Various regularization methods have been proposed for single-orientation quantitative susceptibility mapping (QSM), which is an ill-posed magnetic field to susceptibility source inverse problem. Noise amplification, a major issue in inverse problems, manifests as streaking artifacts and quantification errors in QSM and has not been comparatively evaluated in these algorithms. In this paper, various QSM methods were systematically categorized for noise analysis. Six representative QSM methods were selected from four categories: two non-Bayesian methods with alteration or approximation of the dipole kernel to overcome the ill conditioning; four Bayesian methods using a general mathematical prior or a specific physical structure prior to select a unique solution, and using a data fidelity term with or without noise weighting. The effects of noise in these QSM methods were evaluated by reconstruction errors in simulation and image quality in 50 consecutive human subjects. Bayesian QSM methods with noise weighting consistently reduced root mean squared errors in numerical simulations and increased image quality scores in the human brain images, when compared to non-Bayesian methods and to corresponding Bayesian methods without noise weighting (p ≤ 0.001). In summary, noise effects in QSM can be reduced using Bayesian methods with proper noise weighting.

Liu S, et al. Korean J Radiol. 2021 Oct;22:e128. https://doi.org/10.3348/kjr.2021.0132

Liu S, et al. Korean J Radiol. 2019 Jan;20:e36. https://doi.org/10.3348/kjr.2018.0508

Purpose: The aim of this study was to evaluate the efficacy of neoadjuvant chemotherapy (albumin-bound paclitaxel + carboplatin) combined with the PD-1 inhibitor tislelizumab in patients with potentially resectable stage II to IVb head and neck squamous cell carcinoma (HNSCC) and explore immune and circulating tumor–related features potentially associated with treatment response. Patients and Methods: This was a single-arm phase II trial involving 33 patients with potentially resectable stage II to IVb HNSCC. Participants received two cycles of neoadjuvant therapy followed by surgery. Primary endpoints were pathologic complete response (pCR) rate and major pathologic response (MPR) rate. Safety and exploratory analyses, including circulating tumor cells (CTC), PD-L1 expression, and T-cell senescence, were also assessed. Results: The study demonstrated an objective response rate of 72.7% (24/33) and an R0 resection rate of 93.1% (27/29) in surgical patients. The pCR rate was 44.8%, and the MPR rate was 62.1%. The laryngeal preservation rate was 70.4% (19/27). With a median follow-up of 20.5 months, the 12- and 24-month event-free survival rates were 93.1% (95% confidence interval, 84.3%–100%). Five of six patients with decreased CTC levels achieved MPR (5/6, 83.3%). Among patients whose T-cell senescence decreased, four of six achieved MPR, whereas only two of five with increased T-cell senescence achieved MPR. The pCR rate was significantly higher in patients with PD-L1 combined positive score ≥ 1 compared with those with combined positive score < 1 (55.6% vs. 12.5%). Conclusions: Neoadjuvant immunochemotherapy improves pathologic response and organ preservation in stage II to IVb HNSCC. Dynamic changes in CTCs and T-cell senescence are associated with treatment efficacy, suggesting their potential as early, noninvasive indicators of response, supporting precision treatment strategies for locally advanced HNSCC.

Objective: To investigate the diagnostic value of the Yin-Yang tongue sign in patients with tongue deviation. Methods: According to the presence of the Yin-Yang tongue sign on CT/MR, 107 patients with tongue deviation were divided into a positive group and a negative group. The involvement categories of the hypoglossal canal (HC) in the positive group were evaluated and classified as HC dilation and HC erosion. The correlations between HC involvement categories and the presence of the sign were analysed. Results: There were 55 cases (55/107, 51.4%) in the positive group and 52 cases (52/107, 48.6%) in the negative group. Hypoglossal nerve (HN) involvement mainly occurred in the skull base (61.8%), skull base and carotid space (10.9%), and carotid space segment (12.7%). Neurogenic (50.9%), squamous cell carcinoma (14.5%), and metastases (12.7%) were the predominant aetiologies. The sensitivity, specificity, and accuracy of this sign for suggesting skull base lesions around HC were 72.4%, 80.8%, and 76.6%, respectively. In the positive group, HC dilation was seen in 21 patients (21/55, 38.2%) and 21 cases were all benign. HC erosion were noted in 19 patients (19/55, 34.5%), of whom 12 cases were malignant. Conclusion: The Yin-Yang tongue sign is formed by unilateral tongue atrophy and fat infiltration caused by lesions in the HN pathway, especially compressive or invasive lesions involving the skull base segment.