| Summary: | Background: Myocardial T2* mapping at 1.5T remains the gold standard, but the use of 3T scanners is increasing. We aimed to determine the conversion equations in different scanners with clinically available, vendor-provided T2* mapping sequences using a phantom and evaluated the feasibility of the phantom-based conversion method. Methods: T2* of a phantom with FeCl<sub>3</sub> (five samples, 3.53–20.09 mM) were measured with 1.5T (MR-A1) and 3T scanners (MR-A2, A3, B), and the site-specific equation was determined. T2* was measured in the interventricular septum of three healthy volunteers at 1.5T (T2*<sub>1.5T</sub>, MR-A1) and 3T (T2*<sub>3.0T</sub>, MR-B). T2*<sub>3.0T</sub> was converted based on the equation derived from the phantom (T2*<sub>eq</sub>). Results: R2* at 1.5T and 3T showed linear association, but a different relationship was observed according to the scanners (MR-A2, R2*<sub>1.5T</sub> = 0.76 × R2*<sub>3.0T</sub> − 2.23, <i>R</i><sup>2</sup> = 0.999; MR-A3, R2*<sub>1.5T</sub> = 0.95 × R2*3.0T − 34.28, <i>R</i><sup>2</sup> = 0.973; MR-B, R2*<sub>1.5T</sub> = 0.76 × R2*<sub>3.0T</sub> − 3.02, <i>R</i><sup>2</sup> = 0.999). In the normal myocardium, T2*<sub>eq</sub> and T2*<sub>1.5T</sub> showed no significant difference (35.5 ± 3.5 vs. 34.5 ± 1.2, <i>p</i> = 0.340). The mean squared error between T2*<sub>eq</sub> and T2*<sub>1.5T</sub> was 16.33, and Bland–Altman plots revealed a small bias (−0.94, 95% limits of agreement: −8.86–6.99). Conclusions: a phantom-based, site-specific equation can be utilized to estimate T2* values at 1.5T in centers where only 3T scanners are available.
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