Anzeige
Erschienen in:
23.07.2019 | Research Article
Transverse relaxometry with transmit field-constrained stimulated echo compensation
Erschienen in: Magnetic Resonance Materials in Physics, Biology and Medicine | Ausgabe 6/2019
Einloggen, um Zugang zu erhaltenAbstract
Objective
Purely exponential decay is rarely observed in conventional mono-exponential T2 mapping due to transmit field inhomogeneity and calibration errors, which collectively introduce stimulated and indirect echo pathways. Stimulated echo correction (SEC) requires an additional fit parameter for the transmit field, resulting in greater uncertainty in T2 relative to mono-exponential fitting. The aim of this study was to develop an accurate and precise method for T2 mapping using SEC.
Methods
The proposed method, called two-step SEC (tSEC), leverages spatial correlations in the transmit field to reduce the number of fully independent fitting parameters from three to two. The method involves a two-pass fit: the first pass involves a fast but standard SEC fit. The initially estimated transmit field is smoothed and provided as a fixed input to the second pass.
Results
Simulations and in vivo experiments demonstrated up to 38% and 27% decreases in relative T2 variance with tSEC relative to SEC. Average T2 values were unchanged between tSEC and SEC fits. The proposed method uses the same input data as SEC and exponential fits, so it is applicable to existing data.
Discussion
The proposed method generates reliable and reproducible quantitative T2 maps and should be considered for future relaxometry studies.