Fig. 4.

a) Heating as measured in a 1×3 pixel ROI located at the focus is plotted as a function of time (dual-echo pulse sequence from Fig. 1, BW₂ = −BW₁, under manually de-adjusted linear shim, 0.169 mT/m offset was added to the vertically-oriented, physical-y orientation). Dotted and dashed curves represent measurements from echo #1 and echo #2, respectively, while the solid line shows corrected results obtained through Eq. 9. The corrected results agreed very well with reference results, shown with ‘○’ symbols and obtained using a properly-shimmed product GRE sequence. A scatterplot (b) and a Bland-Altman plot (c) were used to compare the corrected temperature measurements to the reference ones. From (c): Slope/intercept = 1.01/0.01 and R² = 0.996. From (d): Mean difference = 0.06 °C (solid line), 95% confidence intervals = ±0.36 °C (±1.96 standard deviation, dashed lines).