Table I.

Description of cases in the average and subtle mass data sets and the subsets for training and testing in the cross-validation scheme.

	Mass subset 1		Mass subset 2
	Average mass subset	Subtle mass subset	Average mass subset	Subtle mass subset
Total No. of cases	57	54	58	56
Cases with two prior examinations	NA	10	NA	9
Exams with two views	57	58	58	65
Exams with three views	0	6	0	0
Total No. of images	114	134	116	130
No. of negative images	0	25	0	19
No. of mass images for training	114	109	116	111
No. of two-view pairs for testing	57	64	58	65
No. of images for testing	114	128	116	130
No. of malignant masses	36	33	31	29
No. of benign masses	21	21	27	27