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Twinkling Artifact on Color Doppler Sonography: Dependence on Machine Parameters and Underlying Cause

Aya Kamaya1, Theresa Tuthill and Jonathan M. Rubin

1 All authors: Department of Radiology, University of Michigan Hospitals, 1500 E. Medical Center Dr., Ann Arbor, MI 48109-0030.



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  		Fig. 1. —Photograph shows that stone is embedded in adhesive material at bottom of basin that was scanned with linear array probe securely attached to ring clamp.

 


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  		Fig. 2. —Color Doppler sonogram shows stone with varying color-write priority (+8, 0, -8, from left to right) at maximal Doppler gain. Note as color-write priority decreases, amount of twinkling artifact decreases behind stone.

 


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  		Fig. 3. —Graph shows number of color pixels as function of gray-scale gain at color-write priority of -8 and pulse repetition frequency of 700 Hz. Regression line through data is bracketed by 95% confidence limit curves (vertical dashes) above and below regression line (dark dashes). Regression equation is y = -59x + 3100. Data points are represented as plus signs. Error bars around data points represent SDs.

 


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  		Fig. 4. —Spectral Doppler sonogram of a stone at pulse repetition frequency of 8333 Hz and Doppler gain of 65%. Spectrum shows broadband signal that is apparently aliasing. Note image of stone in water bath with sample placed over surface above spectrum.

 


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  		Fig. 5. —Doppler spectrum of flat surface at pulse repetition frequency of 1250 Hz and Doppler gain of 59%. Note spectral bandwidth is narrow compared with stone and wire meshes in Figure 8.

 


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  		Fig. 6. —Graph shows regression line through mean absolute Doppler spectral values as function of pulse repetition frequency for flat surface at Doppler gain of 65% over pulse repetition frequency range of 1250-10,000 Hz. Ninety-five percent confidence interval curves around regression line are so closely applied as to be invisible because of large amount of data collected for each point. Each point represents mean absolute frequency at corresponding pulse repetition frequency. Mean values are represented by plus sign, and error bars represent SDs. Regression equation is y = 0.0018x+0.075.

 


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  		Fig. 7. —Color Doppler sonogram of wire mesh (mesh 40, wire 0.010 inch) fixed to metal plate. Note twinkling artifact behind wire mesh (short arrow). Also note artifact (long arrow) behind wire mesh due to reverberations behind metal support.

 


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  		Fig. 8. —Spectral Doppler sonogram of two wire meshes (mesh 40 and mesh 60) lying on top of each other acquired at pulse repetition frequency of 2500 Hz and Doppler gain of 65%. Image shows broadband signal on top of more intense narrow-band signal surrounding baseline because of underlying flat surface.

 


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  		Fig. 9. —Graph shows regression lines through most broadened spectra from stone ({square}), 40 and 60 wire meshes attached to each other ({circ}), and flat surface (+). Each symbol represents mean absolute spectral frequency above or below baseline at each pulse repetition frequency at Doppler gain of 65% for given structure. Error bars correspond to SDs. Different slopes of regression lines reflect different levels of spectral broadening as function of roughness. This clearly shows that stone had most broadening. Dot—dashes represent regression line for stone, dots alone represent regresion line for 40 + 60 mesh pair, and solid line represents regression line for flat surface.

 


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  		Fig. 10. —Schematic of phase (or clock) jitter causing twinkling artifact. Two arrows from same source are slightly angularly displaced because of phase jitter. However, sonography machine thinks they are along identical paths. {triangleup}L is difference in path length. If path from transducer to rough surface varies one-half wavelength between firings, reflected signals would appear as aliased motion in spectral Doppler mode.

 

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