## 1 Introduction  
Magnetic resonance imaging (MRI) is achieved through the paramagnetism of the hydrogen (!H) protons in the body when placed in a magnetic field. Thus,!H protons in various tissues emit different energy signatures depending on the proton relaxation rate in that tissue. MRI displays these energy differences as contrast in a scan image [1,2]. Generally, the MRI signal intensity (SI) is determined by the gradient strength (\(M_{0}\)), flip angle (\(\alpha\)), repetition time (\(TR\)), echo time (\(TE\)), 1/T1 (\(R_{1}\)), and 1/T2* (\(R^{2*}\)), as shown in Equation (1) [3,4];  
\[\text{SI}=M_{0}\sin(\alpha)\cdot\frac{1-e^{-R_{1}\cdot TR}}{1-\cos(\alpha) \cdot e^{-R_{1}\cdot TR}}\cdot e^{R_{2}\cdot(^{*})TE} \tag{1}\]  
Of the factors that determine the SI; \(\alpha\), \(TR\), \(TE\), and \(M_{0}\) are external factors that can be intentionally controlled from the MRI apparatus. \(R_{1}\) and \(R_{2}\), on the other hand, are unique properties of!H protons in a given magnetic field, and cannot be controlled externally. However, it is possible to increase the SI, for diagnostic purposes, by adjusting \(R_{1}\) relaxation and \(R_{2}\) decay; this is achieved using a gadolinium-based contrast agent (GBCA). GBCAs are administered for MRI to enhance the SI of lesions and to increase the diagnostic value of the imaging technique. In vivo, gadolinium interacts with the normal \({}_{1}\)H spins to reduce the R\({}_{1}\) and R\({}_{2}\) relaxation times. These \({}_{1}\)H protons show faster relaxivity than \({}_{1}\)H protons that are not bound to gadolinium, producing a high SI in MRI images compared to the usual positive magnetic susceptibility [1; 2]. In humans, MRI can be applied to various indications, and in terms of contrast-enhanced imaging using GBCA, contrast-enhanced (CE)-T1 is especially often used in clinical settings. Diagnostically, MRI is useful to evaluate the presence or absence of tumors. Previous studies have only addressed the characteristics of normal body tissues or lesions in T1 images according to sequences and have also shown clinical comparison data according to GBCA concentration. However, how the change in the SI of GBCA is affected by external parameters is currently unknown [5; 6; 7]. Here, we can surmise that the parameters controlling MR physics will affect the relaxation of the \({}_{1}\)H spin that is bonded to gadolinium. This is because the signal strength of each tissue, with different relaxation rates, can be controlled by external parameters. In this study, the main parameters determining the MR SI are TR and TE, as shown in Equation (1). In a conventional spin echo (SE) sequence, TR refers to the time from one 90\({}^{\circ}\) RF pulse to the next 90\({}^{\circ}\) RF pulse, while TE refers to the time from the RF pulse to the echo. The TR and TE parameters can be used to adjust the image contrast in different tissues with different relaxation times. Clinically, in order to achieve a T1 effect in humans, TR is usually in the range 200-600 msec and TE in the range 10-25 msec [8; 9; 10]. It is common to use a 90\({}^{\circ}\) excitation angle and a 180\({}^{\circ}\) refocusing angle for flip angles (FAs). Since TR is directly related to the acquisition time per slice, it is set as low as possible. Thus, in clinical settings, routine values are used for TR and FA, but in the case of TE, there is no specific guideline for CE-T1 in 3.0T MRI. Therefore, in this study, we quantitatively analyzed the SI change of gadolinium, according to TE regulation, through MR in both phantom and clinical tests, and suggested a proper TE value for T1 enhancement.