Data Fitting
Monoexponential T2 Mapping
The T2 signal decay for the mono-exponential model is described mathematically as :
where S0 is the signal intensity immediately following the excitation pulse Dortch, 2020Milford et al., 2015.
In practice, B1 inhomogeneities and RF pulse imperfections can influence the T2 signal decay curve and result in inaccurate T2 estimations. This may cause refocusing pulses to deviate from the ideal 180 degrees, generating additional echoes known as stimulated or spurious echoes. These unwanted echoes can contaminate the signal decay, resulting in erroneous T2 estimations McPhee & Wilman, 2018. To account for these stimulated echoes, some studies have shown that T2 fitting accuracy can be improved either by using only even-numbered echoes Focke et al., 2011Kim et al., 2009, or by discarding the first echo Biasiolli et al., 2013Milford et al., 2015.
- Dortch, R. D. (2020). Quantitative T2 and T2* Mapping. In Advances in Magnetic Resonance Technology and Applications (pp. 47–64). Elsevier.
- Milford, D., Rosbach, N., Bendszus, M., & Heiland, S. (2015). Mono-exponential fitting in T2-relaxometry: Relevance of offset and first echo. PLoS One, 10(12), e0145255.
- McPhee, K. C., & Wilman, A. H. (2018). Limitations of skipping echoes for exponential T2 fitting. J. Magn. Reson. Imaging, 48(5), 1432–1440.
- Focke, N. K., Helms, G., Pantel, P. M., Scheewe, S., Knauth, M., Bachmann, C. G., Ebentheuer, J., Dechent, P., Paulus, W., & Trenkwalder, C. (2011). Differentiation of typical and atypical Parkinson syndromes by quantitative MR imaging. AJNR Am. J. Neuroradiol., 32(11), 2087–2092.
- Kim, D., Jensen, J. H., Wu, E. X., Sheth, S. S., & Brittenham, G. M. (2009). Breathhold multiecho fast spin-echo pulse sequence for accurate R2 measurement in the heart and liver. Magn. Reson. Med., 62(2), 300–306.