[The simultaneous determination of the arterial input function for dynamic susceptibility-weighted magnetic resonance tomography of the A. carotis interna and the A. cerebri media].

Purpose: The determination of the arterial input function (AIF) is necessary for absolute quantification of the regional cerebral blood volume and blood flow using dynamic susceptibility contrast MRI. The suitability of different vessels (ICA--internal carotid artery, MCA--middle cerebral artery) for AIF determination was compared in this study.

Methods: A standard 1.5 T MR system and a simultaneous dual FLASH sequence (TR/TE1/TE2/alpha = 32/15/25/10 degrees) were used to follow a bolus of contrast agent. Slice I was chosen to cut the ICA perpendicularly. Slice II included the MCA. Seventeen data sets from ten subjects were evaluated.

Results: The number of AIF-relevant pixels, the area under the AIF and the maximum concentration were all lower when the AIF was determined from the MCA compared to the ICA. Additionally, the mean transit time (MTT) and the time to maximum concentration (TTM) were longer in the MCA, complicating the computerized identification of AIF-relevant pixels. Data from one subject, who was examined five times, demonstrated that the intraindividual variance of the measured parameters was markedly lower than the interpersonal variance.

Conclusions: It appears to be advantageous to measure the AIF in the ICA rather than the MCA.