QSM-RimDS: A highly sensitive paramagnetic rim lesion detection and segmentation tool for multiple sclerosis lesions

Paramagnetic rim lesions (PRLs) are imaging biomarker of the innate immune response in MS lesions. QSM-RimNet, a state-of-the-art tool for PRLs detection on QSM, can identify PRLs but requires precise QSM lesion mask and does not provide rim segmentation. Therefore, the aims of this study are to develop QSM-RimDS algorithm to detect PRLs using the readily available FLAIR lesion mask and to provide rim segmentation for microglial quantification. QSM-RimDS, a deep-learning based tool for joint PRL rim segmentation and PRL detection has been developed. QSM-RimDS has obtained state-of-the art performance in PRL detection and therefore has the potential to be used in clinical practice as a tool to assist human readers for the time-consuming PRL detection and segmentation task. QSM-RimDS is made publicly available [https://github.com/kennyha85/QSM_RimDS]

Maximum Spherical Mean Value (mSMV) Filtering for Whole Brain Quantitative Susceptibility Mapping

To develop a tissue field filtering algorithm, called maximum Spherical Mean Value (mSMV), for reducing shadow artifacts in quantitative susceptibility mapping (QSM) of the brain without requiring brain tissue erosion. Residual background field is a major source of shadow artifacts in QSM. The mSMV algorithm filters large field values near the border, where the maximum value of the harmonic background field is located. The effectiveness of mSMV for artifact removal was evaluated by comparing with existing QSM algorithms in a simulated numerical brain, 11 healthy volunteers, by assessing image quality in routine clinical patient study $(n=43)$, and by measuring lesion susceptibility values in multiple sclerosis patients $(n=50)$, a total of $n=93$ patients. Numerical simulation showed that mSMV reduces shadow artifacts and improves QSM accuracy. Better shadow reduction, as demonstrated by lower QSM variation in the gray matter and higher QSM image quality score, was also observed in healthy subjects and in patients with hemorrhages, stroke and multiple sclerosis. The mSMV algorithm allows reconstruction of QSMs that are equivalent to those obtained using SMV-filtered dipole inversion without eroding the volume of interest.