Diffusion-weighted imaging (DWI) emphasizes the random movement of water molecules at the microscopic level. A motion-probing gradient is applied to enhance diffusion in DWI, and its strength is called the b value. The apparent diffusion coefficient (ADC) can be calculated using DWI with two or more different b values. ADC values can decrease in pathological conditions characterized by a high cell density [1-3], high viscosity [4], and the presence of cellular edema [5-7].
Echo planar imaging (EPI) is commonly used in DWI to reduce motion artifacts. EPI can perform ultra-fast imaging. However, it is vulnerable to image distortion and magnetic susceptibility artifacts [8]. The radial acquisition regime (RADAR) acquires data in the form of strips (referred to as blades) and fills the data by rotating each repetition time (TR) around its center of origin in the k-space [9-11]. RADAR is based on the fast spin echo (FSE) pulse sequence and has disadvantages (including a long acquisition time) compared with EPI. Nevertheless, it has a high robustness to magnetic susceptibility artifacts [12-13].There have been many reports on image quality assessment in EPI and FSE DWI, such as image distortion and artifacts in anatomical areas affected by magnetic susceptibility [9-13] , however, there are no previous studies addressing how the ADC values are affected. Provided that RADAR DWI is robust to magnetic susceptibility artifacts, ADC value measurements should be accurate even in environments affected by magnetic susceptibility.
The manganese (II) chloride (MnCl2) shortens T2 values by disrupting the local magnetic field due to its magnetic susceptibility. MnCl2 is used in clinical MRI to suppress the gastrointestinal signal during magnetic resonance cholangiopancreatography imaging, taking advantage of this property [14-15].
We hypothesized that in the presence of MnCl2, the ADC values obtained using EPI DWI and RADAR DWI can differ. In the present study, phantoms created with MnCl2 were used to compare ADC values obtained from EPI and RADAR DWI.