Fig. 1From: Finding cancer in mammograms: if you know it’s there, do you know where?Exemplars of target-present images. The red outline depicts the mass (and did not appear in the actual stimuli). a Low-density breast that contains predominately fatty tissue, which is radio-translucent or black/grey. The higher contrast mass is easily seen. b High-density breast that contains normal fibroglandular tissue resulting in a more difficult search. The X-ray beam is attenuated by this tissue and appears radio-opaque or white on a mammogramBack to article page