1. A method of quantifying asymmetry of an object being operated in a computer and comprising acts of importing medical image data sets of an object into a computer; selecting regions of interest of the object in each medical image data set locating the regions of interest of the object in each medical image data set and comprising selecting contrast and threshold arguments defining the regions of interest of the object in each medical image data set; and processing the image data by using the contrast and threshold arguments to locate the regions of interest of the object in each medical image data set; processing the medical image data in each data set by executing an error equation and obtaining optimal parameters corresponding to the error equation; and constructing an optimal symmetry plane with a best symmetry value being a ratio value obtained from the error equation and comprising; (sin α sin β)x+(sin β cos β)y+(cos β sin α)z−(sin α sin β)k d =0 being a symmetry plane of the object wherein parameters α, β and k d are obtained from the step of obtaining the optimal parameters, α is an angle between an x-axis and an intersection line between the symmetry plane and the plane XY, β is an angle between the x-axis and an intersection line between the symmetry plane and the plane XZ and k d is a distance between a point on the symmetry plane and the origin; and obtaining the symmetry plane by substituting the optimal parameters α, β and k d into the equation (sin α sin β)x+(sin β cos β)y+(cos β sin α)z−(sin α sin β)k d =0 of the symmetry plane.