1. An ultrasonic imaging apparatus comprising: a transducer that transmits or receives ultrasonic waves to or from a subject; an image data production unit configured to produce a plurality of image data items on the basis of a plurality of receiving signals due to the transducer; a frame memory configured to preserve the image data items; a temporal change measurement unit configured to measure a temporal change in brightness of each of pixels of image data; an image construction unit configured to construct a color map on the basis of the results of measurement by the temporal change measurement unit; an input unit configured to input display-item information concerning the color map; and a pixel detection unit configured to extract pixels from the color map so as to construct an extractive image; wherein the ultrasonic imaging apparatus further comprising: a mapping parameter estimation unit configured to measure a saturated brightness(I max ) of the contrast medium, and an average brightness (I base ) before injection per each of pixels on the basis of the temporal change measured by the temporal change measurement unit, and configured to calculate a mapping parameter on the basis of the measured temporal change, wherein: the image construction unit configured to construct the color map on the basis of the mapping parameter.