A model‐based framework for correcting inhomogeneity effects in magnetization transfer saturation and inhomogeneous magnetization transfer saturation maps
| Autor: | Gilbert Bruce Pike, Zhe Wu, Jennifer S.W. Campbell, Christopher D. Rowley, Christine L. Tardif, Ilana R. Leppert, David A. Rudko |
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| Rok vydání: | 2021 |
| Předmět: |
Physics
Work (thermodynamics) MT protocol Empirical correction Healthy subjects 030218 nuclear medicine & medical imaging Computational physics 03 medical and health sciences 0302 clinical medicine Linear relationship Range (statistics) Radiology Nuclear Medicine and imaging Magnetization transfer Saturation (chemistry) 030217 neurology & neurosurgery |
| Zdroj: | Magnetic Resonance in Medicine. 86:2192-2207 |
| ISSN: | 1522-2594 0740-3194 |
| DOI: | 10.1002/mrm.28831 |
| Popis: | PURPOSE In this work, we propose that Δ B1+ -induced errors in magnetization transfer (MT) saturation (MTsat ) maps can be corrected with use of an R1 and B1+ map and through numerical simulations of the sequence. THEORY AND METHODS One healthy subject was scanned at 3.0T using a partial quantitative MT protocol to estimate the relationship between observed R1 (R1,obs ) and apparent bound pool size ( M0,appB ) in the brain. MTsat values were simulated for a range of B1+ , R1,obs , and M0,appB . An equation was fit to the simulated MTsat , then a linear relationship between R1,obs and M0,appB was generated. These results were used to generate correction factor maps for the MTsat acquired from single-point data. The proposed correction was compared to an empirical correction factor with different MT-preparation schemes. RESULTS M0,appB was highly correlated with R1,obs (r > 0.96), permitting the use of R1,obs to estimate M0,appB for B1+ correction. All B1+ corrected MTsat maps displayed a decreased correlation with B1+ compared to uncorrected MTsat and MTsat corrected with an empirical factor in the corpus callosum. There was good agreement between the proposed approach and the empirical correction with radiofrequency saturation at 2 kHz, with larger deviations seen when using saturation pulses further off-resonance and in inhomogeneous (ih) MTsat maps. CONCLUSION The proposed correction decreases the dependence of MTsat on B1+ inhomogeneities. Furthermore, this flexible framework permits the use of different saturation protocols, making it useful for correcting B1+ inhomogeneities in ihMT. |
| Databáze: | OpenAIRE |
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