Sequential T1 changes in brain tumor tissue after Gd-DTPA administration were investigated in 10 patients, including 4 meningiomas, 2 gliomas, 3 metastatic cerebral tumors and 1 brain abscess. T1 values were measured serially for 60 minutes following Gd-DTPA injection using a magnetic focusing technique. In vitro T1 of the whole blood samples was also comparatively examined. Time processes in the tissue-blood ratio (TBR) were calculated from two-point relaxation rates at 5 and 30 minutes. The obtained ratios of TBR were ranged from 1.0 to 3.0, probably depending on histological types of brain tumor (the value of 1.0 to 1.5 for meningioma and 1.5 to 3.0 for glioma and metastatic tumor). No significant changes in the T1 value were observed in the examined normal tissue and peritumoral edema. These results indicate that Gd-DTPA plays an important role not only as an image enhancer for tumor tissue but also as an indicator for estimating the blood-brain barrier function.

Adult↗

PubMedDate not supplied

Transfer index of MR relaxation enhancer: a quantitative evaluation of MR contrast enhancement.

To clarify the effects of Gd-DTPA on biological water, we examined the effects of the compound on spin-lattice relaxation rate with various concentrations of gelatin solutions. The results indicate that the effects of relaxation rate of Gd-DTPA in biological water fundamentally correspond to those in aqueous solution. To evaluate the distribution of Gd-DTPA in tissues, we introduced a transfer index that represents the product of tissue-blood ratio of Gd-DTPA and the ratio of extracellular volume of a tissue based on the above findings. The index depends neither on dose of the compound nor on Larmor frequency. The clinical significance of the index was studied in patients with brain tumors. The indexes varied from 0.038 to 0.51, depending on the biological characteristics of the tumors. The transfer index may be used in the quantitative evaluation of MR relaxation enhancement, which may be applied to monitoring therapeutic efficacy and to estimating tissue perfusion.

Brain↗