Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo.
T2 relaxometry has become an important tool in quantitative MRI. Little focus has been put on the effect of the refocusing flip angle upon the offset parameter, which was introduced to account for a signal floor due to noise or to long T2 components. The aim of this study was to show that B1 imperfe...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Public Library of Science (PLoS)
2015-01-01
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| Series: | PLoS ONE |
| Online Access: | http://europepmc.org/articles/PMC4683054?pdf=render |
| _version_ | 1819277027275964416 |
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| author | David Milford Nicolas Rosbach Martin Bendszus Sabine Heiland |
| author_facet | David Milford Nicolas Rosbach Martin Bendszus Sabine Heiland |
| author_sort | David Milford |
| collection | DOAJ |
| description | T2 relaxometry has become an important tool in quantitative MRI. Little focus has been put on the effect of the refocusing flip angle upon the offset parameter, which was introduced to account for a signal floor due to noise or to long T2 components. The aim of this study was to show that B1 imperfections contribute significantly to the offset. We further introduce a simple method to reduce the systematic error in T2 by discarding the first echo and using the offset fitting approach.Signal curves of T2 relaxometry were simulated based on extended phase graph theory and evaluated for 4 different methods (inclusion and exclusion of the first echo, while fitting with and without the offset). We further performed T2 relaxometry in a phantom at 9.4T magnetic resonance imaging scanner and used the same methods for post-processing as in the extended phase graph simulated data. Single spin echo sequences were used to determine the correct T2 time.The simulation data showed that the systematic error in T2 and the offset depends on the refocusing pulse, the echo spacing and the echo train length. The systematic error could be reduced by discarding the first echo. Further reduction of the systematic T2 error was reached by using the offset as fitting parameter. The phantom experiments confirmed these findings.The fitted offset parameter in T2 relaxometry is influenced by imperfect refocusing pulses. Using the offset as a fitting parameter and discarding the first echo is a fast and easy method to minimize the error in T2, particularly for low to intermediate echo train length. |
| first_indexed | 2024-12-23T23:49:35Z |
| format | Article |
| id | doaj.art-831c00172cb9479bac7e03fae4b8ffe6 |
| institution | Directory Open Access Journal |
| issn | 1932-6203 |
| language | English |
| last_indexed | 2024-12-23T23:49:35Z |
| publishDate | 2015-01-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS ONE |
| spelling | doaj.art-831c00172cb9479bac7e03fae4b8ffe62022-12-21T17:25:26ZengPublic Library of Science (PLoS)PLoS ONE1932-62032015-01-011012e014525510.1371/journal.pone.0145255Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo.David MilfordNicolas RosbachMartin BendszusSabine HeilandT2 relaxometry has become an important tool in quantitative MRI. Little focus has been put on the effect of the refocusing flip angle upon the offset parameter, which was introduced to account for a signal floor due to noise or to long T2 components. The aim of this study was to show that B1 imperfections contribute significantly to the offset. We further introduce a simple method to reduce the systematic error in T2 by discarding the first echo and using the offset fitting approach.Signal curves of T2 relaxometry were simulated based on extended phase graph theory and evaluated for 4 different methods (inclusion and exclusion of the first echo, while fitting with and without the offset). We further performed T2 relaxometry in a phantom at 9.4T magnetic resonance imaging scanner and used the same methods for post-processing as in the extended phase graph simulated data. Single spin echo sequences were used to determine the correct T2 time.The simulation data showed that the systematic error in T2 and the offset depends on the refocusing pulse, the echo spacing and the echo train length. The systematic error could be reduced by discarding the first echo. Further reduction of the systematic T2 error was reached by using the offset as fitting parameter. The phantom experiments confirmed these findings.The fitted offset parameter in T2 relaxometry is influenced by imperfect refocusing pulses. Using the offset as a fitting parameter and discarding the first echo is a fast and easy method to minimize the error in T2, particularly for low to intermediate echo train length.http://europepmc.org/articles/PMC4683054?pdf=render |
| spellingShingle | David Milford Nicolas Rosbach Martin Bendszus Sabine Heiland Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo. PLoS ONE |
| title | Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo. |
| title_full | Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo. |
| title_fullStr | Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo. |
| title_full_unstemmed | Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo. |
| title_short | Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo. |
| title_sort | mono exponential fitting in t2 relaxometry relevance of offset and first echo |
| url | http://europepmc.org/articles/PMC4683054?pdf=render |
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