Field inhomogeneity correction for qDESS mapping: application to rapid bilateral knee imaging

$$ mapping is a powerful tool for studying osteoarthritis (OA) changes and bilateral imaging may be useful in investigating the role of between-knee asymmetry in OA onset and progression. The quantitative double-echo in steady-state (qDESS) can provide fast simultaneous bilateral knee $$ and high-resolution morphometry for cartilage and meniscus. The qDESS uses an analytical signal model to compute $$ relaxometry maps, which require knowledge of the flip angle (FA). In the presence of $$ inhomogeneities, inconsistencies between the nominal and actual FA can affect the accuracy of $$ measurements. We propose a pixel-wise $$ correction method for qDESS <$$ mapping exploiting an auxiliary $$ map to compute the actual FA used in the model.

The technique was validated in a phantom and in vivo with simultaneous bilateral knee imaging. $$ measurements of femoral cartilage (FC) of both knees of six healthy participants were repeated longitudinally to investigate the association between $$ variation and $$.

The results showed that applying the $$ correction mitigated $$ variations that were driven by $$ inhomogeneities. Specifically, $$ left-right symmetry increased following the $$ correction ($$= 0.74 > $$ = 0.69). Without the $$ correction, $$ values showed a linear dependence with $$. The linear coefficient decreased using the $$ correction (from 24.3 ± 1.6 ms to 4.1 ± 1.8) and the correlation was not statistically significant after the application of the Bonferroni correction (p value > 0.01).

The study showed that $$ correction could mitigate variations driven by the sensitivity of the qDESS $$ mapping method to $$, therefore, increasing the sensitivity to detect real biological changes. The proposed method may improve the robustness of bilateral qDESS $$ mapping, allowing for an accurate and more efficient evaluation of OA pathways and pathophysiology through longitudinal and cross-sectional studies.