A rule-based computer scheme for centromere identification and polarity assignment of metaphase chromosomes.

Automatic centromere identification and polarity assignment are two key factors in the automatic karyotyping of human chromosomes. A multi-stage rule-based computer scheme has been investigated to automatically detect centomeres and determine polarities for both abnormal and normal metaphase chromosomes. The scheme first implements a modified thinning algorithm to identify the medial axis of a chromosome and extracts three feature profiles. Based on a set of pre-optimized classification rules, the scheme adaptively identifies the centromere and then assigns corresponding polarity. An image dataset of 2287 chromosomes acquired from 24 abnormal and 26 normal Giemsa metaphase cells is utilized to optimize and test the scheme. The overall accuracy is 91.4% for centromere identification and 97.4% for polarity assignment. The experimental results demonstrate that our scheme can be successfully applied to diverse chromosomes, which include those severely bent and abnormal chromosomes extracted from cancer cells.