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In vivo hyperCEST imaging: Experimental considerations for a reliable contrast.
Christian T McHugh1,2, Michele Kelley1,2, Nicholas J Bryden1,2
1Department of Physics and Astronomy, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Magnetic Resonance in Medicine
|October 3, 2021
Summary
Achieving reliable hyperCEST contrast requires establishing a steady-state dissolved-phase xenon (Xe) magnetization. This involves synchronizing magnetic resonance (MR) acquisition with breathing rate for consistent Xe signal intensity.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Hyperpolarized Contrast Agents
- Medical Physics
Background:
- HyperCEST contrast relies on reducing solvent signal after solute magnetization saturation.
- In vivo applications face challenges due to dynamic changes in xenon (Xe) accumulation in tissue.
Purpose of the Study:
- To define experimental conditions for reliable in vivo hyperCEST contrast.
- To address signal variability caused by changing dissolved-phase Xe signal over time.
Main Methods:
- Hyperpolarized 129Xe delivered via mechanical ventilator during exhale phase.
- MR signal acquisition synchronized with breathing (every breath or every 2-4 breaths).
- Serial Z-spectra and hyperCEST imaging before and after cucurbit[6]uril injection.
Main Results:
- Dissolved-phase Xe signal initially increased, then decreased before reaching steady-state.
- Reliable hyperCEST contrast (>40% signal reduction) achieved after steady-state magnetization was established.
- Signal fluctuations and instabilities were assessed post-injection.
Conclusions:
- Reliable hyperCEST contrast is contingent upon achieving steady-state dissolved-phase 129Xe magnetization.
- Steady-state magnetization requires multiple Xe inhalations and RF excitations under stable physiological conditions.
- Synchronization of breathing rate with MR acquisition is crucial for consistent results.
