Determining Whole Lung Perfusion Using Hyperpolarized Xe-129 MRI Ian Gerard Department of Medical Biophysics University Of Western Ontario Six Week Project

x y  z x y z MR Imaging Basics SampleRF CoilGradient Coil SetMagnet B1B1

Hyperpolarized Media (For T = 300 K and B 0 = 3 T ) IsotopeSpin  * 10 7 rad s/T P (ppm) 1 H1/ He1/ C1/ Xe-1/ In General After Hyper-polarization Method

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. F in =F out. Xe   10 1)( SeSS TR T          0 ),(),( 2 2       t trC r trCD Gas Exchange Model S  1 αλ pl (1 – H)F

Methods Ventilator Medical Air & O 2 3 He Or 129 Xe Valve Assembly Acid Port Gas Cylinder 89% 4 He 10% N 2 1% Xe 794.8nm Rb Reservoir Polarization Cell Magnet Circular Polarizer Polarized 129 Xe Out Heater 3T MRI ScannerVentilator Polarized 129 Xe and 3 He

Pilot Results: Xenon

Pulse Sequence Chemically Selective Saturation Recovery (CSSR) t Loop 90 o N. Abdeen et al (2006) Dissolved Phase Maximized Gas Phase Minimized ~193ppm RF Pulse f

Spectroscopy After Applying Pulse Sequence Mansson Model: Valid for all time.

Tissue Spectroscopy and Model Fit Mansson Model:

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

Calculated Lung Perfusion Calculated Lung Perfusion Rat NumberPIP (cmH 2 0)Mean Perfusion (ml s -1 /ml) ± Std Rat 1 7 ± ± ± ± ± ± ± ± 0.04 Rat 2 7 ± ± ± ± ± ± 0.05 Rat 3 11 ± ± ± ± ± ± 0.05 Typical Perfusion value from control rat 1.2 ± 0.2 Mansson et al.

Perfusion and PIP Appears to be some relationship between PIP value and Perfusion

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

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

Acknowledgements Funding: Heather Cadieux Eugene Wong Jake Van Dyk Giles Santyr Matthew Fox Alexei Ouriadov Ryan Kraayvanger William Dominguez Wilfred Lam Peggy Xu Adam Farag Marcus Couch Lynda McCaig Ruud Veldhuizen Jim Lewis