Signal-to-noise ratio (CT)
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Citation:
Murphy A, Signal-to-noise ratio (CT). Reference article, Radiopaedia.org (Accessed on 18 Feb 2025) https://doi.org/10.53347/rID-75581
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75581
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At the time the article was created Andrew Murphy had no recorded disclosures.
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At the time the article was last revised Andrew Murphy had no financial relationships to ineligible companies to disclose.
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Signal-to-noise ratio (SNR) is a generic term which, in radiology, is a measure of true signal (i.e. reflecting actual anatomy) to noise (e.g. random quantum mottle).
Signal-to-noise ratio in CT roughly follows the same principles as those of plain radiographs. It is calculated by comparing the level of the desired signal to the background deviation from normal pixel values. In general, the larger the number of photons transmitted, the greater the SNR.
In CT the signal-to-noise ratio is determined by:
- mAs
- greater mAs increases SNR
- slice thickness
- thicker slices increase SNR
- patient size
- larger patients reduce SNR
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