[en] Objective: To explore the value of 6 commonly-used quantitative measures on cross-sectional MR images to diagnose the patellofemoral instability. Methods: Clinical data of 32 patients with patellofemoral instability(34 knees) confirmed by arthroscopy surgery were retrospective analyzed. Knee MR imaging at full extension of the knee was performed in them. Their MR images were compared with those of 23 asymptomatic volunteers. Trochlear facet asymmetry, lateral trochlear inclination, trochlear depth, patellar tilt angle, lateral patellar displacement, and tibial tuberosity-trochlear groove distance(TTTG) were measured in transverse fat-suppressed turbo spin-echo proton density-weighted MR images. Independent sample t test or Mann-Whitney U test were used to compare the differences of these measurements. ROC was used to calculate the area under curve(AUC) and to define the diagnostic threshold value of each measure. Results: Trochlear facet asymmetry, lateral trochlear inclination, and trochlear depth in patients were 45.0% ± 9.2%,10.9 ° ± 5.0 ° and (3.7 ± 1.3) mm, while these measurements were 68.0% ± 10.5%, 21.1 ° ± 3.4 ° and (6.3 ± 1.0) mm in volunteers. These measures were significantly lower in patients than those in volunteers (f values were 10.123, 10.862 and 9.835, P < 0.01). Patellar tilt angle and lateral patellar displacement were significantly higher in patients than those in volunteers(24.8 ° ± 9.0 ° vs. 12.3 ° ± 5.2 °, 7.36 mm vs. -3.93 mm, t value and Z value were -7.657 and -6.953, P < 0.01). TTTG showed no significant difference between the 2 groups(P = 0.798). AUC of trochlear facet asymmetry, lateral trochlear inclination, trochlear depth, patellar tilt angle, and lateral patellar displacement were 0.957, 0.957, 0.947, 0.921 and 0.961, respectively. The recommended diagnostic threshold values for these 5 measures were < 55%, < 15 °, < 5 mm, > 17 ° and < 3 mm, respectively. The sensitivity for these five measurements were 91.2%(31/34), 85.3%(29/34), 91.2%(31/34), 82.4%(28/34) and 79.4%(27/34),respectively. The specificity for these five measures were 91.3%(42/46), 97.8%(45/46), 89.1%(41/46), 89.1%(41/46) and 100.0%(46/46), respectively. AUC of TTTG was 0.520. Conclusions: At full extension of the knee, trochlear facet asymmetry, lateral trochlear inclination, trochlear depth, patellar tilt angle and lateral patellar displacement are all effective in evaluating patellofemoral instability. The diagnostic value of TTTG is relatively poor. (authors)

[en] Objective: To determine the effect of knee position from full extension to slight flexion on cross-sectional MRI measurements for assessing patellofemoral instability. Methods: 25 healthy volunteers (12 men and 13 women;age range: 19-27 years;average age: 24.61 ± 2.52 years) underwent 3T MRI of both knees in full extension and 20° of flexion. The trochlear facet asymmetry, lateral trochlear inclination, trochlear depth, patellar tilt angle, lateral patellar displacement and tibial tuberosity-trochlear groove d1 stance (TTTG) of each knee were measured on MRI by two observers. Paired sample t test was used to compare the six measurements between full extension and 20 ° of flexion positions. Results: In slight knee flexion, measurements of the patellar tilt angle (9.42° ± 4.61° by observer 1, 8.43 ° ± 4.42° by observer 2) were significantly (both P < 0.001) smaller than that of full knee extension (12.91° ± 5.32°, 12.32° ± 5.53°). Differences in measurements of lateral patellar displacement in flexion (-3.92 ± 2.51 mm, -5.03 ± 2.72 mm) and extension (-2.81 ± 3.22 mm, -3.92 ± 3.33 mm) were also significant (P = 0.006, P = 0.012) as were differences (both P < 0.001) in TTTG measurements between flexion (6.93 ± 3.32 mm, 7.43 ± 4.73 mm) and extension (15.12 ± 2.93 mm, 15.93 ± 3.24 mm) for both observers. There were no significant differences (P > 0.05) in measurements of trochlear facet asymmetry in flexion (73.92% ± 9.21%, 61.93% ± 10.32%) and extension (72.41% ± 12.22%, 62.82% ± 12.83%), lateral trochlear inclination in flexion (19.72° ± 4.21°, 20.23° ± 4.82°) and extension (20.71° ± 4.22°, 20.62° ± 3.73°), or trochlear depth between flexion (6.72 ± 1.11 mm, 5.94 ± 1.03 mm) and extension (6.81 ± 1.12 mm, 5.93 ± 1.24 mm) for both observers. Conclusion: Varying degrees of flexion have significant influence on MRI measurements of patellar tilt angle, lateral patellar displacement, and TTTG without affecting measurements of trochlear facet asymmetry, lateral trochlear inclination, and trochlear depth in healthy volunteers. (authors)

[en] This paper illustrates the direct and indirect effects of democracy on CO₂ emissions in the BRICS countries (Brazil, Russia, India, China, and South Africa) from 1992 to 2018. In view of the distribution heterogeneity of CO₂ emissions, the panel quantile regression model is especially used to explore the nexus among different variables. Furthermore, in order to predict the trends of CO₂ emissions in different countries, we also estimate the kernel density function of CO₂ emissions in the BRICS countries by the quantile-fitted values. The results indicate that the direct impact of democracy on carbon dioxide emissions is significantly negative and great at high-emission countries. Although the indirect effect of democracy is positive in China and negative in Brazil and South Africa, the total effect of democracy on CO₂ emissions remains negative in all BRICS countries. The estimation of kernel density function shows that the distribution of CO₂ emissions in each country is gradually concentrated. Moreover, there is an environmental Kuznets curve depicting the linkage of urbanization and carbon dioxide emissions in Brazil and South Africa. These findings further highlight that the impact of democracy on high-emission and low-emission countries should be taken into account in policymaking to achieve sustainable developments.

[en] To investigate the feasibility of non-contrast-enhanced MR angiography (NCE-MRA) in evaluating the morphology and blood supply of left gastric vein (LGV) in patients with gastroesophageal varices. Between March 2021 and October 2022, patients with gastroesophageal varices and who underwent NCE-MRA were retrospectively reviewed. In order to evaluate the blood supply of LGV, superior mesenteric vein (SMV) and splenic vein (SV) were visualized separately by using inflow-sensitive inversion recovery sequence. Two radiologists independently assessed the image quality, determined the origination and the blood supply of LGV, and measured the diameter of LGV. The origination and diameter of LGV were compared between NCE-MRA and contrast-enhanced CT. Differences in blood supply were compared between LGVs with different originations. A total of 53 patients were enrolled in this study and the image quality was categorized as good or excellent in 52 patients. No significant differences were observed in visualizing the origination and the diameter of LGV between NCE-MRA and contrast-enhanced CT (p > .05). The blood supply of LGV was related to its origination (p < .001). Most LGVs with SV origination were supplied by SV. If LGV was originated from the portal vein (PV), about 70% of them were supplied by both SV and SMV. Compared with LGVs with SV origination, LGVs with PV origination showed more chance to receive blood from SMV (p < .001). Non-contrast-enhanced MR angiography appears to be a reliable technique in evaluating the morphology and blood supply of LGV in patients with gastroesophageal varices. Non-contrast-enhanced MR angiography provides valuable information for the management of gastroesophageal varices. Especially, it benefits patients with renal insufficiency.