Unexpected Lateral Asymmetry in TSE Image Contrast Explained: Tissues with Short T2 Show Extreme Sensitivity to B1 Inhomogeneity

Jaco J.M. Zwanenburg¹, Fredy Visser¹, ², Jeroen Hendrikse¹, Peter R. Luijten¹

In heavily T2-weighted FLAIR images at 7T, a lateral asymmetry was observed in the contrast of the pulvinar, a nucleus of the thalamus. Due to the small distance between the bilateral pulvinars, B1 inhomogeneity seemed unlikely as explanation for the asymmetry in contrast. In this work, however, we show with simulations and experiments that TSE trains exhibit a highly T2 dependent sensitivity to B1 inhomogeneity, which leads to asymmetry in image contrast (rather than in signal intensities alone). This finding urges for careful interpretation of TSE images (also at clinical field strengths), and highlights the need for precise B1 shimming.