# Comparison of twelve‐layer concentric object (TLCO) and Line segmentations methods to determine the renal corticomedullary sodium gradient (CMSG) with a 3 T MRI

## TL;DR

This study compares two MRI methods for measuring sodium levels in the kidney and finds one method more reliable and precise.

## Contribution

The study introduces and validates the TLCO method as a more reliable alternative to the Line method for determining the renal CMSG.

## Key findings

- The TLCO method shows improved reliability, precision, and reproducibility compared to the Line method.
- The CMSG measured using the TLCO method had the lowest standard deviation among tested methods.
- No statistically significant difference was found between the CMSG values obtained by the two methods.

## Abstract

23Na MRI is a functional imaging technique that facilitates measurements of the renal corticomedullary sodium gradient (CMSG). The CMSG can be determined by a region of interest (ROI) in the renal parenchyma along the corticomedullary axis (Line method) or by dividing the renal parenchyma into concentric layers, using the twelve‐layer concentric objects (TLCO) method. The aim of this study was to investigate the differences, strengths, and weaknesses in determining the CMSG using these methods.

Ten healthy volunteers were examined on a 3 T MRI‐system. 23Na images were acquired using a double‐tuned 23Na/1H surface coil and a golden angle (GA) density‐adapted 3D radial (DA‐3D‐RAD) sequence. The CMSG was determined with the Line and TLCO methods. Intra‐ and inter‐reader analyses were performed by two radiologists.

The evaluated CMSG by the two methods does not differ statistically significantly. Compared to the Line method, the TLCO method provides improved results in terms of reliability, precision, reproducibility, and concordance in intra‐ and inter‐reader analyses. A CMSG of (6.7 ± 2.6) mM/mm was determined using the TLCO method in the segmentation process with the lowest standard deviation.

The TLCO method shows superior performance in determining the CMSG compared to the Line method. Accordingly, the use of the TLCO method is recommended for future renal CMSG studies.