Investigation of contrast agent dosage for perfusion-weighted MRI.

Purpose: In this study we investigated, whether increasing the dosage of a paramagnetic contrast agent results in a stronger signal decrease in T-2*-weighted perfusion sequences and therefore more meaningful parameter maps. Material and methods: In a prospective study bolus injection of gadolinium-DTPA was performed at dosages of 0.1, 0.2, and 0.3 mmol/kg body weight (BW) in 10 patients each. Before, during and after bolus injection 40 T-2*-weighted images of a reference brain slice were acquired within 65.6 seconds on a 1.0 T clinical scanner and perfusion parameters were calculated. Results: Due to the limited signal decrease during bolus passage and the resulting low signal-difference-to-noise ratio (Delta S/N) no reliable differentiation of gray and white matter was possible at a contrast agent dosage of 0.1 mmol/kg BW. Only at higher dosages, both, signal decrease and Delta S/N were strong enough to allow differentiation of gray and white matter and to yield reliable parameter maps. Conclusion: For meaningful MR perfusion imaging at 1.0 T and with the given sequence a contrast agent dosage of at least 0.2 mmol/kg BW is necessary, if a 0.5-molar contrast agent is used.