Color and spectral Doppler modes were used. Pulse repetition frequency, color-write priority, gray-scale gain, and spectral Doppler gain were varied. Struvite (ammonium magnesium phosphate) stone fragments, wire mesh, and a flat surface were scanned in a water bath with a sonography scanner using a high-frequency linear array probe fixed in a ring clamp. The objective of our study was to evaluate the color Doppler sonographic effect known as twinkling artifact. The presence of TA should be weighed in the setting of other clinical and radiographic evidence of nephrolithiasis. This may be related to renal location and smaller stone size. Sensitivity, specificity, positive predictive value and negative predictive value of TA for detecting nephrolithiasis were 83%, 78%, 74% and 86% respectively.Ĭompared to the adult literature, TA in children has lower sensitivity, specificity and positive predictive value, but similar negative predictive value for diagnosing nephrolithiasis. The majority of confirmed stones were in the kidney (n=40 82%) and mean size of confirmed stones on ultrasound was 5 mm (range 1.5-10). Nephrolithiasis was diagnosed using TA and confirmed on confirmatory studies for 49 ultrasounds. 135 patients had confirmatory information available (Table 1). Sixty-nine had diffuse twinkle without echogenic focus and 224 showed TA with single echogenic focus. Stone was confirmed either by CT within 3 months of color Doppler ultrasound, visualization on ureteroscopy, or patient report of passing the stone.įive hundred and ninety-nine ultrasound reports were reviewed and 293 met inclusion criteria. Exclusion criteria were age >18, multiple echogenic foci or medullary calcinosis, no follow-up, or TA located outside the kidney or ureter. We reviewed renal ultrasound reports indicating presence or absence of TA associated with a single echogenic focus in the kidney or ureter. We sought to evaluate if TA is reliable for diagnosing nephrolithiasis in the pediatric population. TA has been shown to be highly predictive of nephrolithiasis in adults with renal colic and ureteral stones. Nephrolithiasis is detected on ultrasound by the presence of an echogenic focus, posterior acoustic shadowing and/or twinkle artifact (TA). Qualitatively, lower color scales and color frequencies optimized twinkling, but the most specific qualitative predictor of confidence in twinkling was insensitivity to changes in color scale and color frequency values. Of the 12 markers tested, the markers that twinkled corresponded to surface roughness measured with non-contact 3-D optical imaging. Surface roughness metrics demonstrated a positive estimated correlation with the twinkling scores (rho = 0.33, 95% CI = ). Of these 3 markers, only the cork marker scored a 4 ex vivo and in cadaveric tissue. The 3 markers scoring at least 3 for twinkling in vitro were cork, Q and Vision. The surface roughness characteristics of the markers were measured using 3-D coherence scanning interferometry. Ultrasound color Doppler imaging of 12 biopsy markers was performed and consensus scoring of the degree of twinkling (0 to 4 ) was obtained for each of the markers. The purpose of this research was to test the hypothesis that the surface roughness of biopsy clips would elicit a twinkling signature on color Doppler, making them more readily identifiable by ultrasound. In breast radiology, ultrasound detection of biopsy markers or clips for localization purposes is often challenging, especially in the axilla.

1Twinkle artifact in nephrolithiasis: sagittal images of the left kidney, both gray-scale (left) and color Doppler (r. For example, occult renal calculi obscured by echogenic renal sinus fat can be revealed by their telltale twinkle sign (Fig. Because of its usefulness in detecting pathology, the “twinkle” has graduated from artifact to imaging sign. Another ascribes it to slight time fluctuations in transmitted and reflected waves, amplified by the irregular strongly reflective interface. One theory attributes the artifact to splitting of the acoustic wave by the rough-surfaced reflector. The greater the surface roughness, the greater the “twinkle”. It is most often observed when the acoustic beam encounters a rough surface with crevices. The twinkling or color comet tail artifact appears on Doppler ultrasound (US) scans as a rapidly shifting mixture of red and blue deep to a strongly reflective stationary structure, creating the false impression of movement.

Comet tail artifact