Purpose: To calculate regional cerebral blood volume (rCBV), regional cerebral blood flow (rCBF), and regional mean transit time (rMTT) accurately, an arterial input function (AIF) is required. In this study we identified a number of AIFs using factor analysis of dynamic studies (FADS), and performed the cerebral perfusion calculation pixel by pixel using the AIF that was located geometrically closest to a certain voxel. Materials and Methods:To verify the robustness of the method, simulated images were generated in which dispersion or delay was added in some arteries and in the corresponding cerebral gray matter (GM), white matter (WM), and ischemic tissue. Thereafter, AIFs were determined using the FADS method and simulations were performed using different signal-to-noise ratios (SNRs). Simulations were also carried out using an AIF from a single pixel that was manually selected. In vivo results were obtained from normal volunteers and patients. Results:The FADS method reduced the underestimation of rCBF due to dispersion or delay that often occurs when only one AIF represents the entire brain. Conclusion:This study indicates that the use of FADS and the nearest-AIF method is preferable to manual selection of one single AIF.

Purpose: To examine and compare properties of high-molarity contrast agent gadobutrol (Gadovist) and weakly protein-binding agent gadobenate-dimeglumine (MultiHance ) in dynamic susceptibility contrast (DSC) perfusion imaging at 3 T. Materials and Methods:Sixteen healthy volunteers underwent three separate examinations with contrast agent doses of 0.1 and 0.2 mmol/kg body weight (bw) gadobutrol and 0.1 mmol/kg bw gadobenate-dimeglumine. Maps of relative regional cerebral blood volume (rCBV) and blood flow (rCBF) were calculated using deconvolution based on singular value decomposition. Signal and concentration time curves, the concentration-to-noise ratio (SNR c ), and gray matter (GM)-to-white matter (WM) rCBV and rCBF contrast and ratios were evaluated in a region of interest (ROI)-based analysis. Image quality of calculated parametric maps was assessed in direct visual comparison and with respect to suitability for diagnostic purposes. Results:The contrast agents displayed very similar results in the 0.1 mmol/kg examinations, both with respect to the quantitative evaluation parameters and in the qualitative assessment of the calculated parametric maps. Maps from 0.2 mmol/kg examinations were rated as being superior in quality, but with respect to diagnostic suitability all contrast agents and doses yielded images of sufficient quality. Conclusion:At 3 T, a gadobutrol or gadobenate-dimeglumine dose of 0.1 mmol/kg is sufficient for DSC magnetic resonance imaging (MRI) perfusion assessment. At the used small injection volumes, the tissue concentration curve was determined only by the gadolinium (Gd) dosage in mmol/kg, and the T2* relaxation effects of the two agents can be considered to be nearly identical in the applied gradient-echo (GRE) sequence.

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