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Proceedings Paper

Perception of noise on a PACS display and its influence on signal-to-noise ratio on a film digitizer
Author(s): R. M. Dawood; Andrew Todd-Pokropek; J. O.M.C. Craig; J. H. Highman; A. W. Porter
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Paper Abstract

The signal to noise ratio and the number of useful bits in data derived from laser film digitization has been assessed for different film densities. The spot size of 2lOjim was not modifiable, and films were digitized to l2bits of grey scale. It was found that the useful dynamic range was typically less then 256, and that the least significant bits were priitiarily noise. This study was part of a series of tests that have been perfonned using resolution patterns, low contrast objects and clinical test series, from which it appears that noise needs to be perceptible in the image for good perfonnance in detecting subtle features. Results from the use of the low contrast phantom, comprising 'lesions' of size well above system resolution but with contrasts ranging from greater than to less than the noise level, indicated that reading from the digital display gave better results than reading from film. It is believed that this gain in contrast perception resulted from the use of an appropriate window setting on the digital display such that noise was clearly visible.

Paper Details

Date Published: 1 August 1990
PDF: 5 pages
Proc. SPIE 1234, Medical Imaging IV: PACS Systems Design and Evaluation, (1 August 1990); doi: 10.1117/12.19028
Show Author Affiliations
R. M. Dawood, St. Mary's Hospital (United Kingdom)
Andrew Todd-Pokropek, Univ. College London (United Kingdom)
J. O.M.C. Craig, St. Mary's Hospital (United Kingdom)
J. H. Highman, St. Mary's Hospital (United Kingdom)
A. W. Porter, St. Mary's Hospital (United Kingdom)

Published in SPIE Proceedings Vol. 1234:
Medical Imaging IV: PACS Systems Design and Evaluation
Samuel J. Dwyer; R. Gilbert Jost, Editor(s)

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