1. Imaging cycling hypoxia in canine tumors during radiotherapy dosing
: physics, engineering, and preliminary data
Xiaofeng (Steve) Zhang
Assistant Professor of Radiology DUMC
Consortium for Canine Comparative Oncology (C3O) Symposium
Durham Convention Center
February 23, 2018

2. Intro: tumor hypoxia & RT
Resistance to RT x3
Fluctuate spatiotemporally
Well observed in rodents.
Evidence in canine as well.
No data available in human.
Dewhirst, Cancer Res., 67(3), 854 (2007)
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3. Phys: tissue pO2 & NIR light
Near infrared tissue oximetry:
Tissue “NIR window”
Tissue absorption linked to oxy- & deoxy-Hb
Oxygen saturation and blood perfusion
Penetration ~3 cm (limited by SNR)
Strong tissue scattering  computationally challenging
Detector
Source
Normalized logarithmic scale
Source
Detector
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4. Phys: tissue pO2 & NIR light
400 nm fiber laser
500 nm fiber laser
600 nm fiber laser
700 nm fiber laser
800 nm fiber laser
935 nm LED
3/9

5. Phys: Čerenkov radiation in RT
𝒗>𝒄= 𝒄 𝟎 𝒏
cos 𝜃 = 1 𝛽𝑛 = 𝑐 𝑣 <1 θ
Moving charged particle
EM wave front
Emission spectrum
Energy threshold
- dependent on index of refraction
In tissue (n = 1.40):
220 keV for electron beam
402 MV for proton beam
Index of refraction (n)
1.25
1.3
1.35
1.4
1.45
1.5
1.55
1.6
keV
100
150
200
250
300
350
Electron
Index of refraction (n)
1.25
1.3
1.35
1.4
1.45
1.5
1.55
1.6 MV
250
300
350
400
450
500
550
600
650
Proton
4/9

6. Phys: Čerenkov imaging of pO2
Motivation
Čerenkov radiation links treatment and imaging
“Hub of technologies”: optical photons
Čerenkov radiation of bovine blood
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7. Prelim data: in rat leg muscles
Cerenkov
ROI
Cerenkov vs. validation (linearity)
ROI
Healthy rats (photograph)
Validation (OxyLite)
LINAC: photon, 6 MV, 2 Gy
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8. Engr: triggered imaging
Intensified CMOS camera
Image intensifier
Signal magnification
Room light suppression
Triggered image acquisition
By the “Targ-I signal”
By scattered radiation
Sync/trigger
Oximeter
Control & DAQ
Camera
LINAC head
Anesthesia
Image
Radiation beam
Treatment table
Control
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9. Engr: imaging system Next step: Go to the clinic! 8/9
Image transfer lens
I-CMOS camera
Imaging fiber bundle
Camera controls
Next step:
Go to the clinic!
Imaging lens
Data logger
Imaging platform
OxyLite
APD trigger
OxyLite sensors
8/9

10. Acknowledgement Funding Support C3O Pilot 2017 9/9 Dr. Mark Dewhirst
Duke Rad Onc
Dr. Greg Palmer
Duke Rad Onc
Dr. Mike Nolan
NCSU Vet Med
Dr. Hiroto Yoshikawa
NCSU Vet Med
Funding Support
C3O Pilot 2017
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