Ultrasound Artifacts Research Articles

Rigid registration of 3-D ultrasound with MR images: a new approach combining intensity and gradient information.

We present a new image-based technique to rigidly register intraoperative three-dimensional ultrasound (US) with preoperative magnetic resonance (MR) images. Automatic registration is achieved by maximization of a similarity measure which generalizes the correlation ratio, and whose novelty is to incorporate multivariate information from the MR data (intensity and gradient). In addition, the similarity measure is built upon a robust intensity-based distance measure, which makes it possible to handle a variety of US artifacts. A cross-validation study has been carried out using a number of phantom and clinical data. This indicates that the method is quite robust and that the worst registration errors are of the order of the MR image resolution.

Miscellaneous F20Sonographic tissue characterization based on the parameters derived from computerized processing of gray level data

BackgroundSonographic tissue characterization is a relatively weak arm of ultrasound diagnosis. There is a great influence of the sonographic machine setup on the B‐mode gray level appearance of the ultrasound image. Various ultrasound artefacts can produce significant changes in brightness setting of the details in sonographic pictures. Nevertheless, in certain situations, the ability to specify the sonographic texture of the tissues may reveal interesting information.MethodWe present measurable parameters for the specification of the ‘homogenicity’ of the sonographic texture of the scanned tissue. These parameters are derived from the computerized image processing. The processing includes selection of the region of interest, which is related to the specific tissue in the image plane and distribution analysis of the gray level of pixels within the selected region.ResultsAn implication of this algorithm is demonstrated by texture analysis of the different fetal choroid plexus images as they appear in early anatomical scans (15–17 weeks).Of the effects of B‐mode presets – the dynamic range and rejection level had most significant impact on the texture appearance in view of the studied parameters.There was good correlation between the subjective perception of the tissue homogenicity and the computer analysis results.ConclusionThe proposed texture parameters may lead to the new approach for the sonographic tissue characterization. These parameters may be used for the standardization of ultrasound machine setups as well.

Partial wave analysis of the ultrasound comet tail artifact.

An adaptation of linear acoustic scattering theory is used to describe the comet tail artifact which is observed in the diagnostic ultrasound imaging of small spherical masses. The calculated backscattered pressure wave is shown to correspond well with the appearance of the artifact in a variety of clinical images.

Sources and impact of artifacts on clinical three‐dimensional ultrasound imaging

The purpose of this paper is to investigate, identify and discuss artifacts and their sources arising in three-dimensional ultrasound (3D US) in clinical practice in order to increase the awareness of clinicians and sonographers with respect to common 3D US artifacts and to use this increased awareness to avoid or reduce the occurrence of misdiagnosis in 3D US studies. Patient 3D US data were acquired using several different scanners and reviewed interactively on the scanner and graphics workstations. Artifacts were catalogued according to artifact origin. Two-dimensional ultrasound (2D US) artifacts were classified whether they were of a B-mode or color/power Doppler origin and their presentation in the original scan planes and the resulting volume re-sliced planes and rendered images was identified. Artifacts unique to 3D US were observed, noted and catalogued on the basis of whether they arose during acquisition, rendering or volume editing operations. Acoustic artifacts identified included drop-out, shadowing, etc. whose presentation depended on the relationship between slice and imaging plane orientation. Color/power Doppler artifacts were related to gain, aliasing, and flash which could add apparent structure or confusion to the volume images. Rendered images also demonstrated artifacts due to shadowing and motion of adjacent structures, cardiac motion or pulsatility of the cardiac septum or vessel walls. Editing artifacts potentially removed important structures. Three-dimensional ultrasound is prone to the same types of artifacts encountered in 2D US imaging plus others unique to volume acquisition and visualization. The consequences of these diagnostically significant artifacts include mimicking of abnormal development, masses, or missing structures thus requiring careful study before reaching a diagnosis.

Use of Transesophageal Echocardiography for the Assessment of Traumatic Aortic Injuries.

Acute traumatic lesions of the thoracic aorta or its branches (TLA) constitute highly lethal yet treatable injuries that are increasingly diagnosed in surviving patients. Traumatic disruptions are limited to the region of the aortic isthmus in approximately 90% of cases. Unlike aortography, usually referred as the gold standard diagnostic technique, transesophageal echocardiography (TEE) is a noninvasive imaging modality that can be rapidly performed at the patient bedside. Accordingly, TEE is being increasingly used as a first-line screening test for the evaluation of patients with suspected TLA. The TEE signs associated with TLA depend on the anatomic type of aortic disruption. After a period of validation, multiplane TEE allows accurate diagnosis of traumatic disruptions of the aortic isthmus, with a sensitivity of 88% (range, 57%-100%) and a specificity of 96% (range, 84%-100%). False-negative TEE results have been mainly attributed to lacerations of aortic branches. Accordingly, aortography must be routinely performed when a traumatic injury to brachiocephalic arteries is suspected. False-positive TEE findings have been associated with the presence of ultrasound artifacts or atherosclerotic changes that mimic TLA. Accurate determination of the depth of aortic wall tears and diagnosis of blunt cardiac injuries during the TEE study are crucial to guide patient management. The presence of TEE signs associated with imminent risk of adventitial rupture should lead to prompt surgery. The use of TEE as a first-line imaging modality simplifies the initial assessment of patients at high risk for TLA and helps guide acute management.

A multi-user networked database for analysis of clinical and temperature data from patients treated with simultaneous radiation and ultrasound hyperthermia

A database was developed using commercially available development software that allows the entry of clinical data and automatically analyses temperature and power data from a commercial ultrasound hyperthermia system. The database can be accessed via network connections by more than one authorized user, thus facilitating the entry, management, and analysis of clinical data. The software automatically estimates ultrasound induced temperature artifacts and calculates thermal dose parameters such as T90s, equivalent minutes at 43 , and time at or above index temperatures using the corrected temperatures. These parameters also become part of the database. Digital photographs of treatment setup, probe placement, and tumour or normal tissue response can be included in the database for documentation and reference. Ultrasound diagnostic images that document the depth and reproducibility of probe placement can be scanned into the PC and included in the database as well. This short communication documents experiences developing this tool that may be useful to other investigators.

Artifacts in intravascular ultrasound imaging during coronary artery stent implantation

Intravascular ultrasound imaging is able to provide direct images of the stent meshwork. However, a paradoxical question remains unanswered: Why is it not possible to correct or prevent implantation defects by ultrasound-guided implantation? We postulate that these discrepancies are due to image artifacts. We performed an in vitro experiment allowing detection, physical characterization, and computerized simulations of the various aspects of these artifacts. The width of the echo of a strut is variable, dependent on its distance from the transducer. The stent strut echo orientation is variable, and depends on the position of the transducer inside the stent. The stent contour image depends on the position of the transducer. In conclusion, knowledge of these stent intravascular ultrasound image artifacts enabled us to discriminate accurately between artifacts and real stent implantation defects, and are indispensable for accurate qualitative and quantitative analyses of stents.

A Series of Teaching Phantoms for Displaying Diagnostic Ultrasound Image Artifacts

Much work has been done on ultrasound phantoms foe biopsy and anatomic training of physicians and sonographers. Artifacts observed during scans in vivo also have been described. The authors' purpose in this article is to describe the construction and perdormance of phantoms designed to demonstrate ultrasound image artifacts for teaching purposes. Phantom images exhibiting ringdown, range errors, reverberation, and multipath artifacts produced by scanning intrauterine devices, shotgun pellets, and other objects are illustrated.

Color Doppler twinkling artifact in hyperechoic regions.

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. 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. 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. 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.

Diagnosis of ascending aortic dissection by transesophageal echocardiography: Utility of M-mode in recognizing artifacts

This study sought to assess the reliability of biplanar transesophageal echocardiography in the diagnosis of ascending aortic dissection and to test the utility of M-mode information in the differential diagnosis of ascending aortic ultrasound artifacts and intimal flap images. Transesophageal echocardiography is a useful technique in the diagnosis of aortic dissection. However, ultrasound artifacts in the ascending aorta are an important limitation. Transesophageal echocardiography was performed in 132 consecutive patients with clinically suspected aortic dissection. Two-dimensional and M-mode echocardiography and color Doppler were used to diagnose intimal flap and artifact images. Diagnoses were validated either anatomically or with reference techniques. The sensitivity and specificity of transesophageal echocardiography in the diagnosis of ascending aortic dissection were 96.8% and 100%, respectively. Ninety-three artifacts were observed in 56 (55%) of 101 patients without ascending aortic dissection. Two-dimensional echocardiography easily identified 74 artifacts (80%). Color Doppler showed no ascending flow abnormalities in 71% of artifact images. M-mode echocardiography showed three location and mobility artifact patterns related to the posterior wall of the aorta or the right pulmonary artery. In contrast, intimal flap movement showed no relation to the aortic wall movement in 25 cases (83%). Blind analysis of transesophageal echocardiographic study tapes underlined the utility of M-mode in the differential diagnosis. Ranges of sensitivity, specificity and positive predictive value (established by including doubtful results as either positive or negative) improved from 87.1-93.5% to 93.5-96.8%, from 85.1-94.1% to 99-100% and from 65.9-81.8% to 96.8-100%, respectively, with the inclusion of M-mode data. Biplanar transesophageal echocardiography permits reliable diagnosis of ascending aortic dissection. Ultrasound artifacts are common, but assessment of the location and mobility of intraluminal images by M-mode echocardiography definitely improves diagnostic accuracy.

Endoscopic ultrasonography artifacts and problems of interpretation

Endoscopic ultrasonography artifacts and problems of interpretation

Image Artifacts in Real-Time Ultrasound

A survey of image artifacts in real-time ultrasound is presented. Spatial mapping of detected echoes is based on several assumptions, and violation of any of these assumptions creates artifacts. Drawings and sonograms are used to illustrate image artifacts, including partial volume, attenuation, refraction, reverberation, mirror image, side lobe, comet tail, ring down, and range ambiguity.

The effects of applied pressure on the thickness, layers, and echogenicity of gastrointestinal wall ultrasound images

Endoscopic ultrasound imaging of the gastrointestinal wall can be performed through intraluminal fluid or by direct transducer contact with the wall. We tested the hypothesis that the ultrasound appearance of the gastrointestinal wall is influenced by the amount of pressure applied when the transducer is in contact with the tissue. Fresh autopsy specimens from the porcine gastrointestinal tract were examined in vitro using an 8.5-MHz linear array ultrasound system. As transducer pressure against the wall was increased from 0 to 10 KPa, changes were seen on the images in wall thickness, tissue echogenicity, and the number of layers. The stomach and rectum were more resistant to compression than the esophagus, duodenum, and colon. Wall echogenicity increased with increasing degrees of applied pressure and some layers were obliterated by this pressure. The second ultrasound layer, or deep mucosa, appeared to be the most susceptible to compression. Endoscopic ultrasound imaging artifacts should be reduced by limiting the amount of pressure applied to the wall with the transducer.

Comet-tail artifact from cholesterol crystals: observations in the postlithotripsy gallbladder and an in vitro model.

The "comet tail" is a well-known ultrasound artifact that appears as a series of parallel bands radiating from a source. This artifact was observed in the gallbladder lumen in eight of 10 patients after extracorporeal shock wave lithotripsy of radiolucent calculi. To investigate the cause of the comet tail artifact, cholesterol crystals were studied in an in vitro model. The comet-tail appearance was reproduced in vitro and was found to be directly related to the interrogating frequency and the size of the crystal aggregates. The authors conclude that cholesterol crystals can serve as the source of the comet-tail artifact secondary to reverberation within the crystals.

Hyaline membrane disease in the newborn: Diagnosis by ultrasound

The authors report a new method of diagnosing hyaline membrane disease (HMD) in newborns: ultrasound. Babies with HMD display a specific pattern with retrohepatic hyperechogenicity on abdominal ultrasound. The specificity of the pattern was verified in 40 prematures with respiratory distress syndrome. The sign was present in 24, and in 22 of these the final diagnosis was moderate or marked HMD. In the last 2, mild HMD was suggested. The pattern was absent in the 16 others, none of whom had HMD. The pattern probably results from an ultrasound artifact: summation of multiple aerated airways surrounded by collapsed alveoli. Follow-up examinations were possible in 13 babies with HMD. Hyperechogenicity disappeared in 8 of these patients within 6-9 days and in 3 within 10-20 days; it persisted for 60 and 70 days in 2 with bronchopulmonary dysplasia. In conclusion, retrohepatic hyperechogenicity in newborns is pathognomonic for HMD and allows an instant diagnosis. The persistence of the pattern could be a useful criterion for evaluation of the prognosis.

Ultrasound artifacts affecting the diagnosis of breast masses

An investigation of the outcome of over 1600 breast ultrasound examinations revealed a number of scanning artifacts. Artifactual echoes in cysts resulted from inappropriate scanning factors, including focal zone placement, gain, TGC, and gray scale, and from partial volume effect. The absence of a sign suspicious for carcinoma, posterior shadowing to a solid mass,resulted from faulty focal zone placement, or from the mass resting on chest wall tissue. Pathology was sometimes simulated by postsurgical scars, ducts, and benign calcifications. Corrective procedures to alleviate the various scanning artifacts are recommended.

Pseudoepidural reverberation artifact: a common ultrasound artifact in fetal cranium.

High-intensity reverberation artifacts frequently occur within the fetal cranium during obstetric ultrasound examinations. One hundred ninety-six static ultrasonograms obtained from 100 consecutive obstetric patients were reviewed to determine the incidence, shape, and location of high-intensity reverberation artifacts within the fetal head. Such artifacts occurred in one-third of the fetuses examined. The most common appearance was an arc-shaped artifact that occurred most frequently in the fetal hemicranium farthest from the maternal skin surface. Such an artifact can mimic epidural fluid collections and cause confusion for examiners not familiar with this finding. A discussion of this "pseudoepidural" artifact, its cause, and ways of excluding underlying intracranial pathology is presented.

Artifacts in ultrasound imaging.

Ultrasound imaging artifacts of acoustic origin relating to resolution, propagation path, and attenuation are reviewed. Lateral and axial resolution limitations are artifactual in nature since a failure to resolve means a loss of detail and two adjacent structures may be visualized as one. Apparent resolution close to the transducer (speckle) is not directly related to tissue texture but is a result of interference effects from the distribution of scatterers in the tissue. Reverberation produces a set of equally spaced artifactual echoes distal to the real reflectors. The mirror image artifact is the presentation of objects that are present on one side of a strong reflector, appearing on the other side as well. Shadowing and enhancement are useful artifacts for determining the nature of masses. Enhancement results from low attenuation objects in the sound path while shadowing results from strongly reflecting or strongly attenuating objects. Additional artifacts include section thickness, refraction, multipath, side lobe, grating lobe, focal enhancement, comet tail, ring down, speed error, and range ambiguity.

The ring-down artifact.

"Ring-down" is an ultrasound artifact that appears as a solid streak or a series of parallel bands radiating away from abdominal gas collections. Using an in vitro system of bubbles in water or gelatin, it was found that the ring-down artifact originated from the center of a cluster of four bubbles (bubble tetrahedron), three on top and one nestled beneath. Entrapped between the bubbles is a horn- or bugle-shaped fluid collection that we theorize emits a continuous sound wave back to the transducer when struck by an ultrasound pulse. Electronic processing by the scanner converts this continuous sound wave into the series of bands seen in the ring-down artifact.

Pulmonary edema in dogs, especially the sequence of fluid accumulation in lungs.

Pulmonary edema in dogs, especially the sequence of fluid accumulation in lungs.