Database Characteristics

In contrast with MIAS database where a single scanner was used to digitize the mammograms, in DDSM four different scanners were used. Thus, depending to which of them was used, the mammograms have different characteristics. Table  shows some of these parameters, like the number of bits of the image and the sampling rate.

Table B.3: DDSM digitization characteristics.

		Grey-levels (bits)	Sampling Rate(microns)
-||-	DBA M2100 ImageClear	$12$	$42$
	-||-	Howtek 960	$12$
	-||-	Lumisys 200 Laser	$12$
	-||-	Howtek MultiRad850	$12$
	-||-

Each case of the database is named as M_XXXX_$1$ , where ``M'' represents the used scanner (from ``A'' to ``D''), XXXX is a number of four digits. The four images of the case are stored in a Lossless JPEG format, and the own database provides software to transform the images in a typical raw format.

The annotations stored in each case includes information related to the image (date of study, kind of film), related to the patient (patient's age, density of the breast in BIRADS), related to each image of the case (size), and an overlay file if necessary. In such file, the number of abnormalities and their description (kind of abnormalities, assessment, boundary) are explained.