1 ) To enhance spatial resolution of near-infrared (NIR) imaging in vivo, we performed
computer-aided refocusing of NIR-projection images of human forearm. Simple inverse,
constrained least squares, and Wiener filters were tested as refocusing algorithms. Wiener
filter gave the best result in terms of image quality and computation time. By applying
Wiener filter, we obtained enhanced spatial resolution.
2) We also examined 2-dimensional visualization of Hb oxygenation state using NIR-projection
images of human forearm. Forearm occlusion caused increase in 2-dimensional O.D.
at 700 nm, while slight decrease was observed at 800 nm. On the basis of in vitro experiments
using RBC suspension and test phantoms, we calculated 2-dimensional changes in Hb
oxygenation in the human forearm caused by ischemia.
3) To confirm whether NIR-CT can detect changes in Hb quantity in the living tissues, we
reconstructed CT images from NIR-projection data of mouse abdomen measured at 700 and
800 nm. Infusion of physiological saline into the liver caused decrease in gray level in the
location of the liver in the CT images (700-800 nm), although uncertain artifacts were
observed in the other areas. Although more detailed considerations are required for practical
application of this technique, we have obtained NIR-projection and CT images which
indicate regional changes in the state of Hb in the living tissues.