DIGITALES SUBTRAKTIONS-ABBILDUNGSGERAET

In a digital subtraction imaging apparatus, the digital subtraction between mask images and contrast images is carried out in synchronism with cardiac beats of an object under medical examination such as a patient. The subtraction-imaging apparatus includes a first memory, a second memory, a cardiac-synchronized subtraction unit, and a central processing unit. When the number of the contrast images acquired within one cardiac cycle is smaller than that of the mask images, for example, when four contrast images and five mask images are obtained, the digital subtraction by the subtraction unit, under the control of the central processing unit, is performed between four contrast images and only four mask images, without using the fifth mask image. Conversely, when the number of the contrast images is greater than that of the mask images, for example, when five contrast images and four mask images are obtained, the digital subtraction is effected between four mask images and four contrast images, and furthermore, is performed between the fourth mask image and the fifth contrast image, under the control of the central processing unit.