| Autor: |
Jonathan M, Lommen, Sebastian, Flassbeck, Nicolas G R, Behl, Sebastian, Niesporek, Peter, Bachert, Mark E, Ladd, Armin M, Nagel |
| Rok vydání: |
2017 |
| Předmět: |
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| Zdroj: |
Magnetic resonance in medicine. 80(2) |
| ISSN: |
1522-2594 |
| Popis: |
To investigate and to reduce influences on the determination of the short and long apparent transverse relaxation times ( T2,s*, T2,l*) ofThe accuracy of T2* determination was analyzed in simulations for five different sampling schemes. The influence of noise in the parameter fit was investigated for three different models. A dedicated sampling scheme was developed for brain parenchyma by numerically optimizing the parameter estimation. This scheme was compared in vivo to linear sampling at 7T.For the considered sampling schemes, T2,s* / T2,l* exhibit an average bias of 3% / 4% with a variation of 25% / 15% based on simulations with previously published T2* values. The accuracy could be improved with the optimized sampling scheme by strongly averaging the earliest sample. A fitting model with constant noise floor can increase accuracy while additional fitting of a noise term is only beneficial in case of sampling until late echo time 80 ms. T2* values in white matter were determined to be T2,s* = 5.1 ± 0.8 / 4.2 ± 0.4 ms and T2,l* = 35.7 ± 2.4 / 34.4 ± 1.5 ms using linear/optimized sampling.Voxel-wise T2* determination of |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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