Mapped hemodynamic data acquisition by near infrared CCD imaging

This paper presents undergoing research results of a near infrared CCD imaging system designed for mapped acquisition of hemodynamics data with inexpensive system components. This system is intended for use by clinicians and in phenological practice. The tests that can currently be done with this system are the classical Muscle Pump Test (MPT) and the Vein Occlusion Test (VOT). These are standard tests for venous disorders such as chronic vein insufficiency (CVI) and deep vein thrombosis (DVT). Photoplethysmographic (PPG) systems with NIR optical sensors are in wide use for these tests today. They essentially measure the blood volume changes in the top skin layers by registering the attenuation change in the near infrared. The new principle is based on this method but allows imaging of the vein structure as well as mapping the physiological data to the image. A monochrome CCD camera equipped with a >700 nm filter is mounted on a tripod. A diffuse illumination is applied, then the test is performed. The camera takes a sequence of pictures of the perfusion area of interest, usually the lower leg. The sequence is then evaluated and filtered with digital filter algorithms. This allows calculation of parameters such as venous refilling time, venous pump power and venous drainage. These values are offered to the examiner as mapped data from several selectable regions. From this, conclusions can be taken as to the reason and location of disorders.