The optimal volume of contrast medium must be injected into the patient who emits the maximum signal intensity in an ROI. This study was investigated four different type MRI and one CT contrast agent in vitro and sought to establish relations between concentration, MRI relaxivity, CT Hounsfield unites selected kVp and different MRI T1 sequences. Using a CT contrast medium and four different MRI T1 contrast media, we developed five different phantom series. The MRI contrast media phantom was imaged on 1.5T and 3T MRI systems and measured the R1 and R2 value. A CT scanner was used to obtain images of the Iopromide 370 phantom with the quality of radiation to obtain images. The Pearson's correlation coefficient analyses were conducted between MRI CM phantom series with Iopromide 370 phantom. The non-parametric statistical analyses were performed for the values of kVp. The Delta HU of the test solution of the CT contrast media was produced in the same amount as the exponentially increased concentration of the MRI contrast media according to the increase in the dilution concentration, and was influenced by the quality of the X-ray. Through the results of this experiment that considered the two aforementioned factors, an image with a high diagnosis value can be acquired from the information on the concentration of the MRI T1 contrast media. (C) 2013 Elsevier B. V. All rights reserved.