## Flow velocity estimation by complex ambiguity free joint Spectral and Time domain Optical Coherence Tomography

Optics Express, Vol. 17, Issue 16, pp. 14281-14297 (2009)

http://dx.doi.org/10.1364/OE.17.014281

Acrobat PDF (548 KB)

### Abstract

We show that recently introduced joint Spectral and Time domain Optical Coherence Tomography (STdOCT) can be used for simultaneous complex ambiguity removal and functional Spectral OCT images. This permits to take advantage of higher sensitivity achievable near the zero-path delay. The technique can be used with all Spectral OCT systems that are equipped with an optical delay line (ODL) and provide oversampled scanning patterns. High sensitivity provided by STdOCT allows this technique to be used in Spectral OCT setups with acquisition speed of 100 000 lines/s. We show that different imaging ranges and velocity ranges can be achieved by switching on/off the ODL and a small modification in the processing algorithm. Additionally, the relatively small computational burden of the technique allows for fast computations in the range of less than 5 minutes for 3D data set. We present application of proposed technique to full-range two- and three-dimensional imaging. Morphological and Doppler tomograms of human retina *in-vivo* are shown. Finally, we identify and discuss artifacts of the technique.

© 2009 OSA

## 1. Introduction

18. M. Szkulmowski, A. Szkulmowska, T. Bajraszewski, A. Kowalczyk, and M. Wojtkowski, “Flow velocity estimation using joint Spectral and Time domain Optical Coherence Tomography,” Opt. Express **16**(9), 6008–6025 (2008). [CrossRef] [PubMed]

19. A. Szkulmowska, M. Szkulmowski, D. Szlag, A. Kowalczyk, and M. Wojtkowski, “Three-dimensional quantitative imaging of retinal and choroidal blood flow velocity using joint Spectral and Time domain Optical Coherence Tomography,” Opt. Express **17**(13), 10584–10598 (2009). [CrossRef] [PubMed]

15. Y. Yasuno, S. Makita, T. Endo, G. Aoki, M. Itoh, and T. Yatagai, “Simultaneous B-M-mode scanning method for real-time full-range Fourier domain optical coherence tomography,” Appl. Opt. **45**(8), 1861–1865 (2006). [CrossRef] [PubMed]

20. M. Wojtkowski, A. Kowalczyk, R. Leitgeb, and A. F. Fercher, “Full range complex spectral optical coherence tomography technique in eye imaging,” Opt. Lett. **27**(16), 1415–1417 (2002). [CrossRef]

15. Y. Yasuno, S. Makita, T. Endo, G. Aoki, M. Itoh, and T. Yatagai, “Simultaneous B-M-mode scanning method for real-time full-range Fourier domain optical coherence tomography,” Appl. Opt. **45**(8), 1861–1865 (2006). [CrossRef] [PubMed]

24. R. K. K. Wang, “In vivo full range complex Fourier domain optical coherence tomography,” Appl. Phys. Lett. **90**(5), 054103 (2007). [CrossRef]

27. Y. Yasuno, S. Makita, T. Endo, G. Aoki, H. Sumimura, M. Itoh, and T. Yatagai, “One-shot-phase-shifting Fourier domain optical coherence tomography by reference wavefront tilting,” Opt. Express **12**(25), 6184–6191 (2004). [CrossRef] [PubMed]

28. S. Makita, T. Fabritius, and Y. Yasuno, “Full-range, high-speed, high-resolution 1 microm spectral-domain optical coherence tomography using BM-scan for volumetric imaging of the human posterior eye,” Opt. Express **16**(12), 8406–8420 (2008). [CrossRef] [PubMed]

## 2. Method

*k*domain). Next, uncompensated dispersion is numerically removed and a numerical shaping of the spectral fringes is introduced [29

29. M. Szkulmowski, A. Wojtkowski, T. Bajraszewski, I. Gorczynska, P. Targowski, W. Wasilewski, A. Kowalczyk, and C. Radzewicz, “Quality improvement for high resolution in vivo images by spectral domain optical coherence tomography with supercontinuum source,” Opt. Commun. **246**(4–6), 569–578 (2005). [CrossRef]

### 2.1. Standard STdOCT

*R*), and backscattered on several interfaces in the sample (reflectivity coefficients

_{r}*R*). The wavelength dependent spectral envelope is denoted by

_{s}*S*(

*k*). The phase of the interferometric signal depends on the positions

*z*of the scattering interfaces as well as on the projections

_{s}*ν*=

_{s}*V*cos (

_{s}*α*) of velocity

*V*of the scattering particle in the sample moving in the direction inclined to the probing beam at angle

_{s}*α*.

*ω*= 2

_{s}*ν*that arises for each wavenumber

_{s}k*k*along the time axis encodes the laterally localized velocity of the s-th interface inside the sample. Simultaneously, the frequency of fringes along the wavenumber axis encodes the axial position of the s-th interface. It needs to be pointed out that the frequency of fringe pattern carries information along both spectral and time axes. The observation that the interferogram can be processed in similar way along both dimensions led to development of the joint Spectral and Time OCT (STdOCT).

*kt*domain) to “in-depth position”-“beat frequency” domain (

*zω*domain). Two dimensional Fourier transformation can be calculated using two one-dimensional Fourier transformations conducted consecutively along the wavenumber axis and time axis or in opposite order. In order to emphasize this possibility it is useful to plot a STdOCT diagram that shows all possible Fourier transformations that can be applied to a two-dimensional interferogram, as it is presented in Fig. 1.

*zω*-domain each moving scattering interface is represented by two signal peaks in well determined in-depth position and beat frequency. The two points are positioned symmetrically with respect to the zero-delay and zero-velocity position due to the complex ambiguity problem. This is clearly visible in the case of SOCT signals coming from a moving mirror Fig. 1(a). The fact that the quantitative distributions of velocity versus depth position can be directly observed in the

*zω*-domain is even better visualized in an experiment with Intralipid solution flowing in a capillary, Fig. 1(b). Here we can observe the parabolic flow velocity distribution indicating a laminar flow.

18. M. Szkulmowski, A. Szkulmowska, T. Bajraszewski, A. Kowalczyk, and M. Wojtkowski, “Flow velocity estimation using joint Spectral and Time domain Optical Coherence Tomography,” Opt. Express **16**(9), 6008–6025 (2008). [CrossRef] [PubMed]

*zω*-domain compared to the average signal amplitude in the

*zt*-domain, while the noise floor level remains unchanged. Due to these facts the signal-to-noise ratio increases by the factor proportional to the square root of the number of the averaged spectra. Therefore, we propose to use the

*zω*-domain to retrieve both structural and velocity information. The comparison of the STdOCT and standard SOCT data processing schemes is presented on STdOCT diagrams in Fig. 2. In STdOCT for each in-depth position along the beat frequency axis the signal with maximal amplitude is found. Squared magnitudes of the highest peaks are proportional to the reflectivity of the scattering interfaces. Positions of highest peaks along beat frequency axis are proportional to their velocity. The distribution of the peaks positions as a function of depth gives a velocity A-scan, while the distribution of squared magnitudes as a function of depth forms a structural A-scan. In order to exploit information from all acquired spectra in the standard SOCT procedure, a final tomogram line (A-scan) is created by averaging amplitudes of all Fourier transformed spectra from the

*zt*-domain along the time axis.

*kt*-domain to

*zω*-domain does not have any importance. However, in structural imaging without complex conjugate removal only a half of the in-depth data carries useful information. This fact is depicted in diagrams in Fig. 2, where grey color marks these parts of signal spaces that are used in further processing. Therefore, it is advantageous to perform the transformation in a sequence starting from the transformation along wavenumber axis as depicted in Fig. 2(b). This allows the transformation along time axis to be performed only on one half of the

*zt*-domain thus reducing the calculation burden by a factor of two.

*zt*-domain to the

*zω*-domain, which impacts on the computation time.

### 2.2. Complex ambiguity free STdOCT

*ν*the total time-dependent spectral fringe signal

_{ref}*I*(

*k*,

*t*) can be described by an expression similar to the one shown in Eq. (1):

*zω*-domain the complex conjugate images are positioned on the opposite sides of both zero-delay line (in case of

*z*≠ 0 ) and on opposite sides of zero beat frequency line (in case of

_{s}*ν*≠ 0 ). It is important to note that by the introduction of the additional velocity

_{s}*ν*≠ 0 one shifts the image and its complex conjugate counterpart in opposite directions along the beat frequency axis.

_{ref}*ω*axis. This effect is clearly visualized in Fig. 3(b), which presents data from the same experimental setup as data from Fig. 3(a) but with additionally introduced velocity

*ν*. The conjugate velocity distributions of Intralipid solution are placed on “positive” and “negative” sides of the beat frequency axis.

_{ref}*kω*-domain placed on one side of the zero-velocity position, Fig. 4. Now the resulting beat frequency is proportional to (

*ν*+

_{s}*ν*), so the velocity of inner motion of the sample can be easily extracted.

_{ref}*z*

_{±max}=

*π*/2Δ

*k*, which depends on the sampling period Δ

*k*in the spectral domain, the maximal velocity

*ν*detectable without the 2

*π*ambiguity is determined by the acquisition time of spectral fringe signal Δ

*t*:

*ν*= 0), Eq. (4) determines the maximal velocity detectable inside the sample without the aliasing:

_{ref}*ν*≠ 0 introduced to the system shifts the complex conjugate images along the beat-frequency axis in opposite directions (Fig. 3(b)). If all velocity components of one of the images fit in one half of the velocity range, then the complex conjugate image is placed on the opposite side of the beat-frequency axis. In such a case the beat frequency value ω = 0 separates completely the complex conjugate images in the

_{ref}*kω*-domain. The two images do not overlap if the following conditions are fulfilled:

*ν*=

_{ref}*ν*/2 and are equal:

_{max}*zω*domain located above or below the

*ω*= 0 should be processed to extract the structural and velocity A-scans. If the expected velocity distribution is asymmetrical, it is necessary to change the velocity offset

*ν*to fulfill the conditions given by formulas (5) and (6).

_{ref}*kt*-domain to

*zt*-domain first, and perform the second transformation from

*zt*-domain to

*zω*-domain. In the case of standard STdOCT the latter transformations can be performed only for

*z*≥ 0, Fig. 2(b), as half of the

*zt*and

*zω*-domains carries redundant information.

*kω*- and

*zω*-domains in the case of modified STdOCT processing. Therefore, the total number of Fourier transformations in complex ambiguity free STdOCT can be halved by the proper choice of order of Fourier transformations if no high resolution in velocity is required. In such a case, after transforming data from

*kt*-domain to

*kω*-domain, the following transition to

*zω*-domain can be completed for

*ω*≥ 0 only, Fig. 4(b). This is especially useful for complex ambiguity removal in a real-time tomogram creation for purposes of alignment of the sample. The latter can be also used in the case where no velocity information is required and one is interested only in complex ambiguity removal. This technique has been used by our group for complex ambiguity removal in imaging of whole anterior chamber of the human eye

*in vivo*along with both surfaces of the lens [30

30. I. Grulkowski, M. Gora, M. Szkulmowski, I. Gorczynska, D. Szlag, S. Marcos, A. Kowalczyk, and M. Wojtkowski, “Anterior segment imaging with Spectral OCT system using a high-speed CMOS camera,” Opt. Express **17**(6), 4842–4858 (2009). [CrossRef] [PubMed]

*zω*-domain where the procedure of A-scan creation is performed. As a result, the trade-off between velocity range and structural imaging range is different for the regular and the modified technique. Standard STdOCT gives halved structural imaging range but the velocity detection range is full. On the contrary, the complex ambiguity free STdOCT provides full structural imaging range, but the velocity range is halved. In order to separate complex conjugate images in both techniques the images have to be placed on opposite sides of z-axis (in case of standard STdOCT) or ω-axis (in case of modified STdOCT). It has to be noted that if the SOCT setup allows for offsets’ introduction in both z and ω directions, the transition between the two modalities of STdOCT is straightforward, and allows the user to choose the velocity and imaging range according to current needs.

31. S. H. Yun, G. J. Tearney, J. F. de Boer, and B. E. Bouma, “Motion artifacts in optical coherence tomography with frequency-domain ranging,” Opt. Express **12**(13), 2977–2998 (2004). [CrossRef] [PubMed]

32. A. H. Bachmann, M. L. Villiger, C. Blatter, T. Lasser, and R. A. Leitgeb, “Resonant Doppler flow imaging and optical vivisection of retinal blood vessels,” Opt. Express **15**(2), 408–422 (2007). [CrossRef] [PubMed]

32. A. H. Bachmann, M. L. Villiger, C. Blatter, T. Lasser, and R. A. Leitgeb, “Resonant Doppler flow imaging and optical vivisection of retinal blood vessels,” Opt. Express **15**(2), 408–422 (2007). [CrossRef] [PubMed]

## 3. Experimental set-up

### 3.1. SOCT device

*Fusion*, Femtolasers, Δλ = 160nm, central wavelength 810 nm). Light from the laser is launched to an optical single mode fiber interferometer (AC Photonics Inc., USA) that splits 90% of light energy into the reference arm and the rest into the object arm. The reference arm is equipped with a neutral density filter to adjust light intensity as well as with a dispersion controller to minimize the dispersion mismatch between both arms of the interferometer. Optical delay line (ODL) using galvanometer-based scanner (Cambridge Technology Inc., USA), collimating achromat lens (f1 = 19mm) and another achromat lens L2 (f2 = 40mm) is placed in the reference arm. Detailed description of the ODL is given in the next subsection. The detection arm consists of a custom designed spectrometer containing an achromatic collimating objective (Schneider Optics, USA), a volume holographic diffraction grating (1200 lpmm; Wasatch Photonics, USA) and a f-theta objective (Sill Optics, Germany) imaging the spectral interference fringes at the 12-bit line scan CMOS camera with 4096 pixels (

*Sprint*, Basler AG, Germany). CMOS camera was set to acquire 2048 pixels from 4096 available photosensitive elements. Transversal scanning of the sample is provided by a set of two galvanometer-based optical scanners (Cambridge Technology Inc., USA). Triggers to all scanners and the camera are delivered in analog form by an analog input/output card (National Instruments, USA). The experimental data registration is realized by a framegrabber (National Instruments, USA).

### 3.2. Optical delay line

33. A. G. Podoleanu, G. M. Dobre, and D. A. Jackson, “En-face coherence imaging using galvanometer scanner modulation,” Opt. Lett. **23**(3), 147–149 (1998). [CrossRef]

*z*(

_{δ}*α*) depends on the angle α between the direction perpendicular to the impinging beam and the surface of the scanner:

*α*

_{0}yields:

*ω*

_{SM-Z}=

*dα*/

*dt*:

*zδ*(

*α*) twice.

*α*

_{0}= 45°, therefore Eq. (10) simplifies to:

## 4. Results and discussion

### 4.1. Extinction ratio and scanning protocols for complex ambiguity free STdOCT

*Fast mode*of complex ambiguity free STdOCT, Fig. 4(b), allows for real-time display of images at 5 frames/sec.

*high velocity resolution mode*of complex ambiguity free STdOCT, Fig. 4(a), and provides structural and velocity tomograms in two or three dimensions. As mentioned in previous sections in order to be able to perform quantitative velocity estimation lateral shift between the positions of the scanning beam has to be smaller than the beam diameter, which is assumed to be 20 μm at the retina. Spectra are acquired at 100 000 lines/s with the integration time of 8.7 μs. As a result, the maximal velocity range ν

_{max}is equal to 20.2 mm/s for standard imaging and 10.1 mm/s for complex ambiguity free imaging. Examples of scanning protocols that fulfill this condition are presented in Table 1. It can be seen that in all cases the lateral oversampling factor [37

37. B. H. Park, M. C. Pierce, B. Cense, S. H. Yun, M. Mujat, G. Tearney, B. Bouma, and J. de Boer, “Real-time fiber-based multi-functional spectral-domain optical coherence tomography at 1.3 microm,” Opt. Express **13**(11), 3931–3944 (2005). [CrossRef] [PubMed]

*ν*=

_{ref}*ν*/2, which provides maximal velocity range, according to Eq. (7). The amplitude of the scanner driving signal remains constant. Exactly 543 spectra acquisitions are performed along each monotonic ramp of the signal. The triangular signal is synchronized with the beginning of every B-scan. In all cases one final A-scan is constructed from 16 spectral fringe signals. To create B-scans or velocity maps with a reasonable quality we divided our initial 543 spectral fringes into 105 partially redundant sets of 16 spectral fringes (105 =⌊ (543 -16)/5⌋). Separation between each set of 16 fringes is chosen to be 5, only to optimize the calculation time. This procedure introduces some kind of smoothing or interpolation into the velocity maps. Zero-padding (z-axis) up to 128 data points is performed before applying Fourier transformation, Fig. 2(b) and Fig. 4(a).

_{max}*high velocity resolution mode*) is about 1000 final tomogram lines per second. Total computation time depends on the protocol and is equal 6.7 seconds for the 2D_1 protocol, 9.5 seconds for 2D_2 protocol and 286 seconds (approx. 5 minutes) for 3D_1 protocol.

### 4.2. Complex ambiguity free STdOCT

*in-vitro*flows in glass capillaries as well as in retinal vessels

*in-vivo*.

11. A. Szkulmowska, M. Szkulmowski, A. Kowalczyk, and M. Wojtkowski, “Phase-resolved Doppler optical coherence tomography – limitations and improvements,” Opt. Lett. **33**(13), 1425–1427 (2008). [CrossRef] [PubMed]

*in-vivo*using scanning protocol 2D_2, Table 1. Results are shown in Fig. 8. Sixteen spectra are used to create a single A-scan of the velocity map and complex ambiguity free cross-sectional image from the lateral range of 5 mm. As a result, the effective lateral resolution drops approximately by 50%, to 30 μm. The complex conjugate image is suppressed in both structural and velocity images.

### 4.3. Artifacts

*ν*Δ

_{ref}*t*=

*λ*

_{0}/8, where

*λ*

_{0}is the central wavelength of the light used in the experiments. Therefore, OPD between the two extreme positions of the ODL in case of 543 spectra acquisitions is as large as 55 μm. As a result, tomograms acquired with operating ODL suffer from geometrical distortion caused by the OPD changes during scanning, Fig. 10(a).

*i*·2Δ

*z*·

*k*], where Δ

*z*is the instantaneous OPD introduced by the ODL at the moment of acquisition of the central spectrum from the interferogram. Since the phase element is constant for each A-scan of the tomogram, it can be calculated once and tabularized. Therefore, it can be incorporated in numerical dispersion compensation algorithm at no additional computational cost. The result of the procedure is depicted in Fig. 10(b), where the geometrical distortion is no longer present. This procedure has been applied to all tomograms presented in this paper.

*zω*-domain reveals the parabolic distribution of flow inside the vessel wrapped to the opposite side of the velocity range and thus entering on the opposite side of beat frequency domain, see dotted arrow in Fig. 11(c). Similar artifact has already been reported by Makita et al. [28

28. S. Makita, T. Fabritius, and Y. Yasuno, “Full-range, high-speed, high-resolution 1 microm spectral-domain optical coherence tomography using BM-scan for volumetric imaging of the human posterior eye,” Opt. Express **16**(12), 8406–8420 (2008). [CrossRef] [PubMed]

12. R. K. Wang, S. L. Jacques, Z. Ma, S. Hurst, S. R. Hanson, and A. Gruber, “Three dimensional optical angiography,” Opt. Express **15**(7), 4083–4097 (2007). [CrossRef] [PubMed]

## 5. Conclusions

## Acknowledgments

## References and links

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2. | A. F. Fercher, C. K. Hitzenberger, G. Kamp, and S. Y. Elzaiat, “Measurement of Intraocular Distances by Backscattering Spectral Interferometry,” Opt. Commun. |

3. | G. Hausler and M. W. Lindner, ““Coherence radar” and “spectral radar”-new tools for dermatological diagnosis,” J. Biomed. Opt. |

4. | M. A. Choma, M. V. Sarunic, C. H. Yang, and J. A. Izatt, “Sensitivity advantage of swept source and Fourier domain optical coherence tomography,” Opt. Express |

5. | R. Leitgeb, C. K. Hitzenberger, and A. F. Fercher, “Performance of fourier domain vs. time domain optical coherence tomography,” Opt. Express |

6. | M. Wojtkowski, V. J. Srinivasan, T. H. Ko, J. G. Fujimoto, A. Kowalczyk, and J. S. Duker, “Ultrahigh-resolution, high-speed, Fourier domain optical coherence tomography and methods for dispersion compensation,” Opt. Express |

7. | R. Leitgeb, M. Wojtkowski, A. Kowalczyk, C. K. Hitzenberger, M. Sticker, and A. F. Fercher, “Spectral measurement of absorption by spectroscopic frequency-domain optical coherence tomography,” Opt. Lett. |

8. | R. A. Leitgeb, C. K. Hitzenberger, A. F. Fercher, and T. Bajraszewski, “Phase-shifting algorithm to achieve highspeed long-depth-range probing by frequency-domain optical coherence tomography,” Opt. Lett. |

9. | B. Vakoc, S. Yun, J. de Boer, G. Tearney, and B. Bouma, “Phase-resolved optical frequency domain imaging,” Opt. Express |

10. | S. Makita, Y. Hong, M. Yamanari, T. Yatagai, and Y. Yasuno, “Optical coherence angiography,” Opt. Express |

11. | A. Szkulmowska, M. Szkulmowski, A. Kowalczyk, and M. Wojtkowski, “Phase-resolved Doppler optical coherence tomography – limitations and improvements,” Opt. Lett. |

12. | R. K. Wang, S. L. Jacques, Z. Ma, S. Hurst, S. R. Hanson, and A. Gruber, “Three dimensional optical angiography,” Opt. Express |

13. | L. An and R. K. Wang, “In vivo volumetric imaging of vascular perfusion within human retina and choroids with optical micro-angiography,” Opt. Express |

14. | Y. K. Tao, A. M. Davis, and J. A. Izatt, “Single-pass volumetric bidirectional blood flow imaging spectral domain optical coherence tomography using a modified Hilbert transform,” Opt. Express |

15. | Y. Yasuno, S. Makita, T. Endo, G. Aoki, M. Itoh, and T. Yatagai, “Simultaneous B-M-mode scanning method for real-time full-range Fourier domain optical coherence tomography,” Appl. Opt. |

16. | Y. K. Tao, K. M. Kennedy, and J. A. Izatt, “Velocity-resolved 3D retinal microvessel imaging using single-pass flow imaging spectral domain optical coherence tomography,” Opt. Express |

17. | R. K. Wang and L. An, “Doppler optical micro-angiography for volumetric imaging of vascular perfusion in vivo,” Opt. Express |

18. | M. Szkulmowski, A. Szkulmowska, T. Bajraszewski, A. Kowalczyk, and M. Wojtkowski, “Flow velocity estimation using joint Spectral and Time domain Optical Coherence Tomography,” Opt. Express |

19. | A. Szkulmowska, M. Szkulmowski, D. Szlag, A. Kowalczyk, and M. Wojtkowski, “Three-dimensional quantitative imaging of retinal and choroidal blood flow velocity using joint Spectral and Time domain Optical Coherence Tomography,” Opt. Express |

20. | M. Wojtkowski, A. Kowalczyk, R. Leitgeb, and A. F. Fercher, “Full range complex spectral optical coherence tomography technique in eye imaging,” Opt. Lett. |

21. | M. A. Choma, C. H. Yang, and J. A. Izatt, “Instantaneous quadrature low-coherence interferometry with 3 × 3 fiber-optic couplers,” Opt. Lett. |

22. | P. Targowski, W. Gorczynska, M. Szkulmowski, M. Wojtkowski, and A. Kowalczyk, “Improved complex spectral domain OCT for in vivo eye imaging,” Opt. Commun. |

23. | M. V. Sarunic, B. E. Applegate, and J. A. Izatt, “Spectral domain second-harmonic optical coherence tomography,” Opt. Lett. |

24. | R. K. K. Wang, “In vivo full range complex Fourier domain optical coherence tomography,” Appl. Phys. Lett. |

25. | Y. K. Tao, M. Zhao, and J. A. Izatt, “High-speed complex conjugate resolved retinal spectral domain optical coherence tomography using sinusoidal phase modulation,” Opt. Lett. |

26. | E. Götzinger, M. Pircher, and C. K. Hitzenberger, “High speed spectral domain polarization sensitive optical coherence tomography of the human retina,” Opt. Express |

27. | Y. Yasuno, S. Makita, T. Endo, G. Aoki, H. Sumimura, M. Itoh, and T. Yatagai, “One-shot-phase-shifting Fourier domain optical coherence tomography by reference wavefront tilting,” Opt. Express |

28. | S. Makita, T. Fabritius, and Y. Yasuno, “Full-range, high-speed, high-resolution 1 microm spectral-domain optical coherence tomography using BM-scan for volumetric imaging of the human posterior eye,” Opt. Express |

29. | M. Szkulmowski, A. Wojtkowski, T. Bajraszewski, I. Gorczynska, P. Targowski, W. Wasilewski, A. Kowalczyk, and C. Radzewicz, “Quality improvement for high resolution in vivo images by spectral domain optical coherence tomography with supercontinuum source,” Opt. Commun. |

30. | I. Grulkowski, M. Gora, M. Szkulmowski, I. Gorczynska, D. Szlag, S. Marcos, A. Kowalczyk, and M. Wojtkowski, “Anterior segment imaging with Spectral OCT system using a high-speed CMOS camera,” Opt. Express |

31. | S. H. Yun, G. J. Tearney, J. F. de Boer, and B. E. Bouma, “Motion artifacts in optical coherence tomography with frequency-domain ranging,” Opt. Express |

32. | A. H. Bachmann, M. L. Villiger, C. Blatter, T. Lasser, and R. A. Leitgeb, “Resonant Doppler flow imaging and optical vivisection of retinal blood vessels,” Opt. Express |

33. | A. G. Podoleanu, G. M. Dobre, and D. A. Jackson, “En-face coherence imaging using galvanometer scanner modulation,” Opt. Lett. |

34. | R. A. Leitgeb, R. Michaely, T. Lasser, and S. C. Sekhar, “Complex ambiguity-free Fourier domain optical coherence tomography through transverse scanning,” Opt. Lett. |

35. | L. An and R. K. Wang, “Use of a scanner to modulate spatial interferograms for in vivo full-range Fourier-domain optical coherence tomography,” Opt. Lett. |

36. | B. Baumann, M. Pircher, E. Götzinger, and C. K. Hitzenberger, “Full range complex spectral domain optical coherence tomography without additional phase shifters,” Opt. Express |

37. | B. H. Park, M. C. Pierce, B. Cense, S. H. Yun, M. Mujat, G. Tearney, B. Bouma, and J. de Boer, “Real-time fiber-based multi-functional spectral-domain optical coherence tomography at 1.3 microm,” Opt. Express |

**OCIS Codes**

(170.3880) Medical optics and biotechnology : Medical and biological imaging

(170.4470) Medical optics and biotechnology : Ophthalmology

(170.4500) Medical optics and biotechnology : Optical coherence tomography

(280.2490) Remote sensing and sensors : Flow diagnostics

**ToC Category:**

Medical Optics and Biotechnology

**History**

Original Manuscript: May 22, 2009

Revised Manuscript: July 22, 2009

Manuscript Accepted: July 24, 2009

Published: July 31, 2009

**Virtual Issues**

Vol. 4, Iss. 10 *Virtual Journal for Biomedical Optics*

**Citation**

Maciej Szkulmowski, Ireneusz Grulkowski, Daniel Szlag, Anna Szkulmowska, Andrzej Kowalczyk, and Maciej Wojtkowski, "Flow velocity estimation by complex ambiguity free joint Spectral and Time domain Optical Coherence Tomography," Opt. Express **17**, 14281-14297 (2009)

http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=oe-17-16-14281

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### References

- D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, “Optical coherence tomography,” Science 254(5035), 1178–1181 (1991). [CrossRef] [PubMed]
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- G. Hausler and M. W. Lindner, ““Coherence radar” and “spectral radar”-new tools for dermatological diagnosis,” J. Biomed. Opt. 3(1), 21–31 (1998). [CrossRef]
- M. A. Choma, M. V. Sarunic, C. H. Yang, and J. A. Izatt, “Sensitivity advantage of swept source and Fourier domain optical coherence tomography,” Opt. Express 11(18), 2183–2189 (2003). [CrossRef] [PubMed]
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