1. Vassiliy Tsytsarev University of Maryland school of Medicine
In Vivo Optical Coherent Tomography (OCT) and its Application for Brain Research
Vassiliy Tsytsarev
University of Maryland school of Medicine
In this study, optical-resolution photoacoustic microscopy was used to monitor the somatosensory cortex for vascular responses to direct electrical stimulations through a cranial window.

2. Dependence of Tissue Penetration from Wavelengths
Thickness of tissue probed:
30 mm 100mm 1mm 1cm 10cm l
400 nm
800 nm
1600 nm
10 mm
100 mm
2-Photon Microscopy
Diffuse Optical Tomography
Optical Coherence Tomography
Intrinsic Optical Imaging (IOS)
Photoacoustic
THz imaging
???

3. Depth Penetration / Spatial Resolution
Depth Penetration (μm)
10000
Functional
Magnetic
Resonance
Imaging (fMRI)
Optical Coherence Tomography (OCT)
1000
2-Photon Microscopy
100
Intrinsic and
Voltage-Sensitive Dye Optical
Imaging (IOS)
100 10
Resolution (μm)

4. Optical Coherent Tomography
Broadband
light source
2x2 Coupler
Lateral scanning
Signal
processing
Computer
2x1 Coupler
Moving mirror
Basic principle:
Back-reflected from the tissue light and the light produced by reference arm recombine within the 2 × 2 coupler

5. OCT: experimental setup
Schematic of optical coherence tomography (OCT) and video microscopy
system. DCG, dispersion-compensating glass; TIA, transimpedance amplifier; BPF, bandpass
filter. Also shown is the forepaw stimulation protocol. Aguirre et al, Opt. Lett., 2006

6. OCT cortical functional brain imaging: experimental paradigm
Precise registration of OCT imaging to the region of functional activation. The OCT scan is directed in the region of interest measured with video microscopy (A, B). Horizontal bars in B mark the activated and baseline time windows used to generate the functional map in A. Structural OCT imaging (C) visualizes the skull (S), surface vasculature (V), and meningeal layers, including the dura mater (D).

7. Functional OCT in the rat cortex
Functional OCT in the rat cortex. A fractional change map (A) demonstrates positive (warm colors) and negative (cool colors) changes in OCT signals during stimulation. Temporal sequences (B) reveal the presence of highly localized regions of activation in the cortex that persist throughout stimulation. The horizontal bars in D indicate the time windows used to generate the functional map (A, B, C).

8. Somatosensory cortex OCT functional imaging: forepaw stimulation
Precise co-registration of OCT imaging to the region of functional activation. (A) The OCT scan is directed across the region of interest (indicated by blue double-headarrow) as measured with OISI. Anatomical features such as blood vessels (V) can be visualized in OISI and can be used to co-register with OCT image. (B) Structural OCT image reveals high-resolution visualization of the skull (S), surface vasculature (V), and meningeal layers, including the dura mater (D) and arachnoids (A). Cortex region (C) can also be visualized. (C) Three-dimensional rendering of the volume acquired by OCT. (D) En face OCT image reveals the characteristic blood vessel network which can be used to register the OCT imaging volume with OISI Y. Chen et al. / Journal of Neuroscience Methods 178 (2009)

9. OCT vs IOS: what is the signal base?
Spatial (right) and temporal OCT and IOS response structure

10. Forepaw OCT: temporal dynmics
Spatial-temporal evolution of functional OCT signals in the rat cortex. A fractional change map demonstrates the presence of positive (warm colors) and negative (cool colors) changes in OCT signals during stimulation. Functional OCT images at each individual temporal point (t = 1–15 s) reveal the presence of highly localized regions
of activation in the cortex that persist throughout stimulation. Bar: 500 mkm. Chen et al, 2009

11. Forepaw OCT imaging: crosectional vs frontal
Integrated OCT signal in response to the forepaw electrical
stimulation (Chen et al, 2006)

12. Optical Coherent Tomography of the Epileptic Seizures
EEG
10 s / 2 mV

13. Thank you very much for your attention