Inflammation of tissue is characterized by: redness, swelling and increased temperature which are all caused by vascular changes including vasodilation (widening) and increased permeability (leakage) of blood vessels. Although easy to recognize, it is difficult to quantify the level of inflammation. Our patented Optical Inflammation Detection technology supports the physician in establishing the level of inflammation in rheumatoid arthritis (RA) patients by quantifying the hemodynamic response to an applied stimulus. A pressure cuff around the lower arm is inflated for a short period of time to modify the blood flow in the hands. The venous backflow is hindered whereas the arterial flow continues, resulting in the pooling of blood in the hands. Due to the vascular changes associated with inflammation, the speed and magnitude of blood pooling is different for inflamed and healthy tissue.
The process of blood pooling is measured by diffuse optical transmission. The hands of a patient are illuminated with red/near-infrared light and the transmitted light is detected by a camera on the other side of the patient’s hands. Since blood is a strong absorber in the red/near-infrared region of the spectrum, pooling of blood will result in a decrease of the transmitted light.
A patient scan
The patient inserts his or her hands through a cylindrical opening that holds the pressure cuff and places his or her hands on a glass handrest. When the operator has verified correct hand placement and the patient is in a comfortable position the lid is closed and the hand illumination is turned on. The patient's hands are illuminated by a light source which is positioned below the handrest. Two imaging camera's are placed to record the changing transmission of light through the hands over time.
A complete measurement consists of three phases. During the first phase the baseline transmission is recorded without cuff pressure. In phase two the cuff pressure is applied to measure the increase in blood volume. During the last phase the pressure is released to measure the decrease in blood volume. The whole measurement takes less than 1.5 minutes.
From the local transmission profile a 2D image is created ,representing the vascular response, which is presented to the rheumatologist, together with underlying and historic patient data.
The Optical Inflammation Detection technology supports the rheumatologist in objectively assessing the RA disease activity in a fast, safe, painless and operator independent way.