Real-Time Contrast-Free Ultrasonic Blood Flow
Velocity Profile Measurement
G.G. Koutsouridis, N. Bijnens, P.J. Brands, F.N. van de Vosse and M.C.M. Rutten
Problem Description1. Ultrasonic Perpendicular Velocimetry Wall
Doppler Ultrasound UPVFigure 1 Current ultrasound research system with real-time GPU module design for the UPV method
1. Ultrasonic Perpendicular Velocimetry
(UPV) to RF-data for accurate
velocity and flow assessment is time
consuming due to data size and post
processing [1,2].
WallUltrasound beam Ultrasound beam
Centerline
processing [1,2].
2. Fast Fourier Transform (FFT) on
Butterworth Band Pass Filters (BPF)
for vessel’s wall removal requires
contrast agents dispersion in the fluid
for the application of Cross-
correlation.
Aim In-vitro (aortic-like polyurethane vessel) with Blood Mimicking Fluid (BMF), resembling the
Methods
AimReal-time UPV on Graphics
Processing Unit (GPU) [3].
In-vitro (aortic-like polyurethane vessel) with Blood Mimicking Fluid (BMF), resembling the
rheological (shear thinning) & acoustical (backscattering) Blood’s properties, as contrast agent.
Ex-vivo (porcine carotid arteries) with BMF & contrast-free real Blood, implementing Wavelet
Transform (WT) filtering.
ResultsMethods• In-vitro and Ex-vivo constant and physiological pulsating
flows of 1Hz and peak flow velocity 0.8m/sec.
• Ultrasound RF-data acquired at 33MHz (Fast B-mode)
� 6 seconds of images, at 730frames/sec.
ResultsAcceleration offered by the UPV method for the real-time
(Figure 3.[#]) perpendicular assessment of the velocity profiles.
� 6 seconds of images, at 730frames/sec.
For the UPV technique, the process consisted, among
others (Figure 1), of the following steps:
� Wall removal and contrast-free fluid scattering
enhancement via WT Daubechies8 filtering (localization
3.[1] 3.[2]
enhancement via WT Daubechies8 filtering (localization
in time & frequency) for functions with discontinuities and
sharp peaks (Figure 2).
� High Pass Filtering (HPF) of the sequential frames in the
time direction.
(i) (ii) (iii) (i) (ii) (iii)In-vitro constant flow BMF In-vitro pulsating flow BMF
� Application of improved Cross-correlation for the
assessment of velocity profiles.
3.[3]0.7
0.6
0.7
0.6
(i) (ii) (iii) Ex-vivo pulsating flow Blood 0.4
0.5
0.6
0
0.2
0.4
0.6
va
x(m
/s)
0.4
0.5
0.6
0
0.2
0.4
0.6
va
x(m
/s)
Figure 3.[#] Real-time GPU velocity profile (▪) assessment with: (i) No filtering, (ii) WT and (iii) WT & HPF
0.2
0.3
0.4
v(m
/s) -5 0 5
x 10-3r(m)
0.04
0.06
v (
m/s
)
0.2
0.3
0.4
v(m
/s) -5 0 5
x 10-3
r(m)
0.04
0.06
v (
m/s
)
ConclusionThe WT filtering technique allows measurement of Blood flow
without contrast agents, while the GPU allows a real-time
-5 0 5-0.1
0
0.1
-5 0 50
0.02
0.04
∆ v
(m
/s)
-5 0 5-3
-0.1
0
0.1
r(m)
-5 0 5-3
0
0.02
0.04
∆ v
(m
/s)
without contrast agents, while the GPU allows a real-time
assessment of axial velocity distribution. With a real-time
implementation of the local ultrasound pressure estimation,
real-time characteristic vascular impedance assessment, as a
diagnostic tool, will be feasible even In-vivo.
Figure 2 The effect of WT Daub8 (right) vs BPF (left) on the quality of thevelocity profiles assessed by UPV. Left panels show estimates fromindividual frames, while top and bottom indicate mean values andstandard deviations
-5 0 5
x 10-3r(m)
-5 0 5
x 10-3r(m)x 10
-3r(m) x 10
-3
r(m)diagnostic tool, will be feasible even In-vivo.References[1] Beulen, B.W.A.M.M. et al. (2010), “Perpendicular ultrasound velocity measurement by 2D cross correlation of RF data. Part A:
validation in a straight tube”, Exp Fluids, 49, pp. 1177-1186.
[2] Beulen, B.W.A.M.M. et al. (2011), “Toward noninvasive blood pressure assessment in arteries by using ultrasound”, Ultrasound in
Med. & Biol., 37:5, pp. 788-797.
[3] Owens, J.D. et al. (2008), “GPU Computing: Graphics Processing Units–powerful, programmable and highly parallel–are
increasingly targeting general-purpose computing applications”, Proceeding of the IEEE, 96:5, pp. 879-899.
/ Department of Biomedical Engineering