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Purpose <p>To compare the inter-reader reproducibility of two ROI placement strategies (circular versus freehand geographic) for hepatic PDFF and R2* quantification, and determine R2* thresholds above which conventional techniques show increasing disagreement relative to confounder-corrected chemical shift-encoded (CSE) methods, used as the reference technique.</p> Materials and methods <p>In this retrospective study, consecutive adults underwent abdominal MRI at 1.5 T with CSE and conventional sequences. Four radiologists (two seniors, two fellows) independently measured PDFF and R2* using both strategies. Inter-reader agreement was assessed using ICC; conventional–CSE agreement was evaluated with MAE stratified by R2* thresholds.</p> Results <p>Excellent interreader agreement was observed for all strategies: PDFF ICCs were 0.974 (five-ROI mean) and 0.975 (geographic); R2* ICCs were 0.983 for both. Correlation between strategies was near-perfect (PDFF: <i>r</i> = 0.995; R2*: <i>r</i> = 0.991). No significant differences were found between experience levels. A sliding threshold analysis identified conventional R2* = 45&#xa0;s<sup>⁻¹</sup> as a proposed exploratory cutoff (bootstrap 95% CI: 40–70&#xa0;s<sup>⁻¹</sup>): below this value, conventional PDFF maintained low error (MAE = 3.2% points [pp]; 17.9% exceeding 5 pp), whereas above 80&#xa0;s<sup>⁻¹</sup>, MAE increased to 11.2 pp with 93.8% exceeding 5 pp. Conventional R2* systematically overestimated iron with increasing PDFF (MAE = 12.8&#xa0;s<sup>⁻¹</sup> at PDFF ≥ 20%). In this study, reproducibility refers to inter-reader consistency (ICC), whereas agreement denotes error relative to the CSE reference (MAE).</p> Conclusion <p>Both ROI strategies yield excellent, comparable reproducibility regardless of reader experience. A proposed exploratory three-zone framework using conventional R2* (GREEN &lt; 45&#xa0;s<sup>⁻¹</sup>, YELLOW 45–80, RED ≥ 80) provides preliminary guidance regarding when conventional PDFF shows lower error relative to the CSE reference and when CSE methods should be strongly considered, pending external validation.</p>

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Reproducibility of ROI methods and reliability of conventional versus chemical shift-encoded MRI for hepatic fat and iron quantification

  • 期刊论文

  • 发表日期：

    2026年4月17日

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  • Hilton Leao Filho,
  • Virginia Goncalves,
  • Nathalia Mendonca,
  • Rafael Sachetin,
  • Abdalla Skaf

摘要

Purpose

To compare the inter-reader reproducibility of two ROI placement strategies (circular versus freehand geographic) for hepatic PDFF and R2* quantification, and determine R2* thresholds above which conventional techniques show increasing disagreement relative to confounder-corrected chemical shift-encoded (CSE) methods, used as the reference technique.

Materials and methods

In this retrospective study, consecutive adults underwent abdominal MRI at 1.5 T with CSE and conventional sequences. Four radiologists (two seniors, two fellows) independently measured PDFF and R2* using both strategies. Inter-reader agreement was assessed using ICC; conventional–CSE agreement was evaluated with MAE stratified by R2* thresholds.

Results

Excellent interreader agreement was observed for all strategies: PDFF ICCs were 0.974 (five-ROI mean) and 0.975 (geographic); R2* ICCs were 0.983 for both. Correlation between strategies was near-perfect (PDFF: r = 0.995; R2*: r = 0.991). No significant differences were found between experience levels. A sliding threshold analysis identified conventional R2* = 45 s⁻¹ as a proposed exploratory cutoff (bootstrap 95% CI: 40–70 s⁻¹): below this value, conventional PDFF maintained low error (MAE = 3.2% points [pp]; 17.9% exceeding 5 pp), whereas above 80 s⁻¹, MAE increased to 11.2 pp with 93.8% exceeding 5 pp. Conventional R2* systematically overestimated iron with increasing PDFF (MAE = 12.8 s⁻¹ at PDFF ≥ 20%). In this study, reproducibility refers to inter-reader consistency (ICC), whereas agreement denotes error relative to the CSE reference (MAE).

Conclusion

Both ROI strategies yield excellent, comparable reproducibility regardless of reader experience. A proposed exploratory three-zone framework using conventional R2* (GREEN < 45 s⁻¹, YELLOW 45–80, RED ≥ 80) provides preliminary guidance regarding when conventional PDFF shows lower error relative to the CSE reference and when CSE methods should be strongly considered, pending external validation.