Mariana Torres Carvalho

Publications (18) View all

• Article: Noninvasive volumetric imaging and morphometry of the rodent retina with high-speed, ultrahigh-resolution optical coherence tomography.

  Vivek J Srinivasan, Tony H Ko, Maciej Wojtkowski, Mariana Carvalho, Allen Clermont, Sven-Erik Bursell, Qin Hui Song, Janis Lem, Jay S Duker, Joel S Schuman, James G Fujimoto
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  ABSTRACT: To demonstrate high-speed, ultrahigh-resolution optical coherence tomography (OCT) for noninvasive, in vivo, three-dimensional imaging of the retina in rat and mouse models. A high-speed, ultrahigh-resolution OCT system using spectral, or Fourier domain, detection has been developed for small animal retinal imaging. Imaging is performed with a contact lens and postobjective scanning. An axial image resolution of 2.8 mum is achieved with a spectrally broadband superluminescent diode light source with a bandwidth of approximately 150 nm at approximately 900-nm center wavelength. Imaging can be performed at 24,000 axial scans per second, which is approximately 100 times faster than previous ultrahigh-resolution OCT systems. High-definition and three-dimensional retinal imaging is performed in vivo in mouse and rat models. High-speed, ultrahigh-resolution OCT enabled high-definition, high transverse pixel density imaging of the murine retina and visualization of all major intraretinal layers. Raster scan protocols enabled three-dimensional volumetric imagingand comprehensive retinal segmentation algorithms allowed measurement of retinal layers. An OCT fundus image, akin to a fundus photograph was generated by axial summation of three-dimensional OCT data, thus enabling precise registration of OCT measurements to retinal fundus features. High-speed, ultrahigh-resolution OCT enables imaging of retinal architectural morphology in small animal models. OCT fundus images allow precise registration of OCT images and repeated measurements with respect to retinal fundus features. Three-dimensional OCT imaging enables visualization and quantification of retinal structure, which promises to allow repeated, noninvasive measurements to track disease progression, thereby reducing the need for killing the animal for histology. This capability can accelerate basic research studies in rats and mice and their translation into clinical patient care.
  Investigative Ophthalmology &amp Visual Science 01/2007; 47(12):5522-8. · 3.60 Impact Factor
• Article: High-definition and 3-dimensional imaging of macular pathologies with high-speed ultrahigh-resolution optical coherence tomography.

  Vivek J Srinivasan, Maciej Wojtkowski, Andre J Witkin, Jay S Duker, Tony H Ko, Mariana Carvalho, Joel S Schuman, Andrzej Kowalczyk, James G Fujimoto
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  ABSTRACT: To assess high-speed ultrahigh-resolution optical coherence tomography (OCT) image resolution, acquisition speed, image quality, and retinal coverage for the visualization of macular pathologies. Retrospective cross-sectional study. Five hundred eighty-eight eyes of 327 patients with various macular pathologies. High-speed ultrahigh-resolution OCT images were obtained in 588 eyes of 327 patients with selected macular diseases. Ultrahigh-resolution OCT using Fourier/spectral domain detection achieves approximately 3-mum axial image resolutions, acquisition speeds of approximately 25 000 axial scans per second, and >3 times finer resolution and >50 times higher speed than standard OCT. Three scan protocols were investigated. The first acquires a small number of high-definition images through the fovea. The second acquires a raster series of high-transverse pixel density images. The third acquires 3-dimensional OCT data using a dense raster pattern. Three-dimensional OCT can generate OCT fundus images that enable precise registration of OCT images with the fundus. Using the OCT fundus images, OCT results were correlated with standard ophthalmoscopic examination techniques. High-definition macular pathologies. Macular holes, age-related macular degeneration, epiretinal membranes, diabetic retinopathy, retinal dystrophies, central serous chorioretinopathy, and other pathologies were imaged and correlated with ophthalmic examination, standard OCT, fundus photography, and fluorescein angiography, where applicable. High-speed ultrahigh-resolution OCT generates images of retinal pathologies with improved quality, more comprehensive retinal coverage, and more precise registration than standard OCT. The speed preserves retinal topography, thus enabling the visualization of subtle changes associated with disease. High-definition high-transverse pixel density OCT images improve visualization of photoreceptor and pigment epithelial morphology, as well as thin intraretinal and epiretinal structures. Three-dimensional OCT enables comprehensive retinal coverage, reduces sampling errors, and enables assessment of 3-dimensional pathology. High-definition 3-dimensional imaging using high-speed ultrahigh-resolution OCT improves image quality, retinal coverage, and registration. This new technology has the potential to become a useful tool for elucidating disease pathogenesis and improving disease diagnosis and management.
  Ophthalmology 11/2006; 113(11):2054.e1-14. · 5.45 Impact Factor
• Source

  Available from: Mariana Torres Carvalho

  Thesis: Técnicas de Interferometria óptica aplicada à medicina, odontologia e comunicações ópticas

  Mariana Torres Carvalho
  01/2006, Degree: Doctor in Science, Supervisor: Anderson Stevens Leônidas Gomes
• Article: Transient gain behavior in 1050/1550-nm dual-wavelength pumped TDFAs

  S.R. Luthi, M.T. Carvalho, A.S.L. Gomes
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  ABSTRACT: We present an experimental study on transient events in 1050/1550-nm dual-wavelength pumped thulium-doped fiber amplifiers (TDFAs)-a promising candidate for S-band telecommunication applications. For appropriate power ratios of the two pump wavelengths, transient excursions due to signal add-drop are comparable to those in single-wavelength pumped TDFAs. Pump modulation effects, however, more severely impact the signal gain. With our experimental results, it should be possible to develop transient gain suppression control loops for this TDFA type.
  IEEE Photonics Technology Letters 06/2005; · 2.19 Impact Factor
• Article: Modeling the distributed gain of single--(1050 or 1410 nm) and dual-wavelength--(800 + 1050 nm or 800 + 1410 nm) pumped thulium-doped fiber amplifiers.

  Claudio Floridia, M T Carvalho, S R Lüthi, A S L Gomes
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  ABSTRACT: The distributed gain of single- and dual-wavelength-pumped thulium-doped fiber amplifiers is modeled. The excellent agreement between the model and coherent optical frequency domain reflectometry measurements enables us to estimate intrinsic loss, branching ratios of fluorescence originating from the 3H4 level, and cross sections of upconversion pumping at 1050 and 1410 nm for the Tm3+ ions in the fiber. With the branching ratios obtained it is possible to describe induced signal absorption when pumping at 800 nm.
  Optics Letters 10/2004; 29(17):1983-5. · 3.40 Impact Factor