, side lobe, reverberation and ring down artefacts. A direct link was found between academic qualification, years of experience and practioners’ knowledge among.

Interobserver Agreement and Correlation of an Automated Algorithm for B-Line Identification and Quantification With Expert Sonologist Review in a Handheld Ultrasound Device.

B-lines are ultrasound artifacts that can be used to detect a variety of pathologic lung conditions. Computer-aided methods to detect and quantify B-lines may standardize quantification and improve diagnosis by novice users. We sought to test the performance of an automated algorithm for the detection and quantification of B-lines in a handheld ultrasound device (HHUD). Ultrasound images were prospectively collected on adult emergency department patients with dyspnea. Images from the first 124 patients were used for algorithm development. Clips from 80 unique subjects for testing were randomly selected in a predefined proportion of B-lines (0 B-lines, 1-2 B-lines, 3 or more B-lines) and blindly reviewed by five experts using both a manual and reviewer-adjusted process. Intraclass correlation coefficient (ICC) and weighted kappa were used to measure agreement, while an a priori threshold of an ICC (3,k) of 0.75 and precision of 0.3 were used to define adequate performance. ICC between the algorithm and manual count was 0.84 (95% confidence interval [CI] 0.75-0.90), with a precision of 0.15. ICC between the reviewer-adjusted count and the algorithm count was 0.94 (95% CI 0.90-0.96), and the ICC between the manual and reviewer-adjusted counts was 0.94 (95% CI 0.90-0.96). Weighted kappa was 0.72 (95% CI 0.49-0.95), 0.88 (95% CI 0.74-1), and 0.85 (95% CI 0.89-0.96), respectively. This study demonstrates a high correlation between point-of-care ultrasound experts and an automated algorithm to identify and quantify B-lines using an HHUD. Future research may incorporate this HHUD in clinical studies in multiple settings and users of varying experience levels.

Simple Experimental Models for Elucidating the Mechanism Underlying Vertical Artifacts in Lung Ultrasound: Tools for Revisiting B-Lines.

Using simple experimental models, we evaluated the generation, configuration and echo intensity of vertical artifacts by varying the point or plane of contact and height of objects that correspond to sources of vertical artifacts in the subpleural space. We used an ultrasound gel spot to imitate the source and a block of bacon as a chest wall phantom. As the size of the point of contact between the gel spot on the polypropylene sheet and the phantom decreased by peeling the sheet, a vertical artifact measuring ≤1 cm was generated and/or extended deeper, finally reaching 10 cm in depth. Next, objects of different shapes made using gel balls were used to observe the generation of artifacts and measure and compare the echo intensity. For a given shape, the intensity was markedly higher in one model with the point of contact than in the other model with the plane of contact. With the same point or plane of contact, the echo intensity was higher in the taller model. The size of the point or plane of contact and height of the source were observed to be key factors in the generation, length and echo intensity of the artifacts.

Dependence of lung ultrasound vertical artifacts on frequency, bandwidth, focus and angle of incidence: An in vitro study.

Lung ultrasound (LUS) is nowadays widely adopted by clinicians to evaluate the state of the lung surface. However, being mainly based on the evaluation of vertical artifacts, whose genesis is still unclear, LUS is affected by qualitative and subjective analyses. Even though semi-quantitative approaches supported by computer aided methods can reduce subjectivity, they do not consider the dependence of vertical artifacts on imaging parameters, and could not be classified as fully quantitative. They are indeed mainly based on scoring LUS images, reconstructed with standard clinical scanners, through the sole evaluation of visual patterns, whose visualization depends on imaging parameters. To develop quantitative techniques is therefore fundamental to understand which parameters influence the vertical artifacts' intensity. In this study, we quantitatively analyzed the dependence of nine vertical artifacts observed in a thorax phantom on four parameters, i.e., center frequency, focal point, bandwidth, and angle of incidence. The results showed how the vertical artifacts are significantly affected by these four parameters, and confirm that the center frequency is the most impactful parameter in artifacts' characterization. These parameters should hence be carefully considered when developing a LUS quantitative approach.