At-line validation of optical coherence tomography as in-line/at-line coating thickness measurement method

2019 ◽  
Vol 572 ◽  
pp. 118766 ◽  
Author(s):  
Matthias Wolfgang ◽  
Anna Peter ◽  
Patrick Wahl ◽  
Daniel Markl ◽  
J. Axel Zeitler ◽  
...  
Author(s):  
Rosa Dolz-Marco ◽  
María Andreu-Fenoll ◽  
Pablo Hernández-Martínez ◽  
M. Dolores Pinazo-Durán ◽  
Roberto Gallego-Pinazo

Author(s):  
P.E. Chandler ◽  
M.B.C. Quigley ◽  
J.F. Fletcher

Abstract There are many instances of coatings that require a nondestructive and non-contact measure of coating thickness as part of a quality control system. Specifically, this paper reports on experiments carried out on non-contact measurements of MCrAIY and TBC coatings. The system uses an infra red beam from a solid state laser to generate a thermal wave in the coating. When this wave reaches the substrate an interference effect is caused. The modulated input heating produces a modulated output infra red signal from the surface and at a different wavelength from the laser beam. The output signal has a phase difference from the input signal which is related to the coating thickness. As neither the laser nor the detector are in contact with the surface of the coating and the temperature of the coating is raised by only a few degrees this represents a non-contact NDE system. This system has been tested across a range of coating/substrate combinations. In this paper we give examples of MCrAIY and TBC coatings applied to engine components demonstrating that the accuracy of measurement is only limited by the roughness of the coating structure and substrate. The use of this system for on-line measurement during the spraying process is also discussed and results presented.


2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Christof Haensli ◽  
Katrin Fasler ◽  
Daniel Barthelmes ◽  
Sandrine A. Zweifel

Background/Aims. This study evaluates changes of flow and structure of diabetic retinal neovascularization (NV) treated with intravitreal antivascular endothelial growth factor (VEGF) agents using optical coherence tomography angiography (OCTA). With OCTA, retinal blood vessels are visualized at high resolution to separately look at flow and structure information without the need for dye injection. We introduce a new measurement method including and combining information of flow and structure. Methods. Retrospective observational case series. Patients with proliferative diabetic retinopathy (PDR) were treated with intravitreal antiVEGF injections. Retinal NV were repeatedly imaged using swept-source OCTA (Zeiss PlexElite 9000) at baseline, after initial treatment block with 3-4 monthly injections, and during a follow-up period of up to 51 weeks. Change of size and flow density of the structural and angio area of NV was assessed. Results. Nine NV in eight eyes of five patients were analyzed with a median follow-up time of 45 weeks. After the initial treatment block, en face structural area regressed, 18.7% ± 39.0% (95% CI 44.2–6.8%, p = 0.26 ), and en face angio area regressed, 51.9% ± 29.5% (95% CI 32.6 to 71.2%, p = 0.007 ). Flow density within the en face structural area decreased by 33% ± 19.2% (95% CI 20.5–45.5%, p = 0.0077 ). Flow density within the en face angio area decreased by mean 17.9% ± 25.2% (95% CI 1.4–34.4%, p = 0.066 ). In two fellow eyes, NV recurrence could be observed before the onset of vitreous bleeding in one. Conclusion. Our study introduces a new quantitative measurement for NV in PDR, combining structure and flow measurement. The structure area remained after treatment, while its flow density and angio area regressed. We propose this measurement method as a more physiological and possibly more comparable metrics.


2021 ◽  
pp. bjophthalmol-2018-312337
Author(s):  
Noémie Lauwers ◽  
Katleen Janssens ◽  
Michelle Mertens ◽  
Danny Mathysen ◽  
Martin Lammens ◽  
...  

Background/ObjectiveAnterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM) are two non-invasive imaging techniques used for the measurement of tumour thickness in corneal and bulbar conjunctival tumours. Histopathology (HP), however, remains the gold standard for the measurement of tumour thickness. The aim of this study was to determine whether AS-OCT and UBM are as accurate as HP for measuring tumour thickness.MethodsForty-two corneal and bulbar conjunctival tumours were imaged using AS-OCT and UBM. Images were assessed and tumour thickness was measured. Eleven patients subsequently underwent surgical excision. All specimens were measured during histopathological analysis. The correlation of the thickness measurement on HP to AS-OCT and UBM was then statistically analysed. In cases where the tumour was not excised, thickness measurement comparisons between AS-OCT and UBM were analysed.ResultsAS-OCT and UBM measurements of tumour thickness were found to be significantly positively correlated (p=<0.001), as were UBM and HP thickness measurements (p=0.031). HP and AS-OCT measurements, however, only showed a mild but non-significant positive correlation.ConclusionBoth AS-OCT and UBM are useful techniques to image and measure the thickness of corneal and conjunctival bulbar tumours. While AS-OCT provides better details than UBM, it was more limited in visualising the posterior boundary of the tumour, particularly in malignant tumours. While thickness measurements of both methodologies were correlated, neither should yet be considered as replacements to the gold standard of HP.


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