Key result
Baseline TCD waveforms show greater reproducibility than during interventions, led by the Resistance Index.
Why the study?
Advances in transcranial Doppler (TCD) could improve interpretation of cerebral blood flow hemodynamics, but repeatability and reproducibility of new waveform parameters need evaluation.
Observational (n=5)
A novel TCD waveform analysis method demonstrates reliable reproducibility for specific parameters like Resistance Index, potentially aiding in the interpretation of complex cerebral hemodynamics.
Introduction and Objective Doppler ultrasound is used in nearly every medical discipline for the evaluation of blood flow. The cerebral circulation is of particular interest, but is difficult to interpret because of the complex hemodynamics of the brain's blood flow. However, advances in the field of transcranial Doppler (TCD) could have important clinical and cost-saving benefits. We describe the testing of a novel method for acquiring and analyzing TCD flow velocity waveforms, in conjunction with other physiologic data. We also evaluate the repeatability and reproducibility of the technique. Methods We used custom-designed waveform analysis software to calculate 16 new waveform shape parameters and indices. We present the repeatability and reproducibility results for the new waveform shape parameters, as well as traditional TCD measurements, during repeated vasomotor reactivity studies on five healthy subjects. A ranked score ( mean value of test 1 and 2/coefficient of repeatability) is used to evaluate each parameter. The scores are presented by category: Traditional TCD Measurements, Velocity Minima, Velocity Maxima, Acceleration/Deceleration, Miscellaneous measures (e.g. blood pressure, heart rate), Time Measurements, and Shape Indices. Higher scores indicate better reproducibility. Results The mean scores of all parameters for each testing segment were Baseline 4.60, Hypercapnia 4.34, and Hypocapnia 4.00; showing that Baseline measurements are more easily reproduced than measurements during an intervention, particularly Hypocapnia. Individual parameters with the best reproducibility over all three testing segments are: RI (Resistance Index) 19.02; Mean Resistance ( mean blood pressure/mean velocity) 10.64; Umin (end-diastolic velocity) 9.84; Umaxdias (velocity rise immediately after aortic valve closure) 9.83; and DuDtmax (systolic acceleration) 8.54. We discuss why some parameters are more reliable than others in TCD studies and how the cyclical variations in the cerebral circulation can affect reproducibility. Conclusions This new methodology allows for discrete measurements of Doppler waveforms and would have the ability to track subtle changes during physiological or pharmacological interventions. These advances may aid the interpretation of complex cerebral hemodynamics, and increase the utility of this non-invasive, low-cost technique.
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Byrd-Raynor et al. (2007) conducted an observational in Healthy subjects (n=5). Novel method for acquiring and analyzing TCD flow velocity waveforms vs. Traditional TCD measurements was evaluated on Repeatability and reproducibility ranked score (mean value of test 1 and 2/coefficient of repeatability). Baseline TCD waveform measurements were more easily reproduced than during interventions, with Resistance Index showing the best reproducibility (score 19.02).
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