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Ultrasound NDT is a standard industrial technique for health monitoring and flaw identification in several structures, such as subsea oil pipelines. Its primary purpose is to form a representative image of the internal structure of the inspected object, which provides, in many cases, early warning of structure discontinuities, making it possible to reduce repair costs and mitigate risks. One of the imaging methods that has been receiving increasing attention in the ultrasound and seismology communities is the Full Waveform Inversion (FWI), which estimates the velocity model for the inspection area by confronting the acquired information obtained by the NDT system with theoretical simulated data. Since FWI algorithms rely on successive ultrasonic wave simulations, it is essential to ensure that each simulation is optimized and contributes little to the total running time. Acoustic wave simulations can be optimized using a graphical processing unit (GPU), which provides hardware acceleration through parallelism, where each point of the simulated area can be computed simultaneously. Among all available GPU APIs, WebGPU is the next-generation standard graphics Web API that exposes modern computer graphics capabilities by giving the user low-level, general-purpose access to the GPUs. This API is designed to efficiently map to native GPU APIs, which enables applications to run on different GPUs, making implementations more scalable and interchangeable. Motivated by this flexibility, we explore the acceleration capabilities of the WebGPU API by implementing a WebGPU-based acoustic wave simulator for ultrasound NDT.

Full Waveform Inversion (FWI) is a state-of-the-art method of image reconstruction with promising results for seismology and NDT. FWI estimates the velocity of wave propagation along the inspected object by iteratively comparing acquired data with simulated data. This method is computationally demanding as at least three simulations are needed per iteration, which motivates the research effort for fast simulation methods. When simulating acoustic waves within a finite domain, artificial reflections created at the boundaries yield unrepresentative signal acquisition in the simulation. These reflections disturb the computation of residuals in FWI, creating artifacts that result in inaccurate positioning of flaws and discontinuities. Various absorbing boundary conditions (ABCs) have been proposed to avoid these reflections, e.g., Higdon, Reynolds, and Perfectly Matched Layers (PML). Although Reynolds and Higdon have been used in other applications, they are not well suited for FWI for reasons such as weak absorption rate and excessive introduction of amplitude errors. On the other hand, the PML method, an ABC that gradually attenuates boundary reflections with the addition of layers with matched acoustic impedance, provides adequate attenuation for FWI and can be readily extended to elastic waves. In this work, we describe an implementation of PML in a parallel GPU-accelerated CUDA simulator, which is intended to be integrated into an FWI regression in future works. Finally, we provide examples demonstrating that PML can significantly reduce the domain of simulation of an ultrasound NDT while maintaining simulation accuracy.

Odometer information is an important feature of NDT systems for inspection procedures that involve mechanical scanning. Knowledge of transducer position during the inspection allows for the localization of flaws and the fusion (stitching) of several images into more sophisticated representations of the inspected object. Commercial encoders provide NDT systems with accurate realtime displacement information that can be integrated to obtain odometry. However, this information is typically limited to a single axis. Although composite schemes with more than one encoder can be built to provide 2-D or 3-D spatial information, they are mechanically intricate and lack flexibility and ease of use. We propose a 2-D position-tracking solution that is based on image processing. A miniature camera continuously captures images of the external surface of the inspected object, which are fed to an algorithm that detects and stores 2-D displacement between each pair of consecutive images. Additionally, the orientation quaternions provided by an Inertial Measurement Unit are stored, allowing for posterior 3-D path reconstruction over objects of known geometries, such as oil pipes. Besides logging position and orientation histories, the device also provides real-time displacement information to the NDT system, where it is perceived as a set of single-axis encoders, thus termed “the virtual encoder”. We demonstrate the applicability of the device to both contact and immersion ultrasonic inspections. The results show that the concept is promising, despite being based on simple principles and relatively easy to implement. The source code is provided as additional material in https://github.com/thiagokalid/VirtualEncoder-ECNDT-2023.

Stereoscopic cameras, also known as depth cameras, are increasingly present in robotics navigation and 3D scene reconstruction. Normally, off-the-shelf depth cameras are not suited for underwater environments and exhibit considerable distortions in the provided 3D images when operating underwater. This is mainly due to the large difference in the refractive coefficients of air and water. This issue prevents their use in subsea applications such as the inspection of oil pipelines, valves and manifolds, where these devices could be used for odometry during ultrasonic inspections as well as for 3D scanning. Aiming to allow for such applications, we present a data-driven method for the correction of distortions caused by unaccounted diffractions in depth cameras. First, the distortion is modelled via a series of detections of control points from a standard target at known underwater positions, and an approximation of the inverse distortion is obtained. Then, at runtime, a procedure takes as input the (distorted) point cloud given by the camera at each frame, applies the inverse distortion, and yields a corrected point cloud. We apply the method to data provided by a RealSense D405 camera encased in a sealed acrylic container underwater. The correction makes it possible to use the camera for odometry underwater, clearing the path for the use of off-the-shelf depth cameras in a wide range of subsea applications. The method can be applied for any other transparent fluid.

Ultrasonic (UT) imaging is a widespread technique for nondestructive testing (NDT). The state-of-the-art UT image reconstruction algorithms are based on delay-and-sum (DAS) operations, which assume constant acoustic velocity across the tested objects and also neglects nonlinear effects such as diffractions and multiple reflections. These assumptions limit the reconstruction capabilities of DAS-based algorithms, especially for complex objects composed by several materials. In seismology, Full Waveform Inversion (FWI) methods have been used to obtain subsurface properties based on scattered and transmitted sound waves - which is a very similar problem to ultrasonic imaging in NDT - using the full wave information, showing promising results. In this paper, we present the application of FWI in NDT using simulated data representing acquisitions with a common linear array transducer. We review the theoretical formulation of FWI and discuss some difficulties that arise when it is applied to NDT. Image reconstruction is performed using both a state-of-the-art DAS algorithm, namely the Total Focusing Method, and FWI. The implementation targets a GPU platform, using the CUDA API. This leverages the highly parallelizable nature of the simulations and the FWI algorithm. The obtained results show that FWI can show more internal structures than TFM, with less information about the specimen. To foster further development, all source codes are provided.

Copyright of Mondo Ortodontico is the property of Masson SPA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Mondo Ortodontico is the property of Masson SPA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aim: A retrospective assessment of the lower lip changes consequent to incisor displacement in correction of malocclusion in a sample of 92 post-adolescent subjects., Methods: The study sample comprised two groups, subdivided according to the direction of incisor movement achieved during orthodontic treatment: the retraction group (Group 1), made up of 41 patients in which the maxillary incisor had been moved in a palatal direction (palatal tipping); and the protraction group (Group 2), composed of 51 patients who had undergone labial movement of the upper incisors (labial tipping). In order to evaluate the mean changes in lower lip position, and consequent alterations in the quality of the patients' profiles, between T1 (prior to orthodontic displacement of the incisors) and T2 (following treatment), the following parameters were measured on lateral head film X rays: variation in lower lip vermilion thickness (dLVT); variation in lower lip sulcus depth (dLLSD); variation in lower vermilion height (dLVH); variation in exposure of the upper and lower incisors in relation to the lower stomion (dIs-STOi and dIi-STOi, respectively); variation in upper and lower incisor tipping with respect to the palatal plane (d1/PP and dinf1/PP); and variation in lower facial height (dLFH)., Results: Assessment of the changes due to incisor translocation revealed significant differences between Group 1 and Group 2 in all lower lip soft tissue parameters, except for dLVT, dLVH and dIi-STOi. Furthermore, using multiple linear regression analysis to predict the behaviour of the dependent (cutaneous) lower lip variables, a good coefficient of determination (r-square) value was only obtained for the horizontal variation of the labrale inferius point (dxLi), found to be dependent on horizontal movement of the upper and lower incisors (dxIs and dxIi) and thickness of the lower vermilion (LVT)., Conclusions: The results of this study highlight great variability among the patients studied, and suggest that the behaviour of the soft tissues (lower lip changes) following displacement of the upper and lower incisors is multifactorial and very difficult to predict., (Copyright © 2012 CEO. Published by Elsevier Masson SAS. All rights reserved.)

Post ESWL haemorragic complications are frequent and most patients experience temporary haematuria and focal intrarenal bleeding or perirenal haematoma are detected by NMR or US imaging. By tradition coagulation troubles have been a contraindication for ESWL but literature describes cases of coagulopathic patients treated with ESWL. From January 1992 to July 1993, 4 of our patients with severe haemostatis troubles (severe haemophilia A in two cases, acquired deficit of coagulation factors and mild thrombocytopenia secondary to post-necrotic hepatitis in 1 case and Glanzmann's thrombasthenia in 1 case) underwent ESWL using Dornier HM3 mod. or MPL 9000. An extensive haematological and clinical evaluation pre and post-ESWL with an adequate haematological prophylaxis (transfusion of blood derivatives) has been performed depending on the coagulation disorder. In our patients we did not observe any haemorragic complication and we propose a reappraisal of the contraindications of ESWL in subjects with coagulation disorders: careful evaluation of haemorragic risk factors, by suitable correction measures and close clinical and instrumental monitoring, allows a reduction of the risk of haemorragic complications in coagulopathic patients who undergo ESWL treatment.