Flexible Waveguide Enabled Single-Channel Terahertz Endoscopic System

Feb-11-2015

Pallavi Doradlaa, Karim Alavib , Cecil Josepha, Robert H. Gilesa

aBiomedical Terahertz Technology Center, Department of Physics & Applied Physics,

University of Massachusetts Lowell

bDepartment of Colon and Rectum Surgeries, University of Massachusetts

Medical School Worcester, MA, USA

Motivation

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Colorectal cancer: 3rd most across the world and 4th most in USA1

Approx. 1.4 million new cases diagnosed each year1

Gold standard for colorectal cancer screening: Colonoscopy

Colonoscopy relies on the visual inspection by the physician.

1National Cancer Institute at NIH: http://www.cancer.gov/cancertopics/-types/colon-and-rectal

Aim : Investigating the feasibility of constructing a terahertz endoscope as

an additional tool to aid in the screening of colorectal cancers.

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Outline

Introduction

Previous Work

Endoscope Design

Sample Handling

Colon Cancer Detection

Flexible Waveguides

Polarization Imaging

Endoscopic Imaging

Results & Analysis

2Burkitt et al. “Wheather’s Basic Histopathology,” Churchill Livingston Inc, New York, NY.1996.

Schematic of the Colon structure2

Introduction

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- 30 to 3000 μm - Non Ionizing - High Spatial Resolution

- Security screening - Remote sensing - Bio-Medical Imaging

Applications

3John F. Federici , et. al., “THz Imaging and sensing for security applications”, Semicond. Sci. Technol. 20, S266-80 (2007)4Joseph, et. al., “Dual Frequency CW THz Transmission Imaging of Nonmelanoma Skin Cancers” SPIE, 760104 (2009)

5Terahertz Imaging modules - www.Teraview .com

Security screening & Remote sensing3

Cancer screening5

(In vivo) Bio-medical imaging & Spectroscopy4

6Image of Flexible Endoscope - http://www.sheathes.com/new.html

Optical Endoscope6

Schematic of Terahertz Endoscope

Source – FIR Laser

Light Delivery system –

Flexible Terahertz Waveguide

Lens System – HHS Lens

Detector – Silicon Bolometer

Flexible Waveguides

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Endoscope Design

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Colon structure

Enface histology sections of (HP) Hyperplastic mucosa7, (N) Normal (inset: mucus secreting colon cell),

(P) Sporadic juvenile benign polyp7, (S1) stage I, (S2) stage II, and (S3) stage III colon tissue7.

7Figure – http://www.biologydisease.com/images/histology/colon/hyperplastic-gland-colon.jpg.php

Sample Mounting

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The colorectal tissue specimens were obtained after standard surgical procedures performed at

University of Massachusetts Memorial hospital.

Tissue specimens were mounted in an aluminum sample holder (with 7.5 cm x 2.5 cm opening),

using a 1mm thick slide of z-cut quartz.

To prevent tissue dehydration during imaging process, specimens were covered with a wet gauze

soaked in pH balanced (pH 7.4) saline.

(a) (b) (c)

(d)(e)

Experimental Setup

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Schematic of terahertz polarization imaging setup for colorectal cancer detection

8Pallavi Doradla, et. al., “Detection of colon cancer by continuous-wave terahertz Polarization

imaging technique,” J. Biomed. Opt. Lett. 18 (9), 0905041-3(2013).

Results (Fresh Normal Specimen)

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9Pallavi Doradla, et. al., “Continuous Wave Terahertz Reflection Imaging of Human Colorectal

Tissue”, Proc. of SPIE Vol. 8624, P1-P10 (2013).

5mm

Digital Photograph(a)

N

Co-polarized(b)

N

Cross-polarized(c)

N

RN = 16.5 ± 0.25 % RN = 0.56 ± 0.02

10Pallavi Doradla, et. al., “Terahertz Polarization Imaging for Colon Cancer Detection”,

Proc. of SPIE Vol. 8985, 89850K1-K8 (2014).

5mm

(a) Digital Photograph

C N

(b) Co-pol

C N

RN = 17.09 ± 0.35 % RC = 19.69 ± 0.27%

(c) Cross-pol

RN = 0.56 ± 0.012 % RC = 0.643 ± 0.015%

C N

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Results (Co- Vs. Cross-pol.)

11Pallavi Doradla, et. al., “Detection of colon cancer by continuous-wave terahertz polarization imaging technique,”

Journal of Biomedical Optics Letters, 18 (9), 0905041-3 (2013).

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Results (Normal Vs. Cancerous)

Analysis

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The relative reflectance difference between normal and cancerous colon tissues at 584 GHz

Sample # Co-pol (×10-1%) Cross-pol (%)

Set 1 1.53 7.74

Set 2 3.03 7.74

Set 3 1.56 7.75

Set 4 2.44 7.30

NCR R(1) NC

N

R R

R

(2) NC N C

B B B

R R RR

R R R

(3)

C N

B B NC

N N B

R RR R R R

R R R

(4)

RC – Reflectance value of a cancerous tissue

RN – Reflectance from a normal tissue

Rb – Reflectance from background (Saline)

Input Gaussian Mode Out coming ModePropagation loss of lessthan 1.77dB/m, 0.96 dB/mwere achieved in Ag, Ag/PScoated waveguides bycoupling the lowest lossTE11 and HE11 modesrespectively.

Flexible Terahertz Waveguides

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12Pallavi Doradla, et. al., “Characterization of bending loss in hollow flexible terahertz waveguides,”

Opt. Express 20 (17), 19176 – 19184 (2012).

Modal Characteristics

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13Pallavi Doradla, et. al., “Dual-frequency characterization of bending loss in hollow flexible terahertz

waveguides,” Proc. of SPIE Vol. 8985, 8985181-10 (2014).

Experimental Setup

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Schematic of single-channel terahertz endoscopic system

Transmission Imagery

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Digital photographs and THz transmission imagery of leaf [(a) & (e)],

nylon connectors [(b) & (f)], letter impression [(c) & (g)],

and solid colored shapes printed on a white paper [(d) & (h)].

Reflection Imagery

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Digital photograph and terahertz reflectance images of a quarter coin [(a) & (b)]

and four 450 µm thick copper wires [(c) & (d)].

The co-polarized terahertz response Includes Fresnel reflections from the

air-glass and glass-sample interfaces.

The cross-polarized terahertz response Rejects the specular reflections and

effectively samples the tissue volume.

Polarization Imaging

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Digital photograph, co-, and cross-polarized terahertz reflectance images of a quarter dollar.

Cancer Imaging

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Digital photograph and cross-polarized terahertz reflectance images of human

Colonic tissue sets 1 [(a) & (b)] and 2 [(c) & (d)].

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The relative reflectance difference between normal and cancerous colon tissues at 584 GHz

Sample # Specimen Type THz Pol. Imaging (%) Specimen Type THz Endo. Imaging

Set 1 Fresh 7.74 Fresh 7.67

Set 2 Fresh 7.74 Fresh 7.73

Set 3 Fresh 7.75 Formalin-fixed 5.31

Set 4 Fresh 7.30

Set 5 Formalin-fixed 5.62

C N

B B NC

N N B

R RR R R R

R R R

RC – Reflectance value of a cancerous tissue

RN – Reflectance from a normal tissue

Rb – Reflectance from background (Saline)

Analysis

Conclusion

A prototype continuous-wave terahertz endoscopic system has been successfully

demonstrated.

Imaging system uses a single channel to transmit and collect the back reflected intrinsic

terahertz signal from the sample.

Cross-polarized terahertz reflectance images showed contrast between normal and

cancerous colon tissues by rejecting specular reflections.

The experimental demonstration showed the potential and feasibility of the device in

accessing terahertz reflectivity data from previously inaccessible organs.

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Thank You.!

Figure: From Department of Pathology, Creighton University Medical Center Website

The Colossal Colon is a replica of the human colon that is four feet wide.