The intensity reflection coefficient: a complementary method for investigating blood backscattering properties with...

Area of Science:

• Biomedical Engineering
• Ultrasound Imaging
• Biophysics

Background:

• Parametric imaging of backscatter indices is crucial for ultrasound (US) tissue characterization.
• Red blood cell (RBC) aggregation significantly impacts blood flow properties and US signal characteristics.

Purpose of the Study:

• To introduce and evaluate the US intensity reflection coefficient (IRC) for characterizing porcine blood in a Couette shear flow system.
• To investigate the US properties of RBCs at different shear rates and hematocrits.
• To compare IRC with integrated backscatter power (IBP) and analyze their frequency dependence.

Main Methods:

• Characterization of porcine blood using a Couette shear flow system.
• Measurement of IRC and IBP at shear rates of 5 s⁻¹ and 500 s⁻¹ for hematocrits from 0% to 54%.
• Analysis of spectral slopes for IRC and IBP in the 8-12 MHz frequency range.

Main Results:

• IRC demonstrated a mirrored relationship with IBP, with similar spectral slope behaviors.
• At 500 s⁻¹ (disaggregation), IRC showed a bi-modal variation with a minimum at 23% hematocrit.
• At 5 s⁻¹ (aggregation), the IRC minimum shifted to 13-17% hematocrit, and IBP showed a plateau after 13% hematocrit.
• Transition from low to high shear rate decreased both IRC and IBP levels.
• Spectral slopes indicated Rayleigh scattering for IBP at 500 s⁻¹ and shifted towards lower values at 5 s⁻¹ beyond 13% hematocrit.

Conclusions:

• The intensity reflection coefficient (IRC) shows significant potential for investigating RBC aggregation phenomena.
• IRC offers an advantage due to its straightforward computation compared to other backscatter indices.
• This study highlights IRC as a valuable tool in ultrasound-based blood characterization and tissue analysis.