Flow velocity analysis with joint spectral and time domain OCT

2008 ◽  
Author(s):  
Maciej Szkulmowski ◽  
Maciej Wojtkowski ◽  
Anna Szkulmowska ◽  
Andrzej Kowalczyk
Keyword(s):  
Flow Velocity ◽  
Time Domain ◽  
Velocity Analysis ◽  
Time Domain Oct

Simultaneous analysis of extinction and flow velocity with joint spectral and time domain OCT

2008 ◽  
Author(s):  
Maciej Wojtkowski ◽  
Maciej Szkulmowski ◽  
Tomasz Bajraszewski ◽  
Anna Szkulmowska ◽  
Andrzej Kowalczyk
Keyword(s):  
Flow Velocity ◽  
Time Domain ◽  
Simultaneous Analysis ◽  
Time Domain Oct

Simultaneous complex ambiguity removal and quantitative flow velocity estimation with joint spectral and time domain OCT

2009 ◽  
Author(s):  
Maciej Szkulmowski ◽  
Ireneusz Grulkowski ◽  
Daniel Szlag ◽  
Anna Szkulmowska ◽  
Andrzej Kowalczyk ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Time Domain ◽  
Velocity Estimation ◽  
Time Domain Oct ◽  
Quantitative Flow

Migration velocity analysis based on focusing diffractions generated using the CRS wavefront attributes: Application to real land data

Geophysics ◽  
2021 ◽  
pp. 1-50
Author(s):  
German Garabito ◽  
José Silas dos Santos Silva ◽  
Williams Lima
Keyword(s):  
Time Domain ◽  
Real Data ◽  
Normal Incidence ◽  
Velocity Model ◽  
Migration Velocity ◽  
Velocity Analysis ◽  
Velocity Models ◽  
Time Migration ◽  
Migration Velocity Analysis ◽  
The Time Domain

In land seismic data processing, the prestack time migration (PSTM) image remains the standard imaging output, but a reliable migrated image of the subsurface depends on the accuracy of the migration velocity model. We have adopted two new algorithms for time-domain migration velocity analysis based on wavefield attributes of the common-reflection-surface (CRS) stack method. These attributes, extracted from multicoverage data, were successfully applied to build the velocity model in the depth domain through tomographic inversion of the normal-incidence-point (NIP) wave. However, there is no practical and reliable method for determining an accurate and geologically consistent time-migration velocity model from these CRS attributes. We introduce an interactive method to determine the migration velocity model in the time domain based on the application of NIP wave attributes and the CRS stacking operator for diffractions, to generate synthetic diffractions on the reflection events of the zero-offset (ZO) CRS stacked section. In the ZO data with diffractions, the poststack time migration (post-STM) is applied with a set of constant velocities, and the migration velocities are then selected through a focusing analysis of the simulated diffractions. We also introduce an algorithm to automatically calculate the migration velocity model from the CRS attributes picked for the main reflection events in the ZO data. We determine the precision of our diffraction focusing velocity analysis and the automatic velocity calculation algorithms using two synthetic models. We also applied them to real 2D land data with low quality and low fold to estimate the time-domain migration velocity model. The velocity models obtained through our methods were validated by applying them in the Kirchhoff PSTM of real data, in which the velocity model from the diffraction focusing analysis provided significant improvements in the quality of the migrated image compared to the legacy image and to the migrated image obtained using the automatically calculated velocity model.

scholarly journals Comparison of Fourier-Domain and Time-Domain Optical Coherence Tomography in the Measurement of Thinnest Corneal Thickness in Keratoconus

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Chunxiao Wang ◽  
Xueying Xia ◽  
Bishan Tian ◽  
Shiyou Zhou
Keyword(s):  
Optical Coherence Tomography ◽  
Time Domain ◽  
Pearson Correlation ◽  
Corneal Thickness ◽  
Intraclass Correlation ◽  
Fourier Domain ◽  
Optical Coherence ◽  
Highly Correlated ◽  
Time Domain Oct

Objective. To compare fourier-domain optical coherence tomography (FD-OCT) and time-domain OCT (TD-OCT) in the determination of thinnest corneal thickness (TCT).Methods. This study included 55 keratoconus patients and 50 healthy volunteers. The RTVue-OCT (FD-OCT) and Visante-OCT (TD-OCT) were used for the measurement of the TCT. Three consecutive scans were performed. The comparison and agreement between the two modalities were analyzed by pairedt-test, the Pearson correlation, intraclass correlation coefficient (ICC), and Bland-Altman plots. intraobserver repeatability was analyzed by the intraobserver within-subject standard deviation (S(w)), coefficient of variation (CV(w)), and ICC.Results. The TCT value of normal corneas was higher by RTVue-OCT (530.4 ± 19.7 μm) than Visante-OCT (521.5 ± 18.3 μm) (p<0.001). For keratoconus eyes, the TCT was 425.0 ± 58.2 μm and 424.4 ± 55.7 μm (difference being 0.6 ± 10.2 μm,p=0.604). Strong correlation (r= 0.938∼0.985) (ICC = 0.915–0.984) was observed between the two OCTs, and each OCT exhibited excellent repeatability in determining the TCT in all subjects (ICC = 0.984–0.994).Conclusions. The values of TCT obtained from RTVue-OCT and Visante-OCT were highly correlated; however, the two values were different. Both OCT instruments exhibited good intraobserver reliability. The existence of systematic differences suggested that the two instruments cannot be used interchangeably.

scholarly journals Comparison of Retinal Nerve Fiber Layer Thickness Measurements in Healthy Subjects Using Fourier and Time Domain Optical Coherence Tomography

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Isabel Pinilla ◽  
Elena Garcia-Martin ◽  
Miriam Idoipe ◽  
Eva Sancho ◽  
Isabel Fuertes
Keyword(s):  
Nerve Fiber ◽  
Retinal Nerve Fiber Layer ◽  
Time Domain ◽  
Healthy Subjects ◽  
Fourier Domain ◽  
Average Thickness ◽  
Fiber Layer ◽  
Nerve Fiber Layer ◽  
Fourier Domain Oct ◽  
Time Domain Oct

Purpose. To compare the retinal nerve fiber layer (RNFL) measurements using two different ocular coherence tomography (OCT) devices: Cirrus Fourier domain OCT and Stratus time domain OCT. To analyze reproducibility of Fourier domain measurements in healthy subjects.Methods. One hundred and thirty-two eyes of 132 healthy subjects were scaned on the same day with both instruments, separated by 10 minutes from each other. Thickness of quadrant, average and the 12 different areas around the optic nerve were compared between Cirrus and Stratus. Repeatability, intraclass correlation coefficients (ICCs), and coefficients of variation (COVs) were calculated in RNFL measurements provided by Fourier domain device.Results. The average thickness in the optic cube was 95.50 μm using Cirrus and 97.85 μm using Stratus. Average thickness and temporal quadrant showed significant differences using Cirrus and Stratus methods. Reproducibility was better with Fourier domain OCT (mean COV of 4.54%) than with Stratus time-domain OCT (mean COV of 5.57%).Conclusions. Both scan options give reproducible RNFL thickness measurement, but there are differences between them. Measurements obtained using Fourier domain device show better reproducibility.

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