1. A medical image-editing device comprising: a source of a pixel-based medical image; a computer-implemented display configured to display a plurality of pixel value regions of said pixel-based medical image including an attention region of said medical image and at least one other region of said medical image, said other region of the medical image being different from said attention region; a computer-implemented setting unit configured to set a graphic passing through the attention region and said at least one other region of the medical image and having ending points; and a computer-implemented control configured to determine which of said attention and other regions contains the ending-points of the set graphic, to execute either extension or deletion on the attention region of the medical image according to the result of the determination and the graphic, and to cause the display to display the attention region on which the extension or deletion is executed as a new attention region of said pixel-based medical image, wherein when the medical image-editing device has determined that one of the ending points of said graphic is in the attention region and the other one of the ending points is in said other region, the control of the medical image-editing device executes either the extension or the deletion to extend or delete the attention region based on a ratio between (i) an entire length of the graphic and (ii) a length of the graphic passing through the attention region or the other region.