Ultrasonic Inspection of Titanium Alloys with a Time Reversal Mirror

Ultrasonic Time Reversal Mirror (TRM) is an original solution to detect small cracks in a solid of any geometrical shape. Indeed, nondestructive testing need high resolution capabilities, high reliability and shortest control time. But the more recent techniques need an a priori knowledge of the liquid-solid interface and present limitations. The first of these uses several large prefocussed arrays, one array for each testing depth. Therefore this control system is sensitive to the arrays alignment, limited by the array precision focusing, and requires a complex mechanical follower system. A greater flexibility can be obtained by a second technique that is based on delay lines. But an accurate knowledge of the interface and a high calculs resolution are indispensable

Accumulation and Changes in Composition of Collagens in Subcutaneous Adipose Tissue After Bariatric Surgery

International audienceExtracellular matrix (ECM) in sc adipose tissue (scAT) undergoes pathological remodeling during obesity. However, its evolution during weight loss remains poorly explored.Objective:The objective of the investigation was to study the histological, transcriptomic, and physical characteristics of scAT ECM remodeling during the first year of bariatric surgery (BS)-induced weight loss and their relationships with metabolic and bioclinical improvements.Design, Setting, Patients, and Interventions:A total of 118 morbidly obese candidates for BS were recruited and followed up during 1 year after BS.Main Outcome Measures:scAT surgical biopsy and needle aspiration as well as scAT stiffness measurement were performed in three subgroups before and after BS. Fourteen nonobese, nondiabetic subjects served as controls.Results:Significantly increased picrosirius-red-stained collagen accumulation in scAT after BS was observed along with fat mass loss, despite metabolic and inflammatory improvements and undetectable changes of scAT stiffness. Collagen accumulation positively associated with M2-macrophages (CD163+ cells) before BS but negatively afterward. Expression levels of genes encoding ECM components (eg, COL3A1, COL6A1, COL6A2, ELN), cross-linking enzymes (eg, lysyl oxidase [LOX], LOXL4, transglutaminase), metalloproteinases, and their inhibitors were modified 1 year after BS. LOX expression and protein were significantly decreased and associated with decreased fat mass as well as other cross-linking enzymes. Although total collagen I and VI staining decreased 1 year after BS, we found increased degraded collagen I and III in scAT, suggesting increased degradation.Conclusions:After BS-induced weight loss and related metabolic improvements, scAT displays major collagen remodeling with an increased picrosirius-red staining that relates to increased collagen degradation and importantly decreased cross-linking. These features are in agreement with adequate ECM adaptation during fat mass loss- See more at: http://press.endocrine.org/doi/10.1210/jc.2015-3348#sthash.PLeUvzKd.dpu

Improvement of Time Reversal Processing in Titanium Inspections

We have explained in previous papers [1,2] a completely different NDE technique applied to the titanium alloy billet, the time reversal process, which allows conversion of a divergent wave issuing from a defect into a convergent wave focusing on it. The time reversal method is a self adaptive technique which produces a focussed beam matched to the defect shape and generates an unfocussed wave in the case of a speckle noise source. The results have showed the ability of this technique to focus on defects in a scattering media through a complex interface. However, this technique is subject to the principal NDE systems problem: the false alarms. Indeed, high levels of grain noise can mask signals from smaller or lower acoustic reflectivity flaws and than a grains configuration can be confused with a small defect. In case of the inspection of large titanium parts such those found in the aircraft engine industry (thickness > 5″), the classical techniques are more sensitive to this problem in the deep zones: the grain density often increases with depth du to the forging technique and the backpropagated defect echoes are weak in account of the attenuation.</p

Ultrasonic Inspection of Titanium Alloys with a Time Reversal Mirror

Ultrasonic Time Reversal Mirror (TRM) is an original solution to detect small cracks in a solid of any geometrical shape. Indeed, nondestructive testing need high resolution capabilities, high reliability and shortest control time. But the more recent techniques need an a priori knowledge of the liquid-solid interface and present limitations. The first of these uses several large prefocussed arrays, one array for each testing depth. Therefore this control system is sensitive to the arrays alignment, limited by the array precision focusing, and requires a complex mechanical follower system. A greater flexibility can be obtained by a second technique that is based on delay lines. But an accurate knowledge of the interface and a high calculs resolution are indispensable.</p

High-Resolution Elastography for Thin-Layer Mechanical Characterization: Toward Skin Investigation

International audienceInterest in elasticity estimation for thin layers is increasing because of the various potential applications, including dermatology and cosmetology. In this context, we propose a dedicated elastographic system using 1-D high-frequency transient elastography (HF-TE) to estimate the 1-D Young's modulus through the dermis and hypodermis, which are the two human skin layers of interest in this study. An experimental validation of the HF-TE method was first carried out on two homogeneous tissue-mimicking hard and soft phantoms. The Young's modulus values obtained in these phantoms were compared with those obtained by two complementary shear wave propagation techniques: shear wave-induced resonance elastography (SWIRE) and supersonic shear imaging (SSI). A third two-layer thin phantom, with mechanical properties similar to those of skin, was used to validate the ability of HF-TE to distinguish layers and measure elasticity. Finally, preliminary in~vivo experiments conducted on forearm and cheek skin revealed the promising performance of HF-TE in measuring elasticity in the dermis and hypodermis

Improved ultrasound attenuation measurement method for the non-invasive evaluation of hepatic steatosis using FibroScan ®

International audienceControlled Attenuation Parameter (CAP) is a measurement of ultrasound attenuation used to assess liver steatosis non-invasively. However, the standard method has some limitations. We aimed to assess the performance of a new CAP method by ex vivo and in vivo assessments. The major difference with the new method is that it uses ultrasound data continuously acquired during the imaging phase of the FibroScan examination. Seven reference tissue-mimicking phantoms were used to test the performances. In vivo performances were assessed on two cohorts (in total 195 patients) of patients using magnetic resonance imaging proton density fat fraction (MRI-PDF) as a reference. The precision of CAP was improved by more than 50% on tissue-mimicking phantoms and between 22% and 41% in the in vivo cohort studies. The agreement between both methods was excellent and the correlation between CAP and MRI-PDFF improved in both studies (0.71 to 0.74, 0.70 to 0.76). Using MRI-PDFF as a reference, the diagnostic performance of the new method was at least equal or superior (area under the receiver operating curve 0.889 to 0.900, 0.835 to 0.873). This study suggests that the new continuous CAP method can significantly improve the precision of CAP measurements ex vivo and in vivo