FUNCTIONAL IMAGING OF THE BRAIN WITH LOW-DOSE GADOLINIUM-DTPA AND TURBO-FLASH SEQUENCES

A method for measuring regional blood volume and flow is described bas ed on the reduced relaxation time following intravenous injection of G d-DTPA. The optimal Gd dose and other parameters were first determined using turbo-flash sequences and a dilution phantom. A single maximum was found for a Gd-DTPA concentration of 4 mmol/l. Taking account of n ormal heart/time volumes and in order to stay below this arterial valu e Gd-DTPA was injected as a bolus at the rate of 1 mmol/sec. From the phantom measurements there appears to be a functional connection betwe en measured signal intensity and Gd concentration. The method was appl ied to 15 patients with cerebral tumours, using altogether 26 perfusio n examinations. The results from 4 patients are given as examples; in these, blood volume and flow were calculated for each pixel in a 128 x 128 matrix. It was found that the Gd-DTPA injected is sufficient to b e shown with certainty in the grey and white matter and that this is a ble to demonstrate pathological changes in a functional manner. Compar ison with Gd-DTPA doses such as are used for morphological imaging (ty pically, 10 mmol corresponding to 0.1 mmol/kg body weight) has shown t hat doses above 1.6 mmol may lead to distortion of the concentration c urves.