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Gabor fusion Master Slave Optical Coherence Tomography Authors Ramona Cernat, Adrian Bradu, Niels Møller Israelsen, Ole Bang, Sylvain Rivet, Pearse A. Keane, David-Garway Heath, Ranjan Rajendram, and Adrian Podoleanu Coordinates Gabor fusion master slave optical coherence tomography, Biomed. Opt. Express 8, 813-827 (2017). Abstract This paper describes the application of the Gabor filtering protocol to a Master/Slave (MS) swept source optical coherence tomography (SS)-OCT system at 1300 nm. The MS-OCT system delivers information from selected depths, a property that allows operation similar to that of a time domain OCT system, where dynamic focusing is possible. The Gabor filtering processing following collection of multiple data from different focus positions is different from that utilized by a conventional swept source OCT system using a Fast Fourier transform (FFT) to produce an A-scan. Instead of selecting the bright parts of A-scans for each focus position, to be placed in a final B-scan image (or in a final volume), and discarding the rest, the MS principle can be employed to advantageously deliver signal from the depths within each focus range only. The MS procedure is illustrated on creating volumes of data of constant transversal resolution from a cucumber and from an insect by repeating data acquisition for 4 different focus positions. In addition, advantage is taken from the tolerance to dispersion of the MS principle that allows automatic compensation for dispersion created by layers above the object of interest. ...

Group refractive index and group velocity dispersion measurement by complex master slave interferometry Authors Sylvain Rivet, Adrian Bradu, Fiona Bairstow, Hisham Forrière, and Adrian Podoleanu Coordinates Group refractive index and group velocity dispersion measurement by complex master slave interferometry, Opt. Express 26, 21831-21842 (2018). Abstract This paper demonstrates that the complex master slave interferometry (CMSI) method used in spectral domain interferometry (SDI) can efficiently be used for accurate refractive index and group velocity dispersion measurements of optically transparent samples. For the first time, we demonstrate the relevance of the phase information delivered by CMSI for dispersion evaluations with no need to linearize data. The technique proposed here has been used to accurately measure the group refractive index and the group velocity dispersion of a strong dispersive sample (SF6 glass), and a weak dispersive one (distilled water). The robustness of the technique is demonstrated through the manipulation of several sets of experimental data. ...

{: w=“700” h=“400” .shadow} I had an invited talk at the 1st International Conference Advances in 3OM: Opto-Mechatronics, Opto-Mechanics and Optical Metrology {: .text-center .fs-6} on Combining Photoacoustic and Optical Coherence Tomography Imaging for non-destructive applications. Soon, an SPIE Proceedings on combining these two technologies are going to be published. A link will be posted here. Thanks the organisers for inviting me! Link for proceedings: {: .label .label-yellow } Gianni Nteroli, Adrian Podoleanu, and Adrian Bradu, “Combining photoacoustic and optical coherence tomography imaging for nondestructive testing applications,” Proc. SPIE, 12170, Advances in 3OM: Opto-Mechatronics, Opto-Mechanics, and Optical Metrology; 121700P (2022). ...

Methods for dental shade determination New Proceedings Published! Authors Christa Serban, Gianni Nteroli, Emanuela L. Craciunescu, Meda L. Negrutiu, Helmine Serban, Virgil F. Duma, Adrian Bradu, Adrian Podoleanu, Cosmin Sinescu Coordinates Methods for dental shade determination Proceedings Volume 11942, Lasers in Dentistry XXVIII; 1194206 (2022) Event: SPIE BiOS, 2022, San Francisco, California, United States Goal The aim of this in-vitro study was to evaluate comparatively the capability of software-based color analysis of mobile phone photography, with the spectrophotometric and visual methods for dental shade determination. ...

Multispectral photoacoustic microscopy and optical coherence tomography using a single supercontinuum source Authors Magalie Bondu, Manuel J. Marques, P.M. Moselund, G. Lall, Adrian Bradu, and Adrian Podoleanu Coordinates Multispectral photoacoustic microscopy and optical coherence tomography using a single supercontinuum source, Photoacoustics 9, 21-30 (2018). Abstract In this paper we report on the use of a single supercontinuum (SC) source for multimodal imaging. The 2-octave bandwidth (475-2300 nm) makes the SC source suitable for optical coherence tomography (OCT) as well as for multispectral photoacoustic microscopy (MPAM). The IR band centered at 1310 nm is chosen for OCT to penetrate deeper into tissue with 8 mW average power on the sample. The 500-840 nm band is used for MPAM. The source has the ability to select the central wavelength as well as the spectral bandwidth. An energy of more than 35 nJ within a less than 50 nm bandwidth is achieved on the sample for wavelengths longer than 500 nm. In the present paper, we demonstrate the capabilities of such a multimodality imaging instrument based on a single optical source. In-vitro mouse ear B-scan images are presented. ...

Optical Coherence Tomography Investigations and Modeling of the Sintering of Ceramic Crowns Authors Virgil Florin Duma, Cosmin Sinescu, Adrian Bradu and Adrian Podoleanu, Coordinates Optical Coherence Tomography Investigations and Modeling of the Sintering of Ceramic Crowns, Materials 12, 947 (2019). Abstract Dental prostheses are sintered in ovens that sometimes suffer from a loss of calibration. This can lead to variations of the sintering temperature outside the range recommended by the manufacturer. Stress and even fractures in dental ceramics may occur, and this leads to the necessity to rebuild the dental construct. The aim of this work is to monitor the quality of sintering processes using an established biomedical imaging technique—optical coherence tomography (OCT). ...

Quantitative assessment of rat bone regeneration using complex master-slave optical coherence tomography Authors Ruxandra Elena Luca, Carmen Darinca Todea, Virgil-Florin Duma, Adrian Bradu, Adrian Podoleanu Coordinates Quantitative assessment of rat bone regeneration using complex master-slave optical coherence tomography, Quantitative Imaging in Medicine and Surgery (2019). Background The need for hard and soft tissues in oral implantology determined the development of methods and techniques to increase bone volume and their quality with different alternative materials used as substituents of patient’s natural bone. In addition, laser radiation can be used to accelerate the repair of fractures and to produce an increased volume of formed callus, as well as an increased bone mineral density. ...

Recovering distance information in spectral domain interferometry Authors Adrian Bradu, Niels Møller Israelsen, Michael Maria, Manuel J. Marques, Sylvain Rivet, Thomas Feuchter, Ole Bang and Adrian Podoleanu Coordinates Recovering distance information in spectral domain interferometry," Scientific Reports 8, 15445 (2018). Abstract This work evaluates the performance of the Complex Master Slave (CMS) method, that processes the spectra at the interferometer output of a spectral domain interferometry device without involving Fourier transforms (FT) after data acquisition. Reliability and performance of CMS are compared side by side with the conventional method based on FT, phase calibration with dispersion compensation (PCDC). We demonstrate that both methods provide similar results in terms of resolution and sensitivity drop-off. The mathematical operations required to produce CMS results are highly parallelizable, allowing real-time, simultaneous delivery of data from several points of different optical path differences in the interferometer, not possible via PCDC. ...

Speckle variance OCT for depth resolved assessment of the viability of bovine embryos Authors S. Caujolle, R. Cernat, G. Silvestri, M. J. Marques, Adrian Bradu, T. Feuchter, G. Robinson, D. K. Griffin, and Adrian Podoleanu Coordinates Speckle variance OCT for depth resolved assessment of the viability of bovine embryos, Biomed. Opt. Express 8, 5139-5150 (2017). Abstract The morphology of embryos produced by in vitro fertilization (IVF) is commonly used to estimate their viability. However, imaging by standard microscopy is subjective and unable to assess the embryo on a cellular scale after compaction. Optical coherence tomography is an imaging technique that can produce a depth-resolved profile of a sample and can be coupled with speckle variance (SV) to detect motion on a micron scale. In this study, day 7 post-IVF bovine embryos were observed either short-term (10 minutes) or long-term (over 18 hours) and analyzed by swept source OCT and SV to resolve their depth profile and characterize micron-scale movements potentially associated with viability. The percentage of en-face images showing movement at any given time was calculated as a method to detect the vital status of the embryo. This method could be used to measure the levels of damage sustained by an embryo, for example after cryopreservation, in a rapid and non-invasive way. ...

New journal paper published in Scientific Reports! Authors Gianni Nteroli, Manoj K. Dasa, Giulia Messa, Stella Koutsikou, Magalie Bondu, Peter M. Moselund, Christos Markos, Ole Bang, Adrian Podoleanu, and Adrian Bradu Title and coordinates Two octaves spanning photoacoustic microscopy, Sci Rep 12, 10590 (2022). Abstract In this study, for the first time, a Photoacoustic Microscopy instrument driven by a single optical source operating over a wide spectral range (475–2400 nm), covering slightly more than two octaves is demonstrated. Xenopus laevis tadpoles were imaged in vivo using the whole spectral range of 2000 nm of a supercontinuum optical source, and a novel technique of mapping absorbers is also demonstrated, based on the supposition that only one chromophore contributes to the photoacoustic signal of each individual voxel in the 3D photoacoustic image. By using a narrow spectral window (of 25 nm bandwidth) within the broad spectrum of the supercontinuum source at a time, in-vivo hyper-spectral Photoacoustic images of tadpoles are obtained. By post-processing pairs of images obtained using different spectral windows, maps of five endogenous contrast agents (hemoglobin, melanin, collagen, glucose and lipids) are produced. {: .yellownote} ...