Effect of inversion time on the precision of myocardial late gadolinium enhancement quantification evaluated with synthetic inversion recovery MR imaging.

OBJECTIVES

To evaluate the influence of inversion time (TI) on the precision of myocardial late gadolinium enhancement (LGE) quantification using synthetic inversion recovery (IR) imaging in patients with myocardial infarction (MI).

METHODS

Fifty-three patients with suspected prior MI underwent 1.5-T cardiac MRI with conventional magnitude (MagIR) and phase-sensitive IR (PSIR) LGE imaging and T1 mapping at 15 min post-contrast. T1-based synthetic MagIR and PSIR images were calculated with a TI ranging from -100 to +150 ms at 5-ms intervals relative to the optimal TI (TI). LGE was quantified using a five standard deviation (5SD) and full width at half-maximum (FWHM) thresholds. Measurements were compared using one-way analysis of variance.

RESULTS

The MagIR technique provided precise assessment of LGE area at TIs ≥ TI, while precision was decreased below TI. The LGE area showed significant differences at ≤ -25 ms compared to TI using 5SD (P < 0.001) and at ≤ -65 ms using the FWHM approach (P < 0.001). LGE measurements did not show significant difference over the analysed TI range in the PSIR images using either of the quantification methods.

CONCLUSIONS

T1 map-based PSIR images provide precise quantification of MI independent of TI at the investigated time point post-contrast. MagIR-based MI quantification is precise at TI and at longer TIs while showing decreased precision at TI values below TI.

KEY POINTS

• Synthetic IR imaging retrospectively generates LGE images at any theoretical TI • Synthetic IR imaging can simulate the effect of TI on LGE quantification • Fifteen minutes post-contrast MagIR accurately quantifies infarcts from TI to TI   + 150 ms • Fifteen minutes post-contrast PSIR provides precise infarct size independent of TI • Synthetic IR imaging has further advantages in reducing operator dependence.