Ultrasound Artifacts Research Articles

Lung artefacts and their use.

The science of lung ultrasound has grown tremendously over the last two decades and lung ultrasound has not only enteredthe mainstream of point of care ultrasound but has become a dominant topic. Understanding lung ultrasound signs and artifactsis critical to being able to correlate findings with actual pathology and normal anatomy and physiology. Investigators havedescribed multiple lung ultrasound artifacts and findings and it is important to understand both the physics and anatomic basisbehind them. Additionally, ultrasound machine use and transducer selection can significantly affect results obtained on patientduring an examination and the provider must carefully choose the correct settings. This manuscript describes the state of theart in ultrasound artifact recognition and correlation as well as management of ultrasound technology to optimize diagnosticsuccess.

Verification of Balloon Integrity by Ultrasound Imaging in Accelerated Partial Breast Irradiation

<p class="cco-body"><em><span lang="EN-GB">Purpose</span></em><span lang="EN-GB">: An overview of the ultrasound imaging artifacts encountered in Mammosite balloon APBI is presented. Analysis of ultrasound measurement errors and the dosimetric impact of balloon leakage were used to determine whether clinically relevant changes in balloon size can be reliably detected. <em>Methods</em>: Ultrasound imaging of a Mammosite balloon phantom was performed to better understand measurement errors and accuracy. The dose to the prescription point as a function of balloon diameter was computed for different sized balloons. The results were compared to phantom measurements of balloon diameter versus filling volume to assess the dose change that would result from tissue moving inward with a shrinking balloon boundary. In APBI patients undergoing a course of 10 treatment fractions, the accuracy and variability of balloon size measured with ultrasound imaging was compared to CT. <em>Results</em>: Ultrasound artifacts combine to form a false image of the distal balloon boundary. Proper US probe orientation and choice of measurement point locations improved distance measurement accuracy. A 1 mm change in balloon diameter is measurable with ±0.1 mm error and corresponds to <4% change in dose 1 cm from the balloon. Measurement errors relative to CT averaged less than 1.4 mm and variability (standard deviation) over the course of treatment averaged 1.9 mm. <em>Conclusions</em>: Properly performed ultrasound image acquisition and analysis can detect dosimetrically relevant changes in the size of a leaking balloon. This study confirms that US imaging is a valid method of verifying APBI balloon integrity over the course of treatment.</span></p>

Color-Doppler ultrasound imaging of in situ human kidney stones in a hyperbaric chamber

Overpressure has been shown to reduce the color-Doppler ultrasound twinkling artifact on ex vivo human kidney stones, leading to the hypothesis that surface crevice microbubbles cause twinkling. For the first time, we investigate the effect of overpressure on in situ human kidney stones. Thus far, five human subjects with kidney stones known to twinkle have been imaged with a Philips/ATL P4-2 transducer and Verasonics ultrasound system for 45 minutes in a hyperbaric chamber. Subjects breathed ambient air while exposed to a maximum pressure of 4 atmospheres absolute (ATA), except for a scheduled decompression stop at 1.6 ATA where subjects breathed pure oxygen. Twinkling was quantified in terms of Doppler power over 2 min intervals before pressurization (baseline), at 4 ATA, and at 1.6 ATA. Preliminary results (averaged over 3 of the 5 subjects) indicate no change in twinkling at 4 ATA compared to baseline levels (ratio of Doppler powers = 1.09±0.27). Twinkling almost doubled, though, during the pure oxygen stage at 1.6 ATA compared to baseline levels (ratio of Doppler powers = 1.85±0.58). The increase in twinkling associated with breathing pure oxygen continues to support the crevice microbubble hypothesis. Higher pressures than explored in this study may be needed to reduce twinkling on in situ stones, as was often the case in studies using ex vivo human kidney stones. [Work supported by the National Space Biomedical Research Institute through NASA NCC 9-58 and NIH grants DK043881 and DK092197.]

GPU-Based Simulation of Ultrasound Imaging Artifacts for Cryosurgery Training.

This study presents an efficient computational technique for the simulation of ultrasound imaging artifacts associated with cryosurgery based on nonlinear ray tracing. This study is part of an ongoing effort to develop computerized training tools for cryosurgery, with prostate cryosurgery as a development model. The capability of performing virtual cryosurgical procedures on a variety of test cases is essential for effective surgical training. Simulated ultrasound imaging artifacts include reverberation and reflection of the cryoprobes in the unfrozen tissue, reflections caused by the freezing front, shadowing caused by the frozen region, and tissue property changes in repeated freeze-thaw cycles procedures. The simulated artifacts appear to preserve the key features observed in a clinical setting. This study displays an example of how training may benefit from toggling between the undisturbed ultrasound image, the simulated temperature field, the simulated imaging artifacts, and an augmented hybrid presentation of the temperature field superimposed on the ultrasound image. The proposed method is demonstrated on a graphic processing unit at 100 frames per second, on a mid-range personal workstation, at two orders of magnitude faster than a typical cryoprocedure. This performance is based on computation with C++ accelerated massive parallelism and its interoperability with the DirectX-rendering application programming interface.

Ultrasound artifacts and their diagnostic significance in internal medicine and gastroenterology - part 2: color and spectral Doppler artifacts

Artifacts in ultrasonographic diagnostics are a result of the physical properties of the ultrasound waves and are caused by interaction of the ultrasound waves with biological structures and tissues of the body and with foreign materials. On the one hand, they may be diagnostically helpful. On the other hand, they may be distracting and may lead to misdiagnosis. Profound knowledge of the causes, avoidance, and interpretation of artifacts is a necessary precondition for correct clinical appraisal of ultrasound images. Part 1 of this review commented on the physics of artifacts and described the most important B-mode artifacts. Part 2 focuses on the clinically relevant artifacts in Doppler and color-coded duplex sonography. Problems and pitfalls of interpretation arising from artifacts, as well as the diagnostic use of Doppler and colour-coded duplex sonography, are discussed.

Ultrasound artifacts and their diagnostic significance in internal medicine and gastroenterology - Part 1: B-mode artifacts

Artifacts in ultrasonographic diagnostics are a result of the physical properties of the ultrasound waves and are caused by interaction of the ultrasound waves with biological structures and tissues and with foreign bodies. On the one hand, they may be distracting and may lead to misdiagnosis. On the other hand, they may be diagnostically helpful. Ultrasound imaging suffers from artifacts, because in reality, parameters assumed to be constant values, such as sound speed, sound rectilinear propagation, attenuation, etc., are often different from the actual parameters. Moreover, inadequate device settings may cause artifacts. Profound knowledge of the causes, avoidance, and interpretation of artifacts is a necessary precondition for correct clinical appraisal of ultrasound images. Part 1 of this review comments on the physics of artifacts and describes the most important B-mode artifacts. Pitfalls, as well as diagnostic chances resulting from B-mode artifacts, are discussed.

Elevational spatial compounding for enhancing image quality in echocardiography.

IntroductionEchocardiography is commonly used in clinical practice for the real-time assessment of cardiac morphology and function. Nevertheless, due to the nature of the data acquisition, cardiac ultrasound images are often corrupted by a range of acoustic artefacts, including acoustic noise, speckle and shadowing. Spatial compounding techniques have long been recognised for their ability to suppress common ultrasound artefacts, enhancing the imaged cardiac structures. However, they require extended acquisition times as well as accurate spatio-temporal alignment of the compounded data. Elevational spatial compounding acquires and compounds adjacent partially decorrelated planes of the same cardiac structure.MethodsThis paper employs an anthropomorphic left ventricle phantom to examine the effect of acquisition parameters, such as inter-slice angular displacement and 3D sector angular range, on the elevational spatial compounding of cardiac ultrasound data.Results and conclusionElevational spatial compounding can produce substantial noise and speckle suppression as well as visual enhancement of tissue structures even for small acquisition sector widths (2.5° to 6.5°). In addition, elevational spatial compounding eliminates the need for extended acquisition times as well as the need for temporal alignment of the compounded datasets. However, moderate spatial registration may still be required to reduce any tissue/chamber blurring side effects that may be introduced.

The effect of ambient pressure on the color Doppler ultrasound twinkling artifact

Recently, our group discovered that overpressure suppressed the color Doppler ultrasound twinkling artifact on ex vivo calcium oxalate monohydrate (COM) kidney stones, suggesting that trapped microbubbles on the stone surface cause twinkling (Lu et al. 2013). Yet the hypothesis is not fully accepted, partly because bubbles were not observed. Here, we extend the overpressure results to include under-pressure and use high-speed photography to visualize the bubbles. A programmable ultrasound system with Philips/ATL P4-2 transducer was used. Ex vivo COM stones were placed in a hydraulic pressure chamber and imaged acoustically through an acrylic window. The overpressure threshold to diminish twinkling was found to vary significantly, with twinkling eliminated at pressures of 3 ATA (atmospheres absolute) up to >8 ATA, even within the same stone. When the stones were exposed to 0.2 ATA (under-pressure), twinkling increased. High-speed photography during Doppler ultrasound revealed only one instance of an oscillating bubble. However, when stones were exposed repeatedly to a pre-focal, off-axis lithotripter pulse (p+ = 1.5 MPa, p- = 2.5 MPa), stones that twinkled had bubbles emerge from the same location with each pulse whereas stones that did not twinkle had a random bubble distribution. [Work supported by NSBRI through NASA NCC 9-58 and NIH DK043881, DK092197.]

Segmentation of multiple heart cavities in 3-D transesophageal ultrasound images.

Three-dimensional transesophageal echocardiography (TEE) is an excellent modality for real-time visualization of the heart and monitoring of interventions. To improve the usability of 3-D TEE for intervention monitoring and catheter guidance, automated segmentation is desired. However, 3-D TEE segmentation is still a challenging task due to the complex anatomy with multiple cavities, the limited TEE field of view, and typical ultrasound artifacts. We propose to segment all cavities within the TEE view with a multi-cavity active shape model (ASM) in conjunction with a tissue/blood classification based on a gamma mixture model (GMM). 3-D TEE image data of twenty patients were acquired with a Philips X7-2t matrix TEE probe. Tissue probability maps were estimated by a two-class (blood/tissue) GMM. A statistical shape model containing the left ventricle, right ventricle, left atrium, right atrium, and aorta was derived from computed tomography angiography (CTA) segmentations by principal component analysis. ASMs of the whole heart and individual cavities were generated and consecutively fitted to tissue probability maps. First, an average whole-heart model was aligned with the 3-D TEE based on three manually indicated anatomical landmarks. Second, pose and shape of the whole-heart ASM were fitted by a weighted update scheme excluding parts outside of the image sector. Third, pose and shape of ASM for individual heart cavities were initialized by the previous whole heart ASM and updated in a regularized manner to fit the tissue probability maps. The ASM segmentations were validated against manual outlines by two observers and CTA derived segmentations. Dice coefficients and point-to-surface distances were used to determine segmentation accuracy. ASM segmentations were successful in 19 of 20 cases. The median Dice coefficient for all successful segmentations versus the average observer ranged from 90% to 71% compared with an inter-observer range of 95% to 84%. The agreement against the CTA segmentations was slightly lower with a median Dice coefficient between 85% and 57%. In this work, we successfully showed the accuracy and robustness of the proposed multi-cavity segmentation scheme. This is a promising development for intraoperative procedure guidance, e.g., in cardiac electrophysiology.

Ultrasound Diagnosis of Acute Pulmonary Edema: the Oblivion of a Great Future Behind Us

To the Editor: Al Deeb et al. write in their conclusion: “In patients with a moderate to high pretest probability, a point-of-care ultrasound study showing B-lines can be used to strengthen an emergency physician's working diagnosis of acute cardiogenic pulmonary edema. In patients with a low pretest probability, a negative point-of-care ultrasound study can almost exclude the possibility of acute cardiogenic pulmonary edema.”1 However, as reported elsewhere,2-4 acute severe dyspnea due to causes other than pulmonary edema, including exacerbation of chronic obstructive pulmonary disease and pulmonary fibrosis, presents with the same B-line profile as acute pulmonary edema. It is therefore obvious that in a clinical scenario of severe dyspnea, preliminary diagnosis by history and clinical examination takes precedence and, in fact, is almost all that the physician and the patient need for effective intervention. Indeed, the reference tool in acute pulmonary edema is auscultation, and the level of wet sounds,2 whose features, however, not to mention the extension of lung involvement, were not reported in any of the source articles. Furthermore, those articles also fail to inform us of the ultrasound time course of the observed pulmonary edema cases, from the onset to improvement or recovery or to the worsening of the clinical situation.4 Al Deeb et al. appropriately address the limitations of the current statements on this subject, writing “Further studies including large numbers of ED patients presenting with undifferentiated dyspnea are required to gain more valid and reliable estimates of test accuracy in ED patients.”1 We would add that, since the diagnosis of acute pulmonary edema can be challenging, misunderstandings or mistakes are not impossible, and it is noteworthy that no short-term (minutes-hours) study is yet available, even after many years of reports and recommendations to that effect. Further studies are indeed urgently needed, provided, however, that the basic methodology is still considered sound. As quoted by Liu et al.5 in their intelligent but rather colorful appraisal of the situation, according to De Bono “An expert is someone who has succeeded in making decisions and judgments simpler through knowing what to pay attention to and what to ignore.” In this field we suggest that, when managing a patient with acute severe dyspnea that could be due to acute pulmonary edema, in the absence of reliable evidence of the validity of ultrasound artifacts as a diagnostic tool, “what to pay attention to” is physical examination and other scientific procedures, and “what to ignore” is the B-line count. Indeed, this is erratic at best, and we feel that research efforts would be better spent seeking to consolidate best practice in diagnostics and patient care, rather than starting out on the slippery slope to oblivion of established practice.

Lung ultrasound in quantifying lung water in septic shock patients

Quantification of lung ultrasound (LUS) artifacts (B-lines) is used to assess pulmonary congestion in emergency medicine and cardiology [1,2]. We investigated B-lines in relation to extravascular lung-water index (EVLWI) from invasive transpulmonary thermodilution in septic shock patients. Our aim was to evaluate the role of LUS in an intensive care setting.

Not All Radiopaque Foreign Bodies Shadow on Ultrasound

Foreign body ingestion is a common indication for imaging children. Ultrasound can be a useful adjunct to serial radiographs for evaluation of foreign bodies in the enteric tract. This case report describes a child who swallowed a single magnetic rock. Follow-up radiographs 4 days later could not determine progression of the foreign body beyond the stomach. Ultrasound was used to locate it, showing a structure with unexpected posterior reverberation artifact in the stomach. This was correlated with a similar magnet in a water bath demonstrating identical reverberation artifact. This report discusses the underlying factors for the different sonographic appearances and associated ultrasound artifacts of foreign bodies. This knowledge is important when performing sonography as adjunct modality for identification of foreign bodies in the gastrointestinal tract.

Simplicity is the ultimate sophistication. PR electrocardiographic intervals for smart forecasting of decline in renal function

Simplicity is the ultimate sophistication. PR electrocardiographic intervals for smart forecasting of decline in renal function

Clinical implications of ultrasound artifacts in the cervicofacial area following injection of permanent facial fillers.

To evaluate ultrasound (US) findings in the cervicofacial area following injection of permanent facial fillers during a long-term follow-up period. Fifty-seven consecutive patients with a history of previous facial filler injection were enrolled at a single institution between 2010 and 2014. All patients were female, and the mean age of the patients was 60.8 years. The mean follow-up period following injection of facial fillers was 16.6 years (range 2-30 years). We analyzed US findings in the face (injection site) and neck (noninjection site). In all patients, face US revealed a snowstorm appearance with strong posterior acoustic shadows and multifocal small anechoic lesions with posterior stepladder artifacts in the subcutaneous fat. Neck US demonstrated the same artifacts as those on the face through local spread of fillers in 14 patients (26.4 %) and abnormal cervical lymph nodes through lymphatic spread in 34 patients (59.6 %). In abnormal cervical lymph nodes, hyperechogenicity and multiple hyperechoic foci were observed in 26 (45.6 %) and 19 (33.3 %) patients, respectively. Various artifacts may be demonstrated on US in patients with injection of permanent facial fillers. When hyperechogenicity or multiple hyperehoic foci are seen in cervical lymph nodes, the possibility of migration of facial fillers to the cervical area should be considered.

Segmentation of Multi-Center 3D Left Ventricular Echocardiograms by Active Appearance Models

Segmentation of 3D echocardiograms (3DEs) is still a challenging task due to the low signal-to-noise ratio, the limited field of view, and typical ultrasound artifacts. We propose to segment the left ventricular endocardial surface by using Active Appearance Models (AAMs). Separate end-diastolic (ED) and end-systolic (ES) AAMs were built from presegmented 3DEs of the CETUS training data and 25 previously acquired 3DEs, imaged using various 3DE equipment. The AAMs fully automatically segmented the 15 training sets in a leave-one-out cross validation, comparing two training populations and various initialization strategies. All segmentations took about 15 seconds per patient. The comparison on the CETUS training data shows that the AAM benefits from additional training data and more accurate initialization. The results on the CETUS training and testing data confirm good ED and ES segmentation accuracy on multi-center, multi-vendor, multi-pathology data, and corresponding EF estimation. Selection from different initialization strategies, based on the minimal residual error, and propagation of detected ED contours to initialize ES detection, contributed to more accurate segmentations in this heterogeneous population.

Artificial Neural Network Application in the Diagnosis of Disease Conditions with Liver Ultrasound Images

The preliminary study presented within this paper shows a comparative study of various texture features extracted from liver ultrasonic images by employing Multilayer Perceptron (MLP), a type of artificial neural network, to study the presence of disease conditions. An ultrasound (US) image shows echo-texture patterns, which defines the organ characteristics. Ultrasound images of liver disease conditions such as “fatty liver,” “cirrhosis,” and “hepatomegaly” produce distinctive echo patterns. However, various ultrasound imaging artifacts and speckle noise make these echo-texture patterns difficult to identify and often hard to distinguish visually. Here, based on the extracted features from the ultrasonic images, we employed an artificial neural network for the diagnosis of disease conditions in liver and finding of the best classifier that distinguishes between abnormal and normal conditions of the liver. Comparison of the overall performance of all the feature classifiers concluded that “mixed feature set” is the best feature set. It showed an excellent rate of accuracy for the training data set. The gray level run length matrix (GLRLM) feature shows better results when the network was tested against unknown data.

A LOCALIZED GLOBAL DEFORMATION MODEL TO TRACK MYOCARDIAL MOTION USING ECHOCARDIOGRAPHY

In this paper, we propose a robust real-time myocardial border tracking algorithm for echocardiography. Commonly, after an initial contour of LV border is traced at one or two frame from the entire cardiac cycle, LV contour tracking is performed over the remaining frames. Among a variety of tracking techniques, optical flow method is the most widely used for motion estimation of moving objects. However, when echocardiography data is heavily corrupted in some local regions, the errors bring the tracking point out of the endocardial border, resulting in distorted LV contours. This shape distortion often occurs in practice since the data acquisition is affected by ultrasound artifacts, dropout or shadowing phenomena of cardiac walls. The proposed method deals with this shape distortion problem and reflects the motion realistic LV shape by applying global deformation modeled as affine transform partitively to the contour. We partition the tracking points on the contour into a few groups and determine each affine transform governing the motion of the partitioned contour points. To compute the coefficients of each affine transform, we use the least squares method with equality constraints that are given by the relationship between the coefficients and a few contour points showing good tracking results. Many real experiments show that the proposed method supports better performance than existing methods.

Ultrasound Artifacts

Ultrasound has become a widely used diagnostic imaging modality in medicine because of its safety and portability. Because of rapid advances in technology, in recent years, sonographic imaging quality has significantly increased. Despite these advances, the potential to encounter artifacts while imaging remains.This article classifies both common and uncommon gray-scale and Doppler ultrasound artifacts into those resulting from physiology and those caused by hardware. A brief applied-physics explanation for each artifact is listed along with an illustrated diagram. The imaging appearance of artifacts is presented in case examples, along with strategies to minimize the artifacts in real time or use them for clinical advantage where applicable.

WE-D-18C-01: Art of Imaging: Diagnostic Ultrasound Image Artifacts

Assumptions followed during construction of B-mode and color flow images are that the pulse-echo transit time can be converted to reflector depth through uniform tissue models, echoes originate only from locations along the transmit-receive axes of pulse propagation, and first order correction schemes adequately account for acoustic wave attenuation and absorption. The latter allows the display brightness to encode tissue echogenicity. This course will challenge participants to identify imaging artifacts whose origins stem from the more complex and realistic propagating and scattering conditions common in clinical ultrasound. Speckle, a very common artifact but a clinically employed feature, originates from simultaneous echoes from diffuse scatterers and is a result of coherent detection of signals. One of the most bothersome artifacts are those due to reverberations especially that originating from superficial tissue interfaces. Methods to overcome these will be discussed. This presentation also will describe and illustrate speed of sound, refraction, enhancement, shadowing, mirroring, beam width, beam-forming, and slice thickness artifacts. All are useful examples of limitations introduced by acoustic waves propagating through complex tissue paths. New formats for physician board certification exams are demanding the inclusion of image-based examples of ultrasound physics. Instructors' knowledge of, and access to examples of ultrasound artifacts are important in this effort. The presentation will incorporate an audience response system to challenge participants in correct identification of some of these artifacts. Learning Objectives: 1. Review basic mechanisms for producing ultrasound images. 2. Identify the etiology of speckle, reverberation noise, beam width and slice thickness artifacts, and artifacts associated with pulse propagation. 3. Discuss methods that reduce the impact of artifacts OR employ artifacts effectively to facilitate clinical diagnosis.

TU-F-12A-08: Verification of APBI Balloon Integrity Using Ultrasound Imaging

Purpose: An overview of the ultrasound imaging artifacts encountered in Mammosite balloon APBI is presented. The goal was to determine whether clinically relevant changes in balloon size resulting from leakage can be detected by ultrasound imaging and also to compare the magnitude of size variations using both ultrasound and CT imaging. Methods: Ultrasound imaging of a Mammosite balloon phantom was performed to better understand measurement errors and accuracy. The dose to the prescription point as a function of balloon diameter was computed for different sized balloons. The results were compared to phantom measurements of balloon diameter versus filling volume to assess the dose change that would result from tissue moving inward with a shrinking balloon boundary. In APBI patients undergoing a course of 10 treatment fractions, an assessment was made of the variability and accuracy of balloon size measured with ultrasound imaging compared to CT. Results: Ultrasound artifacts combine to form a false image of the distal balloon boundary. Proper US probe orientation and choice of measurement point locations improves distance measurement accuracy. A 1 mm change in balloon diameter is measurable with ±0.1 mm error; this 1 mm change corresponding to <4% change in dose at a distance 1 cm from the balloon. In patients, the implanted balloon diameters ranged from 3.4 to 5.8 cm. Measurement errors relative to CT averaged less than 1.4 mm and variability (standard deviation) over the course of treatment averaged 1.9 mm. Conclusion: Complex and misleading image artifacts can be minimized by proper probe orientation, and accurate balloon diameter measurement requires consistent image analysis methods. Ultrasound imaging can detect dosimetrically relevant changes in the size of a leaking Mammosite balloon, therefore ultrasound imaging can be used for verification of balloon integrity over the course of APBI treatment.