2013년 제1차 디지털의료기기 지식연구회 - Biomedical Imaging Sensor (Optical Coherence Tomography) -

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Jeehyun Kim, Ph.D.

Kyungpook National University

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What is OCT (Optical Coherence Tomography)?

Non invasive optical imaging technique with high resolution even in highly scattering media.

OCT is originated from OCDR.

OCDR have previously been utilized for characterization of bulk-, integrated-, fiber-optic structures.

First OCT system (MIT, Fujimoto group)

Science, HUANG et al., vol: 254, pg: 1178-80, 1991

·

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4.7T MRI (1.8 x 1.3 cm) OCT (2 x 1.8 mm) Histology Visualization of freeze lesion in neonatal rat brain

Evaluation of epilepsy detection in an animal model

Comparison of Imaging Modalities

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OCT Applications

Eye

Tooth

Ear

Mouth

Lung

Trachea Skin

Colon

Intestine

Rectum

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1. Principle of OCT

· Optical delayed reflection image using optical coherence interferometer

2. Main components of OCT system

· Broadband light source · Interferometer

· Beam scanning optics · Electronic devices for signal processing

3. Advantages

· Simplicity · Low cost · High resolution

· in vivo · Real time monitoring · Noninvasive

· Flexible application 4. Performance of OCT

· Image resolution : 1-15 mm

· Probing depth : transparent tissue ( 2 mm )

highly scattering tissue ( 1.0 ~ 1.5 mm )

Characteristics of OCT

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Low Coherence Source

Reference mirror

Photodetector Beam splitter

Interference fringes are observed only when the optical path length difference in the interferometer is within the coherence length of the source.

Operating Principle of OCT

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Three scattering surfaces

Low coherence source

Reference mirror

Photodetector Beam splitter

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Comparison of Imaging Modalities

Resolution (mm)

Field of View

In Depth Cost Speed Capability of

Probe Imaging

CT ^500-1000 ^{Full Body} ^High ^{1-2 sec.} ^Poor

MRI ^500-1000 ^{Full Body} ^{Very High} ^{5-10 min.} ^Poor

US ^100-200 ^{10-20 cm} ^Low ^{Video Rate} ^Good

Endoscopy ^10-50 _Imaging^Surface ^Low ^{Video Rate} ^Excellent

OCT ^2-10 ^{2-3 mm} ^Low ^{Video Rate} ^Good

MPM ^0.2-1 ^{50-400 mm} ^Middle ^{Video Rate} ^Poor

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Schematic Diagram of Potable OCT System

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3D OCT images

Liver

Small intestine Heart

Gall bladder Stomach

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3D OCT images

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In vivo imaging: Rat

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10.5 cm

11.5 cm

9.5 cm

12 cm

Length adjustable tube

8.5 cm

Lens 1 Lens 2

Eyecup mounted probe tip

Handheld OCT probe

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Choroid ILM GCL

INL Corneal Stroma

Aqueous Corneal Epithelium

IS/OS RPE

ONL

A

B

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Real time display

OCT/ODT

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* GPU Computing

*

The use of GPU to perform general purpose scientific and engineering computing.

*

NVIDIA 社, CUDA(Compute Unified Device Architecture)

*

AMD 社, APP(Accelerated Parallel Processing)

: Massively

parallel computing

Floating-Point Operations per Second for the CPU and GPU

(*NVIDIA CUDA C Programming Guide ver 3.2)

"Real-time display on Fourier domain optical coherence tomography system using a graphics processing unit", Yuuki Watanabe, JBO LETTERS 2009

(* 1024 x 1000 , 27.9 frame / sec)

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* Schematic of High speed SD-ODT

Specifications of Major H/W

CPU

Core 2 Quad Q8200, Intel Clock rate: 2.33GHz GPU

Geforce GTX480, NVIDIA Clock rate: 700 MHz , 480 CUDA porcessor Line scan camera

Sprint spl4096-140k, Basler AG Line pixel : 4096 pixel

Line rate : 140 kHz Frame Grabber

PCIe-1433, NI

Camera Link rate: 850 MB/s System performance

Depth Resolution : 6 µm Transverse Resolution : 15 µm Frame rate : 110 frame/sec Spectrometer

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* Signal Processing for ODT

● Kasai autocorrelation method

IEEE TRANSACTIONS ON SONICS AND ULTRASONICS, Vol. SU-32, NO. 3 .

C. Kasai, 1985

● Optical doppler tomography using Kasai algorithm

f_k = doppler frequency shift f_s = Sampling frequency I : in-phase

Q : quadrature

1.5 1.0 0.5 0 -0.5 -1.0 -1.5

• ODT image of flowing

particles in a capillary tube

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* signal processing based on GPU

Buffer 1

Buffer 2

k-domain Linearization

CUFFT

ODT Processing Log

Scaling

OCT Image

ODT Image OCT & ODT

Image Display

OCT ODT

Next

Loop

Data acquisition thread (CPU thread 1)

Display thread (CPU thread 2)

Signal processing thread (GPU thread 1)

Loop

FFT

ODT Image

<Y> = I^m,n+1Q^m,n- Q^m,n+1I^m,n,

<X> = Qm,n+1Qm,n + Im,n+1Im,n

<Integrated Y> = ∑ ∑ <Y>,

<Integrated X> = ∑ ∑<X>

f ^d= ^

arctan^Integrated Y>

Integrated X>

m=1 n=1 M N-1

Doppler Frequency Shift

data

thread event Buffer Ring

(Hundreds of cores)GPU

(Multiple cores)CPU

CPU & GPU hybrid

parallel

architecture CPU & GPU hybrid

parallel

architecture

Step 1

Step 2

Step 3

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* Results

• 30 mm/sec ( 122 fps) • 40 mm/sec (120 fps)

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LED Volume imaging with OCT

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Fluorescence material

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Fluorescence Material

Electrode

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Fluorescence Material

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2013년 제1차 디지털의료기기 지식연구회 - Biomedical Imaging Sensor (Optical Coherence Tomography) -

Jeehyun Kim, Ph.D.

Kyungpook National University

What is OCT (Optical Coherence Tomography)?

4.7T MRI (1.8 x 1.3 cm) OCT (2 x 1.8 mm) Histology Visualization of freeze lesion in neonatal rat brain

Evaluation of epilepsy detection in an animal model

Comparison of Imaging Modalities

OCT Applications

Characteristics of OCT

Interference fringes are observed only when the optical path length difference in the interferometer is within the coherence length of the source.

Operating Principle of OCT

Comparison of Imaging Modalities

Schematic Diagram of Potable OCT System

3D OCT images

3D OCT images

In vivo imaging: Rat

Handheld OCT probe

A

B

Real time display

OCT/ODT

* GPU Computing

*

*

*

* Schematic of High speed SD-ODT

* Signal Processing for ODT

* signal processing based on GPU

* Results

LED Volume imaging with OCT

Fluorescence Material

Thank you