Chromosome classification based on optical density profiles

The study of human chromosomes with respect to the health monitoring, clinical karyotyping, abnormality detection, and genetic counseling, has urged the development of an efficient automatic system to improve the speed, reliability and capacity for chromosome analysis and classification 1-5. Prior to 1970, chromosomes in blood cells were analyzed in terms of their size and gross morphology. In normal cells, there are forty-six chromosomes which form twenty-two homologous pairs plus two sex chromosomes, XX or XY. These twenty-two homologous pairs of chromosomes are divided into seven groups: A, B, C, D, E, F, and G groups. There are seven pairs in C-group, three pairs in A-, D-, E-groups, and two pairs in B-, F-, and G-groups. The size and shape of X-chromosomes are similar to those of C-chromosomes, and the size and shape of Y-chromosomes similar to those of G-chromosomes. The identification and karyotyping of chromosomes images are usually done based on measurements of choromosome arm length, centromere position, and integrated optical density which represents the amount of DNA in the chro- mosome3,6. The optical density profile of a chromosome image along its longitudinal axis was sometimes used to determine the chromosome´s centromere which corresponds to the location of the minimum point on the density profile7,8. Recently, such density profiles have also been used in automatic recognition of radiation induced chromosome aberrations, in particular, the recognition of dicentrics among the normal chromo- somes9. From the optical density profiles the amplitudes of the thrid through twelfth spatial spectral components were selected as features, the dicentrics were properly detected in a study involving seven irradiated human blood cells.