Tracer kinetics of gadolinium contrast medium are represented by two-compartment model as: dC_myo(t)/dt=K1C_blood(t)- k2C_myo(t), where K1 and k2 are the unidirectional transfer constants of influx and efflux of gadolinium contrast medium into and out of the myocardial tissue, respectively. Quantitative analysis of first-pass perfusion MRI with two-compartment model-based Patlak plot analysis can provide absolute quantification of K1, and MBF with the correction of the extraction fraction. Thus far, however, k2 has rarely been studied except for small number of studies [1], though the addition of k2 allows for more detailed myocardial tissue characterization. The ratio of the concentration of contrast medium in LV blood to that in extracellular space at equilibrium constitutes partition coefficient (lambda) [2]. With the recent advent of T1-mapping, lambda is calculated from pre- and post-contrast T1 maps of LV blood and myocardium, which is converted to extracellular volume fraction (ECV) with hematocrit correction. Lambda is also defied as K1 divided by k2 using two-compartment model [3]. Consequently, contrast-enhanced cardiac MR (CMR) including first-pass perfusion MRI and pre- and post-contrast T1-mapping has a potential for synergistic quantification of k2 as well as K1, MBF, lambda and ECV. The purposes of this study were to present a synergistic evaluation of contrast-enhanced CMR yielding myocardial tissue kinetic parameters including k2 and to demonstrate its value in patients with previous myocardial infarction (MI).Nineteen patients with previous MI (16 men, 68±9 years old) who underwent contrast-enhanced CMR including first-pass perfusion, LGE and pre- and post-contrast T1-mapping using a modified Look-Locker inversion recovery (MOLLI) sequence at 3T were studied. Blood samples were taken for hematocrit measurement. First-pass perfusion MR images at rest were acquired with a saturation recovery TFE sequence on 3 short-axis slices every heart beats. In order to perform saturation correction of the blood signal, we initially obtained first-pass MR images by administrating 10x diluted Gd-DOTA (0.003mmol/kg). Then first-pass MR images were acquired with a gadolinium dose of 0.03mmol/kg.　After correcting saturation of the blood signal, K1 was quantified by a Patlak plot method from arterial input and myocardial output function using AHA 16 segment model. Then, K1 was converted to absolute MBF with the correction of extraction fraction of gadolinium contrast medium [4]. MOLLI T1 maps were acquired pre- and 15min post-contrast. Myocardial and blood T1 values were quantified on the corresponding slices of pre- and post-contrast MOLLI images with a heart rate correction. Lambda was calculated from the pre- and post-contrast myocardial and blood T1 in each segment. Then, ECV was generated from lambda and hematocrit measures. Then, k2 was determined as the K1 divided by lambda in each segment. On the corresponding slices of LGE images, extent of MI was measured in each segment. Myocardial segments were divided into the following 3 groups; segments without MI, segments with MI of <50% and segments with MI of >50%.Quantitative measurement was successful in all 304 myocardial segments (205 segments without MI, 55 segments with MI of <50% and 44 segments with MI of >50%) in 19 patients. The results are presented in Table 1 and Figure 1. A representative case is demonstrated in Figure 2. Lower K1, k2 and MBF and higher lambda and ECV were observed in myocardial segments with MI as compared to those without MI. Significant differences were observed for all of K1, k2, MBF, lambda and ECV among the 3 groups of myocardial segments divided based on the presence or absence as well as the severity of MI within the segment.The results in this study demonstrated that our new approach that synergistically analyzes both quantitative perfusion MRI and pre-and post-contrast T1-mapping acquired in a single CMR examination allows for quantification of k2, in addition to K1, MBF, lambda and ECV. The trend of lower k2 in myocardial segments with MI compared to those without MI found in this study are similar to results in previous studies [1], while the finding of lower K1/ MBF and higher lambda/ ECV in myocardial segments with severer MI are in line with the results in the literature. Significant differences observed in k2, K1, MBF, lambda and ECV among the 3 groups of myocardial segments categorized by MI severity indicates the value of synergistic assessment of quantitative first-pass perfusion MRI and pre-and post-contrast T1-mapping.