Flexible Waveguide Enabled Single-Channel Terahertz Endoscopic System Feb-11-2015 Pallavi Doradla a , Karim Alavi b , Cecil Joseph a , Robert H. Giles a a Biomedical Terahertz Technology Center, Department of Physics & Applied Physics, University of Massachusetts Lowell b Department of Colon and Rectum Surgeries, University of Massachusetts Medical School Worcester, MA, USA
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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
2
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.
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
9
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)
10
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
11
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).
12
Results (Normal Vs. Cancerous)
Analysis
13
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
14
12Pallavi Doradla, et. al., “Characterization of bending loss in hollow flexible terahertz waveguides,”
Opt. Express 20 (17), 19176 – 19184 (2012).
Modal Characteristics
15
4
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
16
Schematic of single-channel terahertz endoscopic system
Transmission Imagery
17
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
18
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
19
Digital photograph, co-, and cross-polarized terahertz reflectance images of a quarter dollar.
Cancer Imaging
20
Digital photograph and cross-polarized terahertz reflectance images of human