Kidney stone twinkling power in elevated oxygen, carbon dioxide, and nitrogen environments

Abstract

Clinically, ∼66% of kidney stones exhibit the Doppler ultrasound twinkling artifact. Previous studies show breathing pure oxygen at elevated pressures increases twinkling compared to ambient air. Here, we investigate how different gases influence twinkling on ex vivo and in vivo human kidney stones. 38 kidney stones were imaged with a research ultrasound system and ATL L7-4 transducer in elevated oxygen, carbon dioxide, and nitrogen environments. In vivo stones were imaged with the same ultrasound system and ATL C5-2 transducer in 25 human subjects before and after breathing pure oxygen for 15 min. IQ data were processed by calculating the average Doppler power, or twinkling, for a region of interest containing the stone. In the lab, increasing oxygen by 55%, carbon dioxide by 100%, and nitrogen by 17% increased twinkling power an average of 70 ± 28%, 137 ± 53%, and 79 ± 31%, respectively. In human subjects, breathing oxygen increased twinkling power an average of 27 ± 58%, with seven subjects showing a strong increase (>30%); stone composition and patient age influenced twinkling in patients breathing oxygen. These results suggest that varying ambient gases may be leveraged to increase the consistency of twinkling and improve kidney stone detection with ultrasound. [Work supported by the PSU Center for Biodevices.]