Established DCE-MRI protocols present a tradeoff between spatial and temporal resolution especially for bolus tracking of first-pass perfusion procedures. Quantitative analyses require both high temporal resolution for the rapid arterial input functions (AIF) and high spatial resolution for monitoring corresponding tissue responses. These prerequisites are met with recent advances in real-time MRI¹. The aim of this work is to develop a suitable real-time MRI sequence for quantitative DCR-MRI using undersampled radial FLASH and image reconstruction by nonlinear inversion (NLINV) and test its performance with use of a commercial perfusion phantom.Flow Phantom and Injection Protocol: As a ground truth experiment a commercial multi-modality DCE Perfusion Flow Phantom (Shelley Medical Imaging Technologies, London, Ontario Canada) was used driven by a positive displacement pump to allow for flow of demineralised water. Inside the phantom inflowing liquids are divided into two outputs. The first is the outlet of a perforated distribution tube which leaks into a cylindrical compartment whose output provides the phantom’s response². Gd-based contrast agent (Gadovist, Bayer HealthCare Pharmaceuticals, Berlin, Germany) is injected via a clinical power injector connected by 1/4'' PVC tubing with 6 m tubing length from the injection site to imaging plane, where a plastic bottle provides a water surrounding for the three tubes (ID 9.5 mm) connected to the phantom. Pump flow rate was set to 300 ml/min and the ratio of output to input flow to 1/2. 10 ml of contrast agent with a concentration of 10 mM of Gd at a rate of 1ml/s was injected. Acquisition and Reconstruction: A radial FLASH sequence (TE/TR 1.58/2.55 ms, resolution 1 x 1 x 8 mm³) acquired two perpendicular sections in an interleaved way, i.e. parallel to the tubing for saturation of the inflowing spins [Fig.1a)] and perpendicular for imaging [Fig.1b)]. To achieve high temporal resolution 21 radial views were acquired and reconstructed using NLINV¹ (temporal resolution of 107 ms). However, the coil sensitivity profiles were kept fixed (similar to³) to allow for quantitative analysis of time series. The influence of the flip angle was investigated for 15°, 20°, and 25°. All experiments were performed at 3 T (MAGNETOM Prisma, Siemens Healthcare, Erlangen, Germany) using a 18 channel body array coil. Image Analysis: All images were analyzed using Matlab (Math Works, Massachusetts, USA). The diameter of the three ROIs were chosen to be 80% of the diameter of the inner tube. Quantitative perfusion parameters (K^trans and k_ep) were calculated pixelwise for the normalized signal intensity using a least-squares fit and the standard Tofts model⁴.Bolus tracking with high CNR was possible for all three acquisition protocols. Figure 2 shows the normalized ROI signal intensities over time for the 25° flip angle measurement. Both, AIF (ROI 1) and Phantom Outlet (ROI 2) show the same enhancement indicating a successful suppression of the inflow effect, because the flow rates in ROI 1and ROI 2/ROI 3 differ by factor of 2 (300 ml/s vs. 150 ml/s). The measured phantom response (ROI 3) was fitted by the standard Tofts model (using ROI 1 as AIF). Values for maximum enhancement (Peak Intensity) and area under curve (AUC) for all data sets are listed in Table 1. All values increase with increasing flip angle. Figure 3 shows the quantitative parameter maps K^trans and k_ep obtained by a pixelwise fit.The deviation in peak intensity and AUC across the ROIs decreases with higher flip angles. This has probably two reasons: Firstly, the suppression of the inflow effect is more effective when presaturation with a higher flip angle is performed, and secondly, linearity between contrast agent concentration and signal enhancement for T1-weighted images increases when going to higher flip angles. All phantom responses can be well described by the standard Tofts model, independent of the chosen flip angle. However, the quantitative analysis is affected by both, inflow effects and nonlinearity between concentration and signal enhancement, since all three data sets show an overestimation of the expected K^trans (0.9 ml/min/g). Future research will focus on a separation of these effects to obtain a full ground truth experiment for DCE first pass perfusion with clinical parameter settings.We presented a ground truth DCE-MRI experiment for quantitative analysis of image series with high spatial and high temporal resolution as obtained by current real-time MRI methods¹. The quantitative analysis for flip angles over 20° revealed good agreement with expected values rendering this setup an excellent candidate for future optimization of protocol and reconstruction parameters.