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