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Reproducibility of brain metabolite concentration measurements in lesion free white matter at 1.5 T.

Busch MH, Vollmann W, Mateiescu S, Stolze M, Deli M, Garmer M, Grönemeyer DH - BMC Med Imaging (2015)

Bottom Line: This parameter set is different to the one delivering the best individual fit results.All spectra were acquired in "lesion free" (no lesion signs found in MR imaging) white matter.Thus the results are limited to lesion free brain tissue.

View Article: PubMed Central - PubMed

Affiliation: Grönemeyer Institut für Mikrotherapie, Universitätsstraße 142, D-44799, Bochum, Germany. busch@groenemeyer.com.

ABSTRACT

Background: Post processing for brain spectra has a great influence on the fit quality of individual spectra, as well as on the reproducibility of results from comparable spectra. This investigation used pairs of spectra, identical in system parameters, position and time assumed to differ only in noise. The metabolite amplitudes of fitted time domain spectroscopic data were tested on reproducibility for the main brain metabolites.

Methods: Proton spectra of white matter brain tissue were acquired with a short spin echo time of 30 ms and a moderate repetition time of 1500 ms at 1.5 T. The pairs were investigated with one time domain post-processing algorithm using different parameters. The number of metabolites, the use of prior knowledge, base line parameters and common or individual damping were varied to evaluate the best reproducibility.

Results: The protocols with most reproducible amplitudes for N-acetylaspartate, creatine, choline, myo-inositol and the combined Glx line of glutamate and glutamine in lesion free white matter have the following common features: common damping of the main metabolites, a baseline using only the points of the first 10 ms, no additional lipid/macromolecule lines and Glx is taken as the sum of separately fitted glutamate and glutamine. This parameter set is different to the one delivering the best individual fit results.

Discussion: All spectra were acquired in "lesion free" (no lesion signs found in MR imaging) white matter. Spectra of brain lesions, for example tumors, can be drastically different. Thus the results are limited to lesion free brain tissue. Nevertheless the application to studies is broad, because small alterations in brain biochemistry of lesion free areas had been detected nearby tumors, in patients with multiple sclerosis, drug abuse or psychiatric disorders.

Conclusion: Main metabolite amplitudes inside healthy brain can be quantified with a normalized root mean square deviation around 5 % using CH3 of creatine as reference. Only the reproducibility of myo-inositol is roughly twice as bad. The reproducibility should be similar using other references like internal or external water for an absolute concentration evaluation and are not influenced by relaxation corrections with literature values.

No MeSH data available.


Related in: MedlinePlus

Decision flow chart showing the protocols tested on eleven pairs towards an increasing reproducibility
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Fig4: Decision flow chart showing the protocols tested on eleven pairs towards an increasing reproducibility

Mentions: The flow chart of Fig. 4 shows the strategy for the evaluation of the best protocols using eleven pairs, one from each participant. For each question protocols with a significantly lower reproducibility performance were ruled out from further questions. Compared protocols with a difference in the sum of all rn numbers lower than 3 % were defined as similar and both were used for further investigations. Protocols 6, 9a, 13a, 14, 18, 19a are left after this decision process. These protocols except 9a were investigated with all 54 pairs for the detection of the best reproducibility. 9a was replaced for total evaluation by the more reproducible protocols 10 and 12. These seven protocols have the best reproducibility sum (< 31 %) of all main metabolite.Fig. 4


Reproducibility of brain metabolite concentration measurements in lesion free white matter at 1.5 T.

Busch MH, Vollmann W, Mateiescu S, Stolze M, Deli M, Garmer M, Grönemeyer DH - BMC Med Imaging (2015)

Decision flow chart showing the protocols tested on eleven pairs towards an increasing reproducibility
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4588462&req=5

Fig4: Decision flow chart showing the protocols tested on eleven pairs towards an increasing reproducibility
Mentions: The flow chart of Fig. 4 shows the strategy for the evaluation of the best protocols using eleven pairs, one from each participant. For each question protocols with a significantly lower reproducibility performance were ruled out from further questions. Compared protocols with a difference in the sum of all rn numbers lower than 3 % were defined as similar and both were used for further investigations. Protocols 6, 9a, 13a, 14, 18, 19a are left after this decision process. These protocols except 9a were investigated with all 54 pairs for the detection of the best reproducibility. 9a was replaced for total evaluation by the more reproducible protocols 10 and 12. These seven protocols have the best reproducibility sum (< 31 %) of all main metabolite.Fig. 4

Bottom Line: This parameter set is different to the one delivering the best individual fit results.All spectra were acquired in "lesion free" (no lesion signs found in MR imaging) white matter.Thus the results are limited to lesion free brain tissue.

View Article: PubMed Central - PubMed

Affiliation: Grönemeyer Institut für Mikrotherapie, Universitätsstraße 142, D-44799, Bochum, Germany. busch@groenemeyer.com.

ABSTRACT

Background: Post processing for brain spectra has a great influence on the fit quality of individual spectra, as well as on the reproducibility of results from comparable spectra. This investigation used pairs of spectra, identical in system parameters, position and time assumed to differ only in noise. The metabolite amplitudes of fitted time domain spectroscopic data were tested on reproducibility for the main brain metabolites.

Methods: Proton spectra of white matter brain tissue were acquired with a short spin echo time of 30 ms and a moderate repetition time of 1500 ms at 1.5 T. The pairs were investigated with one time domain post-processing algorithm using different parameters. The number of metabolites, the use of prior knowledge, base line parameters and common or individual damping were varied to evaluate the best reproducibility.

Results: The protocols with most reproducible amplitudes for N-acetylaspartate, creatine, choline, myo-inositol and the combined Glx line of glutamate and glutamine in lesion free white matter have the following common features: common damping of the main metabolites, a baseline using only the points of the first 10 ms, no additional lipid/macromolecule lines and Glx is taken as the sum of separately fitted glutamate and glutamine. This parameter set is different to the one delivering the best individual fit results.

Discussion: All spectra were acquired in "lesion free" (no lesion signs found in MR imaging) white matter. Spectra of brain lesions, for example tumors, can be drastically different. Thus the results are limited to lesion free brain tissue. Nevertheless the application to studies is broad, because small alterations in brain biochemistry of lesion free areas had been detected nearby tumors, in patients with multiple sclerosis, drug abuse or psychiatric disorders.

Conclusion: Main metabolite amplitudes inside healthy brain can be quantified with a normalized root mean square deviation around 5 % using CH3 of creatine as reference. Only the reproducibility of myo-inositol is roughly twice as bad. The reproducibility should be similar using other references like internal or external water for an absolute concentration evaluation and are not influenced by relaxation corrections with literature values.

No MeSH data available.


Related in: MedlinePlus