Comparison of FOCUS and Conventional DWI for Evaluation of Intra-pelvic Tumor

Introduction: MR imaging has played an important role in evaluating the intra-pelvic tumor such as uterine, prostatic, and rectal cancer. Now, diffusion weighted imaging (DWI) with single-shot echo planar imaging (ss-EPI) is a useful tool for detection of the intra-pelvic tumor. However, DWI with ss-EPI is susceptible to inhomogeneity of magnetic field and may result in distortion of imaging. Field-of-view (FOV) optimized and constrained undistorted single-shot (FOCUS) is one of the new methods. With this method, we can decrease the required readout duration for single shot EPI by using a 2D spatially selective echo-planar RF excitation pulse and a 180 degrees refocusing pulse, consequently, acquire high spatial resolution images with less distortion. The purpose of this study was to compare the performance of FOCUS DWI for evaluation of intra-pelvic tumor with that of conventional DWI. Materials and Methods: 14 patients with pelvic tumor (rectum: 4, uterus and vulva: 2, urinary bladder: 6, prostate: 2, respectively) were included in this study, who underwent MRI on a 3T unit (MR750W, GE Healthcare). The spatial resolution of FOCUS DWI was as follows; FOV: 24*12cm, Matrix: 128*64, section thickness: 4-5 mm, and that of