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SNR. Definition Averaging uncorrelated noise Thermal vs. physiological. Averaging to beat down noise. If noise is uncorrelated:. Signal-to-Noise Ratio (SNR). Thermal noise ( th ) is uncorrelated and normally and uniformly distributed Imaging noise
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SNR • Definition • Averaging uncorrelated noise • Thermal vs. physiological SNR
Averaging to beat down noise If noise is uncorrelated: SNR
Signal-to-Noise Ratio (SNR) • Thermal noise (th) is uncorrelated and normally and uniformly distributed • Imaging noise • Physiological noise (phys) has all sorts of correlations and is different in gray matter, white matter … • Brain noise SNR
Caveat: estimating zero-mean noise in magnitude images Gaussian distribution Rician distribution SNR
Big voxel: dominated by phys. noise Phys. noise masked by thermal noise SNR lower in gray matter SNR