MRI texture analysis of subchondral bone at the tibial plateau

OBJECTIVES: To determine the feasibility of MRI texture analysis as a method of quantifying subchondral bone architecture in knee osteoarthritis (OA).   METHODS: Asymptomatic subjects aged 20-30 (group 1, n = 10), symptomatic patients aged 40-50 (group 2, n = 10) and patients scheduled for knee replacement aged 55-85 (group 3, n = 10) underwent high spatial resolution T1-weighted coronal 3T knee MRI. Regions of interest were created in the medial (MT) and lateral (LT) tibial subchondral bone from which 20 texture parameters were calculated. T2 mapping of the tibial cartilage was performed in groups 1 and 2. Mean parameter values were compared between groups using ANOVA. Linear discriminant analysis (LDA) was used to evaluate the ability of texture analysis to classify subjects correctly.   RESULTS: Significant differences in 18/20 and 12/20 subchondral bone texture parameters were demonstrated between groups at the MT and LT respectively. There was no significant difference in mean MT or LT cartilage T2 values between group 1 and group 2. LDA demonstrated subject classification accuracy of 97 % (95 % CI 91-100 %).   CONCLUSION: MRI texture analysis of tibial subchondral bone may allow detection of alteration in subchondral bone architecture in OA. This has potential applications in understanding OA pathogenesis and assessing response to treatment.   KEY POINTS: • Improved techniques to monitor OA disease progression and treatment response are desirable • Subchondral bone (SB) may play significant role in the development of OA • MRI texture analysis is a method of quantifying changes in SB architecture • Pilot study showed that this technique is feasible and reliable • Significant differences in SB texture were demonstrated between individuals with/without OA

A dissimilarity-based multiple classifier system for trabecular bone texture in detection and prediction of progression of knee osteoarthritis

There is a growing need for classification systems that can accurately detect and predict knee osteoarthritis (OA) from plain radiographs. For this purpose, a system based on a support vector machine (SVM) classifier and distances measured between trabecular bone (TB) texture images was developed and tested in previous work. Unlike other systems, it allows an image classification without the calculation and selection of numerous texture features, and it is invariant to a range of imaging conditions encountered in a routine X-ray screening of knees. Although the system exhibited 85.4% classification accuracy in OA detection, which was higher than those obtained from other systems, its performance could be further improved. To achieve this, a dissimilarity-based multiple classifier (DMC) system is developed in this study. The system measures distances between TB texture images and generates a diverse ensemble of classifiers using prototype selection, bootstrapping of training set and heterogeneous classifiers. A measure of competence is used to select accurate (i.e. better-than-random) classifiers from the ensemble, which are then combined through the majority voting rule. To evaluate the newly developed system in OA detection (prediction of OA progression), TB texture images selected on standardised radiographs of healthy and OA (non-progressive and progressive OA) knees were used. The results obtained showed that the DMC system has higher classification accuracies for the detection (90.51% with 87.65% specificity and 93.33% sensitivity) and prediction (80% with 82.00% specificity and 77.97% sensitivity) than other systems, indicating its potential as a decision-support tool for the assessment of radiographic knee OA

The influence of social support on ethnic differences in well-being and depression in adolescents: findings from the prospective Olympic Regeneration in East London (ORiEL) study.

PURPOSE: This study examines the extent to which in adolescent positive mental well-being and depressive symptoms vary across ethnic groups, and prospectively examines whether social support is protective against low/poor well-being and depression. METHODS: A longitudinal survey of 2426 adolescents from the Olympic Regeneration in East London study measured well-being and depressive symptoms at baseline at ages 11-12 and at follow-up two years later at ages 13-14. Social support was assessed at ages 11-12 years by the Multidimensional Scale of Perceived Social Support, by the level of parental support for school, by the frequency of family activities and by friendship choices. Ethnic differences in well-being and depression in Bangladeshi (N = 337) and Black African (N = 249) adolescents compared to their White UK counterparts (N = 380) were estimated adjusted stepwise for socio-demographic factors and domains of social support. RESULTS: Black African and Bangladeshi adolescents scored significantly higher for well-being than their White UK counterparts. There were no significant ethnic differences in the prevalence of depressive symptoms. Lower levels of social support were prospectively associated with lower well-being and higher rates of depression in all ethnic groups. Adjustment for multiple domains of social support did not account for ethnic differences in well-being. CONCLUSION: Bangladeshi and Black African adolescents in East London may have a positive mental health advantage over their White UK counterparts though social support did not fully explain this difference. Further investigation of the reasons for lower well-being in the White UK group is needed

Lesão pulmonar de reperfusão

A lesão de isquemia-reperfusão constitui-se em um evento fisiopatológico comum a diversas doenças da prática clínica diária. O pulmão pode ser alvo da lesão de isquemia-reperfusão diretamente, como no edema pulmonar após transplante ou na resolução de tromboembolismo; ou ainda ser atingido à distância, como nos casos de choque ou por lesão de reperfusão em intestino ou em membros inferiores, como ocorre no pinçamento da aorta, utilizado nas cirurgias de aneurisma. Dentre os mediadores envolvidos na lesão de isquemia-reperfusão, foram identificados espécies reativas tóxicas de oxigênio (ERTO), mediadores lipídicos, como a tromboxana, moléculas de adesão em neutrófilos e endotélio, fator de necrose tumoral, dentre outros. As medidas terapêuticas para a lesão de reperfusão ainda são utilizadas no plano experimental e em poucos estudos clínicos. São utilizados: antioxidantes, bloqueadores de mediadores lipídicos, inibidores da interação entre leucócito e endotélio ou substâncias que favoreçam o fluxo sanguíneo pós-isquêmico.<br>The ischemia-reperfusion injury is a common pathophysiologic phenomenon in many diseases seen in daily clinical practice. The lung can be affected both directly, as in pulmonary edema after lung transplant or after resolution of pulmonary thromboembolism, and indirectly, as in shock states or after reperfusion injury in distant organs as intestine or lower extremities. The latter situation can occur secondary to aortic occlusion for surgical procedures. Many mediators have been implicated in the ischemia-reperfusion injury: oxygen free radicals, lipid products as thromboxane, adhesion molecules involved in leukocyte-endothelial interaction, tumor necrosis factor, among others. Therapeutic strategies for the reperfusion injury are used only at the experimental level and in very few clinical studies. Antioxidants, inhibitors of lipid mediators and of the leukocyte-endothelial interaction and promoters of blood flow in post-ischemic vessels have been used