Robust fat saturation applied to late enhancement
KeywordsLate Gadolinium Enhancement Inversion Pulse Heart Rate Variation Late Gadolinium Enhancement Imaging Healthy Myocardium
Late Gadolinium Enhancement (LGE) allows imaging of infarction and cardiomyopathies by measuring the accumulation of contrast agent within the myocardium. The shortened T1 relaxation time compared to healthy myocardium is imaged by an inversion recovery (IR) prepared segmented fast gradient echo sequence in which pathology and fat show as bright signal. The fat signal can lead to misinterpretation and poor visualization of epicardial enhancement. In previous work fat was suppressed by using two appropriately timed fat-selective RF pulses which re-invert and invert fat signal [Foo et al., JMRI, 2007] but this technique was sensitive to off-resonance and heart rate variations. The goal of the present work is to make two improvements to fat-saturated LGE: (1) increase robustness against B0 and B1 variations by using asymmetric adiabatic RF pulses, and (2) increase robustness against heart rate variations through dynamic timing of fat-selective RF pulses.
Benefits of fat-saturated LGE imaging include avoiding image wrapping of subcutaneous fat and therefore reduced possible misdiagnosis (Figure 2(b)), and in patients with pericardial enhancement the ability to rule out epicardial fat and better visualization of pathology (Figure 2(c)). The selectivity improvement of fat-selective pulses was particularly important at 1.5T where the chemical shift difference between fat and water is only 220 Hz. The technique presented here was proven to be robust in more than 20 cases.
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