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Approximate scaling of the SSFP steady state.
1School of Medicine, Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar der TUM, Technical University of Munich, Munich, Germany.
Magnetic Resonance in Medicine
|January 27, 2023
Summary
Steady-state free precession (SSFP) sequences show a universal scaling law, improving relaxometry accuracy. Simultaneous estimation of T1 and T2 is not recommended from SSFP alone.
Area of Science:
- Magnetic Resonance Imaging
- Quantitative MRI
Background:
- Steady-state free precession (SSFP) sequences are widely used in magnetic resonance imaging.
- Understanding the behavior of SSFP signals is crucial for accurate quantitative MRI.
- The influence of flip angle variations on SSFP signal characteristics requires detailed investigation.
Purpose of the Study:
- To investigate the steady-state behavior of rapid SSFP sequences.
- To identify and characterize a universal scaling law in SSFP signals.
- To assess the impact of this scaling law on relaxometry precision.
Main Methods:
- Derivation and numerical testing of an approximate scaling law for SSFP.
- Calculation of the Cramér-Rao bound (CRB) for estimator precision.
- Monte Carlo (MC) simulations to evaluate relaxometry experiment performance.
Main Results:
- A universal approximate scaling law was observed in SSFP steady states for small to moderate flip angles.
- Significant precision loss was found for simultaneous T1 and T2 estimation using pure SSFP steady states.
- Accurate T1 estimates were achievable even without knowing the exact flip angle.
Conclusions:
- Simultaneous estimation of T1 and T2 from SSFP steady states alone is not recommended.
- Adding transient state information can improve simultaneous estimation.
- Residual effects of the scaling law may still necessitate careful consideration in relaxometry analysis.
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