Dataset Information

Coil-to-coil physiological noise correlations and their impact on functional MRI time-series signal-to-noise ratio.

ABSTRACT: Physiological nuisance fluctuations ("physiological noise") are a major contribution to the time-series signal-to-noise ratio (tSNR) of functional imaging. While thermal noise correlations between array coil elements have a well-characterized effect on the image Signal to Noise Ratio (SNR0 ), the element-to-element covariance matrix of the time-series fluctuations has not yet been analyzed. We examine this effect with a goal of ultimately improving the combination of multichannel array data.We extend the theoretical relationship between tSNR and SNR0 to include a time-series noise covariance matrix ?t , distinct from the thermal noise covariance matrix ?0 , and compare its structure to ?0 and the signal coupling matrix SSH formed from the signal intensity vectors S.Inclusion of the measured time-series noise covariance matrix into the model relating tSNR and SNR0 improves the fit of experimental multichannel data and is shown to be distinct from ?0 or SSH .Time-series noise covariances in array coils are found to differ from ?0 and more surprisingly, from the signal coupling matrix SSH . Correct characterization of the time-series noise has implications for the analysis of time-series data and for improving the coil element combination process. Magn Reson Med 76:1708-1719, 2016. © 2016 International Society for Magnetic Resonance in Medicine.

SUBMITTER: Triantafyllou C

PROVIDER: S-EPMC5565210 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Coil-to-coil physiological noise correlations and their impact on functional MRI time-series signal-to-noise ratio.

Triantafyllou Christina C Polimeni Jonathan R JR Keil Boris B Wald Lawrence L LL

Magnetic resonance in medicine 20160112 6

<h4>Purpose</h4>Physiological nuisance fluctuations ("physiological noise") are a major contribution to the time-series signal-to-noise ratio (tSNR) of functional imaging. While thermal noise correlations between array coil elements have a well-characterized effect on the image Signal to Noise Ratio (SNR<sub>0</sub> ), the element-to-element covariance matrix of the time-series fluctuations has not yet been analyzed. We examine this effect with a goal of ultimately improving the combination of m ...[more]

PMID: 26756964

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Project description:MotivationTarget-specific hybridization depends on oligo-probe characteristics that improve hybridization specificity and minimize genome-wide cross-hybridization. Interplay between specific hybridization and genome-wide cross-hybridization has been insufficiently studied, despite its crucial role in efficient probe design and in data analysis.ResultsIn this study, we defined hybridization specificity as a ratio between oligo target-specific hybridization and oligo genome-wide cross-hybridization. A microarray database, derived from the Genomic Comparison Hybridization (GCH) experiment and performed using the Affymetrix platform, contains two different types of probes. The first type of oligo-probes does not have a specific target on the genome and their hybridization signals are derived from genome-wide cross-hybridization alone. The second type includes oligonucleotides that have a specific target on the genomic DNA and their signals are derived from specific and cross-hybridization components combined together in a total signal. A comparative analysis of hybridization specificity of oligo-probes, as well as their nucleotide sequences and thermodynamic features was performed on the database. The comparison has revealed that hybridization specificity was negatively affected by low stability of the fully-paired oligo-target duplex, stable probe self-folding, G-rich content, including GGG motifs, low sequence complexity and nucleotide composition symmetry.ConclusionFiltering out the probes with defined 'negative' characteristics significantly increases specific hybridization and dramatically decreasing genome-wide cross-hybridization. Selected oligo-probes have two times higher hybridization specificity on average, compared to the probes that were filtered from the analysis by applying suggested cutoff thresholds to the described parameters. A new approach for efficient oligo-probe design is described in our study.Contactshabalin@ncbi.nlm.nih.gov or olga.matveeva@gmail.comSupplementary informationSupplementary data are available at Bioinformatics online.

Dataset Information

Coil-to-coil physiological noise correlations and their impact on functional MRI time-series signal-to-noise ratio.

Publications

Coil-to-coil physiological noise correlations and their impact on functional MRI time-series signal-to-noise ratio.

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