[Formula: see text] Field inhomogeneity correction for qDESS [Formula: see text] mapping: application to rapid bilateral knee imaging.

ABSTRACT

PURPOSE: [Formula see text] 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 [Formula see text] and high-resolution morphometry for cartilage and meniscus. The qDESS uses an analytical signal model to compute [Formula see text] relaxometry maps, which require knowledge of the flip angle (FA). In the presence of [Formula see text] inhomogeneities, inconsistencies between the nominal and actual FA can affect the accuracy of [Formula see text] measurements. We propose a pixel-wise [Formula see text] correction method for qDESS [Formula see text] mapping exploiting an auxiliary [Formula see text] map to compute the actual FA used in the model. METHODS: The technique was validated in a phantom and in vivo with simultaneous bilateral knee imaging. [Formula see text] measurements of femoral cartilage (FC) of both knees of six healthy participants were repeated longitudinally to investigate the association between [Formula see text] variation and [Formula see text]. RESULTS: The results showed that applying the [Formula see text] correction mitigated [Formula see text] variations that were driven by [Formula see text] inhomogeneities. Specifically, [Formula see text] left-right symmetry increased following the [Formula see text] correction ([Formula see text] = 0.74 > [Formula see text] = 0.69). Without the [Formula see text] correction, [Formula see text] values showed a linear dependence with [Formula see text]. The linear coefficient decreased using the [Formula see text] 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). CONCLUSION: The study showed that [Formula see text] correction could mitigate variations driven by the sensitivity of the qDESS [Formula see text] mapping method to [Formula see text], therefore, increasing the sensitivity to detect real biological changes. The proposed method may improve the robustness of bilateral qDESS [Formula see text] mapping, allowing for an accurate and more efficient evaluation of OA pathways and pathophysiology through longitudinal and cross-sectional studies.