Twinkling artifact in color Doppler imaging of the orbit

Emergency Ocular Ultrasound - Common Traumatic and Non-Traumatic Emergencies Diagnosed with Bedside Ultrasound

Point-of-care ocular ultrasound (POCOUS) in the ambulatory and critical care setting has become an invaluable diagnostic tool for patients presenting with traumatic or atraumatic vision and ocular complaints. Sonographic bedside evaluation is intuitive and easy to perform and can accurately diagnose a variety of pathologies. These include detachment or hemorrhage of the retina or vitreous, lens dislocation, retrobulbar hematoma or air, as well as ocular foreign bodies, infections, tumors, and increased optic nerve sheath diameter that can be assessed in the setting of suspected increased intracranial pressure. The ocular anatomy is easy to visualize with sonography, as the eye is a superficial structure filled with fluid. Over the last two decades, a large number of scientific publications have documented that POCOUS in emergent or critical care settings is an accurate diagnostic tool and expands and improves emergency diagnosis and management. This article will review POCOUS exam techniques as well as normal sonographic findings and common pathologies.

An In vitro Study of Guidewire-Related Color Doppler Twinkling Artifacts in Echocardiography

Purpose:

This study sought to determine the association between twinkling artifacts on color Doppler ultrasound and different types of guidewires.

Materials and Methods:

Twenty-two commonly used guidewires were classified into three groups according to decreasing diameter (Group 1, 0.035”; Group 2, 0.018”; and Group 3, 0.014”) and tested in vitro. Severity of twinkling was visually graded into four categories (0–3, from weak to strong).

Results:

The percentages (tips/shafts) of twinkling artifacts were 100%/100% for Group 1; 0%/33.3% for Group 2; and 18.8%/31% for Group 3. The mean scores (tips/shafts) were 2.3/2.7 for Group 1; 0/0.3 for Group 2; and 0.3/0.4 for Group 3. Among them, both two guidewires with strong twinkling artifacts (score = 3) exhibited extensive rough surfaces on microscopic pictures.

Conclusion:

The twinkling artifacts were more likely to present in guidewires with larger diameters (from 0.014” to 0.035”) in our study settings. The surface roughness may be the contribution to the twinkling artifact. Internal heterogeneities, such as types of material, types of coating, tip loading, and spring coil length, do not show influence on the twinkling artifact.

Limitations of Color Doppler Sonography in the Imaging of Ocular Vessels

PURPOSE

To describe a case where detection of blood flow in the central retinal artery and the central retinal vein was limited by an artifact evoked by the optic disc drusen. METHODS Case report.

RESULTS

During color Doppler sonography, examination of optic disc drusen may generate an artifact--the so-called twinkling artifact--which can simulate blood flow and make evaluation of the central retinal vessels impossible.

CONCLUSIONS

Twinkling artifact does not allow evaluation of color Doppler sonography in the imaging of ocular vessels.

Visual field loss in optic disc drusen patients correlates with central retinal artery blood velocity patterns

PURPOSE

(1) To characterize the retrobulbar circulation in patients with optic disc drusen (ODD) using colour Doppler imaging; (2) to explore the differences in retrobulbar hemodynamics in patients with primary open-angle glaucoma (POAG).

METHODS

Retrospective analysis using three diagnostic groups: patients with ODD, age-matched healthy controls and age- and visual defect-matched patients with POAG. Subjects with history of ocular trauma or ocular diseases including vascular-related diseases were excluded. Kruskal-Wallis and Spearman's correlation tests were performed to compare and explore the correlations between the hemodynamic parameters and visual field damage.

RESULTS

Sixty patients were included and equally divided between the three groups. Patients with ODD had lower systolic and diastolic flow velocities in the central retinal artery (CRA) when compared to healthy individuals, but no difference was found with the glaucoma group (p < 0.005 versus healthy; p range 0.30-0.37 versus POAG). The systolic shift in flow patterns correlated with the extent of visual field defect in ODD patients (p < 0.001, r = -0.78, confidence interval: -0.43 to -0.92), but not in POAG (p = 0.73). Short ciliary arteries from ODD patients had lower mean systolic flow velocities when compared to both healthy individuals and patients with POAG (p < 0.01 versus healthy; p ≤ 0.04 versus POAG). The ophthalmic artery in ODD group had significantly higher mean blood velocities than in the POAG (p = 0.04), while showing a significant overlap in Doppler waveform variables to the control group (p range 0.08-0.97).

CONCLUSIONS

Similar to patients with glaucoma, individuals with ODD have low blood flow velocities in the vessels around the optic nerve head. Unlike patients with glaucoma, however, their CRA's blood flow velocity patterns correlate with the extent of the visual field defects.

A novel approach for quantification and analysis of the color Doppler twinkling artifact with application in noninvasive surface roughness characterization: an in vitro phantom study

OBJECTIVES

The twinkling artifact is an undesired phenomenon within color Doppler sonograms that usually appears at the site of internal calcifications. Since the appearance of the twinkling artifact is correlated with the roughness of the calculi, noninvasive roughness estimation of the internal stones may be considered as a potential twinkling artifact application. This article proposes a novel quantitative approach for measurement and analysis of twinkling artifact data for roughness estimation.

METHODS

A phantom was developed with 7 quantified levels of roughness. The Doppler system was initially calibrated by the proposed procedure to facilitate the analysis. A total of 1050 twinkling artifact images were acquired from the phantom, and 32 novel numerical measures were introduced and computed for each image. The measures were then ranked on the basis of roughness quantification ability using different methods. The performance of the proposed twinkling artifact-based surface roughness quantification method was finally investigated for different combinations of features and classifiers.

RESULTS

Eleven features were shown to be the most efficient numerical twinkling artifact measures in roughness characterization. The linear classifier outperformed other methods for twinkling artifact classification. The pixel count measures produced better results among the other categories. The sequential selection method showed higher accuracy than other individual rankings. The best roughness recognition average accuracy of 98.33% was obtained by the first 5 principle components and the linear classifier.

CONCLUSIONS

The proposed twinkling artifact analysis method could recognize the phantom surface roughness with average accuracy of 98.33%. This method may also be applicable for noninvasive calculi characterization in treatment management.

Systematic analysis of factors related to display of the twinkling artifact by a phantom: an optimized investigation

OBJECTIVES

The purpose of this study was to analyze factors related to display of the twinkling artifact by a phantom.

METHODS

An in vitro phantom made of sandpaper was designed to mimic rough physiologic surfaces prone to generating the twinkling artifact. Sandpaper strips embedded in a plastic box were scanned through a water path under different machine settings with only 1 parameter varied each time. After choosing the best settings for displaying the twinkling artifact, 4 types of sandpaper with different roughness were scanned. The resulting images were recorded at random, and the number of color pixels in the color box of each image was calculated by a custom-designed program developed using commercially available software. All data were then evaluated by regression analysis, a paired 2-tailed Student t test, and single-factor analysis of variance.

RESULTS

The highest color write priority and color gain, which were just below the threshold for color noise, a focus depth setting below the sandpaper, a maximum wall filter under a higher pulse repetition frequency, and a color box adjusted properly in the fundamental imaging mode (P < .001) were found to most readily improve the twinkling artifact intensity. The roughness of the sandpaper was shown to be highly correlated with the twinkling artifact intensity (R(2) = 0.832; P < .001).

CONCLUSIONS

The twinkling artifact was influenced by some machine parameters and the roughness of the sandpaper. By adjusting some ultrasound machine parameters, a better image reflecting the twinkling artifact can be shown in clinical practice and research.

Color Doppler twinkling artifact of calcified cardiac valves in vitro: a not well known phenomenon in echocardiography

The color Doppler twinkling artifact manifests as a rapidly changing mixture of red and blue colors behind strongly reflective structures. The twinkling artifact occurs behind diseased cardiac valves, although the phenomenon is not well described. This study sought to determine the presence of the color Doppler twinkling artifact in calcified cardiac valves in vitro using soft tissue radiography for reference. Seventeen specimens of diseased cardiac valves from patients undergoing valve replacement surgery were studied. The overall sensitivity and specificity for the detection of calcifications using the presence of the twinkling artifact were 66.7% and 81.8%, respectively. If valves with only microcalcifications or smooth calcifications were eliminated from the analysis, all (100%) of the three valves with irregular macrocalcifications exhibited the twinkling artifact. It is important to recognize this artifact because it may lead to misdiagnosis of vascular flow in echocardiography.

Color Doppler twinkling artifact in fetuses with echogenic intracardiac foci: echocardiographic observation and clinical significance

OBJECTIVE

To evaluate echocardiographic characteristics and clinical relevance of color Doppler twinkling artifacts in fetuses with isolated echogenic intracardiac foci (EIF).

METHODS

This study included 50 fetuses with EIF, at 18-38 weeks of gestation. Echocardiographic examination, which was performed using a 1.0-5.0-MHz phased array probe, included gray-scale, color and spectral Doppler imaging. Twinkling artifacts were assessed using fetal color Doppler echocardiography on isolated EIF situated in the left and/or right ventricles. The prevalence, appearance and clinical relevance of the color Doppler twinkling artifacts were analyzed.

RESULTS

Eight of 50 fetuses with EIF (16%) showed color Doppler twinkling artifacts, which appeared as a rapidly changing color complex seen persistently behind the EIF. The spectra obtained in all eight with color Doppler artifacts were composed of straight vertical bands occurring in mid to late systole and early diastole. After birth, none of 50 fetuses with EIF had structural heart diseases or showed clinical signs of cardiac failure.

CONCLUSIONS

Color Doppler twinkling artifacts from isolated EIF occur in some fetuses and may be considered as an additional echocardiographic feature of EIF. Attention should be paid to the identification and interpretation of these artifacts so that they may be accurately distinguished from true color flow generated by atrioventricular valvular regurgitation jets.

[Twinkling artifact on Doppler US: clinical presentations]

Twinkling artifact characterized by a rapidly fluctuating mixture of Doppler signals occurs behind a strongly reflecting granular interface such as urinary tract stones or gallstones. It may occurs in association with several clinical situations, and may sometimes be helpful for diagnosis while it may sometimes be a pitfall that must be recognized by the sonographer. After reviewing the technical nature of this artifact, several cases will be presented to illustrate the advantages and pitfalls related to this artifact.

Color Doppler twinkling artifact in intrauterine fetal demise

PURPOSE

To determine whether twinkling artifacts on color and power Doppler sonography could be used as a new sonographic sign of intrauterine fetal demise (IUFD).

METHODS

In this prospective study, 24 consecutive pregnant women with IUFD were included after fetal sonographic examinations. Sonographic examination included gray-scale, color, power, and spectral Doppler imaging. The sonograms were then analyzed for the presence, appearance, and intensity of the twinkling artifacts.

RESULTS

Twinkling artifacts on color Doppler were observed in all of the 24 IUFD as a rapidly changing color Doppler signal complex associated persistently with different parts of the fetal body. The artifacts were localized especially in the neck, back, and iliac regions. Artifact intensity correlated with the time elapsed since death.

CONCLUSION

Twinkling artifact was noted in all dead fetuses on color, power, and spectral Doppler examinations. Thus, the observation of these artifacts may be considered as a new sonographic sign of fetal demise, which may reflect the time elapsed since death.

Diagnostic value of colour Doppler twinkling artefact in sites negative for stones on B mode renal sonography

The aim of the study was to investigate the diagnostic value of the colour Doppler twinkling artefact (TA) in renal stone disease. To enhance the evidence of TA, a preliminary in vitro study was performed to optimise the setting of colour Doppler sonography. In the in vitro study, an oxen kidney was examined using an high-frequency (12.5 MHz) linear array probe in a water bath before and after the inoculation of an aliquot of powder obtained by fragmentation of a calcium oxalate stone. In the clinical study, 67 patients with diagnosis of urinary stone based on B-mode sonography and 67 matched control subjects were examined with colour Doppler sonography using a low-frequency (2.5 MHz) curvilinear phased array probe. In vitro, the injection of calcium oxalate powder in a bovine kidney sample induced the appearance of spots without any back shadowing appearance on B mode but with a large number of TA on colour Doppler. In vivo, TA was much more frequent in patients with stone disease (95.5%) compared to controls (9.0%) (P < 0.001). TA was highly associated to renal stone disease and was also present in renal areas where a stone was undetected with B mode approach suggesting its diagnostic role although further studies are needed to confirm its accuracy. The type of instrumentation and its setting is crucial to obtain reproducible results.

TWINKLING ARTIFACT IN SMALL ANIMAL COLOR-DOPPLER SONOGRAPHY

Twinkling artifact is a recently described color-Doppler phenomenon that has not been studied in the veterinary field. Our purpose was to assess the grade of the artifact in vitro with varying urolith compositions, and to evaluate its potential role in clinical practice. Five canine and feline uroliths types of 100% mineral composition were studied in vitro with color-Doppler sonography, and a prospective study was performed in 41 patients with renal, bladder, gallbladder, or digestive focal hyperechogenicities. The images were analyzed for the presence and the grade of the artifact. Phantom study demonstrated the constant occurrence of the artifact regardless of the mineral composition of uroliths. Mottled and rough surfaced stones produced higher grades of twinkling artifact. High-grade, color-twinkling artifact generated by stones occured frequently in vivo. Bladder crystalluria was more frequently detected by artifact visualization than sample urinalysis performed by cystocentesis. In veterinary medicine, twinkling artifact may thus be considered an additional sonographic feature of urinary stones, and can lead to a more appropriate management of patients presenting gray-scale sonographic focal hyperechogenicities.

Color Doppler twinkling artifact in a calcified liver mass

Twinkling artifact in color Doppler imaging is related both to the presence of a strongly reflective structure and to the scanner's settings. This artifact has been described in association with calculi and various foreign bodies, but to our knowledge it has not been reported in a hepatic mass. If a calcified hepatic mass is examined with color Doppler Mapping without using spectral Doppler analysis, misinterpreted as real blood flow and lead to the erroneous of hypervascular mass.

Use of twinkling artifact in sonographic detection of intestinal pneumatosis

Intestinal pneumatosis is a relatively rare condition that has been associated with a wide variety of abnormalities. Traditionally, this entity has been diagnosed by radiographic films, contrast series, or more accurately by computed tomography. However, reports describing findings of intestinal pneumatosis on sonographic examination, which is an important initial diagnostic tool for abdominal diseases, are limited. We suggest that twinkling artifact may be of value in the sonographic diagnosis of this condition. We report two cases of intestinal pneumatosis that were diagnosed initially by sonography with the aid of twinkling artifact.

Differentiation of cavernous hemangioma from schwannoma of the orbit: a dynamic MRI study

OBJECTIVE

The purpose of this study was to determine the capability of dynamic contrast MRI to differentiate hemangioma from schwannoma of the orbit.

MATERIALS AND METHODS

Sixteen patients (three males and 13 females; mean age, 39 +/- 17.3 [SD] years; age range, 10-71 years) with unilateral orbital tumors, including eight cavernous hemangiomas and eight schwannomas, were examined. In addition to conventional MRI, we performed a dynamic contrast study (fast spin-echo sequence, 20-sec interval) after bolus administration of the contrast material (gadopentetate dimeglumine, 0.1 mmol/kg). We evaluated the features of the contrast enhancement spread pattern and the tumors' time-intensity curves.

RESULTS

In the early phase, all the hemangiomas started the enhancement from one point or portion, although all the schwannomas started the enhancement from a wide area. The difference in the contrast-enhancement spread pattern features between the two types of tumors was statistically significant (p < 0.0001). The gradient of the time-intensity curve did not show a significant difference.

CONCLUSION

Hemangioma and schwannoma of the orbit can be differentiated by the contrast-enhancement spread pattern on dynamic MRI.