In spectral domain optical coherence tomography (SD-OCT), any transverse motion component of a detected obliquely moving sample results in a nonlinear relationship between the Doppler phase shift and the axial sample velocity restricting phase-resolved Doppler OCT. To circumvent the limitation, we propose the lateral resonant Doppler flow quantification in spectral domain OCT, where the scanner movement velocity is matched to the transverse velocity component of the sample motion.

Recently, optical coherence tomography (OCT) was utilized in multiple studies for structural and functional imaging of the middle ear and the tympanic membrane. Since Doppler OCT allows both, the spatially resolved measurement of the tympanic membrane oscillation and high-resolution imaging, it is regarded as a promising tool for future in vivo applications. In this study, Doppler OCT is utilized for the visualization of the tympanic membrane oscillation in temporal bones with simulated Eustachian catarrh, which was realized by generating a depression in the tympanic cavity. The transfer function, meaning the oscillation amplitude normalized to the applied sound pressure, is measured frequency resolved in the range from 0.5 kHz to 6 kHz and with a lateral spatial resolution of 0.4 mm. Typical oscillation patterns could be observed in case of ambient pressure in the tympanic cavity. Under depression the characteristic oscillation patterns were observed with widely congruent appearance but at higher frequencies.

<p>Cilj ovog istraživanja bio je da se utvrdi razlika u debljini sloja retinalnih nervnih vlakana (RNFL) i parametara glave očnog živca kod pacijenata sa preperimetrijskim glaukomom i pacijenata sa glaukomom otvorenog ugla (POAG) u odnosu na zdravu populaciju, kao i da se utvrdi razlika u debljini RNFL i parametara glave očnog živca kod pacijenata sa POAG u odnosu na stepen progresije bolesti. Materijal i metode: U ovu kliničku, analitičku i opservacionu, po tipu &bdquo;slučaj-kontrola&ldquo; studiju, bilo je uključeno 120 pacijenata. Na osnovu kliničkog nalaza formirane su četiri grupe. Prva grupa (grupa zdravih): 30 pacijenata bez glaucoma i drugih očnih bolesti. Druga grupa (grupa sa početnim POAG): 30 pacijenata sa POAG, sa karakterističnim o&scaron;tećenjem glave očnog živca i RNFL, kod kojih je srednja vrednost devijacije standardizovane automatske perimetrije MD&lt;-6dB (prema Hodap klasifkaciji) sa karakterističnim glaukomskim ispadima u vidnom polju. Treća grupa (grupa sa srednje uznapredovalim POAG): 30 pacijenata sa POAG, kod kojih je srednja vrednost devijacije standardizovane automatske perimetrije MD od -6dB do -12dB (prema Hodap klasifkaciji). Četvrta grupa (grupa sa preperimetrijskim glaukom): 30 pacijenata sa promenama na glavi očnog živca karakterističnim za glaukomsku neuropatiju, kod kojih ne postoje funkcionalni ispadi tj. standardna automatizovana perimetrija pokazuje normalne vrednosti MD parametara (od -2 dB do +2dB). Kod svih pacijenata bio je urađen kompletan oftalmolo&scaron;ki pregled, kompjuterizovano vidno polje i optička koherentna tomografija peripapilarne regije RNFL i glave očnog živca (na aparatu Stratus OCT 3000, Carl Zeiss Meditec). Rezultati su pokazali da je debljina RNFL-a kod pacijenata sa početnim POAG manja u odnosu na zdravu populaciju. Najveće sniženje debljine RNFL je u sektorima 1,6,7 i 8h. Jedino u sektoru 4h i 9h ne dolazi do smanjenja debljine RNFL-a. Najveće smanjenje debljine RNFL je u gornjem i donjem kvadrantu, te oni imaju visoku specifičnost za diskriminaciju između zdravih i pacijenata sa početnim POAG. Parametri glave očnog živca: volumen ekskavacije, vertikalni C/D, horizontalni C/D i ukupni C/D odnos kod pacijenata sa početnim POAG povećani su u odnosu na zdravu populaciju. Parametri glave očnog živca: povr&scaron;ina neuroretinalnog oboda i volumen neuroretinalnog oboda, kod pacijenata sa početnim POAG smanjeni su u odnosu na zdravu populaciju. Debljina RNFL kod pacijenata sa srednje uznapredovalim POAG smanjena je i u odnosu na pacijente sa početnim POAG i u odnosu na zdravu populaciju (59,69&plusmn;10,63 &mu;m vs 73,44&plusmn;12,16&mu;m vs 105,57&plusmn;11,34 &mu;m). Parametri glave očnog živca prate ove promene. Ukupna povr&scaron;ina glave očnog živca se statistički značajno ne menja između zdravih osoba, pacijenata sa početnim i srednje uznapredovalim glaukomom otvorenog ugla i kod pacijenata sa preperimetrijskim glaukomom, te ovaj parametar ne determini&scaron;e glaukomsku bolest. Postojanje i napredovanje glaukoma kod pacijenata dovodi do istanjenja&nbsp; peripapilarnog RNFL &scaron;to je praćeno povećanjem ekskavacije glave očnog živca. Sa smanjenjem MD vrednosti dolazi do sledstvenih promena većine parametara. Postoji pozitivna korelacija između uznapredovalosti galukoma i srednje vrednosti debljine RNFL. Promena ove vrednosti najbolje pokazuje da dolazi do progresije POAG. Parametri glave očnog živca koji najbolje oslikavaju progresiju glaukoma su: ukupni C/D, vertikalni C/D i horizontalni C/D odnos. Debljina RNFL-a kod pacijenata sa preperimetrijskim glaukomom je značajno manja u od nosu na zdravu populaciju (83,65&plusmn;9,24&mu;m vs 105,57&plusmn;11,34&mu;m). To se posebno izražava u gornjem kvadrantu, dok u temporalnom kvadrantu ne dolazi do promena. Parametar S zajedno sa srednjom vrednosti debljine RNFL predstavljaju najbolje pokazatelje nastajanja preperimetrijskog glaukoma. Sektor 1h je sektor sa visokom specifično&scaron;ću za diskriminaciju izmeĎu zdravih i pacijenata sa preperimetrijskim glaukomom. Parametri glave očnog živca: volumen ekskavacije, vertikalni C/D, horizontalni C/D i srednji C/D odnos, kod pacijenata sa preperimetrijskim glaukomom statistički su značajno povećavani i u odnosu na zdravu populaciju. Parametri glave očnog živca: povr&scaron;ina neuroretinalnog oboda i volumen neuroretinalnog oboda, kod pacijenata sa preperimetrijskim glaukomom statistički su značajno manji u odnosu na zdravu populaciju. Najbolji prediktori nastanka i napredovanja glaukomske bolesti su sledeći parametri: AvgThic, debljina RNFL po kvadrantima-S,I,N; parametric debljine RNFL: Smax, Savg, Iavg; kao i parametri PNO: RimArea, RimVol, DiscArea, CupAear, C/DHorRat, C/DVertRat, C/DAreaRat. ROC kriva je pokazala da su sledeću parametri lo&scaron;i marker za progresiju bolesti: debljine RNFL kavdranta T, Imax i upVol. Zaključak: Određivanje parametara glave očnog živca i debljine peripapilarnih RNFL kod pacijenata sa glaukomom, optičkom koherentnom tomografijom, predstavlja metodu koja izdvaja pacijente sa preperimetrijskim glaukomom od zdrave populacije. Ono posebno ukazuje na sektore, kvadrante i parametre koji su najosetljiviji na glaukomsku noksu i koji prvi postaju patolo&scaron;ki pri nastanku glaukoma. Takođe, ukazuje i na razliku između pojedinih stepena glaukomske bolesti. Na ovaj način se omogućuje sigurna i rana dijagnoza glaukoma, njegovo pravovremeno lečenje i bolja prognoza kod pacijenata sa POAG.</p> / <p>Aim: The aim of this study was to determine the difference in thickness of retinal nerve fibre layer (RNFL) and parameters of optic nerve head in patients with preperimetric glaucoma and in patients with open angle glaucoma (POAG) in comparison to healthy population, as well as to determine the difference in thickness of RNFL and parameters of optic nerve head in patients with POAG according to progression of the disease. Material and methods: This clinical study was analytical and opservational, &bdquo;case-control&ldquo; type of study. 120 patients were included. On the basis of clinical finding 4 groups were formed. First group (healthy): 30 patients without glaucoma and with no other ocular disease. Second group (group of patients with mild POAG): 30 patients with POAG, with characteristical optic nerve head and RNFL damage, in whom the value of standard deviation of standardised automatic perimetry is MD&lt;-6dB (according to Hodap classification) with typical glaucomatous visual field defects. Third group (group of patients with moderate POAG): 30 patients with POAG in whom the mean value of standard deviation of standardised automatic perimetry, MD is from -6dB to -12dB (according to Hodap classification). Fourth group (group of patients with preperimetric glaucoma): 30 patients with changes of optic nerve head that are typical of glaucomatous neuropathy in whom there are no functional changes and with normal values of MD parameters of standardised automatic perimetry. In all patients complete ophthalmological examination, complete visual field and optic coherent tomography of peripapillar region of RNFL and optic nerve head (using Stratus OCT 3000, Carl Zeiss Meditec) were performed.The results showed that thickness of RNFL in patients with mild POAG is lesser than in healthy subjects. The greatest decrease in RNFL thickness is in sectors 1,6,7 and 8h. Only in sectors 4h and 9h there is no decrease in RNFL thickness. The greatest decrease in RNFL thickness is in upper and lower quadrant, so they are highly specific in determination between healthy subjects and patients with mild POAG. Parameters of optic nerve head such as: excavation volume, vertical C/D, horisontal C/D and total C/D ratio in patients with mild POAG are higher comparing to healthy population. Parameters of optic nerve head such as: neuroretinal rim area and neuroretinal rim volume in patients with mild POAG are lower than in healthy population. RNFL thickness in patients with moderate POAG is lesser than in patients with mild POAG, as well as in healthy subjects. Optic nerve head parameters follow these changes. Total optic nerve head area does not change in healthy subjects, in patients with mild and moderate open angle glaucoma and in patients with preperimetric glaucoma, so this parameter does not determine glaucomatous disease. The existence and progression of glaucoma in patients leads to thinning of peripapillar RNFL which is followed by increase of excavation of optic nerve head. With decrease of MD value there are consecutive changes in most parameters. There is positive correlation between progression of glaucoma and average thickness of RNFL. The change of this value shows the best if there is progression of POAG. Paremeters of optic nerve head that are the best determinants of progression of glaucoma are: total C/D, vertical C/D and horisontal C/D ratio. Thickness of RNFL in patients with preperimetric glaucoma is significantly lesser than in healthy subjects. It is particularly seen in upper quadrant, while in temporal quadrant there are no changes. Parameter S together with mean value of RNFL thickness is the best parameter of appearance of preperimetric glaucoma. Sector 1h is the sector that is highly specific in discrimination between healthy subjects and patients with preperimetric glaucoma. Optic nerve head parameters such as: volume of excavation, vertical C/D, horizontal C/D and C/D mean ratio in patients with preperimetric glaucoma are statistically significantly higher than in healthy population. Optic nerve head parameters such as: neuroretinal rim area and neuroretinal rim volume in patients with preperimetric glaucoma are statistically significantly lower than in healthy population. The best predictors of appearance and progression of glaucomatous disease are: AvgThic, RNFL thickness in quadrants: S,I,N; RNFL:Smax, Savg, Iavg; as well as PNO: RimArea, RimVol, DiscArea, CupAear, C/DHorRat, C/DVertRat, C/DAreaRat. ROC curve has shown that the following parameters are bad markers for progression of the disease: RNFL thickness in quadrant T, Imax and CupVol. Conclusion: Determination of parameters of optic nerve head and peripapillar RNFL in patients with glaucoma using optical coherent tomography represents the method that distinguishes the patients with preperimetric glaucoma from healthy subjects. It particularly points the sectors, quadrants and parameters that are the most sensitive to glaucomatous disease and that first become pathological when disease appears. It also indicates the difference between certain levels of glaucomatous disease. In this way safe and early diagnosis of glaucoma is provided, as well as adequate therapy and better prognosis in patients with POAG.</p>

La microscopie par cohérence optique (OCM) est une technique d'imagerie tomographique basée sur l'interférométrie en lumière blanche permettant d'imager les milieux biologiques à l'échelle microscopique. L'OCM est une méthode particulièrement adaptée à l'imagerie dermatologique, en particulier pour le diagnostic du cancer de la peau, car elle permet d'obtenir des images similaires aux images histologiques sans nécessiter d'effectuer de biopsie.Ces travaux de thèse portent sur le développement de la microscopie par cohérence optique pour l'imagerie de la peau, dans le but de fournir au dermatologue un outil d'imagerie compact, adapté à l'imagerie dermatologique in vivo, et permettant d'obtenir des images à la fois structurelles et fonctionnelles.Un dispositif de microscopie par cohérence optique plein champ (FF-OCM) compact, à éclairage par LED blanche, a tout d'abord été développé, permettant d'obtenir des images tomographiques à très haute résolution (0.7 μm × 1.8 μm) jusqu’à ∼200 μm de profondeur dans la peau. En utilisant une LED de haute puissance, des images de peau in vivo ont pu être obtenues.A partir de ce dispositif de FF-OCM, des méthodes d'imagerie fonctionnelle permettant de cartographier les écoulements sanguins (angiographie) ont été mises en oeuvre. Quatre méthodes, basées sur une analyse du signal interférométrique (temporelle ou fréquentielle), d'images de phase ou d'images d'amplitude ont permis d'imager de l'intralipide s'écoulant dans un modèle de capillaire sanguin.L'imagerie fonctionnelle polarimétrique a aussi été explorée en FF-OCM. Une optimisation du contraste des images polarimétriques a été obtenue en modifiant les composants polarisants d'un montage conventionnel de FF-OCM polarimétrique en fonction de l'échantillon imagé. Cette méthode a été testée sur un échantillon polarisant simple.Finalement, une nouvelle méthode d'OCM, la microscopie par cohérence optique confocale à éclairage « ligne » (LC-OCM) a été étudiée, dans le but de développer un système permettant d'imager la peau in vivo, avec une plus grande profondeur de pénétration dans les tissus que la FF-OCM. Ce système, combinant un filtrage interférométrique et un filtrage confocal, a permis d'obtenir des images de peau in vivo en coupe verticale et en coupe en face, avec une résolution spatiale similaire à celle de la FF-OCM, mais à une profondeur supérieure atteignant 300 μm. / Optical coherence microscopy (OCM) is a technique for tomographic imaging based on white light interferometry, making it possible to image biological media with micrometer-scale spatial resolution. OCM is particularly well-suited to dermatological imaging, especially skin cancer diagnosis, since it provides images that are similar to histological images without the need for biopsy.This PhD thesis focuses on the development of OCM for skin imaging, with the aim of providing a compact, in vivo imaging tool for the dermatologist, capable of acquiring structural and functional images of the skin.A compact, full-field OCM (FF-OCM) system illuminated by a white LED was first developed, making it possible to obtain tomographic images at an ultra-high resolution (0.7 μm × 1.8 μm), up to ∼200 μm in depth within the skin. Using a high power LED, in vivo skin images could be obtained.Using this FF-OCM setup, functional imaging methods for blood flow mapping (angiography) were implemented. Four methods, based on temporal or frequency analysis of the interferometric signal, phase images or amplitude images, have been shown to be able to image intralipid flow within a model blood capillary.Functional polarimetric imaging has also been explored in FF-OCM. Contrast optimization in polarimetric images has been obtained by modifying the polarizing components of the conventional polarization sensitive FF-OCM setup depending on the sample to be imaged. This method has been tested on a simple polarizing sample.Finally, a new OCM method, line-field confocal OCM (LC-OCM), has been studied. The goal here was to develop a system capable of imaging the skin in vivo, with a tissue penetration depth greater than what is possible for FF-OCM. This system, which combines interferometric filtering and confocal filtering, makes it possible to obtain in vivo skin images in vertical and en face slices, with a spatial resolution similar to that of FF-OCM, but with a greater penetration depth of 300 μm.

Insight Photonic Solutions Inc. has continued to develop their patented VT-DBR laser design; these wavelength tunable lasers promise marked image-quality and acquisition time improvements in SS-OCT applications. To be well suited for SS-OCT, tunable lasers must be capable of producing a highly linear wavelength sweep across a tuning range well-matched to the medium being imaged; many different tunable lasers used in SS-OCT are compared to identify the optimal solution. This work electrically and spectrally characterizes two completely new all-semiconductor VT-DBR designs to compare, as well. The Neptune VT-DBR, an O-band laser, operates around the 1310 nm range and is a robust solution for many OCT applications. The VTL-2 is the first 1060 nm VT-DBR laser to be demonstrated. It offers improved penetration through water over earlier designs which operate at longer wavelengths (e.g. - 1550 nm and 1310 nm), making it an optimal solution for the relatively deep imaging requirements of the human eye; the non-invasive nature of OCT makes it the ideal imaging technology for ophthalmology. Each laser has five semiconductor P-N junction segments that collectively enable precise akinetic wavelength-tuning (i.e. - the tuning mechanism has no moving parts). In an SS-OCT system utilizing one of these laser packages, the segments are synchronously driven with high speed current signals that achieve the desired wavelength, power, and sweep pattern of the optical output. To validate the laser’s fast tuning response time necessary for its use in SS-OCT, a circuit model of each tuning section is created; each laser section is modeled as a diode with a significant lead inductance. The dynamic resistance, effective capacitance, and lead inductance of this model are measured as a function of bias current and the response time corresponding to each bias condition is determined. Tuning maps, spectral linewidths, and side-mode suppression ratio (SMSR) measurements important to SS-OCT performance are also collected. Measured response times vary from 700 ps to 2 ns for the Neptune and 1.2 to 2.3 ns for the VTL-2. Linewidth measurements range from 9 MHz to 124 MHz for the Neptune and 300 kHz to 2 MHz for the VTL-2. SMSR measurements greater than 38 dB and 40 dB were observed for the Neptune and VTL-2, respectively. Collectively, these results implicate the VT-DBR lasers as ideal tunable sources for use in SS-OCT applications.

In dental research, the morphometric assessment of restorations is a challenge. This also applies to the assessment of the length of interfacial adhesive defects in composite restorations as a measure of tooth-restoration bond failure. The determined mean fractions of interfacial gap length on enamel and dentin interfaces deviate from the true means (N → ∞), depending on the number (Ni) of object layers assessed. Cervical composite restorations were imaged with spectral domain optical coherence tomography (SD-OCT). The mean fractions of interfacial gap length on enamel and dentin were determined for an increasing number of OCT cross-sectional images (B-scans) per restoration and were graphically displayed as a function of the number of B-scans. As the number of B-scans increased, the calculated object means approached a range of ±2.5%. This analysis is appropriate for displaying the relationship between the determined mean fraction of interfacial gap length at the enamel/dentin-restoration interface and the number of B-scans.

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In breast cancer assessment, tissue removed during biopsy or surgery is sent to a pathology lab for analysis. To achieve high sensitivity for detecting disease, the diagnostic gold standard requires submission of a substantial portion of the resected specimen, which results in a labor and time-intensive process to obtain a diagnosis. There is an unmet need to identify regions of diagnostic interest in breast tissue samples to increase the efficiency of the clinical pathology workflow. Optical coherence tomography (OCT), a noninvasive imaging modality capable of depth-resolved, high-resolution, and in vivo imaging of tissue at large fields of view, enables effective assessment of this tissue. However, there is a two-fold problem: the large size of resected tissue to be imaged within clinical time constraints, and the high density of multi-dimensional OCT image data. An approach that enables comprehensive imaging by reducing both imaging time and data density is compressed sensing (CS), a theory that enables undersampling far below the Nyquist sampling rate and guarantees high accuracy image recovery. Therefore, the objective of this work is to demonstrate that compressed sensing techniques can be applied to OCT imaging to revise current optical hardware and improve the efficiency of image acquisition. CS-OCT has high potential for significantly altering the presently established workflow for breast cancer assessment. In this work, we prove that current OCT systems require further reduction of data sampling rate, to enable effective integration of the systems into the clinical pathology workflow. In addition, we identify challenges associated with the matching of OCT and histologic data that may be important to consider in the context of in vivo imaging. Further, we demonstrate the application of a novel and improved compressed sensing algorithm capable of reconstructing OCT volumes from highly undersampled imaging data. We show that these reconstructions preserve high spatial resolution and key image features, and we illustrate its improved performance over traditional reconstruction methods. Lastly, we integrate our compressed sensing techniques to physical OCT hardware. We demonstrate a pilot OCT system that integrates efficient undersampling schemes with subsequently successful 3-D image reconstructions. We evaluate acquisition patterns that take advantage of the typical forward and backward scan cycle of OCT systems to accomplish native subsampling of target data to varying degrees of compression. Using our CS-OCT algorithm, we successfully reconstruct OCT image volumes and demonstrate qualitative and quantitative preservation of image quality down to compression levels of 5% of total data.