Presentation
Screening abdominal ultrasound.
Patient Data
In the upper third of the right kidney a fluid filled cyst is visible, showing focal wall calcification. Behind the calcification a colour comet tail or twinkling artifact is visible.
From the parameters of the colour Doppler imaging note the relatively low (1 kHz) pulse repetition frequency (PRF), and that the focus is positioned slightly below the level of the calcification.
The twinkling artifact is best appreciated on the cine loop.
Case Discussion
The twinkling artifact is capricious at best, often not seen even behind stones and calcifications that are obvious using conventional B-mode ultrasound. This is no small part because, optimal parameters for detecting it remain controversial, some authors arguing for high PRF 1 while other studies demonstrating the benefits of low PRF 2. The importance of the appropriate positioning of the focus (at least at the level or slightly below the lesion) is however generally agreed upon. The twinkling artifact is a finicky beast and the parameters required to facilitate it depend largely on the manufacturer and the type of transducer. Factory presets are usually not optimal for visualising it, thus, for a new device it is best to figure out for ourselves the optimal PRF and colour Doppler gain that make it stand out more.
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