Ex vivo cortical porosity and thickness predictions at the tibia using full-spectrum ultrasonic guided-wave analysis.

The estimation of cortical thickness (Ct.Th) and porosity (Ct.Po) at the tibia using axial transmission ultrasound was successfully validated ex vivo against site-matched micro-computed tomography. The assessment of cortical parameters based on full-spectrum guided-wave analysis might improve the prediction of bone fractures in a cost-effective and radiation-free manner. PURPOSE: Cortical thickness (Ct.Th) and porosity (Ct.Po) are key parameters for the identification of patients with fragile bones. The main objective of this ex vivo study was to validate the measurement of Ct.Po and Ct.Th at the tibia using a non-ionizing, low-cost, and portable 500-kHz ultrasound axial transmission system. Additional ultrasonic velocities and site-matched reference parameters were included in the study to broaden the analysis. METHODS: Guided waves were successfully measured ex vivo in 17 human tibiae using a novel 500-kHz bi-directional axial transmission probe. Theoretical dispersion curves of a transverse isotropic free plate model with invariant matrix stiffness were fitted to the experimental dispersion curves in order to estimate Ct.Th and Ct.Po. In addition, the velocities of the first arriving signal (υFAS) and A0 mode (υA0) were measured. Reference Ct.Po, Ct.Th, and vBMD were obtained from site-matched micro-computed tomography. Scanning acoustic microscopy (SAM) provided the acoustic impedance of the axial cortical bone matrix. RESULTS: The best predictions of Ct.Po (R2 = 0.83, RMSE = 2.2%) and Ct.Th (R2 = 0.92, RMSE = 0.2 mm, one outlier excluded) were obtained from the plate model. The second best predictors of Ct.Po and Ct.Th were vBMD (R2 = 0.77, RMSE = 2.6%) and υA0 (R2 = 0.28, RMSE = 0.67 mm), respectively. CONCLUSIONS: Ct.Th and Ct.Po were accurately predicted at the human tibia ex vivo using a transverse isotropic free plate model with invariant matrix stiffness. The model-based predictions were not further enhanced when we accounted for variations in axial tissue stiffness as reflected by the acoustic impedance from SAM.

GTCreator: a flexible annotation tool for image-based datasets.

PURPOSE: Methodology evaluation for decision support systems for health is a time-consuming task. To assess performance of polyp detection methods in colonoscopy videos, clinicians have to deal with the annotation of thousands of images. Current existing tools could be improved in terms of flexibility and ease of use. METHODS: We introduce GTCreator, a flexible annotation tool for providing image and text annotations to image-based datasets. It keeps the main basic functionalities of other similar tools while extending other capabilities such as allowing multiple annotators to work simultaneously on the same task or enhanced dataset browsing and easy annotation transfer aiming to speed up annotation processes in large datasets. RESULTS: The comparison with other similar tools shows that GTCreator allows to obtain fast and precise annotation of image datasets, being the only one which offers full annotation editing and browsing capabilites. CONCLUSION: Our proposed annotation tool has been proven to be efficient for large image dataset annotation, as well as showing potential of use in other stages of method evaluation such as experimental setup or results analysis.

Capillarys 2 Flex Piercing: Analytical performance assessment according to CLSI protocols for HbA1c quantification.

HbA1c is used for monitoring diabetic balance. In this paper we report an assessment of the analytical performances of Capillarys 2 Flex Piercing (C2FP) for HbA1c measurement using CE (Capillary Electrophoresis). CLSI (Clinical and Laboratory Standard Institute) protocols are used for the evaluation of apparatus performances: precision, linearity, method comparison, trueness and common interferences. HbA1c CVs average in intra-assay was 1.6% between run imprecision CV ranged from 0.1 to 1.8%. The linearity was demonstrated between 4.7 and 15.0%. The comparison study revealed that Bland Altman plot mean difference was equal to -0.03 (CI 95% (-0.05 to -0.0003)) and Passing-Bablok regression intercept was -0.05, CI95%(-0.13 -  -0.05); slope: 1.00, CI95%[1.00-1.01]. A strong correlation (r > 0.99) was proved. No significant effects of hemoglobin variants were seen with CE on HbA1c measurement. No problem related to sample-to-sample carry over was noted. No interferences of LA1c and cHb were observed. CE allowed quantification of HbA1c even at low level of total hemoglobin (40 g/L) in contrast to HPLC. Furthermore, this analyzer offered the opportunity of quantifying the HbA2 simultaneously with HbA1c . This evaluation showed that C2FP is a convenient system for the control of diabetes and the detection of hemoglobinopathies.