Experiments were undertaken in our laboratory to establish relationships between flow parameters calculated from implanted ultrasonic cuff signals and those obtained with a transcutaneous probe. Analog signals were received from crystals surgically implanted on the right carotid, right femoral, and abdominal aorta of a mature male beagle dog. Near these locations, transcutaneous measurements were made using a prescribed technique. From these ultrasonic signals, the following time dependent flow parameters were calculated: spatial velocities, velocity profiles, diameters, flows, and velocity frequency distributions. Using these measurements, a comparison between the implanted cuff and transcutaneous probe was made. In addition to high reproductibility, results confirm a strong correlation between the two techniques; consequently, the validity of the less traumatic transcutaneous method is substantiated.

Animals↗

PubMed1975

Ultrasonic blood flow measurements: transcutaneous compared with implanted cuff.

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Anesthesia, General↗

PubMedDate not supplied

Noninvasive Doppler assessment of renal artery stenosis and hemodynamics.

We present a review of ultrasonic Doppler methods (duplex scanning) used in the noninvasive assessment of renal artery stenosis and hemodynamics. The clinically successful applications of ultrasonic Doppler methods to the noninvasive assessment of the peripheral and cerebral vasculatures have prompted investigators to apply these methods to the renal artery. Various Doppler criteria for the diagnosis of renal artery stenosis have given sensitivities and specificities that range from 31% to 91% and 88% to 100%, respectively. Furthermore, estimates of renal vascular flows and resistances can be made in echogenic subjects. The technical success rate of the method is operator dependent, consequently, reliable duplex scanning of the renal arteries may be limited to experienced ultrasound laboratories.

Blood Flow Velocity↗

PubMedDate not supplied

A comparison of digital and analog methods of Doppler spectral analysis for quantifying flow.

Ultrasonic methods can be used for calculating flow when the mean Doppler frequency is representative of spatial average velocity. We have examined the capabilities of two commercially available methods of Doppler spectral analysis for providing measurements of spatial average velocity and flow. In a steady state flow model, Doppler audio spectra were recorded using a 5-MHz duplex scanner. Fast Fourier transform (FFT) spectral analysis was used to determine mean (M), mode (MO), and maximum (MAX) frequencies. An analog method (offset zero crossing detector = ZC) was used to determine root mean square (RMS) frequencies. The results of comparing Doppler flow estimates (QM, QMO, QMAX and QRMS) with direct flow measurements (n = 10; range = 128-1098 ml/min) were (1) QM = 0.67Q + 23 ml/min (SEE = 36 ml/min); (2) QMO = 0.96Q + 152 ml/min (SEE = 32 ml/min); (3) QMAX = 1.19Q + 171 ml/min (SEE = 23 ml/min); and (4) QRMS = 0.93Q + 76ml/min (SEE = 92 ml/min). Estimates of flow using M and RMS frequencies were adversely affected by experimental conditions likely to result in turbulence. We conclude that application of commercially available FFT determined M frequencies could result in significant errors in calculations of spatial average velocity and flow. Alternatively, FFT determined MO frequencies and ZC determined RMS frequencies resulted in accurate estimates of flow in this model. This study demonstrates the importance of evaluating the capabilities of commercially available methods of Doppler spectral analysis when using ultrasound for determining velocity and flow.

Blood Flow Velocity↗

PubMedDate not supplied