- Poster presentation
- Open Access
Analysis of the transient phase of balanced SSFP with non-continuous RF for cardiac imaging
- Glenn S Slavin1
© Slavin; licensee BioMed Central Ltd. 2010
Published: 21 January 2010
The transient phase of balanced SSFP (bSSFP) is the period during which magnetization approaches steady state. The transient phase of non-ECG-gated, continuous-RF bSSFP has been characterized by a simple exponential decay with a time constant that is a flip-angle-weighted average of T1 and T2 . Cardiac imaging applications, however, often utilize bSSFP with non-continuous RF excitation. The example considered here, Look-Locker-based T1 mapping, begins with an ECG trigger, and is followed by magnetization preparation, a bSSFP imaging segment, and a recovery time prior to the subsequent ECG trigger. Multiple time points are acquired, separated by the R-R interval TRR. The description of the continuous-RF transient phase is not applicable in this case.
The goal of this work was to develop an analytical expression for the transient phase of bSSFP with non-continuous RF excitation. The resulting equation can be applied to Look-Locker acquisitions to provide true quantification of T1 (and T2), rather than an "apparent" T1 (T1*).
Bloch simulation of the pulse sequence in Figure 1 was performed, and T1* was determined by curve fitting. T1, T2, and T1* were then calculated using λ eig (T1, T2) and showed perfect agreement.
Previously reported cardiac T1 mapping techniques using bSSFP have employed various assumptions and approximations to estimate T1. This work presents an analytical expression for the transient phase of non-continuous-RF bSSFP. It provides the ability to directly quantify T1&T2 for cardiac imaging while obviating such assumptions in acquisition or post-processing.