Abstract
The dynamics of contrast medium were studied in RGC5-transplanted and RSV-induced primary brain tumors of rats by soluble substance macro and micro-autoradiography. The distribution of 125I-labeled meglumine diatrizoate in the brain, brain tumors and the liver was followed up to two hours after intravenous administration.
Immediately after administration, the contrast medium flowed in the blood vessels of the brain, but not in those of the tumors. It took about five minutes until the contrast medium flowed in almost all the blood vessels of the viable tumor tissues. This clearly proved a distinct delay in the vascular circulation within the tumor tissues in spite of the increased vascularity. Once it flowed in the blood vessels of the tumors, the contrast medium was rapidly extravasated into the viable tumor parenchyma five minutes after the administration. Spreading from the viable tumor tissues, the contrast medium accumulated in the area of central necrosis including the cyst, and the concentration of contrast medium in the necrotic zone and cyst became almost equal to that in the viable tumor tissues after about thirty minutes. The velocity of the washing out of contrast medium from the tumor tissues was very slow compared with that from the blood vessels or brain tissues. Two hours after administration, the contrast medium still remained dense in the areas of central necrosis, especially in the cyst, in contrast to the areas of the viable tumor tissues. In the peritumoral brain tissues, the contrast medium was not extravasated diffusely from the vessels. However, the contrast medium slowly spread from tumor tissues showing a high concentration of contrast medium to the peritumoral regions one or two hours after administration.
There was moderate and diffuse distribution of contrast medium in the brain tissues distant from the tumors only immediately after administration, possibly because of the transient breakdown of the blood-brain barrier due to high osmolality of the contrast medium. However, there was no distinct uptake of contrast medium in such areas thereafter.
The dynamics of the contrast medium were studied by calculating the tissue-blood ratio (TBR) of the concentration of the contrast medium in macroautoradiography. The TBR calculation enabled us to analyse the dynamics of the contrast medium quantitatively. This method shows the characteristics of the dynamics of the contrast medium in the brain and brain tumors and might be useful in the differential diagnosis of various lesions.
