title: Factors influencing the renal arterial Doppler waveform: a simulation study using an electrical circuit model (secondary publication).
abstract: OBJECTIVE
  The goal of this study was to evaluate the effect of vascular compliance, resistance, and pulse rate on the resistive index (RI) by using an electrical circuit model to simulate renal blood flow.
  
  
  METHODS
  In order to analyze the renal arterial Doppler waveform, we modeled the renal blood-flow circuit with an equivalent simple electrical circuit containing resistance, inductance, and capacitance. The relationships among the impedance, resistance, and compliance of the circuit were derived from well-known equations, including Kirchhoff's current law for alternating current circuits. Simulated velocity-time profiles for pulsatile flow were generated using Mathematica (Wolfram Research) and the influence of resistance, compliance, and pulse rate on waveforms and the RI was evaluated.
  
  
  RESULTS
  Resistance and compliance were found to alter the waveforms independently. The impedance of the circuit increased with increasing proximal compliance, proximal resistance, and distal resistance. The impedance decreased with increasing distal compliance. The RI of the circuit decreased with increasing proximal compliance and resistance. The RI increased with increasing distal compliance and resistance. No positive correlation between impedance and the RI was found. Pulse rate was found to be an extrinsic factor that also influenced the RI.
  
  
  CONCLUSIONS
  This simulation study using an electrical circuit model led to a better understanding of the renal arterial Doppler waveform and the RI, which may be useful for interpreting Doppler findings in various clinical settings.
authors.affiliation: Department of Radiology, SMG-SNU Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Chang Kyu
authors.identifier: 0000-0003-4922-5107
authors.initials: CK
authors.lastname: Sung
authors.affiliation: Department of Radiological Science, College of Health Science, Yonsei University, Wonju, Korea.
authors.forename: Bong Soo
authors.identifier: 0000-0001-6614-7185
authors.initials: BS
authors.lastname: Han
authors.affiliation: Department of Radiology, Institute of Radiation Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Seung Hyup
authors.identifier: 0000-0002-9339-5907
authors.initials: SH
authors.lastname: Kim
keywords: Computer simulation; Renal artery; Ultrasonography, Doppler