Contrast-to-noise ratio (CNR) as a quality parameter in fMRI

Geissler, Alexander, Gartus, Andreas, Foki, Thomas, Tahamtan, Amir Reza, Beisteiner, Roland and Barth, Markus (2007) Contrast-to-noise ratio (CNR) as a quality parameter in fMRI. Journal of Magnetic Resonance Imaging, 25 6: 1263-1270. doi:10.1002/jmri.20935

Author Geissler, Alexander
Gartus, Andreas
Foki, Thomas
Tahamtan, Amir Reza
Beisteiner, Roland
Barth, Markus
Title Contrast-to-noise ratio (CNR) as a quality parameter in fMRI
Journal name Journal of Magnetic Resonance Imaging   Check publisher's open access policy
ISSN 1053-1807
Publication date 2007-06-01
Year available 2007
Sub-type Article (original research)
DOI 10.1002/jmri.20935
Open Access Status Not yet assessed
Volume 25
Issue 6
Start page 1263
End page 1270
Total pages 8
Place of publication Hoboken, NJ, United States
Publisher John Wiley & Sons
Language eng
Formatted abstract
Purpose: To evaluate the impact of data quality on the localization of brain activation in functional magnetic resonance imaging (fMRI) and to explore whether the temporal contrast-to-noise-ratio (CNR) provides a quantitative parameter to estimate fMRI quality.

Materials and Methods: We investigated two methods for defining the CNR by comparing them on a single-run, single session, as well as on a group-wise basis. The CNRs of healthy subjects and a group of patients with brain lesions were calculated using two different strategies: one based on a general linear model (GLM) analysis (CNR_SPM), and one that acts as an adaptive low-pass filter and assumes that the high-frequency components contain the temporal noise (GNR_SG). Runs with low CNR were identified as outliers using a common exclusion criterion (2 x standard deviation (SD)).

Results: The results of the two CNR methods are highly correlated. Both between and within subjects and patients the CNR showed quite large variations, but the average CNR did not differ between a group of healthy subjects and a patient group. In total, seven of 213 runs (3.3% of all runs) had to be excluded when CNR_SG was used, and 14 of 213 (6.6%) runs had to be excluded when CNR_SPM was used.

Conclusion: Calculating the CNR using an adaptive low-pass filter gives similar results to a GLM-based approach and could be advantageous for cases in which the hemodynamic response function (HRF) differs significantly from common assumptions. The CNR can be used to identify and exclude runs with suboptimal CNR, and to identify sessions with insufficient data quality. The CNR may serve as a quantitative and intuitive parameter to assess the performancejand quality of clinical fMRI investigations, including information on both functional performance (contrast) and data quality (noise caused by the system and physiology).
Keyword Brain mapping
Functional MRI
Healthy subjects
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Centre for Advanced Imaging Publications
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Citation counts: TR Web of Science Citation Count  Cited 24 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 30 times in Scopus Article | Citations
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