Reader and case sample combinations needed for 0.80 power based on the data of:

Krupinski EA, Johnson J, Roehrig H, Nafziger J, Lubin J. On-axis and off-axis viewing of images on CRT displays and LCDs: Observer performance and vision model predictions. Academic Radiology 2005;12:957-964.

Readers: 6 board certified family physicians

Cases: 80 breast images (40 with benign and 40 with malignant masses) downloaded from the Digital Database for Screening Mammography (Heath M, Bowyers KW, Kopans D, et al. Current status of the digital database for screening mammography. In: Karssemeijer N, Thijssen M, Hendriks J, van Erning  L, ads. Digital Mammography. Boston, MA: Klu-wer Academic Publishers, 1998; 457-460. (http://marathon.csee.usf.edu/Mammography/Database.htmi. Accessed: June 16, 2005.). A larger series of images was created by extracting 512 X 512 regions of interest (ROIs) around each mass. Digital processing with a median filter was used to remove the masses and generate signal-absent versions of the images. To create lower contrast (75%, 50%, and 25%) versions of the masses, weighted superposition of the signal-present and signal-absent image versions were used. The final test set had five versions of each of the 80 base images (100%, or original contrast; 75%; 50%; 25%; and 0%, or signal-absent), yielding 400 test images. They were down sampled from 512 X 512 to 256 X 256 pixel ROIs.

Conditions: The four viewing conditions were (1) LCD on-axis, (2) LCD off-axis, (3) CRT on-axis, and (4) CRT off-axis.

ROC Model = PropROC, Parameter = AUC,

AUCs = 0.887, 0.910, 0.899, 0.863.

Readers = 6, Cases = 400,

MS( Treatment*Reader ) = 0.05331279,

MS( Treatment*Case ) = 0.10428066,

MS( Treatment*Reader*Case ) = 0.05682980.

AUC Difference = 0.03

Readers	Readers and Cases Random	Cases Random	Readers Random
3	737	471	1114
4	485	388	526
5	385	339	339
6	331	306	250
7	297	282	199
8	273	264	165
9	256	251	141
10	242	239	123
11	232	230	110
12	223	223	99
13	216	217	90
14	210	211	82
15	205	206	76

AUC Difference = 0.05

Readers	Readers and Cases Random	Cases Random	Readers Random
3	288	171	451
4	183	141	200
5	143	123	127
6	122	112	93
7	109	103	73
8	100	97	61
9	94	92	52
10	89	88	45
11	85	85	40
12	81	82	36
13	79	80	33
14	77	78	30
15	75	76	28

AUC Difference = 0.10

Readers	Readers and Cases Random	Cases Random	Readers Random
3	75	45	119
4	47	37	52
5	37	33	32
6	31	30	24
7	28	28	20
8	26	26	20
9	24	25	20
10	23	24	20
11	22	23	20
12	21	22	20
13	20	22	20
14	20	21	20
15	20	21	20