1. An ultrasound diagnostic apparatus comprising: an ultrasound probe configured to transmit ultrasound waves to a subject and receive an echo, the subject including body tissue; a location sensor configured to detect a location of the ultrasound probe; a location calculation device configured to calculate a location of echo data in a first coordinate system in a three-dimensional space having a certain point as an origin based on the probe location detected by the location sensor; a deformation calculation device configured to perform a deformation calculation to deform a shape of the body tissue in a first image of an ultrasound image based on the echo data and a medical image captured in advance by a medical imaging apparatus other than the ultrasound diagnostic apparatus to a shape of the body tissue of a second image of the ultrasound image and the medical image, the ultrasound image having the first coordinate system; and a display image control device configured to: perform a coordinate conversion between the first coordinate system of the ultrasound image and a second coordinate system of the medical image; and display a deformed image based on the deformation calculation by the deformation calculation device and the second image about a same cross-section on a display device.