Measurement of cochlear blood flow by direct visualization technique : comparison with laser Doppler method

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Derect visualization of blood flow in stria vascularis of the cochlea was investigated without any dye or fluorescence by means of image analysis program in 1994. To observe the blood flow in the stria vascularis, the bony wall on the second turn of the cochlea was removed carefully. The membranous labyrinth was exposed and visualized directly by Olympus microscope (SZ 6045, TRPT). This direct visualization technique of blood flow was fairly difficult, but exercise allowed the investigators to have a success in 2 out of 3 guinea pigs. The image analysis was possible, however, it was unreliable, if the surgical exposure and direct visualization were not performed under samely stable conditions.Thus, dye and fluorescence was tried to make the image clear in 1996. However, those technique did not produce more reliable image analysis, and the result was as same as that of the direct visualization without dye and fluprescence.Therefore, we compared the result obtasined by direct visualization without dye and fluorescence with that obtained by laser Doppler method.In direct visualization technique, only a large amount of adrenalin induced a significant change of cochlear blood flow, meanwhile laser Doppler method induce significant changes in cochlear blood flow by less amount of adrenalin. Our result suggests that laser Doppler technique is more sensitive than direct visualization technique. However, direct visualization technique offers the total observation of blood flow, and then it would be a useful technique if the contrast of erythrocytes in the blood flow is sufficiently enhanced by some methods.