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Structural lattices with quasi-periodic patterns possess interesting dynamic features that can be exploited to control, localize and redirect propagating waves. In this work, we show that the properties of a large class of quasi-periodic locally resonant systems (approximated as periodic, with arbitrarily large period) can be performed by defining an equivalent discrete system. Several properties of wave propagation can a priori be demonstrated with reference to this system. Results in terms of bulk spectrum, showing the Hofstadter butterfly pattern, and of topological modes are then discussed in detail with reference to a simple example of quasi-periodic lattice. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 2)'. [ABSTRACT FROM AUTHOR]

Simple Summary: In this retrospective study of 61 patients with diffuse gliomas, APT-weighted imaging in the solid tumor component provided quantitative metrics associated with WHO grade and survival. Mean APT values of the necrotic component showed high variability between subjects, warranting further investigation. These results highlight the importance of assessing the different tumor components with APT-weighted imaging, to provide useful diagnostic and prognostic information for the management of patients with gliomas. Amide Proton Transfer-weighted (APTw) imaging is a molecular MRI technique used to quantify protein concentrations in gliomas, which have heterogeneous components with varying cellularity and metabolic activity. This study aimed to assess the correlation between the component-specific APT signal of the neoplasm and WHO grade, molecular profile and survival status. Sixty-one patients with adult-type diffuse gliomas were retrospectively analyzed. APT values were semi-automatically extracted from tumor solid and, whenever present, necrotic components. APT values were compared between groups stratified by WHO grade, IDH-mutation, MGMT promoter methylation and 1- and 2-year survival status using Wilcoxon rank-sum test, adjusting for multiple comparisons. Overall survival (OS) was analyzed in the subgroup of 48 patients with grade 4 tumors using Cox proportional-hazards models. Random-effects models were used to assess inter-subject heterogeneity of the mean APT values in each tumor component. APT values of the solid component significantly differed between patients with grades 2–3 and 4 tumors (mean 1.58 ± 0.50 vs. 2.04 ± 0.56, p = 0.028) and correlated with OS after 1 year (1.81 ± 0.58 in survivors vs. 2.17 ± 0.51 in deceased patients, p = 0.030). APT values did not differ by IDH-mutation, MGMT methylation, and 2-year survival status. Within grade 4 glioma patients, higher APT kurtosis of the solid component was a negative prognostic factor (hazard ratio = 1.60, p = 0.040). Mean APT values of the necrosis showed high inter-subject variability, although most necrotic tumors were grade 4 and IDH wildtype. In conclusion, APTw imaging in the solid component provided metrics associated with glioma grade and survival status but showed weak correlation with IDH-mutation and MGMT promoter methylation status, in contrast to previous works. Further research is needed to understand APT signal variability within the necrotic component of high-grade gliomas. [ABSTRACT FROM AUTHOR]

The methylation of the O6-methylguanine-DNA methyltransferase (MGMT) promoter is a molecular marker associated with a better response to chemotherapy in patients with glioblastoma (GB). Standard pre-operative magnetic resonance imaging (MRI) analysis is not adequate to detect MGMT promoter methylation. This study aims to evaluate whether the radiomic features extracted from multiple tumor subregions using multiparametric MRI can predict MGMT promoter methylation status in GB patients. This retrospective single-institution study included a cohort of 277 GB patients whose 3D post-contrast T1-weighted images and 3D fluid-attenuated inversion recovery (FLAIR) images were acquired using two MRI scanners. Three separate regions of interest (ROIs) showing tumor enhancement, necrosis, and FLAIR hyperintensities were manually segmented for each patient. Two machine learning algorithms (support vector machine (SVM) and random forest) were built for MGMT promoter methylation prediction from a training cohort (196 patients) and tested on a separate validation cohort (81 patients), based on a set of automatically selected radiomic features, with and without demographic variables (i.e., patients' age and sex). In the training set, SVM based on the selected radiomic features of the three separate ROIs achieved the best performances, with an average of 83.0% (standard deviation: 5.7%) for accuracy and 0.894 (0.056) for the area under the curve (AUC) computed through cross-validation. In the test set, all classification performances dropped: the best was obtained by SVM based on the selected features extracted from the whole tumor lesion constructed by merging the three ROIs, with 64.2% (95% confidence interval: 52.8–74.6%) accuracy and 0.572 (0.439–0.705) for AUC. The performances did not change when the patients' age and sex were included with the radiomic features into the models. Our study confirms the presence of a subtle association between imaging characteristics and MGMT promoter methylation status. However, further verification of the strength of this association is needed, as the low diagnostic performance obtained in this validation cohort is not sufficiently robust to allow clinically meaningful predictions. [ABSTRACT FROM AUTHOR]

The present study clinically and radiographically compares the outcome of implants inserted in maxillary sinuses augmented with concentrated growth factors (CGFs) or demineralized bovine bone matrix (DBBM) in a one-stage lateral approach. In 20 patients with a residual bone height of 1 to 4 mm, lateral sinus floor elevation was performed, using CGFs or DBBM as the sole grafting material, with simultaneous implant placement. Outcome variables were implant and prosthesis failures, complications, subjective satisfaction, and radiographic changes in marginal bone level (MBL) 12 months after surgery. The patients were consecutively recruited: 10 to the CGF group and 10 to the DBBM group. No implant failed in either group at 12 months postsurgery, and there were no complications. There was no statistically significant difference in MBL change between the CGF and DBBM groups (difference of --0.3 mm, favoring the CGF group; 95% confidence interval [CI]: -0.8 to 0.2; P = .18). There was no statistically significant difference in satisfaction (difference of 0.2, favoring the CGF group; 95% CI: -0.2 to 0.6; P = .29). Within the limitations of the present study, the lateral sinus floor elevation performed with the use of CGFs as the sole grafting material showed implant survival rates and marginal bone level changes comparable to DBBM grafting. [ABSTRACT FROM AUTHOR]

This study presents the histomorphometric results of the Wafer Technique, which is based on guided bone regeneration and onlay grafts for 3D bone augmentation. This two-stage technique utilizes autogenous cortical bone plates and collagen membranes, forming a barrier containing a mixture of deproteinized bovine bone matrix, autologous blood, and bone grafted from intraoral sites. Twelve patients were treated. At 6 months postsurgery, histologic analysis of the regenerated areas revealed the presence of compact newly formed bone with no sign of inflammation. The percentages of new bone and native bone (mineralized tissue) were 16.4% (95% CI: 9.5% to 23.2%) and 42.6% (95% CI: 28.2% to 57.0%), respectively. Twenty-five implants were placed. The procedure has been proven to be safe and reliable, and only one transient complication was observed. [ABSTRACT FROM AUTHOR]