title: Trend of contrast detection threshold with and without localization.
abstract: Published information on contrast detection threshold is based primarily on research using a location-known methodology. In previous work on testing the Digital Imaging and Communications in Medicine (DICOM) Grayscale Standard Display Function (GSDF) for perceptual linearity, this research group used a location-unknown methodology to more closely reflect clinical practice. A high false-positive rate resulted in a high variance leading to the conclusion that the impact on results of employing a location-known methodology needed to be explored. Fourteen readers reviewed two sets of simulated mammographic background images, one with the location-unknown and one with the location-known methodology. The results of the reader study were analyzed using Reader Operating Characteristic (ROC) methodology and a paired t test. Contrast detection threshold was analyzed using contingency tables. No statistically significant difference was found in GSDF testing, but a highly statistical significant difference (p value <0.0001) was seen in the ROC (AUC) curve between the location-unknown and the location-known methodologies. Location-known methodology not only improved the power of the GSDF test but also affected the contrast detection threshold which changed from +3 when the location was unknown to +2 gray levels for the location-known images. The selection of location known versus unknown in experimental design must be carefully considered to ensure that the conclusions of the experiment reflect the study's objectives.
authors.affiliation: Analogic Corporation, 8 Centennial Drive, Peabody, MA, 01960, USA, dleong@analogic.com.
authors.forename: David L
authors.initials: DL
authors.lastname: Leong
authors.forename: Louise
authors.initials: L
authors.lastname: Rainford
authors.forename: Tamara Miner
authors.initials: TM
authors.lastname: Haygood
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Whitman
authors.forename: William R
authors.initials: WR
authors.lastname: Geiser
authors.forename: Beatriz E
authors.initials: BE
authors.lastname: Adrada
authors.forename: Lumarie
authors.initials: L
authors.lastname: Santiago
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Brennan
mesh_terms: D000704:Analysis of Variance; D019540:Area Under Curve; D001943:Breast Neoplasms / Q000473:pathology; D003287:Contrast Media / Q000494:pharmacology; D015350:Contrast Sensitivity; D003626:Data Display; D004305:Dose-Response Relationship, Drug; D005260:Female; D005544:Forecasting; D006801:Humans; D008327:Mammography / Q000379:methods* / Q000639:trends; D012372:ROC Curve; D011856:Radiographic Image Enhancement / Q000379:methods* / Q000639:trends; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D019275:Radiopharmaceuticals / Q000494:pharmacology
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals