Optical Technique Better Measures Blood Coagulation

A new optical approach could help doctors quickly determine a patient’s blood coagulation status in near real time.

A team at Massachusetts General Hospital has developed an optical device that requires only a few drops of blood and just a few minutes to measure the key coagulation parameters that can guide medical decisions, such as how much blood to transfuse or what doses of anticoagulant drugs to administer.

Laser speckle patterns captured from a human blood sample show time-dependent speckle intensity modulation during coagulation. Images courtesy of Massachusetts General Hospital.

“Currently, the most comprehensive measures of coagulation are a battery of lab tests that are expensive and can take hours to perform,” said Seemantini Nadkarni, an assistant professor at the Wellman Center for Photomedicine at MGH and Harvard Medical School.

The new optical technique, called laser speckle rheology (LSR), entails shining laser light into a sample and monitoring the patterns of light that bounce back. The researchers previously used the technique to measure the mechanical properties of different tissue types and found it to be extremely sensitive to the coagulation of blood.

When light hits a blood sample, blood cells and platelets scatter the light. In unclotted blood, these light-scattering particles move easily about, making a speckle pattern fluctuate rapidly. The researchers said this looks similar to a starry night sky.

Blood sample cartridges employed for laser speckle rheology measurements.

A miniature high-speed camera was used to record this pattern, which then correlated the intensity of changes with two important blood sample measurements: clotting time and concentration of the protein fibrinogen.

“As the blood starts to coagulate, blood cells and platelets come together within a fibrin network to form a clot,” Nadkarni said. “The motion is restricted as the sample gets stiffer, and the twinkling of the speckle pattern is reduced significantly.”

The LSR device could also help patients whose blood coagulates too easily, forming clots inside of blood vessels in conditions such as thrombosis.

Currently, the device is about the size of a tissue box and must be connected to a computer. However, the team expects to further miniaturize the system, aiming to perform clinical studies with a handheld version that is smaller than a cellphone within the next year.

The research is published in Biomedical Optics Express.

For more information, visit www.massgeneral.org.