抄録
Thirty-one patients with brain tumor were studied by CT delayed scan performed 60 and 120 minutes after intravenous administration of contrast medium. Dynamics of contrast enhancement (CE) in the lesion were analyzed quantitatively and qualitatively by calculating the tissue-blood ratio (TBR) at each scan. Since the individual blood contrast medium concentration had a wide range of values in spite of a settled dose given by body weight, it was necessary to calculate the TBR to analyze the intensity of CE qualitatively. Dynamics of CE are shown as relative TBR (R-TBR) which represents the ratio of TBR 60 minutes (TBR1) and 120 minutes (TBR2) after intravenous administration of contrast medium to the initial TBR (TBR0). The higher R-TBR means the higher retention of contrast medium in the tumors. R-TBR2 (TBR2/TBR0) was found to be very useful for differential diagnosis of brain tumors.
The R-TBR2 could be classified into three types : less than 1.5 (type 1); 1.5 to 3.0 (type II) ; and more than 3.0 (type III). In the glioma group, 7 of 8 astrocytomas, grade 3 and 4, were type III ; and all of 3 astrocytomas grade 2, were type II . All of 7 meningiomas were type I. In 5 pituitary adenomas, 4 were type II and 1 was type I. In 4 neurinomas, 3 were type III, and 1 was type II . In 4 metastatic tumors, 2 were type II, and 2 were type III. By this method meningioma, pituitary adenoma and neurinoma may be differentiated from each other. We can also presume the degree of malignancy and its distribution in glioma. The possibility of differential tumor diagnosis and mechanism about various types of dynamics of CE are discussed.
