KEYWORDS: Turbulence, Independent component analysis, Data modeling, Statistical modeling, Simulation of CCA and DLA aggregates, Doppler effect, Ultrasonography, In vitro testing, Arteries, Modeling
An in vitro flow system has been used to assess the flow disturbances downstream of the stenosis in a family of seven
carotid bifurcation phantoms modelling varying plaque build-up both axially symmetrically (concentrically) and
asymmetrically (eccentrically). Radio frequency data were collected for 10 s at each of over 1000 sites within each
model, and a sliding 1024-point FFT is applied to the data to extract the Doppler spectrum every 12 ms. From this, the
ensemble average over 10 cardiac cycles of the spectral mean velocity, and the root mean square over these same 10
cardiac cycles - the turbulence intensity (TI), can be obtained as a function of an ensemble averaged cardiac cycle at
each spatial point in all phantoms. TI was investigated by looking at the average over a 25 mm2 square region of interest
in the ICA centered 2 cm distal to the apex of the bifurcation.
TI in the region of interest increased with stenosis severity; at 23ms following peak systole, the time point when TI was
maximal for the majority of models, this ranged from 2.4±0.1 cm/s in the non-diseased model to 6.6±0.3, 16.0±1.4 and
26.1±1.3 cm/s in the 30, 50 and 70% concentrically stenosed (by NASCET criteria) models, respectively. Similarly, TI
was 8.3±0.7, 19.9±1.1, and 26.2±1.2 cm/s in the 30, 50 and 70% eccentrically stenosed models, respectively. Differences
in TI between models, both in increasing stenosis severity and between eccentricities, were statistically different except
between the 70% concentric and eccentric models.
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