Fig. 1.
L-curve for ℓ1-regularized QSM results for a young subject. X-axis: data consistency term ||δ – F−1 DF χ||2 in regularized reconstruction for varying values of the smoothing parameter λ. Y-axis: regularization term ||G χ||1. Setting λ = 5·10−5 yielded an under-regularized susceptibility map with ringing artifacts (a), whereas using λ = 10−3 resulted an over-regularized reconstruction (c). For λ = 2·10−4, the operating point with the largest curvature on the L-curve was obtained (b). This setting was used for the reported ℓ1-regularized results.