An image capturing apparatus for a breast examination in which a breakthrough mammary gland density can be adduced. A mammary gland density is calculated by recognizing a distribution of mammary gland tissues of a subject according to a distribution of radioactive pharmaceuticals distributed in a breast. An imaged image of the distribution of the radioactive pharmaceuticals is one type of function image, and represents activity in the subject. Therefore, it is possible to calculate the mammary gland density based on a mammary gland tissue of which the activity is active (an active mammary gland tissue) in the mammary gland tissues.
