title: Evaluation of irreversible compression of digitized posterior-anterior chest radiographs.
abstract: The purpose of this article is to assess lossy image compression of digitized chest radiographs using radiologist assessment of anatomic structures and numerical measurements of image accuracy. Forty posterior-anterior (PA) chest radiographs were digitized and compressed using an irreversible wavelet technique at 10, 20, 40, and 80:1. These were presented in a blinded fashion with an uncompressed image for A-B comparison of 11 anatomic structures as well as overall quality assessments. Mean error, root-mean square (RMS) error, maximum pixel error, and number of pixels within 1% of original value were also computed for compression ratios from ratios from 5:1 to 80:1. We found that at low compression (10:1) there was a slight preference for compressed images. There was no significant difference at 20:1 and 40:1. There was a slight preference on some structures for the original compared with 80:1 compressed images. Numerical measures showed high image faithfulness, both in terms of number of pixels that were within 1% of their original value, and by the average error for all pixels. Our findings suggest that lossy compression at 40:1 or more can be used without perceptible loss in the representation of anatomic structures. On this finding, we will do a receiver-operator characteristic (ROC) analysis of nodule detection in lossy compressed images using 40:1 compression.
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Erickson
authors.forename: A
authors.initials: A
authors.lastname: Manduca
authors.forename: K R
authors.initials: KR
authors.lastname: Persons
authors.forename: F
authors.initials: F
authors.lastname: Earnest
authors.forename: T E
authors.initials: TE
authors.lastname: Hartman
authors.forename: G F
authors.initials: GF
authors.lastname: Harms
authors.forename: L R
authors.initials: LR
authors.lastname: Brown
mesh_terms: D016477:Artifacts; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D011856:Radiographic Image Enhancement; D013902:Radiography, Thoracic / Q000379:methods* / Q000592:standards; D011873:Radiology Information Systems