Observer Performance Using Monitors With Different Phosphors Elizabeth A. Krupinski, PhD Hans Roehrig, PhD University of Arizona Tucson, AZ

P104 vs P45 b P104 bigger grain sizebigger grain size fewer grains per pixelfewer grains per pixel two componentstwo components more non-uniformitymore non-uniformity b Lower SNR for P104

Examples P45 Phosphor P104 Phosphor

Max SNR / CRT Pixel Luminance (cd/m 2 ) S N R / C R T - P i x e l P45 Phosphor P 104 Phosphor.

Display Function Command Level (ADU) L u m i n a n c e (cd/m 2 ) P45 P104

Veiling Glare Disk Diameter in # of Pixels P45 P104 Veiling glare ratio

Pixel Emitted intensity # Pixels in Pixel String P i x e l E m i t t e d I n t e n s i t y P104 P45

MTF M TF Frequency (lp/mm) Vertical MTF Horizontal MTF 113 ADU 200 ADU 113 ADU 200 ADU ADU 200 ADU 113 ADU 200 ADU Vertical MTF Horizontal MTF P45P104

Luminance Uniformity

JND Performance F = df = 23 p <

Methods & Materials b 20 chest images 5 lesion free5 lesion free 15 solitary pulmonary nodule15 solitary pulmonary nodule b Image Systems P45 & P104 monitors 1600 x 1200 resolution1600 x 1200 resolution Pixel size = mmPixel size = mm b 6 radiologists as observers

Images - Conventional radiographs 150 mA 125 kVp - CT confirmation - Digitized with VIDAR VXR x 2552 x 16-bits

Viewing Conditions b Eye-position recorded ASL 4000 SU with head-trackerASL 4000 SU with head-tracker < 1 deg accuracy< 1 deg accuracy b Ambient lights off b No time restrictions b ~ 2 weeks between sessions

ROC Az Results b MeanAz : P45 = P104 = P104 = b ANOVA Treatment : F = , p = Treatment : F = , p = Cases : F = , p = Cases : F = , p = Readers : F = , p = Readers : F = , p = No significant interaction effectsNo significant interaction effects

Eye-Position Results

Eye-Position Results* b Mean Viewing Times Overall - P45 = seconds - P104 = seconds * ~ 75% of the data. Future will split out lesion vs lesion-free images & residents vs radiologists * ~ 75% of the data. Future will split out lesion vs lesion-free images & residents vs radiologists

Eye-Position Results b Median Dwell Times x Decision (msec) P45P104 TP =2043<2237 FN = 1528>1411 FP = 1986<1958 TN = 470<513

Eye-Position Results b Mean Time to First “Hit” nodules (msec) P45P104 TP = 312<369 FN = 563<602

Conclusions b Phosphor may not affect diagnostic accuracy b May affect search parameters b Might influence purchase & clinical use choices

Caveats b Detection not classification b Pulmonary nodules only b No image processing (window / level) allowed b Task & stimuli may influence results b Further studies should be done