% % This file was created by the TYPO3 extension % bib % --- Timezone: CET % Creation date: 2024-03-29 % Creation time: 16-26-35 % --- Number of references % 5 % @Article { Elster2005a, title = {Quantitative magnetic resonance spectroscopy: semi-parametric modeling and determination of uncertainties}, journal = {Magnetic resonance in medicine}, year = {2005}, volume = {53}, number = {6}, pages = {1288--96}, abstract = {A semi-parametric approach for the quantitative analysis of magnetic resonance (MR) spectra is proposed and an uncertainty analysis is given. Single resonances are described by parametric models or by parametrized in vitro spectra and the baseline is determined nonparametrically by regularization. By viewing baseline estimation in a reproducing kernel Hilbert space, an explicit parametric solution for the baseline is derived. A Bayesian point of view is adopted to derive uncertainties, and the many parameters associated with the baseline solution are treated as nuisance parameters. The derived uncertainties formally reduce to Cram{{\'e}}r-Rao lower bounds for the parametric part of the model in the case of a vanishing baseline. The proposed uncertainty calculation was applied to simulated and measured MR spectra and the results were compared to Cram{{\'e}}r-Rao lower bounds derived after the nonparametrically estimated baselines were subtracted from the spectra. In particular, for high SNR and strong baseline contributions the proposed procedure yields a more appropriate characterization of the accuracy of parameter estimates than Cr{{\'e}}mer-Rao lower bounds, which tend to overestimate accuracy.}, keywords = {Bayes Theorem,Brain Chemistry,Computer Simulation,Computer-Assisted,Humans,Least-Squares Analysis,Magnetic Resonance Spectroscopy,Magnetic Resonance Spectroscopy: methods,Models, Statistical,Regression,Signal Processing, Computer-Assisted,Statistical}, tags = {8.42, Unsicherheit, in-vivo}, web_url = {http://www.ncbi.nlm.nih.gov/pubmed/15906296}, ISSN = {0740-3194}, DOI = {10.1002/mrm.20500}, author = {Elster, C and Schubert, F and Link, A and Walzel, M and Seifert, F and Rinneberg, H} } @Inproceedings { Schubert2004, title = {Spectral fitting in MRS:Uncertainties of parameter estimates for semi-parametric MR spectrum modelling}, year = {2004}, tags = {8.42, in-vivo}, booktitle = {Proc. Intl. Soc. Magnet. Reson. Med}, event_name = {Intl. Soc. Magnet. Reson. Med.}, author = {Schubert, F and Elster, C and Link, A and Seifert, F and Walzel, M and Rinneberg, H} } @Article { Schubert2002, title = {Serial 1H-MRS in relapsing-remitting multiple sclerosis: effects of interferon-\(\beta\) therapy on absolute metabolite concentrations}, journal = {Magnetic Resonance Materials in Physics, Biology and Medicine}, year = {2002}, volume = {14}, number = {3}, pages = {213 - 222}, abstract = {To assess the applicability of magnetic resonance spectroscopy (MRS) for long-term follow-up of neurological diseases a longitudinal 1H-MRS study at 3 T was carried out on ten patients having relapsing-remitting multiple sclerosis (MS) who, after baseline examination, received interferon-\(\beta\) (IFN) 1b. At 8–20 examinations within up to 34 months absolute concentrations of N-acetylaspartate (NAA), total creatine (tG), and choline-containing compounds (tCho) were determined in a large non-enhancing lesion and contralateral normal appearing white matter (NAWM). {MR} spectra were analyzed using a novel time domain-frequency domain method including non-parametric background characterization. For comparison at baseline, ten healthy controls were examined. The concentrations of tCho and tCr were found to be higher in {MS} brain than in control brain. Besides a non-significantly lower {NAA} concentration in lesions there were no concentration differences between lesions and NAWM. Over the follow-up period the measured metabolite concentrations exhibited a high variability. Most concentrations remained within this scatter, and statistical tests revealed significant fluctuations in the levels of metabolites in one case only. This stability of the metabolite concentrations over time might result from {IFN} therapy as for the spontaneous course of relapsing-remitting {MS} decreasing metabolite (NAA/tCr) ratios have been reported. The results further suggest that future treatment trials intending to use metabolite concentrations as a secondary outcome indicator use even longer observation periods and, besides group analysis of large cohorts, investigate the time behavior of selected single cases. The biochemical abnormalities found in {NAWM} emphasize the importance of analyzing both lesion and NAWM.}, keywords = {Therapy monitoring}, tags = {8.42, in-vivo}, web_url = {http://www.sciencedirect.com/science/article/pii/S1352866102000662}, ISSN = {1352-8661}, DOI = {10.1016/s1352-8661(02)00066-2}, author = {Schubert, F and Seifert, F and Elster, C and Link, Alfred and Walzel, M and Mientus, S and Haas, J and Rinneberg, H} } @Inbook { Elster2001b, title = {Assessment of current methods of analysis for quantitative in-vivo magnetic resonance spectroscopy}, year = {2001}, volume = {Advanced Mathematical \& Computational Tools in Metrology V}, pages = {134-141}, tags = {8.42, in-vivo}, editor = {P. Ciarlini, M.G. Cox, E. Filipe, F. Pavese, D. Richter}, publisher = {World Scientific Singapore}, series = {Series on Advances in Mathematics for Applied Sciences}, edition = {57}, author = {Elster, C and Link, A and Schubert, F and Seifert, F and Walzel, M and Richter, D and Rinneberg, H} } @Article { Elster2000a, title = {Quantitative MRS: comparison of time domain and time domain frequency domain methods using a novel test procedure}, journal = {Magnetic Resonance Imaging}, year = {2000}, volume = {18}, number = {5}, pages = {597 - 606}, abstract = {For quantitative analysis of in vivo {MR} spectra, a state-of-the-art time domain method was compared with a recently reported time domain frequency domain method which uses wavelets for background characterization. The comparison was made on the basis of results for simulated test problems that were constructed by combining measured and simulated {MRS} data at different signal-to-noise ratios in order to simultaneously reflect real world difficulties, in particular the overlapping background problem, and to allow for quantitative judgment of a method's accuracy. Incorporating prior knowledge was also considered. The results obtained give insight into the accuracy of the methods when applied to measured {MRS} data. Due to the improved background characterization, the time domain frequency domain method outperformed the time domain method in some of the test cases. Both methods were also applied to serial brain {MR} spectra of a healthy volunteer on 10 occasions.}, keywords = {Frequency domain}, tags = {8.42, in-vivo}, web_url = {http://www.sciencedirect.com/science/article/pii/S0730725X00001405}, ISSN = {0730-725X}, DOI = {10.1016/S0730-725X(00)00140-5}, author = {Elster, C and Link, A and Schubert, F and Seifert, F and Walzel, M and Rinneberg, H} }