Defence: Monitoring Blood Clot Formation and Lysis in Vitro using High Frequency Photoacoustics

Supervisor: Dr. Michael Kolios and Dr. Mark McVey

Clotting is a survival mechanism that prevents blood loss after injury. An imbalance in clotting
factors can lead to lethal consequences such as exsanguination or inappropriate clotting. Existing
methods to monitor clot formation and lysis measure viscoelasticity of whole blood or optical density of
plasma over time. Though these methods provide insights into coagulation and fibrinolysis, they require
1-3 millilitres of blood which can worsen anemia especially in small pediatric patients or provide partial
information as seen with acellular plasma-based measurements. To overcome these limitations, a high
frequency (HF) photoacoustic (PA) imaging was developed to detect clot formation and lysis in whole
blood. Frequency spectra showed continuous changes in unclotted blood which became more stable
during clotting. After clot lysis, the mean value of the frequency spectra changed continuously as seen
with whole blood. HFPA imaging can measure clotting and lysis kinetics with small volumes of blood
(25µL/test).