Ultrasound imaging artifacts: How to recognize them and how to avoid them

Ultrasound Physics

With the growing use of point-of-care ultrasound (POCUS) in various clinical settings, it is essential for users of ultrasound to have a thorough understanding of the basics of ultrasound physics, including sound wave properties, its interaction with various tissues, common artifacts, and knobology. The authors introduce and discuss these concepts in this article, with a focus on clinical implications.

'Color Doppler stripes' make it difficult to diagnose the severity of valvular heart diseases: a report of two cases

BACKGROUND

Echocardiography remains the reference-standard imaging technique for assessing valvular heart disease (VHD), but artifacts like the 'color Doppler stripe' can complicate diagnosis. This artifact is not widely recognized and can mimic severe VHD, leading to potential misdiagnoses. We present two cases where color Doppler stripes mimicked severe VHD, highlighting the need for awareness and accurate interpretation in echocardiographic assessments.

CASE PRESENTATIONS

Case 1: An 85-year-old patient was referred for mitral valve surgery due to suspected severe mitral regurgitation (MR). Upon evaluation, transthoracic echocardiography (TTE) showed mitral valve prolapse (P3) and a high-echoic, vibrating structure attached to the mitral valve, indicative of chordal rupture. Color Doppler echocardiography revealed strong systolic signals in the left atrium, mimicking severe MR. Transesophageal echocardiography (TEE) also detected the vibrating structure and color Doppler stripes in the left atrium, left ventricle, and outside the cardiac chambers. The PISA method on TEE indicated moderate MR and left ventriculography showed Sellers grade II MR. The artifact was identified as color Doppler stripes caused by the vibrating high-echoic structure from the ruptured chorda. Case 2: A 64-year-old patient with severe aortic stenosis, end-stage kidney disease requiring hemodialysis, and a history of coronary bypass grafting presented for routine follow-up. B-mode echocardiography showed a severely calcified tricuspid aortic valve with a vibrating calcified nodule and restricted opening, corresponding to severe aortic stenosis. During systole, color Doppler signals were observed around the aortic, pulmonary, and tricuspid valves, mimicking significant pulmonary stenosis and tricuspid regurgitation. However, pulmonary stenosis was ruled out as the pulmonary valve opening was normal. Mild tricuspid regurgitation was confirmed in the apical view.

CONCLUSIONS

These cases highlight the diagnostic challenges posed by color Doppler stripes. Recognizing and understanding this artifact are crucial for the accurate diagnosis and management of VHD, ensuring appropriate treatment and patient outcomes.

A Case of a Mirror Image Artifact in the Forearm

Teaching point: To emphasize the importance of recognizing mirror image artifacts in musculoskeletal ultrasound to avoid misdiagnosis, unnecessary interventions, and additional diagnostic procedures that can lead to patient anxiety, increased healthcare costs, and potential harm.

Multimodality imaging in patients with implantable loop recorders: Tips and tricks

An implantable loop recorder (ILR) is a leadless rectangular device used for prolonged electrocardiographic monitoring for up to 3 years. This miniaturized device, inserted subcutaneously, allows clinicians to investigate possible cardiac rhythm disturbances in patients suffering from recurrent unexplained syncope. As the age of the population increases rapidly and the number of ILR patients amplifies, the clinical significance of ILRs is undeniable. Although radioopaque and easily seen on plain chest radiographs and other imaging modalities, ILRs may represent a challenge for clinicians and radiologists to recognize their classic appearance and differentiate them from numerous other cardiac devices. This article aims to summarize current literature on ILRs, their basic function, types, and indications for implantation, but most of all, it aims to familiarize clinicians and radiologists with common imaging features of these devices, safety issues, and artifact-reducing methods. Specifically, this review discusses the typical appearance of ILRs on major diagnostic imaging modalities, including chest X-ray, mammography, ultrasonography, computed tomography, and magnetic resonance imaging (MRI). Furthermore, optimization strategies to mitigate image artifacts and safety issues regarding MRI are discussed.

Deep Learning-Based Evaluation of Ultrasound Images for Benign Skin Tumors

In this study, a combined convolutional neural network for the diagnosis of three benign skin tumors was designed, and its effectiveness was verified through quantitative and statistical analysis. To this end, 698 sonographic images were taken and diagnosed at the Department of Dermatology at Severance Hospital in Seoul, Korea, between 10 November 2017 and 17 January 2020. Through an empirical process, a convolutional neural network combining two structures, which consist of a residual structure and an attention-gated structure, was designed. Five-fold cross-validation was applied, and the train set for each fold was augmented by the Fast AutoAugment technique. As a result of training, for three benign skin tumors, an average accuracy of 95.87%, an average sensitivity of 90.10%, and an average specificity of 96.23% were derived. Also, through statistical analysis using a class activation map and physicians' findings, it was found that the judgment criteria of physicians and the trained combined convolutional neural network were similar. This study suggests that the model designed and trained in this study can be a diagnostic aid to assist physicians and enable more efficient and accurate diagnoses.

A Sticky Situation: The Unfortunate Consequence of Chewing Gum

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Foreign substances can interfere with the TEE probe, causing poor image quality.

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Operators should be aware of the reasons for diffusely anechoic TEE images.

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Poor identification of echocardiographic artifacts may lead to adverse outcomes.

Clinical expert consensus document on rotational atherectomy from the Japanese association of cardiovascular intervention and therapeutics: update 2023

The Task Force on Rotational Atherectomy of the Japanese Association of Cardiovascular Intervention and Therapeutics (CVIT) proposed the expert consensus document to summarize the techniques and evidences regarding rotational atherectomy (RA) in 2020. Because the revascularization strategy to severely calcified lesions is the hottest topic in contemporary percutaneous coronary intervention (PCI), many evidences related to RA have been published since 2020. Latest advancements have been incorporated in this updated expert consensus document.

Medical imaging training with eye movement modeling examples: A randomized controlled study

PURPOSE

To determine whether ultrasound training in which the expert's eye movements are superimposed to the underlying ultrasound video (eye movement modeling examples; EMMEs) leads to better learner outcomes than traditional eye movement-free instructions.

MATERIALS AND METHODS

106 undergraduate medical students were randomized in two groups; 51 students in the EMME group watched 5-min ultrasound examination videos combined with the eye movements of an expert performing the task. The identical videos without the eye movements were shown to 55 students in the control group. Performance and behavioral parameters were compared prepost interventional using ANOVAs. Additionally, cognitive load, and prior knowledge in anatomy were surveyed.

RESULTS

After training, the EMME group identified more sonoanatomical structures correctly, and completed the tasks faster than the control group. This effect was partly mediated by a reduction of extraneous cognitive load. Participants with greater prior anatomical knowledge benefited the most from the EMME training.

CONCLUSION

Displaying experts' eye movements in medical imaging training appears to be an effective way to foster medical interpretation skills of undergraduate medical students. One underlying mechanism might be that practicing with eye movements reduces cognitive load and helps learners activate their prior knowledge.

Impact of ultrasound reverberation in calcified coronary arteries: Intravascular ultrasound study

BACKGROUND AND AIMS

Intravascular ultrasound (IVUS) often allows us to observe reverberations behind calcification in percutaneous coronary intervention (PCI) to heavily calcified lesions. However, clinical significance of reverberations remains unknown. The aim of this study was to assess the impact of reverberations on stent expansion and clinical outcomes after PCI with rotational atherectomy (RA) to heavily calcified lesions.

METHODS

We considered 250 calcified lesions that underwent IVUS-guided PCI with RA. According to the number of reverberations (NR), those lesions were divided into the high NR (≥3) group (n = 36) and the low NR (≤2) group (n = 214). Stent expansion and the cumulative incidence of ischemia-driven target lesion revascularization (ID-TLR) were compared between the high and low NR groups.

RESULTS

The high NR group showed significantly smaller stent expansion rate than the low NR group (67.7% vs. 75.9%, respectively, p=0.02). The multivariate logistic regression analysis showed that high NR and calcified nodule were significantly associated with stent underexpansion. The incidence of ID-TLR was significantly higher in the high NR group than in the low NR group (p=0.03). In multivariate Cox hazard analysis, high NR and acute coronary syndrome were significantly associated with ID-TLR.

CONCLUSIONS

High NR was significantly associated with stent underexpansion and ID-TLR. When high NR was detected by IVUS, the PCI strategy was be planned carefully to avoid stent underexpansion. The follow-up program of the patients with high NR might need to be scheduled prudently because of the high risk of TLR.

Quantitative Assessment of Lung Ultrasound Grayscale Images Based on Shannon Entropy for the Detection of Pulmonary Aeration: An Animal Study

OBJECTIVE

Lung ultrasound (LUS) is a radiation-free, affordable, and bedside monitoring method that can detect changes in pulmonary aeration before hypoxic damage. However, visual scoring methods of LUS only enable subjective diagnosis. Therefore, quantitative analysis of LUS is necessary for obtaining objective information on pulmonary aeration. Because raw data are not always available in conventional ultrasound systems, Shannon entropy (ShanEn) of information theory without the requirement of raw data is valuable. In this study, we explored the feasibility of ShanEn estimated through grayscale histogram (GSH) analysis of LUS images for the quantification of pulmonary aeration.

METHODS

Different degrees of pulmonary aeration caused by edema was induced in 32 male New Zealand rabbits intravenously injected with 0.1 mL/kg saline (the control group) and 0.025, 0.05, and 0.1 mL/kg oleic acid (mild, moderate, and severe groups, respectively). In vivo grayscale LUS images were acquired using a commercial point-of-care ultrasound system for estimation of GSH and corresponding ShanEn. Both lungs of each rabbit were dissected, weighed, and dried to determine the wet weight-to-dry weight ratio (W/D) through gravimetry.

RESULTS

The determination coefficients of linear correlations between ShanEn and W/D increased from 0.0487 to 0.7477 with gain and dynamic range (DR). In contrast to visual scoring methods of pulmonary aeration that use median gain and low DR, ShanEn for quantifying pulmonary aeration requires high gain and DR.

CONCLUSION

The current findings indicate that ShanEn estimated through GSH analysis of LUS images acquired using conventional ultrasonic imaging systems has great potential to provide objective information on pulmonary aeration.

Intravascular ultrasound-factors associated with slow flow following rotational atherectomy in heavily calcified coronary artery

Intravascular ultrasound (IVUS) can provide useful information in patients undergoing complex percutaneous coronary intervention with rotational atherectomy (RA). The association between IVUS findings and slow flow following rotational atherectomy (RA) has not been investigated, although slow flow has been shown to be an unfavorable sign with worse outcomes. The aim of this study was to determine the IVUS-factors associated with slow flow just after RA. We retrospectively enrolled 290 lesions (5316 IVUS-frames) with RA, which were divided into the slow flow group (n = 43 with 1029 IVUS-frames) and the non-slow flow group (n = 247 with 4287 IVUS-frames) based on the presence of slow flow. Multivariate regression analysis assessed the IVUS-factors associated with slow flow. Slow flow was significantly associated with long lesion length, the maximum number of reverberations [odds ratio (OR) 1.49; 95% confidence interval (CI) 1.07–2.07, p = 0.02] and nearly circumferential calcification at minimal lumen area (MLA) (≥ 300°) (OR, 2.21; 95% CI 1.13–4.32; p = 0.02). According to the maximum number of reverberations, the incidence of slow flow was 2.2% (n = 0), 11.9% (n = 1), 19.5% (n = 2), 22.5% (n = 3), and 44.4% (n = 4). In conclusion, IVUS findings such as longer lesion length, the maximum number of reverberations, and the greater arc of calcification at MLA may predict slow flow after RA. The operators need to pay more attention to the presence of reverberations to enhance the procedure safety.

Establishing a risk assessment framework for point-of-care ultrasound

Point-of-care ultrasound (POCUS) refers to the use of portable ultrasound (US) applications at the bedside, performed directly by the treating physician, for either diagnostic or procedure guidance purposes. It is being rapidly adopted by traditionally non-imaging medical specialties across the globe. Recent international evidence-based guidelines on POCUS for critically ill neonates and children were issued by the POCUS Working Group of the European Society of Pediatric and Neonatal Intensive Care (ESPNIC). Currently there are no standardized national or international guidelines for its implementation into clinical practice or even the training curriculum to monitor quality assurance. Further, there are no definitions or methods of POCUS competency measurement across its varied clinical applications.

CONCLUSION

The Hippocratic Oath suggests medical providers do no harm to their patients. In our continued quest to uphold this value, providers seeking solutions to clinical problems must often weigh the benefit of an intervention with the risk of harm to the patient. Technologies to guide diagnosis and medical management present unique considerations when assessing possible risk to the patient. Frequently risk extends beyond the patient and impacts providers and the institutions in which they practice. POCUS is an emerging technology increasingly incorporated in the care of children across varied clinical specialties. Concerns have been raised by clinical colleagues and regulatory agencies regarding appropriate POCUS use and oversight. We present a framework for assessing the risk of POCUS use in pediatrics and suggest methods of mitigating risk to optimize safety and outcomes for patients, providers, and institutions.

WHAT IS KNOWN

• The use POCUS by traditionally non-imaging pediatric specialty physicians for both diagnostic and procedural guidance is rapidly increasing. • Although there are international guidelines for its indications, currently there is no standardized guidance on its implementation in clinical practice.

WHAT IS NEW

• Although standards for pediatric specialty-specific POCUS curriculum and training to competency have not been defined, POCUS is likely to be most successfully incorporated in clinical care when programmatic infrastructural elements are present. • Risk assessment is a forward-thinking process and requires an imprecise calculus that integrates considerations of the technology, the provider, and the context in which medical care is delivered. Medicolegal considerations vary across countries and frequently change, requiring providers and institutions to understand local regulatory requirements and legal frameworks to mitigate the potential risks of POCUS.

Good and bad boundaries in ultrasound compounding: preserving anatomic boundaries while suppressing artifacts

Purpose

Ultrasound compounding is to combine sonographic information captured from different angles and produce a single image. It is important for multi-view reconstruction, but as of yet there is no consensus on best practices for compounding. Current popular methods inevitably suppress or altogether leave out bright or dark regions that are useful and potentially introduce new artifacts. In this work, we establish a new algorithm to compound the overlapping pixels from different viewpoints in ultrasound.

Methods

Inspired by image fusion algorithms and ultrasound confidence, we uniquely leverage Laplacian and Gaussian pyramids to preserve the maximum boundary contrast without overemphasizing noise, speckles, and other artifacts in the compounded image, while taking the direction of the ultrasound probe into account. Besides, we designed an algorithm that detects the useful boundaries in ultrasound images to further improve the boundary contrast.

Results

We evaluate our algorithm by comparing it with previous algorithms both qualitatively and quantitatively, and we show that our approach not only preserves both light and dark details, but also somewhat suppresses noise and artifacts, rather than amplifying them. We also show that our algorithm can improve the performance of downstream tasks like segmentation.

Conclusion

Our proposed method that is based on confidence, contrast, and both Gaussian and Laplacian pyramids appears to be better at preserving contrast at anatomic boundaries while suppressing artifacts than any of the other approaches we tested. This algorithm may have future utility with downstream tasks such as 3D ultrasound volume reconstruction and segmentation.

AI-Assisted Echocardiographic Prescreening of Heart Failure With Preserved Ejection Fraction on the Basis of Intrabeat Dynamics

OBJECTIVES

The aim of this study was to establish a rapid prescreening tool for heart failure with preserved ejection fraction (HFpEF) by using artificial intelligence (AI) techniques to detect abnormal echocardiographic patterns in structure and function on the basis of intrabeat dynamic changes in the left ventricle and the left atrium.

BACKGROUND

Although diagnostic criteria for HFpEF have been established, rapid and accurate assessment of HFpEF using echocardiography remains challenging and highly desirable.

METHODS

In total, 1,041 patients with HFpEF and 1,263 asymptomatic individuals were included in the study. The participants' 4-chamber view images were extracted from the echocardiographic files and randomly separated into training, validation, and internal testing data sets. An external testing data set comprising 150 patients with symptomatic chronic obstructive pulmonary disease and 315 patients with HFpEF from another hospital was used for further model validation. The intrabeat dynamics of the geometric measures were extracted frame by frame from the image sequence to train the AI models.

RESULTS

The accuracy, sensitivity, and specificity of the best AI model for detecting HFpEF were 0.91, 0.96, and 0.85, respectively. The model was further validated using an external testing data set, and the accuracy, sensitivity, and specificity became 0.85, 0.79, and 0.89, respectively. The area under the receiver-operating characteristic curve was used to evaluate model classification ability. The highest area under the curve in the internal testing data set and external testing data set was 0.95.

CONCLUSIONS

The AI system developed in this study, incorporating the novel concept of intrabeat dynamics, is a rapid, time-saving, and accurate prescreening method to facilitate HFpEF diagnosis. In addition to the classification of diagnostic outcomes, such an approach can automatically generate valuable quantitative metrics to assist clinicians in the diagnosis of HFpEF.

Ultrasound Frequency-Based Monitoring for Bone Healing

Correct assessment of the bone healing process is required for the management of limb immobilization during the treatment of bone injuries, including fractures and defects. Although the monitoring of bone healing using ultrasound poses several advantages regarding cost and ionizing radiation exposure compared with other dominant imaging methods, such as radiography and computed tomography (CT), traditional ultrasound B-mode imaging lacks reliability and objectivity. However, the body structures can be quantitatively observed by ultrasound frequency-based methods, and therefore, the disadvantages of B-mode imaging can be overcome. In this study, we created a femoral bone hole model of a rat and observed the bone healing process using the quantitative ultrasound method and micro-CT, which provides a reliable assessment of the tissue microstructure of the bone. This study analyzed the correlation between these two assessments. The results revealed that the quantitative ultrasound measurements correlated with the CT measurements for rat bone healing. This ultrasound frequency-based method could have the potential to serve as a novel modality for quantitative monitoring of bone healing with the advantages of being less invasive and easily accessible. Impact statement Bone healing monitoring with ultrasound is advantageous as it is less invasive and easily accessible; however, the traditional B-mode method lacks reliability and objectivity. This study demonstrated that the proposed ultrasound frequency-based monitoring method can quantitatively observe bone healing and strongly correlates with the computed tomography measurements for rat bone healing. This method has the potential to become a reliable modality for monitoring bone healing.

Refraction artifact on abdominal sonogram

Ultrasonography (US) is the first-line diagnostic tool for observing the whole abdomen. Unfortunately, a wide spectrum of refraction-related artefactual images is very frequently encountered in routine US examinations. In addition, most practitioners currently perform abdominal US examinations without sufficient knowledge of refraction artifacts (RAs). This review article was designed to present many representative RA images seen in the clinical setting, with a brief explanation of the mechanism of these images, in certain cases through an analyzed and reconstructed method using computer simulation that supports clinical observations. RAs are encountered not only with B-mode US but also with Doppler US, contrast-enhanced US, and shear wave elastography. RAs change their appearance according to the situation, but they always have a significant effect on detailed interpretation of abdominal US images. Correct diagnosis of abdominal US relies on a deep understanding of each characteristic artifactual finding, which necessitates knowledge of basic US physics. When analyzing mass lesions, computer simulation analysis helps to reveal the global images of RAs around a lesion.

Point-of-care ultrasound for the early diagnosis of emphysematous pyelonephritis: A case report and literature review

BACKGROUND

Emphysematous pyelonephritis (EPN) is a rare but fatal necrotic infection of the kidney, which usually leads to septic shock. Therefore, early diagnosis and optimized therapy are of paramount importance. In the past two decades, point-of-care ultrasound (POCUS) has been widely used in clinical practice, especially in emergency and critical care settings, and helps to rapidly identify the source of infection in sepsis. We report a rare case in which a “falls” sign on POCUS played a pivotal role in the early diagnosis of EPN.

CASE SUMMARY

A 57-year-old man presented with fever and lumbago for 3 d prior to admission. He went to the emergency room, and the initial POCUS detected gas bubbles in the hepatorenal space showing a hyperechoic focus with dirty shadowing and comet-tail artifacts. This imaging feature was like a mini waterfall. His blood and urine culture demonstrated Escherichia coli bacteremia, and EPN associated with septic shock was diagnosed. The patient did not respond to broad-spectrum antibiotic treatment and a perirenal abscess developed. He subsequently underwent computed tomography-guided percutaneous catheter drainage, and fully recovered. We also review the literature on the sonographic features of POCUS in EPN.

CONCLUSION

This case indicates that a “falls” sign on POCUS facilitates the rapid diagnosis of severe EPN at the bedside.

American Society of Regional Anesthesia and Pain Medicine expert panel recommendations on point-of-care ultrasound education and training for regional anesthesiologists and pain physicians-part I: clinical indications

Point-of-care ultrasound (POCUS) is a critical skill for all regional anesthesiologists and pain physicians to help diagnose relevant complications related to routine practice and guide perioperative management. In an effort to inform the regional anesthesia and pain community as well as address a need for structured education and training, the American Society of Regional Anesthesia and Pain Medicine (ASRA) commissioned this narrative review to provide recommendations for POCUS. The guidelines were written by content and educational experts and approved by the Guidelines Committee and the Board of Directors of the ASRA. In part I of this two-part series, clinical indications for POCUS in the perioperative and chronic pain setting are described. The clinical review addresses airway ultrasound, lung ultrasound, gastric ultrasound, the focus assessment with sonography for trauma examination and focused cardiac ultrasound for the regional anesthesiologist and pain physician. It also provides foundational knowledge regarding ultrasound physics, discusses the impact of handheld devices and finally, offers insight into the role of POCUS in the pediatric population.

Artifacts in Musculoskeletal Ultrasonography: From Physics to Clinics

Ultrasound appears to be the most useful imaging tool in the diagnosis and guided treatment of musculoskeletal disorders. However, ultrasonography has been criticized for being user dependent. Therefore, medical professionals should be familiar with the basic principles of ultrasound imaging (e.g., physics and technical skills) to diminish artifacts and avoid misinterpretation. In this review, we focused on the physics of common artifacts, their clinical significance, and the ways to tackle them in daily practice during musculoskeletal imaging. In particular, artifacts pertaining to the focal zone, beam attenuation, path and side lobe of the beam, speed of the sound, and range ambiguity were described.

Artifacts in Musculoskeletal Ultrasonography: From Physics to Clinics

Ultrasound appears to be the most useful imaging tool in the diagnosis and guided treatment of musculoskeletal disorders. However, ultrasonography has been criticized for being user dependent. Therefore, medical professionals should be familiar with the basic principles of ultrasound imaging (e.g., physics and technical skills) to diminish artifacts and avoid misinterpretation. In this review, we focused on the physics of common artifacts, their clinical significance, and the ways to tackle them in daily practice during musculoskeletal imaging. In particular, artifacts pertaining to the focal zone, beam attenuation, path and side lobe of the beam, speed of the sound, and range ambiguity were described.

A single atrial septal defect masquerading as multiple defects due to a refraction artifact – A cautionary note

Echocardiography is useful for making a diagnosis of atrial septal defect (ASD) by directly visualizing the shunt flow. Herein, we present a case in which a single ostium secundum type ASD masqueraded as multiple defects on color flow imaging by transthoracic echocardiography. We confirmed by transesophageal echocardiography that this patient actually had a single ASD. An echocardiographic refraction artifact was considered to be the cause of this phenomenon. We need to be aware of the existence of this artifact to avoid misdiagnosis.

〈Learning objective: Echocardiography is useful for making a diagnosis of atrial septal defect (ASD). We present the case with a single ostium secundum type ASD which masqueraded as multiple defects on color flow imaging due to a refraction artifact. Refraction artifacts can make multiple false flow signals on color imaging. This case emphasizes the importance of an understanding of the existence of this artifact in not only B mode imaging but also color Doppler imaging.〉

Diagnostic problems in two-dimensional shear wave elastography of the liver

Two-dimensional shear wave elastography (2D-SWE) is used in the clinical setting for observation of the liver. Unfortunately, a wide spectrum of artifactual images are frequently encountered in 2D-SWE, the precise mechanisms of which remain incompletely understood. This review was designed to present many of the artifactual images seen in 2D-SWE of the liver and to analyze them by computer simulation models that support clinical observations. Our computer simulations yielded the following suggestions: (1) When performing 2D-SWE in patients with chronic hepatic disease, especially liver cirrhosis, it is recommended to measure shear wave values through the least irregular hepatic surface; (2) The most useful 2D-SWE in patients with focal lesion will detect lesions that are poorly visible on B-mode ultrasound and will differentiate true tumors from pseudo-tumors (e.g., irregular fatty change); and (3) Measurement of shear wave values in the area posterior to a focal lesion must be avoided.