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Title: Preparing digitized cervigrams for colposcopy research and education: determination of optimal resolution and compression parameters.
Authors: Jeronimo J,  Long R,  Neve L,  Ferris D,  Noller K,  Spitzer M,  Mitra S,  Guo J,  Nutter B,  Castle P,  Herrero R,  Rodriguez AC,  Schiffman M
Journal: J Low Genit Tract Dis
Date: 2006 Jan
Branches: MEB
PubMed ID: 16378030
PMC ID: not available
Abstract: OBJECTIVE: Visual assessment of digitized cervigrams through the Internet needs to be optimized. The National Cancer Institute and National Library of Medicine are involved in a large effort to improve colposcopic assessment and, in preparation, are conducting methodologic research. MATERIALS AND METHODS: We selected 50 cervigrams with diagnoses ranging from normal to cervical intraepithelial neoplasia 3 or invasive cancer. Those pictures were scanned at 5 resolution levels from 1,550 to 4,000 dots per inch (dpi) and were presented to 4 expert colposcopists to assess image quality. After the ideal resolution level was determined, pictures were compressed at 7 compression ratios from 20:1 to 80:1 to determine the optimal level of compression that permitted full assessment of key visual details. RESULTS: There were no statistically significant differences between the 3,000 and 4,000 dpi pictures. At 2,000 dpi resolution, only one colposcopist found a slightly statistically significant difference (p = 0.02) compared with the gold standard. There was a clear loss of quality of the pictures at 1,660 dpi. At compression ratio 60:1, 3 of 4 evaluators found statistically significant differences when comparing against the gold standard. CONCLUSIONS: Our results suggest that 2,000 dpi is the optimal level for digitizing cervigrams, and the optimal compression ratio is 50:1 using a novel wavelet-based technology. At these parameters, pictures have no significant differences with the gold standard.