A NEW APPROACH TO CT DIAGNOSIS WITH APPLICATION OF VASCULAR PERMEABILITY OF CONTRAST MEDIA - TISSUE CHARACTERIZATION BY USING PERFUSION IMAGE.

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A new approach to CT diagnosis for tissue characterization was experimentally studied by using two different molecular sized contrast media. The contrast media used were iopamidol (molecular weight 777) and iodoethylated starch (IES : molecular weight : 60,000) which was developed in our laboratory. Dynamic CT was performed on VX2 tumor of rabbit rabbit, implanted at the thigh. The first dynamic CT was done with iopamidol and after ascertaining that the tumor attenuation had returned to the pre-contrast level, the second dynamic CT was performed on the same slice with IES.The time-density curves obtained at the same areas on the images with each contrast agent were compared. Perfusion images were obtained with subtracting IES-image from iopamidol-image.Histologic specimens obtained at the corresponding areas of images were examined comparing to the time-density curves and perfusion images. The attenuation difference between the two density curves was well correlated to tumor viability. we considered that iopamidol could rapidly permeate to extravascular space, while IES could not, staying mostly within the intravascular space. And thus, the attenuation difference between the two curves and perfusion images suggested to be an indicator of the dynamics of extravascular perfusion, providing a new information to CT diagnosis.