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.

Date Published: 25 March 2011
PDF: 7 pages
Proc. SPIE 7968, Medical Imaging 2011: Ultrasonic Imaging, Tomography, and Therapy, 796810 (25 March 2011); doi: 10.1117/12.878775

Published in SPIE Proceedings Vol. 7968:
Medical Imaging 2011: Ultrasonic Imaging, Tomography, and Therapy
Jan D'hooge; Marvin M. Doyley, Editor(s)