Real-time measurement of renal blood flow in healthy subjects using contrast-enhanced ultrasound

Abstract

Current methods for measuring renal blood flow (RBF) are time consuming and not widely available. Contrast-enhanced ultrasound (CEU) is a safe and noninvasive imaging technique suitable for assessment of tissue blood flow, which has been used clinically to assess myocardial blood flow. We tested the utility of CEU in monitoring changes in RBF in healthy volunteers. We utilized CEU to monitor the expected increase in RBF following a high protein meal in healthy adults. Renal cortical perfusion was assessed by CEU using low mechanical index (MI) power modulation Angio during continuous infusions of Definity. Following destruction of tissue microbubbles using ultrasound at a MI of 1.0, the rate of tissue replenishment with microbubbles and the plateau acoustic intensity (AI) were used to estimate the RBF velocity and cortical blood volume, respectively. Healthy adults (n = 19, mean age 26.6 yr) were enrolled. The A.beta parameter of CEU, representing mean RBF increased by 42.8%from a baseline of 17.05 +/- 6.23 to 23.60 +/- 6.76 dB/s 2 h after the ingestion of the high-protein meal (P = 0.002). Similarly, there was a 37.3%increase in the beta parameter, representing the geometric mean of blood velocity after the high protein meal (P < 0.001). The change in cortical blood volume was not significant (P = 0.89). Infusion time of Definity was 6.3 +/- 2.0 min. The ultrasound contrast agent was tolerated well with no serious adverse events. CEU is a fast, noninvasive, and practical imaging technique that may be useful for monitoring renal blood velocity, volume, and flow.

Effects of high-fat diet and losartan on renal cortical blood flow using contrast ultrasound imaging

“…Previous studies have extracted quantitative parameters relating to blood volume and velocity based on curve fitting of time-intensity data. The most common analysis utilizes a shifted exponential function (26,31,57,67,68). This method relies upon the a priori assumption that the time-intensity curve follows the mathematical model used, an assumption about which there is some disagreement in the field (2,18,32,36,42).…”

Contrast-enhanced ultrasound: A promising method for renal microvascular perfusion evaluation

“…Against this backdrop, CEUS offers a novel approach for RBF evaluation, without the abovementioned concerns, as it appears to be fast, noninvasive, and safe. Observations in healthy volunteers reveal that CEUS-ascertained parameters exhibit good correlation with findings obtained using PAH [31] . CEUS has also been used to evaluate renal microvascular perfusion following the administration of vasoactive drugs.…”

Doppler ultrasound measurements of renal functional reserve in healthy subjects

“…Kalantarinia et al [25] utilized contrast-enhanced ultrasound (CEUS) to monitor the expected increase in renal blood flow following a high protein meal in healthy adults. CEUS is a suitable imaging technique for the assessment of renal blood flow, but the disadvantage of this technique is to inject intravenously ultrasound-contrast agents (gas-filled microbubbles) to enhance the ultrasound image.…”