for outlining boundaries of the heart ventricle
from X-ray image. The X-ray image is initially divided
into many M×M (M= 32 in most cases) operational regions as
shown in Fig. 7a. A threshold value is then determined from
the histogram of this M×M sub-image using an automatic
thresholding algorithm. The algorithm is an unsupervised
thresholding method by iteratively choosing the threshold
value Ts with the following equation