Gadodiamide injection for Enhancement of MRI in the CNS. Applications, dose, field and time dependence

Sammanfattning: Aims of the study The aims of this study using Gadodiamide injection were to investigate: · Whether Gadodiamide injection was comparable to Gd-DTPA for the enhancement of CNS lesions. · The contrast effect at different field strengths. · The effective time-window for the enhancement of blood-brain barrier damage. · The relations between the concentration of contrast agent and enhancement in phantoms, and to correlate the results to doses given to patients. · The use of a higher dose in two important clinical problems; the detection of metastases in the brain, and the evaluation of patients with failed back surgery syndrome (patients with recurrent pain after surgery for lumbar disc herniation). Results and conclusions · Gadodiamide injection was comparable to Gd-DTPA with regard to both safety and diagnostic efficacy in the CNS. · The contrast effect of Gadolinium contrast agents is higher at 1.5 T than at 0.3 T both in phantoms and patients with a maximum ratio (signal lesion / signal grey matter) more than 50% higher at 1.5T. · To achieve high contrast effect, heavily T1-weighted images are also important at both field strengths, as prolonging the repetition time from 400 ms to 600 ms reduced the ratio by 15-45% depending on concentration. · The effective time-window for imaging of blood-brain barrier damage is between 2-5 and 25-30 minutes after injection and several scans can be performed without loss of enhancement. · To provide maximum detectability of blood-brain-barrier-damage in patients with brain lesions, higher doses of Gd contrast media should be useful, as the doses used clinically today do not utilize the maximum contrast effect, either at high or low field strength. However, higher doses are more important at low field strengths because the contrast effect is lower than at high field strengths. · High-dose (0.3 mmol/kg b.w.) contrast-enhanced T1-weighted spin-echo MRI with Gadodiamide injection allowed detection of significantly (p<<0.01) more and smaller metastases than standard-dose (0.1 mmol/kg b.w.) MRI at 0.3 T. High-dose contrast-enhanced MRI with Gadodiamide injection is an efficient way to improve the detection of brain metastases. This should also be true for blood-brain barrier disruptions of other causes. · High-dose (0.3 mmol/kg b.w.) contrast-enhanced T1-weighted spin-echo MRI at 0.3T did not increase the diagnostic information in patients with recurrent pain after surgery for lumbar disc herniation compared to standard-dose (0.1 mmol/kg b.w.) MRI. The high dose images were considered more informative than the standard dose images when compared in pairs but gave no additional or different diagnostic information when evaluated separately.