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Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is commonly used in clinical practice to detect tumor blood supply, and it has recently been applied to assess skeletal vasculature. In this study, we retrospectively analyzed DCE-MRI data from 37 patients with osteonecrosis of the femoral head to evaluate alterations in microvascular circulation of the femoral head. Time-intensity curves (TICs) in the region of interest were classified into different lesion stages. In the greater trochanter area, extracellular space volume per unit volume of tissue was significantly higher in Association Research Circulation Osseous (ARCO) stage III than in ARCO stage II (P<.05 and power ≥ 0.8), while other parameters showed no statistical difference (P>.05 and/or power < 0.8). In the necrotic area, contrast enhancement ratio and maximum slope of increase were significantly lower in ARCO stage III than in ARCO stage II (P<.05 and power ≥ 0.8), while other parameters showed no statistical difference (P>.05 and/or power < 0.8). In the repair reaction area, all parameters were significantly higher in ARCO stage III than in ARCO stage II (P<.05 and power ≥ 0.8). TIC classification showed that the greater trochanter area mainly exhibited type C (plateau type), the necrotic area mainly exhibited type B (out-flow type), and the repair reaction area mainly exhibited type A (inflow type). We believe that the exchange capacity of the vessels has a much greater impact on femoral head necrosis than the number of vessels, while the generation of the repair area greatly affects the prognosis of femoral head necrosis. These findings suggest that DCE-MRI can provide a good assessment of osteonecrosis of the femoral head perfusion and can serve as a new reference for clinical treatment decisions. [Orthopedics. 2024;47(2):e73–e78.] [ABSTRACT FROM AUTHOR]

Background: Parkinson's disease (PD) has been regarded as a disconnection syndrome with functional and structural disturbances. However, as the anatomic determinants, the structural disconnections in PD have yet to be fully elucidated. Purpose: To non-invasively construct structural networks based on microstructural complexity and to further investigate their potential topological abnormalities in PD given the technical superiority of diffusion kurtosis imaging (DKI) to the quantification of microstructure. Material and Methods: The microstructural data of gray matter in both the PD group and the healthy control (HC) group were acquired using DKI. The structural networks were constructed at the group level by a covariation approach, followed by the calculation of topological properties based on graph theory and statistical comparisons between groups. Results: A total of 51 patients with PD and 50 HCs were enrolled. Individuals were matched between groups with respect to demographic characteristics (P >0.05). The constructed structural networks in both the PD and HC groups featured small-world properties. In comparison with the HC group, the PD group exhibited significantly altered global properties, with higher normalized characteristic path lengths, clustering coefficients, local efficiency values, and characteristic path lengths and lower global efficiency values (P <0.05). In terms of nodal centralities, extensive nodal disruptions were observed in patients with PD (P <0.05); these disruptions were mainly distributed in the sensorimotor network, default mode network, frontal-parietal network, visual network, and subcortical network. Conclusion: These findings contribute to the technical application of DKI and the elucidation of disconnection syndrome in PD. [ABSTRACT FROM AUTHOR]

Biocrusts are a dominant component in drylands worldwide and play critical roles in supporting soil microbial diversity and carbon (C) stocks. Nitrogen (N) fertilization associated with human activities threatens drylands, which are often considered N‐limited ecosystems. Here, we conducted a field experiment in two contrasting soil types (loess vs. sand) to investigate the impacts of low (30 kg N ha−1 year−1) and high (90 kg N ha−1 year−1) fertilization on moss‐biocrust dominated traits, soil nutrients, microbial taxonomic richness, soil C stocks and respiration rates (Rs). We showed that 5 months of N addition resulted in reductions in soil organic C content by 91% and increased both soil microbial richness and diversity. Our results further showed that relative to controls, low levels of N addition increased biocrust Rs by 52% through increased moss biomass and density (38% and 73%) and microbial taxonomic richness and diversity (18% and 23%), while no significant changes in biocrust Rs were observed after high levels of N addition. Considering multiple environmental factors simultaneously, we show that N fertilization indirectly promoted soil respiration and C losses via increases in microbial richness and diversity, which are critical drivers of soil function. Our work provides solid evidence that N deposition, even at low levels of N addition, can result in rapid losses of C in dryland soils. Our findings suggest that to maintain healthy dryland ecosystems and promote C, we must mitigate future land degradation and minimize anthropogenic N deposition. [ABSTRACT FROM AUTHOR]

Background: Intravoxel incoherent motion (IVIM) MRI has not been widely used and its role in evaluating exertional heat illness (EHI)‐related myocardial involvement remains unknown. Purpose: To investigate the feasibility of strain curve‐derived trigger delay (TD) IVIM‐MRI and its role in assessing myocardial diffusion and microvascular perfusion of EHI patients. Study Type: Prospective. Subjects: A total of 42 male EHI patients (median age: 21 years) and 22 age‐ and sex‐matched healthy controls (HC). Field Strength/Sequence: A 3‐T, diffusion‐weighted spin‐echo echo‐planar‐imaging sequence. Assessment: IVIM‐MRI was acquired by conventional TD method (group A) or strain curve‐based TD method (group B) in random order. IVIM image quality was evaluated on a 3‐point Likert scale (1, nondiagnostic; 2, moderate; 3, good). Technical success was defined as image quality score = 3. IVIM‐MRI‐derived parameters (pseudo diffusion in the capillaries [D*], perfusion fraction [f], and slow apparent diffusion coefficient [D]) were compared between EHI and HC. Statistical Tests: Student's t‐tests, chi‐square tests, one‐way analysis of variance, receiver operating characteristic (ROC) curve analysis, Pearson's correlation coefficient (r). The statistical significance level was set at P < 0.05. Results: IVIM‐MRI image quality score (median [interquartile range]: 3 [2, 3] vs. 2 [1–3]) and technical success rate (61.9%[13/21] vs. 28.6%[6/21]) were significantly improved in group B. EHI patients showed significantly decreased D* (118.1 ± 23.3 × 10−3 mm2/sec vs. 142.7 ± 42.6 × 10−3 mm2/sec) and f values (0.42 ± 0.12 vs. 0.51 ± 0.11) and significantly higher D values (3.0 ± 0.9 × 10−3 mm2/sec vs. 2.5 ± 0.6 × 10−3 mm2/sec) compared to HC. Relative to D and D*, f showed the most robust efficacy for detecting EHI‐related myocardial injury with the highest area under the ROC curve (0.906: 95% confidence interval, 0.799, 0.967) and sensitivity of 88.5% and specificity of 85.6%. Conclusion: The strain curve‐based TD method significantly improved image quality and technical success rate of IVIM‐MRI, and f value may be an effective biomarker to assess myocardial microcirculation abnormalities of EHI patients. Evidence Level: 2. Technical Efficacy: Stage 3. [ABSTRACT FROM AUTHOR]