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SSFP signal with finite RF pulses
Oliver Bieri1, Klaus Scheffler
1Division of Radiological Physics, Department of Medical Radiology, University of Basel Hospital, Basel, Switzerland. oliver.bieri@unibas.ch
Magnetic Resonance in Medicine
|September 26, 2009
Summary
Steady state free precession (SSFP) signal theory needs revision due to finite radiofrequency (RF) pulse durations. Our analysis reveals significant signal modulations, necessitating updated SSFP equations for accurate quantitative imaging.
Area of Science:
- Magnetic Resonance Imaging
- Biophysics
Background:
- Steady state free precession (SSFP) imaging relies on theoretical models assuming instantaneous radiofrequency (RF) pulses.
- Practical RF pulse durations deviate from this assumption, potentially impacting SSFP signal accuracy.
Purpose of the Study:
- To analyze the effects of finite RF pulse durations on balanced SSFP signal formation.
- To revise the theoretical framework of SSFP signal description for practical applications.
Main Methods:
- Analysis of SSFP signal formation considering finite RF pulse time.
- Systematic evaluation as a function of RF time, pulse repetition time, flip angle (alpha), and relaxation times (T(1,2)).
Main Results:
- Finite RF pulses cause signal modulations ranging from a few percent to over 100%, depending on parameters.
- Significant deviations from instantaneous pulse theory observed, particularly with higher flip angles and shorter T(2)/T(1) ratios.
- A modified SSFP equation accurately describes signals across diverse practical and physiological parameters.
Conclusions:
- The assumption of instantaneous RF pulses in SSFP theory is a limitation for real-world applications.
- A revised SSFP equation accounting for finite RF pulse effects is necessary for completeness and quantitative accuracy.
- The derived modification offers a more robust framework for SSFP signal description.
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