Determining Whole Lung Perfusion Using Hyperpolarized Xe-129 MRI

1
Determining Whole Lung Perfusion Using
Hyperpolarized Xe-129 MRI

• Ian Gerard
• Department of Medical Biophysics
• University Of Western Ontario
• Six Week Project

2
MR Imaging Basics
B1
Sample
RF Coil
Gradient Coil Set
Magnet
z
y
x
3
Hyperpolarized Media
Isotope Spin ?? 107 rad s/T P
(ppm) 1H 1/2 26.75 5.11 3He 1/2 20.37 3.89
13C 1/2 6.73 1.28 129Xe -1/2 7.40 1.41
(For T 300 K and B0 3 T )
In General
After Hyper-polarization Method
4
Gas Exchange Model
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. FinFout.
5
Methods
Medical Air O2
Ventilator
Valve Assembly
3He Or 129Xe
Acid Port
3T MRI Scanner
Ventilator
Heater
Rb Reservoir
Polarization Cell
Gas Cylinder89 4He 10 N2 1 Xe
794.8nm
Circular Polarizer
Magnet
Polarized 129Xe Out
Polarized 129Xe and 3He
6
Pilot Results Xenon
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Pulse Sequence
Chemically Selective Saturation Recovery (CSSR)
193ppm
RF Pulse
90o
90o
f
Dissolved Phase Maximized
Gas Phase Minimized
t
Loop
N. Abdeen et al (2006)
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Spectroscopy After Applying Pulse Sequence
Mansson Model
Valid for all time.
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Tissue Spectroscopy and Model Fit
Mansson Model
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Results Representative Figure
Linear fit applied to long time values Slope and
intercept values are S1 and S0 respectively and
used to calculate lung perfusion
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Calculated Lung Perfusion
Typical Perfusion value from control rat 1.2
0.2 Mansson et al.
Rat Number PIP (cmH20) Mean Perfusion (ml s-1/ml) Std
Rat 1 7 0.1 0.74 0.05
Rat 1 11 0.1 1.01 0.01
Rat 1 12 0.1 1.17 0.03
Rat 1 17 0.1 1.29 0.04
Rat 2 7 0.1 0.84 0.05
Rat 2 12 0.1 1.07 0.02
Rat 2 17 0.1 1.36 0.05
Rat 3 11 0.1 1.14 0.15
Rat 3 13 0.1 1.34 0.06
Rat 3 15 0.1 1.40 0.05
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Perfusion and PIP

• Appears to be some relationship between PIP value
  and Perfusion

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Discussion

• 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

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Conclusions 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

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Acknowledgements
Lynda McCaig Ruud Veldhuizen Jim Lewis
Funding