T(2)STIR preparation for single-shot cardiovascular magnetic resonance myocardial edema imaging

BACKGROUND: Myocardial edema in acute myocardial infarction (AMI) is commonly imaged using dark-blood short tau inversion recovery turbo spin echo (STIR-TSE) cardiovascular magnetic resonance (CMR). The technique is sensitive to cardiac motion and coil sensitivity variation, leading to myocardial signal nonuniformity and impeding reliable depiction of edematous tissues. T(2)-prepared balanced steady state free precession (T(2)p-bSSFP) imaging has been proposed, but its contrast is low, and averaging is commonly needed. T(2) mapping is useful but requires a long scan time and breathholding. We propose here a single-shot magnetization prepared sequence that increases the contrast between edema and normal myocardium and apply it to myocardial edema imaging. METHODS: A magnetization preparation module (T(2)STIR) is designed to exploit the simultaneous elevation of T(1) and T(2) in edema to improve the depiction of edematous myocardium. The module tips magnetization down to the –z axis after T(2) preparation. Transverse magnetization is sampled at the fat null point using bSSFP readout and allows for single-shot myocardial edema imaging. The sequence (T(2)STIR-bSSFP) was studied for its contrast behavior using simulation and phantoms. It was then evaluated on 7 healthy subjects and 7 AMI patients by comparing it to T(2)p-bSSFP and T(2) mapping using the contrast-to-noise ratio (CNR) and the contrast ratio as performance indices. RESULTS: In simulation and phantom studies, T(2)STIR-bSSFP had improved contrast between edema and normal myocardium compared with the other two edema imaging techniques. In patients, the CNR of T(2)STIR-bSSFP was higher than T(2)p-bSSFP (5.9 ± 2.6 vs. 2.8 ± 2.0, P < 0.05) but had no significant difference compared with that of the T(2) map (T(2) map: 6.6 ± 3.3 vs. 5.9 ± 2.6, P = 0.62). The contrast ratio of T(2)STIR-bSSFP (2.4 ± 0.8) was higher than that of the T(2) map (1.3 ± 0.1, P < 0.01) and T(2)p-bSSFP (1.4 ± 0.5, P < 0.05). CONCLUSION: T(2)STIR-bSSFP has improved contrast between edematous and normal myocardium compared with commonly used bSSFP-based edema imaging techniques. T(2)STIR-bSSFP also differentiates between fat that was robustly suppressed and fluids around the heart. The technique is useful for single-shot edema imaging in AMI patients.