Methods for the computation of templates from quantitative magnetic susceptibility maps (QSM): Toward improved atlas- and voxel-based analyses (VBA).

PURPOSE: To develop and assess a method for the creation of templates for voxel-based analysis (VBA) and atlas-based approaches using quantitative magnetic susceptibility mapping (QSM). MATERIALS AND METHODS: We studied four strategies for the creation of magnetic susceptibility brain templates, derived as successive extensions of the conventional template generation (CONV) based on only T1 -weighted (T1 w) images. One method that used only T1 w images involved a minor improvement of CONV (U-CONV). One method used only magnetic susceptibility maps as input for template generation (DIRECT), and the other two used a linear combination of susceptibility and T1 w images (HYBRID) and an algorithm that directly used both image modalities (MULTI), respectively. The strategies were evaluated in a group of N = 10 healthy human subjects and semiquantitatively assessed by three experienced raters. Template quality was compared statistically via worth estimates (WEs) obtained with a log-linear Bradley-Terry model. RESULTS: The overall quality of the templates was better for strategies including both susceptibility and T1 w contrast (MULTI: WE = 0.62; HYBRID: WE = 0.21), but the best method depended on the anatomical region of interest. While methods using only one modality resulted in lower WEs, lowest overall WEs were obtained when only T1 w images were used (DIRECT: WE = 0.12; U-CONV: WE = 0.05). CONCLUSION: Template generation strategies that employ only magnetic susceptibility contrast or both magnetic susceptibility and T1 w contrast produce templates with the highest quality. The optimal approach depends on the anatomical structures of interest. The established approach of using only T1 w images (CONV) results in reduced image quality compared to all other approaches studied. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1474-1484.

Reserve-related activities and MRI metrics in multiple sclerosis patients and healthy controls: an observational study.

BACKGROUND: To examine whether past and current reserve-related activities make the brain less susceptible to MS pathology (i.e., lesions or disease-related atrophy). METHODS: This secondary analysis of a cohort study included 276 healthy controls (HC), and 65 clinically isolated syndrome (CIS), 352 relapsing-remitting MS (RR) and 109 secondary- progressive MS (SPMS) patients. Past reserve-related activities comprised educational and occupational attainment. Current reserve-related activities comprised strenuous and non-strenuous activities. MRI was performed on 3 T scanner. Regression and non-parametric analysis examined relationships between MRI metrics and reserve-related activities. RESULTS: Multivariate models (HC as referent) revealed significant interactions in predicting strenuous reserve-related activities with chronic lesion burden (for CIS), brain- (for RR & SPMS), subcortical- (for CIS, RR, & SPMS) and amygdala- (for RR) volumes. Maximal Lifetime Brain Growth was higher for RR patients who engaged in running before and after diagnosis, rather than only before or never. Residual Brain Volume was higher in RR patients who did weights-exercise before and after diagnosis, as compared to only before. CONCLUSIONS: Reserve-related activities are related to brain health cross-sectionally in all MS subgroups, and longitudinally in RR patients. Consistent with reserve theory, RR patients who maintained strenuous activities had higher Maximal Lifetime Brain Growth and Residual Brain Volume. The study's limitations are discussed, including the potential for recall bias and design limitations that preclude causal inference.

Resolution of Cardiogenic Shock Using Echocardiography-Guided Pacing Optimization in Intensive Care: A Case Series.

OBJECTIVE: Inotropic and vasopressor drugs are routinely used in critically ill patients to maintain adequate blood pressure and cardiac output in patients with cardiogenic shock although potentially at the expense of increasing myocardial oxygen demand. Pacing optimization has been demonstrated as effective in reducing catecholamine requirements in patients with chronic heart failure by improving cardiac efficiency; however, there are no reports relating to the effectiveness of pacemaker optimization on cardiac output in critically ill patients with cardiogenic shock in the intensive care. DATA SOURCES: Retrospective data analysis. STUDY SELECTION: Twenty-bed adult tertiary cardiothoracic ICU, university hospital. DATA EXTRACTION: Eight sequential patients receiving dual chamber pacemaker with DDD modality with cardiogenic shock and hemodynamic instability refractory to catecholamines underwent echocardiography-guided pacemaker optimization of cardiac output. An iterative method with Doppler echocardiography was used to assess changes in cardiac output, left ventricular filling time, ejection time, total isovolumic time, mitral regurgitation, ejection fraction, and blood pressure at different increments of heart rate, and atrioventricular and interventricular delay. All results are shown as median (minimum/maximum level) or mean ± SD. DATA SYNTHESIS: Using echocardiography-guided pacemaker optimization on cardiac output, the cardiac output increased from 3.2 (2.3/3.8) to 5.7 L/min (4.85/7.1) and cardiac index from 1.64 (1.1/1.9) to 2.68 L/min/m (2.1/3.2) and the total isovolumic time reduced from 22.8 to normal values (<14). In association, the glomerular filtration rate increased significantly except in one patient with stage IV chronic kidney disease. All inotropes and vasopressors were discontinued within 12 hours of pacemaker optimization on cardiac output, and all patients were discharged from the ICU within 1 week. CONCLUSIONS: Echocardiography-guided pacemaker optimization of cardiac output is a feasible bedside therapeutic option, which should be considered when standard medical treatments are insufficient for the treatment of cardiogenic shock refractory to inotropic support, thereby minimizing the detrimental effect of catecholamines.