Tissue Sodium Magnetic Resonance Imaging: Agreement and Repeatability of Manual Region of Interest Segmentation Methods

Abstract

To the Editor: Sodium-23 magnetic resonance imaging ( 23 Na MRI) has been used to noninvasively quantify tissue sodium (Na + ) in various conditions including hypertension, inflammation, and cardiovascular and metabolic disease. 1 While the reliability and agreement in serial 23 Na MR images 2,3 has been established, there is a paucity of studies focused on the agreement and reliability of the various manual region of interest (ROI) segmentation methods and the agreement between different methods. This study assesses this deficiency in published literature. Concise MethodsComplete methods are included in the Data S1. 23 Na MRI scans were completed with a 23 Na/ 1 H radiofrequency knee-coil (Rapid Biomedical, Rimpar, Germany) on a 3 T MAGNETOM Prisma Fit (Siemens Healthcare, Erlangen, Germany, software version VE11C). Affine registration was performed between 23 Na MR and 1 H proton images. Three raters used Insight Toolkit (ITK-SNAP) software (version 3.8.0) for ROI segmentation on a T1 image coregistered to 23 Na image (method definitions and visual examples in Fig. 1