Experimental Apparatus. 1. External container is filled with water. 2. Phantom is submerged inside. 3. Pump pulls water from phantom. 4. Pump releases water ...
Perfusion Phantom for Arterial Spin Labeled MRI Hyo Min Lee1,2, Marta Vidorreta3,4, Yulin Vince Chang3, John Alan Detre3,4 1Department
of Bioengineering, University of Pennsylvania; 2Institute for Biomedical Engineering, University and ETH Zurich; 3Department of Radiology, University of Pennsylvania; 4Department of Neurology, University of Pennsylvania
INTRODUCTION
DISCUSSION
RESULTS
Arterial spin labeled (ASL) perfusion MRI • Allows absolute quantification of cerebral blood flow (CBF) • Found broad clinical applications in brain1-2, lung3, heart4, kidney5
Perfusion signals increased proportionally to label duration (LD) until arrival time was reached and then decayed with T1, though the flow did not uniformly perfuse the sponge (Fig 3).
Compartmentalized pattern in the perfusion image showed that flow did not uniformly perfuse the sponge. Incorporating one or two more generations of branches is expected to result in uniform perfusion.
Difficulty in calibrating ASL MRI sequences in vivo • Regional variations of CBF within and across subjects
Future work will aim to assess labeling efficiency in the stem as well as the effects of pulsatile flow patterns in labeling efficiency.
This poster describes a prototype perfusion phantom • Based on 3D printing • Bubble trap mechanism for active debubbling • Reliable ex vivo assessment of ASL MRI sequences
If successfully developed, the perfusion phantom may be used to: • Detect hardware imperfection related to ASL performance • Verify labeling and imaging modules • Calibrate sensitivity and CBF quantifications
CONCLUSION
METHODS Fig. 3. M0 and perfusion images for each post label delays
Production • Design implemented in Blender • Printed with ABSplus and SST • SST removed in heated Na2O2 solution
When LD was varied from 1 – 3 s (Fig 4A and 4B), measured perfusion signals closely follow theoretical predictions.
Experimental Apparatus 1. External container is filled with water 2. Phantom is submerged inside 3. Pump pulls water from phantom 4. Pump releases water into reservoir 5. Released water resides in reservoir – Bubbles escape from reservoir – Mz equilibrium is reached 6. Water re-enters the phantom Scanning Protocol • IR-FLASH for T1 • FSE for T2 • pCASL6-EPI7 • pCASL-bSSFP8 − PLD = 100-2500 ms − 5 LC pairs − PR = 75-300 mL/min − LD = 1-3 s Partners
Similarly, when pump rate was varied from 75 – 300 mL/min (Fig 4C and 4D), measured perfusion signals closely followed the theoretical predictions.
Fig. 1. Phantom
Fig. 2. Experimental Apparatus
Fig. 4. Measured and predicted perfusion curves as a function of label duration (top) and pump rate (bottom)
Overall, these results show a good quantitative agreement between the measured and predicted perfusion signals.
We presented a prototype perfusion phantom whose perfusion signal characteristics are in a good quantitative agreement with the theoretical predictions based on general kinetic model9.
REFERENCES [1] Pollock et al., Magn Reson Imaging Clin N Am 2009;17(2):315–338 [2] Detre et al., J Magn Reson Imag 2012;35(5):1026-37 [3] Mai et al., j Magn Reson Imag 1999;9(3):483-487 [4] Chalela et al., Stroke 2000;31-680-687 [5] De Bazelaire et al., Acad Radiol 2005;12(3):347-357 [6] Dai et al., Magn Reson Med 2008;60:1488-1497 [7] Mansfield P, J Phys C Solid State Phys 1977;10(3):55-58 [8] Carr HY, Phys Rev 1958;112(5):1693-1701 [9] Buxton et al., Magn Reson Med 1998;40(3):383-396
AKNOWLEDGEMENT NIH grants MH080729 and EB015893
