Calculation of Haemorheological
Properties for Cardiovascular Diagnosis based on Ultra Sound
Measurements of Velocity Profiles
M. Alizadeh, G. Benderoth, S. Kasseckert, M. Rzepka, M. Stanull, S.
Vogt, R. Moosdorf, G. Silber
Background: Vessel diseases like
atherosclerosis and thromboembolies go along with changes of blood
flow. To diagnose such diseases only the volume rate (perfusion) at
particular vessels is used at the moment. But even this diagnostic
method is conducted by a possible error margin of up to 100% because
the calculation of the flow rate is based on the assumption of blood
being an ideal fluid. Moreover for a more advanced diagnosis such
values like the shear rate and the shear stress are necessary which
can’t be derived from the flow rate.
Methods: Velocity profiles of steady and pulsatile blood flows
are measured by colour flow imaging at a circulation circuit with a
specially developed device for reproducible in vitro-measurements. The
resulting velocity field data are analysed with different constitutive
models (newtonian, casson, power law, gradient fluid) by determining
the model parameters with non linear optimisation algorithms. Finally
the values of the volume rate, the shear stress and the shear rate are
determined for each model by using the obtained parameter sets.
Results and Conclusion: It can be shown that with parameter
sets derived from colour flow mapping for established constitutive
models of non newtonian fluids a good accordance of the calculated and
measured values of the volume rate and with an additionally determined
pressure gradient even for the shear rate and stress can be obtained.
This is valide for steady and pulsatile blood flow as well. So a
possible method for determining rheological properties in vascular
diagnosis can be generated and be used for vascular diagnosis in
clinical routine and in mobile acute medicine as well without
additional effort.
(CVE. 2005; 10 (1): 81-93)
Key words: colour flow imaging, non-newtonian
models, volume rate, shear rate, shear stress
Prof. Gerhard Silber, M.D.
Institute for Material Science
University of Applied Sciences
Nibelungenplatz 1
60318 Frankfurt a.M.
Germany
E-mail: silber@fb2.fh-frankfurt.de
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