An Implantable Probe for Chronic Observation of Microcirculation

Abstract

Whether the pulsatile flow is essential for living body or not is long-term controversial point between circulatory physiologist and artificial heart researchers. Especially, since an axial flow pump, continuous flow pump, has begun to use clinically in 2001, and could keep the patients alive for more than few years, this problem has become to be thought as very important physiological and pathophysiological problem. The objective of this study is to develop an implantable probe to observe microcirculation under artificial circulation.

The principle of the probe developed in this study is the following; A thin living tissue put directly on a highly integrated CCD(charge coupled device) and illuminated from the backside of the tissue with LED(light emitting diode). The microvascular nets in the tissue will be projected on the CCD surface like a contact photograph, which produces an image on a TV screen. The problems are how to magnify to be able to observe erythrocyte flow, how to control the focus, how to electrically insulate and how to compactmize.

After several method trials to magnify the image, a micro lens having 2 mm in diameter, 2mm long and 6 times magnification, was designed and made with acrylic resin. The lens was installed into a CCD camera with 8 mm in diameter and 60 mm long. The camera could magnify an image about 650 times on a 14 inches TV screen. A clear microcirculation image including capillary flow could be observed when the camera was implanted into the connective tissue under the skin of a rabbit. Now focus control system is develo** for the camera to be implanted chronically in animal