Preliminary studies of the application of near infrared spectroscopy in the diagnosis of deep vein thrombosis

A feasibility study for diagnosing deep vein thrombosis utilizing near-infrared continuous wave spectroscopy was performed, as a real-time, non-invasive, and inexpensive method. The probe contains two light sources and two detectors with optical filters that monitor reflected light at wavelengths 760 and 850 nm to measure the changes in the amount of deoxyhemoglobin and oxyhemoglobin, respectively. These changes and the blood volume changes are recorded while the subject performs a series of light leg exercises. The test protocol is designed to determine the muscle tissue blood volume capacity, rate of blood filling (venous valve functionality test), and efficiency to promote one-directional venous flow from the leg to heart. The subject pool consists of the patients with leg deep vein thrombosis (DVT) diagnosed by the Johns Hopkins Hospital Vascular Surgery Department and of normal subjects as the control. Abnormal venous systems showed distinct characteristics: high blood volume in the leg; high rate of blood filling while the subject stands upright; and the inability to decrease the blood volume during the muscle contraction. The NIR device proved to be an inexpensive, effective, and portable device that can detect DVT in the leg in real-time.