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Determining Whole Lung Determining Whole Lung Perfusion Using Perfusion Using
Hyperpolarized Xe-129 MRIHyperpolarized Xe-129 MRI
Ian Gerard
Department of Medical Biophysics
University Of Western Ontario
Six Week Project
x
y
z
x
y
z
MR Imaging BasicsMR Imaging Basics
Sample RF Coil Gradient Coil Set Magnet
B1
Hyperpolarized MediaHyperpolarized Media
(For T = 300 K and B0 = 3 T )
Isotope Spin * 107rad s/T
P (ppm)1H 1/2 26.75 5.113He 1/2 20.37 3.8913C 1/2 6.73 1.28129Xe -1/2 7.40 1.41
510thPP PNM
In General After Hyper-polarization Method
VA
Ca(t)
ra
Lt
LcCt(r,t)
Cc(r,t)
FIN FOUT
Capillary
Tissue
GasVA
Ca(t)
ra
Lt
LcCt(r,t)
Cc(r,t)
FIN FOUT
Capillary
Tissue
Gas
Fig 1: Alveolar-Capillary model of Mansson [2]. Va is the alveolar volume measured at standard temperature and pressure. ra is the radius of the alveolus. Lt and Lc are the compartment lengths for tissue and capillary. C(r,t) is the xenon concentration in each respective compartment as a function of distance and time. F is the rate of pulmonary flow. Fin=Fout.
XeXe
Xe
Xe
Xe
Xe
10 1)( SeSS TRT
0),(),(
2
2
t
trC
r
trCDTRT
Gas Exchange ModelGas Exchange Model
S 1
αλpl
(1 – H)F
MethodsMethods
Ventilator
Medical Air & O2
3HeOr
129XeValve
Assembly Acid Port
Gas Cylinder89% 4He10% N2
1% Xe794.8nm
Rb Reservoir
Polarization Cell
Magnet Circular Polarizer
Polarized 129Xe Out
Heater
3T MRI Scanner Ventilator
Polarized 129Xe and 3He
Pilot Results: XenonPilot Results: Xenon
Pulse SequencePulse Sequence
i
Chemically Selective Saturation Recovery (CSSR) Chemically Selective Saturation Recovery (CSSR)
tLoop
90o 90o
N. Abdeen et al (2006)
DissolvedPhase Maximized
Gas Phase Minimized
~193ppmRF Pulse
f
Spectroscopy After Applying Spectroscopy After Applying Pulse SequencePulse Sequence
1/
0 )1()( SeSS TrTt
Mansson Model:
1
/0 )1()( SeSS TrT
Valid for all time.
Tissue Spectroscopy and Model Tissue Spectroscopy and Model FitFit
1
/0 )1()( SeSS TrT
Mansson Model:
Results: Representative FigureResults: Representative Figure
10)( SSS
Linear fit applied to long time values
Slope and intercept values are S1 and S0 respectively and used to calculate lung perfusion
Calculated Lung PerfusionCalculated Lung Perfusion
Rat Number PIP (cmH20) Mean Perfusion (ml s-1/ml) ± Std
Rat 1
7 ± 0.1 0.74 ± 0.05
11 ± 0.1 1.01 ± 0.01
12 ± 0.1 1.17 ± 0.03
17 ± 0.1 1.29 ± 0.04
Rat 27 ± 0.1 0.84 ± 0.05
12 ± 0.1 1.07 ±0.02
17 ± 0.1 1.36 ± 0.05Rat 311 ± 0.1 1.14 ± 0.15
13 ± 0.1 1.34 ±0.06
15 ± 0.1 1.40 ± 0.05
Typical Perfusion value from control rat 1.2 ± 0.2 Mansson et al.
Perfusion and PIPPerfusion and PIP
• Appears to be some relationship between PIP value and Perfusion
DiscussionDiscussion
• Values agree with control perfusion from Mansson et al.
• Something interesting may be happening at low pressure.
• There may be a relationship between Perfusion and PIP
• Hematocrit and typical perfusion values used were for Wistar rats while Sprague-Dawley rats were actually used but assumed equal for the project
Conclusions and Future WorkConclusions and Future Work
• Successfully able to estimate whole lung perfusion using Mansson model and other minor assumptions
• Investigate the effects of low PIP on perfusion
• Next Step: Create a perfusion map determining lung perfusion on a pixel by pixel basis
AcknowledgementsAcknowledgements
Funding:
Heather Cadieux Eugene WongJake Van Dyk
Giles SantyrMatthew FoxAlexei OuriadovRyan KraayvangerWilliam DominguezWilfred LamPeggy XuAdam FaragMarcus Couch
Lynda McCaigRuud VeldhuizenJim Lewis