<p><strong>PURPOSE: </strong>To compare the reproducibility and accuracy of R2-relaxometry MRI for estimation&nbsp;of liver iron concentration (LIC) between in-house analysis and FDA-approved commercially available third party results.</p>

<p><strong>METHODS: </strong>All MR studies were performed on a 1.5T scanner.&nbsp;Multi-echo spin-echo scans with a fixed TR and increasing TE values of 6&nbsp;ms, 9&nbsp;ms, 12&nbsp;ms, 15&nbsp;ms, and 18&nbsp;ms (spaced at 3&nbsp;ms intervals) were used. Post-processing of the images to calculate mean relaxivity, R2, included drawing of regions of interest to include the whole liver on mid-slice. The relationship between liver R2 values and estimated LIC calculated with in-house analysis and values&nbsp;reported by an external company (FerriScan, Resonance Health, Australia) were assessed with correlation coefficients and Bland-Altman difference plots. Continuous variables are presented as mean ± standard deviation. Significance was set at p value &lt; 0.05.</p>

<p><strong>RESULTS: </strong>474 studies from 175 patients were included in the study (mean age 10.4 ± 4.2&nbsp;years (range 1-18&nbsp;years); 254 studies from girls, 220 studies from boys). LIC ranged from 0.6 to 43&nbsp;mg/g dry tissue, covering a broad range from normal levels to extremely high iron levels. Linearity between proprietary and in-house methods was excellent across the observed range for R2 (31.5 to 334.8&nbsp;s); showing a correlation coefficient of r = 0.87, p &lt; 0.001. Bland-Altman R2 difference plot between the two methods shows a mean bias of + 21.5&nbsp;s (range - 47.0 to + 90.0&nbsp;s between two standard deviations). LIC reported by FerriScan compared with LIC estimated in-house with R2 as reported by FerriScan agreed strongly, (r = 1.0, p &lt; 0.001).</p>

<p><strong>CONCLUSION: </strong>R2 relaxometry MR imaging for liver iron concentration estimation is reproducible between proprietary FDA-approved commercial software and in-house analysis methods.</p>