Preserving Hyperpolarization of 129Xe for Transport

Zach ZytnerProject Supervisor: Giles Santyr

Medical Biophysics 3970March 23, 2011

Introduction

• MR imaging with hyperpolarized noble gases – Greater resolution in lung imaging without

harmful radiation– Effectiveness depends on nuclei high-spin

polarization achieved outside system

• Preserving the 129Xe polarization permits transporting the HNG to other research sites

Transportation Box

Solenoid coil 12V NiMH Battery

Glassvial

Current control

Current display (mA)

Powerswitch

Recharging terminal• Solenoid coil (ID 15.3cm) • Power supply (battery - 1650mA)

Method I: Project LayoutXe sample

Solenoid coil

• Sustainability of battery• Collection of polarized Xe• Signal data at time

intervals through polarimetry

• Determination of box’s T1

Method II: Mapping the Field with Current

• Maximum current = 1650 mA

• Maximum field = 36.5 G (3.65 mT)

Method III: Characterizing Field vs. Time

• 18 hour charge shows rapid decay of field

• Best charging time shows box can maintain magnetic field

Polarimetry StationHelmholtz Coil

RF coilStage for gas sample

• Pulse and response frequencies within 50Hz for accurate measurement of signal

Longitudinal Spin Relaxation• Optical pumping of Rb followed by spin

exchange with Xe nucleus• Longitudinal relaxation time (T1) is the time

taken to return to equilibrium within the lattice after an RF pulse excitation

Results I: Signal for 90mL Xe bag at t = 2 mins

Results II: Signal for 90mL Xe bag at t = 122 mins

Results III: Response Amplitude from Excel Trend Lines vs. Time

• Extrapolated signal @ t = 0 is 27.5mV

• Signal = 5.37 mV at 122 mins

Results IV: Response Amplitude from Polarimetry Software Trend Lines vs. Time

• Extrapolated signal @ t = 0 is 43.1 mV

• Signal = 2 mV at 122 mins

Results V: T1 Determination

• Signal from Excel trend lines

T1 = 75 mins = 1.25 hrs

• Signal from polarimetry software trend lines

T1 = 40 mins = 0.67 hrs

Discussion• With the current battery, transportation box

must be charged more than 24 hours to maintain a sustainable magnetic field

• Signals obtained from the station is contaminated with noise

• With the current signals at ~ t = 0, T1 found to be 40-75 minutes

Conclusions

• The transportation box could likely preserve hyperpolarization in 129Xe if travelling short distances

• Recommendation: use battery with long life with short charging time

Acknowledgements

Giles SantyrAdam FaragMathieu BoudreauAlexei OuriadovMatthew FoxMarcus CouchJulie TanguayIan GerardElaine Hegarty

Funding: