title: Readout-segmented echo-planar imaging in diffusion-weighted imaging of the kidney: comparison with single-shot echo-planar imaging in image quality.
abstract: OBJECTIVE
  The purpose of this study was to compare the image quality of readout-segmented echo-planar imaging (RS-EPI) and that of standard single-shot echo-planar imaging (SS-EPI) in the kidney in a rat model.
  
  
  METHODS
  Twelve Wistar rats undergoing MRI examinations were imaged with two diffusion-weighted (DW) imaging protocols: a standard SS-EPI and a new RS-EPI protocol, both with a 1.0 × 1.0 × 3.0 mm voxel. The two groups of diffusion-weighted images were independently scored on geometric distortion, image blurring, signal dropout, and the overall image quality by two radiologists. Signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) were measured on both sequences. Inter-rater agreement (IRA) was evaluated by Fleiss kappa (κ) and inter-class correlation coefficient (ICC) statistics. Comparisons of image qualities were made by Wilcoxon signed-rank test and paired-sample t test.
  
  
  RESULTS
  Both RS-EPI and SS-EPI had good IRAs in scoring image qualities (κ = 0.607-0.833) and measuring renal ADCs (ICC = 0.828-0.945). Compared to SS-EPI, RS-EPI produced less geometric distortion (median score 1.5 versus 2.5, p < 0.0001), less image blurring (1.75 versus 2.0, p = 0.0003), less signal dropout (1.0 versus 3.0, p = 0.0001), and a lower score in overall image artifacts (4.25 versus 7.25; p < 0.0001). RS-EPI had higher SNR of renal DW images than SS-EPI (p < 0.001). The intra-variability of ADCs in cortex, outer medulla, and inner medulla ranged from 9.6% to 11.1% (Pearson correlation coefficient ρ = 0.675-0.729; p < 0.001) between the two protocols.
  
  
  CONCLUSIONS
  We showed that for DWI of the kidney at 1.0 × 1.0 × 3.0 mm(3) voxel sizes, the new protocol provided better image quality than standard SS-EPI protocol.
authors.affiliation: Department of Radiology, The First Affiliated Hospital with Nanjing Medical University, No. 300, Guangzhou Road, Nanjing, 210000, China. njmu_wcj@163.com.
authors.forename: Chen-Jiang
authors.initials: CJ
authors.lastname: Wu
authors.affiliation: Department of Radiology, The First Affiliated Hospital with Nanjing Medical University, No. 300, Guangzhou Road, Nanjing, 210000, China. njmu_wq@163.com.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Radiology, The First Affiliated Hospital with Nanjing Medical University, No. 300, Guangzhou Road, Nanjing, 210000, China. njmu_zj@163.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Radiology, The First Affiliated Hospital with Nanjing Medical University, No. 300, Guangzhou Road, Nanjing, 210000, China. njmu_wxn@163.com.
authors.forename: Xiao-Ning
authors.initials: XN
authors.lastname: Wang
authors.affiliation: Department of Radiology, The First Affiliated Hospital with Nanjing Medical University, No. 300, Guangzhou Road, Nanjing, 210000, China. njmu_lxs@163.com.
authors.forename: Xi-Sheng
authors.initials: XS
authors.lastname: Liu
authors.affiliation: Department of Radiology, The First Affiliated Hospital with Nanjing Medical University, No. 300, Guangzhou Road, Nanjing, 210000, China. njmu_zyd@163.com.
authors.forename: Yu-Dong
authors.initials: YD
authors.lastname: Zhang
authors.affiliation: Department of Radiology, The First Affiliated Hospital with Nanjing Medical University, No. 300, Guangzhou Road, Nanjing, 210000, China. njmu_shb@163.com.
authors.forename: Hai-Bin
authors.initials: HB
authors.lastname: Shi
mesh_terms: D000818:Animals; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000033:anatomy & histology*; D023421:Models, Animal; D051381:Rats; D017208:Rats, Wistar; D059629:Signal-To-Noise Ratio
keywords: Diffusion-weighted imaging; Kidney; Magnetic resonance imaging; Readout-segmented echo-planar imaging; Single-shot echo-planar imaging