1635 Yeung

CT Perfusion Imaging
Ivan Yeung, Ph.D.
Dept of Radiation Physics, Princess Margaret Hospital
Dept of Radiation Oncology, University of Toronto
University of Toronto
1st Commercial CT Unit
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In 1972, Sir Godfrey Hounsfield introduced the first EMI
CT scanner.
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It takes 5 min to scan and 2.5 hours to reconstruct.
Designed as a revolutionary anatomical imaging tool.
EMI
scanner
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Development of CT
• CT was quickly development, during the 80’s, CT
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•
•
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has become a work horse in almost everyy radiology
gy
department.
Due to presence of cables, the fastest CT scan was
done every 44-6 seconds
seconds.
First attempt to use CT to measure function – tissue
perfusion – is with stable XenonXenon-133.
‘Messy’ experiment: patient breathes in Xenon, it
diffuses from lung to blood, then carry to tissue
Nice property – high diffusion coefficient across
capillary.
Can be described by oneone-compartment model.
Hence less computational demand and sparse
sampling is ok.
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One--Compartment Model
One
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Slip Ring Technology (mid 90’s)
90 s)
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Power and data transfer via
contact around gantry
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Gantry moves in one
di ti
direction
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Gantry can move up to 1/3
sec per rotation
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High temporal resolution
Data able to handle more
complex model – exchange
of contrast agent
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Distributed Model
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F – Perfusion, blow flow through the capillary
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PS – Leakiness from intravascular to extravascular space
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MTT – Time to take bolus to travel across the capillary
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Perfusion CT
contrast injector
AIF(t)
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Model
Tissue(t)
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Tracer Kinetics Models
AIF(t)
Model
Tissue(t)
GE Perfusion
P f i
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…
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Non--linear Curve Fitting
Non
AIF(t)
()
Model
F1, PS1, Vb1….
F2, PS2, Vb2….
Tissue(t)
ssue( )
Measured
Fitted
F3, PS3, Vb3….
.
Fn, PSn, Vbn…
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Patients received Sorafenib + Rad
Pt # 1
Baseline
Day 7
Day 21
CT
Perfusion
Map
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0.022
0.02
0.018
0.016
0.014
0.012
0.01
0.008
0.006
0.004
0.002
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Patients received Sorafenib + Rad
Pt # 2
Baseline
Day 7
Day 21
CT
0.05
Perfusion
Map
0.04
0.03
0.02
0.01
0
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Preclinical Cervix Tumor xenograft in mice
Perfusion
High
Low
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Perfusion CT on Mouse 1 (anti(anti-vascular drug)
Enhanced CT
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Blood
ood Flow
o
Blood Volume
MTT
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Advancement in Perfusion CT
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True 4D CT – True 3D volume scan is possible
Dose reduction schemes: intermittent XX-ray on, low
dose CT, less frequent sampling
Optimization of protocol
Limited speed conecone-beam CT perfusion
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Dynamic Contrast Enhanced Perfusion CT
vs Contrast
C t t CBCT
CT
Acquisition over time
CBCT
Acquisition over time
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Multiple CT images at
different time
Single contrast enhanced
CBCT image
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DCE--CBCT
DCE
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Assume each voxel behaves as a single compartment with its washwash-in
and washout behaviour
2t
2
2
C b ( t ) = Ie − kt [ t 2 e α t − e α t + 2 e α t − 2 ]
where Cb(t) – contrast enhancement
α
αin each voxel
α
t
– time
I,, α, k – unknown p
parameters
640 projections were obtained in 2
min. The net (i.e. contrast – baseline)
contrast projections were used for
optimization in Matlab for a volume of
128x128x40.
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t=1s
, 3o
6o
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t=0s, 0o
s,
Reconstruct the kinetics behavior
according to the formula for each
voxel by optimization to determine the
3 unknown parameters (I, α, k) with
projection data
t= 2
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Results: CT and Estimated CBCT Tissue
E h
Enhancement
t and
dP
Perfusion
f i
CT
CBCT
Nett
N
Enhancement
Perfusion
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Conclusions
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CT originally designed for anatomy
Functional measurement (F, PS, MTT) can be
performed for clinical and preclinical studies
On--going Advancement in perfusion CT
On
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Acknowledgement
Lab members (p
(past/present)
p
)
Collaborators
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Sunmo Kim
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Richard Hill
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Masoom Haider
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Brian Lim
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Mike Milosevic
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Doug
g Moseley
y
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Richard Clarkson
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Rob Bristow
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Young--Bin Cho
Young
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Qiulin Tang
g
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Anthony
y Fyles
y
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TingTing
g-Yim Lee
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Bill Qian
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David Hedley
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David Jaffray
y
Funding Sources
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Jeff Siewerdsen
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Terry Fox Foundation
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YoungYoung
g-Bin Cho
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Canadian Institute of Health Research
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