Etiology of the color Doppler ultrasound twinkling artifact on in situ human kidney stones

Abstract

Hyperbaric pressures of 0.3–10 MPa (absolute) have been shown to reduce the magnitude of the color Doppler ultrasound twinkling artifact on ex vivo human kidney stones, supporting the hypothesis that surface crevice microbubbles cause twinkling. For the first time, we investigate the etiology of twinkling on in situ human kidney stones. Eight human subjects with kidney stones known to twinkle were imaged with a Philips/ATL P4-2 transducer and Verasonics ultrasound system for 45 minutes while inside a hyperbaric chamber. Subjects breathed ambient air while the pressure in the chamber cycled to a maximum pressure of 0.4 MPa, with a scheduled decompression stop at 0.16 MPa where subjects breathed pure oxygen. Preliminary results show no change in the twinkling amplitude at 0.4 MPa compared to the baseline measurements before pressurization; however, a statistically significant increase in the twinkling amplitude was observed when subjects breathed pure oxygen at 0.16 MPa (p = 0.046). The increase in the twinkling amplitude upon changing respiratory gas composition further supports the crevice microbubble hypothesis of twinkling. Higher pressures than explored in this study may be needed to reduce twinkling on in situ human kidney stones. [Work supported by the National Space Biomedical Research Institute through NASA NCC 9-58 and NIH grant DK043881.]