RESUMO
BACKGROUND: Volumetric laser endomicroscopy (VLE) allows for near-microscopic imaging of the superficial esophageal wall and may improve detection of early neoplasia in Barrett's esophagus (BE). Interpretation of a 6-cm long, circumferential VLE "full scan" may however be challenging for endoscopists. We aimed to evaluate the accuracy of VLE experts in correctly diagnosing VLE full scans of early neoplasia and non-dysplastic BE (NDBE). METHODS: 29 VLE full scan videos (15 neoplastic and 14 NDBE) were randomly evaluated by 12 VLE experts using a web-based module. Experts were blinded to the endoscopic BE images and histology. The 15 neoplastic cases contained a subtle endoscopically visible lesion, which on endoscopic resection showed high grade dysplasia or cancer. NDBE cases had no visible lesions and an absence of dysplasia in all biopsies. VLE videos were first scored as "neoplastic" or "NDBE." If neoplastic, assessors located the area most suspicious for neoplasia. Primary outcome was the performance of VLE experts in differentiating between non-dysplastic and neoplastic full scan videos, calculated by accuracy, sensitivity, and specificity. Secondary outcomes included correct location of neoplasia, interobserver agreement, and level of confidence. RESULTS: VLE experts correctly labelled 73â% (95â% confidence interval [CI] 67â%â-â79â%) of neoplastic VLE videos. In 54â% (range 27â%â-â66â%) both neoplastic diagnosis and lesion location were correct. NDBE videos were consistent with endoscopic biopsies in 52â% (95â%CI 46â%â-â57â%). Interobserver agreement was fair (kappa 0.28). High level of confidence was associated with a higher rate of correct neoplastic diagnosis (81â%) and lesion location (73â%). CONCLUSIONS: Identification of subtle neoplastic lesions in VLE full scans by experts was disappointing. Future studies should focus on improving methodologies for reviewing full scans, development of refined VLE criteria for neoplasia, and computer-aided diagnosis of VLE scans.
Assuntos
Esôfago de Barrett , Neoplasias Esofágicas , Esôfago de Barrett/diagnóstico por imagem , Neoplasias Esofágicas/diagnóstico por imagem , Esofagoscopia , Humanos , Lasers , Microscopia ConfocalRESUMO
Volumetric laser endomicroscopy (VLE) has been shown to improve detection of early neoplasia in Barrett's esophagus (BE). However, diagnostic performance using histopathology-correlated VLE regions of interest (ROIs) has not been adequately studied. We evaluated the diagnostic accuracy of VLE assessors for identification of early BE neoplasia in histopathology-correlated VLE ROIs. In total, 191 ROIs (120 nondysplastic and 71 neoplastic) from 50 BE patients were evaluated in a random order using a web-based module. All ROIs contained histopathology correlations enabled by VLE laser marking. Assessors were blinded to endoscopic BE images and histology. ROIs were first scored as nondysplastic or neoplastic. Level of confidence was assigned to the predicted diagnosis. Outcome measures were: (i) diagnostic performance of VLE assessors for identification of BE neoplasia in all VLE ROIs, defined as accuracy, sensitivity, and specificity; (ii) diagnostic performance of VLE assessors for only high level of confidence predictions; and (iii) interobserver agreement. Accuracy, sensitivity, and specificity for BE neoplasia identification were 79% (confidence interval [CI], 75-83), 75% (CI, 71-79), and 81% (CI, 76-86), respectively. When neoplasia was identified with a high level of confidence, accuracy, sensitivity, and specificity were 88%, 83%, and 90%, respectively. The overall strength of interobserver agreement was fair (k = 0.29). VLE assessors can identify BE neoplasia with reasonable diagnostic accuracy in histopathology-correlated VLE ROIs, and accuracy is enhanced when BE neoplasia is identified with high level of confidence. Future work should focus on renewed VLE image reviewing criteria and real-time automatic assessment of VLE scans.
Assuntos
Esôfago de Barrett , Neoplasias Esofágicas , Esofagoscopia , Humanos , Lasers , Microscopia ConfocalRESUMO
BACKGROUND: Radiofrequency ablation (RFA) treatment outcomes vary for unknown reasons. One hypothesis is that variations in Barrett's epithelial thickness (BET) are associated with reduced RFA efficacy for thicker BET and strictures for thinner BET. Volumetric laser endomicroscopy (VLE) is an imaging modality that acquires high-resolution, depth-resolved images of BE. However, the attenuation of light by tissue and the lack of layering in Barrett's tissue challenge BET measurements and the study of relationships between thickness and RFA outcomes. We aimed to quantify BET and compared the reliability of standard and contrast-enhanced VLE images. METHODS: Baseline VLE scans from BE patients without prior ablative therapy and a Prague (M) length of > 1 cm were obtained from the US VLE Registry. An algorithm was applied to the VLE images to flatten the mucosal surface and enhance the contrast of different esophageal wall layers. Subsequently, BET was measured by two independent VLE readers using both contrast- and non-contrast-enhanced datasets. In order to validate these adjusted images, intra- and interobserver agreements were calculated. RESULTS: VLE scans from fifty-seven patients were included in this study. BET was measured at eight equidistant locations on the selected cross-sectional images at 0.5 cm intervals from the GEJ to the proximal-most extent of BE. The intra-observer coefficients of the two readers for the contrast-enhanced images were 0.818 (95% CI 0.798-0.836) and 0.890 (95% CI 0.878-0.900). The interobserver agreement for the contrast-enhanced images (0.880; 95% CI 0.867-0.891) was significantly better than for the original images (0.778; 95% CI 0.754-0.799). CONCLUSION: We developed an algorithm that improves VLE visualization of the mucosal layers of the esophageal wall and enables rapid and reliable measurement of BET. Interobserver variability measurements were significantly reduced when using contrast enhancement. Studies are underway to correlate BET with treatment response.
Assuntos
Esôfago de Barrett/patologia , Mucosa Esofágica/patologia , Esofagoscópios , Esofagoscopia/instrumentação , Lasers , Microscopia/instrumentação , Idoso , Algoritmos , Esôfago de Barrett/cirurgia , Tomada de Decisão Clínica , Desenho de Equipamento , Mucosa Esofágica/cirurgia , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Variações Dependentes do Observador , Seleção de Pacientes , Valor Preditivo dos Testes , Ablação por Radiofrequência , Sistema de Registros , Reprodutibilidade dos TestesRESUMO
Spectrally encoded confocal microscopy and optical frequency domain imaging are two non-contact optical imaging technologies that provide images of tissue cellular and architectural morphology, which are both used for histopathological diagnosis. Although spectrally encoded confocal microscopy has better transverse resolution than optical frequency domain imaging, optical frequency domain imaging can penetrate deeper into tissues, which potentially enables the visualization of different morphologic features. We have developed a co-registered spectrally encoded confocal microscopy and optical frequency domain imaging system and have obtained preliminary images from human oesophageal biopsy samples to compare the capabilities of these imaging techniques for diagnosing oesophageal pathology.
Assuntos
Processamento de Imagem Assistida por Computador/métodos , Microscopia Confocal/métodos , Patologia/métodos , Tomografia de Coerência Óptica/métodos , Doenças do Esôfago/diagnóstico , Esôfago/patologia , HumanosRESUMO
A novel heterodyne Doppler interferometer method for compensating motion artifacts caused by cardiac motion in intracoronary optical frequency domain imaging (OFDI) is demonstrated. To track the relative motion of a catheter with regard to the vessel, a motion tracking system is incorporated with a standard OFDI system by using wavelength division multiplexing (WDM) techniques. Without affecting the imaging beam, dual WDM monochromatic beams are utilized for tracking the relative radial and longitudinal velocities of a catheter-based fiber probe. Our results demonstrate that tracking instantaneous velocity can be used to compensate for distortion in the images due to motion artifacts, thus leading to accurate reconstruction and volumetric measurements with catheter-based imaging.
Assuntos
Artefatos , Angiografia Coronária/instrumentação , Endoscópios , Aumento da Imagem/instrumentação , Interferometria/instrumentação , Animais , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Movimento (Física) , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Understanding pediatric voice development and laryngeal pathology is predicated on a detailed knowledge of the microanatomy of the layered structure of the vocal fold. Our current knowledge of this microanatomy and its temporal evolution is limited by the lack of pediatric specimen availability. By providing the capability to image pediatric vocal folds in vivo, a noninvasive microscopy technique could greatly expand the existing database of pediatric laryngeal microanatomy and could furthermore make longitudinal studies possible. A variety of natural-contrast optical imaging technologies, including optical frequency domain imaging (OFDI), full-field optical coherence microscopy (FF-OCM), and spectrally encoded confocal microscopy (SECM) have been recently developed for noninvasive diagnosis in adult patients. In this paper, we demonstrate the potential of these three techniques for laryngeal investigation by obtaining images of excised porcine vocal fold samples. In our study, OFDI allowed visualization of the vocal fold architecture deep within the tissue, from the superficial mucosa to the vocalis muscle. The micron-level resolution of SECM allowed investigation of cells and extracellular matrix fibrils from the superficial mucosa to the intermediate layer of the lamina propria (LP) (350 microm penetration depth). The large field of view (up to 700 microm), penetration depth (up to 500 microm), and resolution (2x2x1microm [XxYxZ]) of FF-OCM enabled comprehensive three-dimensional evaluation of the layered structure of the LP. Our results suggest that these techniques provide important and complementary cellular and structural information, which may be useful for investigating pediatric vocal fold maturation in vivo.
Assuntos
Prega Vocal/crescimento & desenvolvimento , Animais , Matriz Extracelular , Interpretação de Imagem Assistida por Computador , Músculos Laríngeos/anatomia & histologia , Músculos Laríngeos/crescimento & desenvolvimento , Microscopia Confocal , Mucosa/anatomia & histologia , Mucosa/crescimento & desenvolvimento , Suínos , Tomografia de Coerência Óptica , Prega Vocal/anatomia & histologiaRESUMO
Spectral-domain optical coherence phase microscopy (SD-OCPM) measures minute phase changes in transparent biological specimens using a common path interferometer and a spectrometer based optical coherence tomography system. The Fourier transform of the acquired interference spectrum in spectral-domain optical coherence tomography (SD-OCT) is complex and the phase is affected by contributions from inherent random noise. To reduce this phase noise, knowledge of the probability density function (PDF) of data becomes essential. In the present work, the intensity and phase PDFs of the complex interference signal are theoretically derived and the optical path length (OPL) PDF is experimentally validated. The full knowledge of the PDFs is exploited for optimal estimation (Maximum Likelihood estimation) of the intensity, phase, and signal-to-noise ratio (SNR) in SD-OCPM. Maximum likelihood (ML) estimates of the intensity, SNR, and OPL images are presented for two different scan modes using Bovine Pulmonary Artery Endothelial (BPAE) cells. To investigate the phase accuracy of SD-OCPM, we experimentally calculate and compare the cumulative distribution functions (CDFs) of the OPL standard deviation and the square root of the Cramér-Rao lower bound (1/ square root 2SNR ) over 100 BPAE images for two different scan modes. The correction to the OPL measurement by applying ML estimation to SD-OCPM for BPAE cells is demonstrated.
RESUMO
The capability to image tissue motion such as blood flow through an endoscope could have many applications in medicine. Spectrally encoded endoscopy (SEE) is a recently introduced technique that utilizes a single optical fiber and miniature diffractive optics to obtain endoscopic images through small diameter probes. Using spectral-domain interferometry, SEE is furthermore capable of three-dimensional volume imaging at video rates. Here we show that by measuring relative spectral phases, this technology can additionally measure Doppler shifts. Doppler SEE is demonstrated in flowing Intralipid phantoms and vibrating middle ear ossicles.
Assuntos
Velocidade do Fluxo Sanguíneo/fisiologia , Endoscópios , Tecnologia de Fibra Óptica/instrumentação , Imageamento Tridimensional/instrumentação , Interferometria/instrumentação , Fluxometria por Laser-Doppler/instrumentação , Refratometria/instrumentação , Humanos , Miniaturização , Fibras Ópticas , Imagens de FantasmasRESUMO
We demonstrate a novel high-speed polarization-sensitive optical frequency domain imaging system employing high-speed polarization modulation. Rapid and continuous polarization modulation of light prior to illumination of the sample is accomplished by shifting the frequency of one polarization eigenstate by an amount equal to one quarter of the digitization sampling frequency. This approach enables polarization-sensitive imaging with a single detection channel and overcomes artifacts that may arise from temporal variations of the birefringence in fiber-optic imaging probes and spatial variation of birefringence in the sample.
Assuntos
Óptica e Fotônica , Animais , Galinhas , Vasos Coronários/ultraestrutura , Microscopia de Polarização/métodos , Músculo Esquelético/ultraestrutura , SuínosRESUMO
Polarization sensitive optical coherence tomography (PS-OCT) provides a cross-sectional image of birefringence in biological samples that is complementary in many applications to the standard reflectance-based image. Recent ex vivo studies have demonstrated that birefringence mapping enables the characterization of collagen and smooth muscle concentration and distribution in vascular tissues. Instruments capable of applying these measurements percutaneously in vivo may provide new insights into coronary atherosclerosis and acute myocardial infarction. We have developed a polarization sensitive optical frequency domain imaging (PS-OFDI) system that enables high-speed intravascular birefringence imaging through a fiber-optic catheter. The novel design of this system utilizes frequency multiplexing to simultaneously measure reflectance of two incident polarization states, overcoming concerns regarding temporal variations of the catheter fiber birefringence and spatial variations in the birefringence of the sample. We demonstrate circular cross-sectional birefringence imaging of a human coronary artery ex vivo through a flexible fiber-optic catheter with an A-line rate of 62 kHz and a ranging depth of 6.2 mm.
Assuntos
Vasos Coronários/ultraestrutura , Tecnologia de Fibra Óptica/instrumentação , Aumento da Imagem/instrumentação , Microscopia de Polarização/instrumentação , Tomografia de Coerência Óptica/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Tecnologia de Fibra Óptica/métodos , Humanos , Aumento da Imagem/métodos , Microscopia de Polarização/métodos , Fibras Ópticas , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Tomografia de Coerência Óptica/métodosRESUMO
Endoscopic imaging below tissue surfaces and through turbid media may provide improved diagnostic capabilities and visibility in surgical settings. Spectrally encoded endoscopy (SEE) is a recently developed method that utilizes a single optical fiber, miniature optics and a diffractive grating for high-speed imaging through small diameter, flexible endoscopic probes. SEE has also been shown to provide three-dimensional topological imaging capabilities. In this paper, we have configured SEE to additionally image beneath tissue surfaces, by increasing the system's sensitivity and acquiring the complex spectral density for each spectrally resolved point on the sample. In order to demonstrate the capability of SEE to obtain subsurface information, we have utilized the system to image a resolution target through intralipid solution, and conduct volumetric imaging of a mouse embryo and excised human middle-ear ossicles. Our results demonstrate that real-time subsurface imaging is possible with this miniature endoscopy technique.
Assuntos
Compressão de Dados/métodos , Endoscópios , Aumento da Imagem/instrumentação , Imageamento Tridimensional/instrumentação , Microscopia/instrumentação , Análise Espectral/instrumentação , Tomografia Óptica/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Estudos de ViabilidadeRESUMO
A technique for increasing the ranging depth in optical frequency domain imaging utilizing frequency encoding is presented. Ranging depth is enhanced by using two interferometer reference arms with different path lengths and independent modulation frequencies (25 and 50 MHz). With this configuration, the sensitivity decreases by 6 dB over a depth range of 7 mm, approximately a threefold improvement over the conventional optical frequency domain imaging technique. We demonstrate that the reference arm frequency separation, tuning speed, center wavelength, and instantaneous coherence length determine the signal-to-cross-talk ratio.
Assuntos
Algoritmos , Compressão de Dados/métodos , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Processamento de Sinais Assistido por Computador , Tomografia de Coerência Óptica/métodos , Análise de Fourier , Sensibilidade e EspecificidadeRESUMO
Noninvasive measurements of the scattering coefficients of optically turbid media using angle-resolved optical frequency-domain imaging (OFDI) are demonstrated. It is shown that, by incoherently averaging OFDI reflectance signals acquired at different backscattering angles, speckle noise is reduced, allowing scattering coefficients to be extracted from a single A-line with much higher accuracy than with measurements from conventional OFDI and optical coherence tomography systems. Modeling speckle as a random phasor sum, the relationship between the measurement accuracy and the number of compounded angles is derived. The sensitivity analysis is validated with measurements from a tissue phantom.
Assuntos
Óptica e Fotônica , Tomografia de Coerência Óptica/métodos , Calibragem , Modelos Lineares , Modelos Estatísticos , Imagens de Fantasmas , Probabilidade , Refratometria , Análise de Regressão , Reprodutibilidade dos Testes , Espalhamento de RadiaçãoRESUMO
Imaging large tissue areas with microscopic resolution in vivo may offer an alternative to random excisional biopsy. We present an approach for performing confocal imaging of large tissue surface areas using spectrally encoded confocal microscopy (SECM). We demonstrate a single-optical-fiber SECM apparatus, designed for imaging luminal organs, that is capable of imaging with a transverse resolution of 2.1 microm over a subsurface area of 16 cm2 in less than 1 min. Due to the unique probe configuration and scanning geometry, the speed and resolution of this new imaging technology are sufficient for comprehensively imaging large tissues areas at a microscopic scale in times that are appropriate for clinical use.
Assuntos
Intestinos/ultraestrutura , Animais , Microscopia Confocal/instrumentação , Microscopia Confocal/métodos , Imagens de Fantasmas , SuínosRESUMO
Recently, we have experimentally demonstrated a new form of cross-sectional, coherence-gated fluorescence imaging referred to as SD-FCT ('spectral-domain fluorescence coherence tomography'). Imaging in SD-FCT is accomplished by spectrally detecting self-interference of the spontaneous emission of fluorophores, thereby providing depth-resolved information on the axial positions of fluorescent probes. Here, we present a theoretical investigation of the factors affecting the detected SD-FCT signal through scattering media. An imaging equation for SD-FCT is derived that includes the effects of defocusing, numerical-aperture, and the optical properties of the medium. A comparison between the optical sectioning capabilities of SD-FCT and confocal microscopy is also presented. Our results suggest that coherence gating in fluorescence imaging may provide an improved approach for depth-resolved imaging of fluorescently labeled samples; high axial resolution (a few microns) can be achieved with low numerical apertures (NA<0.09) while maintaining a large depth of field (a few hundreds of microns) in a relatively low scattering medium (6 mean free paths), whereas moderate NA's can be used to enhance depth selectivity in more highly scattering biological samples.
RESUMO
We present a novel method for rapidly acquiring optical coherence tomography (OCT) images at multiple backscattering angles. By angularly compounding these images, high levels of speckle reduction were achieved. Signal-to-noise ratio (SNR) improvements of 3.4 dB were obtained from a homogeneous tissue phantom, which was in good agreement with the predictions of a statistical model of speckle that incorporated the optical parameters of the imaging system. In addition, the fast acquisition rate of the system (10 kHz A-line repetition rate) allowed angular compounding to be performed in vivo without significant motion artifacts. Speckle-reduced OCT images of human dermis show greatly improved delineation of tissue microstructure.
RESUMO
Recent results have demonstrated unprecedented wavelength-tuning speed and repetition rate performance of semiconductor ring lasers incorporating scanning filters. However, several unique operational characteristics of these lasers have not been adequately explained, and the lack of an accurate model has hindered optimization. We numerically investigated the characteristics of these sources, using a semiconductor optical amplifier (SOA) traveling-wave Langevin model, and found good agreement with experimental measurements. In particular, we explored the role of the SOA refractive-index nonlinearities in determining the intracavity frequency-shift-broadening and the emitted power dependence on scan speed and direction. Our model predicts both continuous-wave and pulse operation and shows a universal relationship between the output power of lasers that have different cavity lengths and the filter peak frequency shift per round trip, therefore revealing the advantage of short cavities for high-speed biomedical imaging.
Assuntos
Amplificadores Eletrônicos , Engenharia Biomédica/instrumentação , Engenharia Biomédica/métodos , Desenho Assistido por Computador , Lasers , Refratometria/instrumentação , Refratometria/métodos , Simulação por Computador , Desenho de Equipamento , Análise de Falha de Equipamento/métodos , Modelos Teóricos , Dinâmica não Linear , Óptica e Fotônica , Reprodutibilidade dos Testes , Semicondutores , Sensibilidade e EspecificidadeRESUMO
A novel optical frequency-domain imaging system is demonstrated that employs a passive optical demodulation circuit and a chirped digital acquisition clock derived from a voltage-controlled oscillator. The demodulation circuit allows the separation of signals from positive and negative depths to better than 50 dB, thereby eliminating depth degeneracy and doubling the imaging depth range. Our system design is compatible with dual-balanced and polarization-diverse detection, important techniques in the practical biomedical application of optical frequency-domain imaging.
Assuntos
Aumento da Imagem/instrumentação , Imageamento Tridimensional/instrumentação , Óptica e Fotônica/instrumentação , Refratometria/instrumentação , Processamento de Sinais Assistido por Computador/instrumentação , Tomografia de Coerência Óptica/instrumentação , Conversão Análogo-Digital , Desenho de Equipamento , Análise de Falha de Equipamento , Aumento da Imagem/métodos , Imageamento Tridimensional/métodos , Refratometria/métodos , Tomografia de Coerência Óptica/métodosRESUMO
We present ultra-high resolution optical coherence tomography (OCT) structural intensity and optical Doppler tomography (ODT) flow velocity images of the human retina in vivo. The ultra-high speed OCT system is based on Spectral Domain or Fourier Domain technology, which provides a sensitivity advantage over conventional OCT of more than 2 orders of magnitude. This sensitivity improvement allows video rate OCT and ODT cross sectional imaging of retinal structures. Images will be presented with axial resolutions of 6 and 3.5 microns. We observed small features in the inner and outer plexiform layers, which are believed to be small blood vessels. Flow velocity images will be presented showing pulsatile flow in retinal arteries and veins.