Automatic counting of FISH spots in interphase cells for prenatal characterization of aneuploidies

Fluorescent In-Situ Hybridization (FISH) is becoming an accepted technique for identification of aneuploidies in interphase fetal cells obtained by either CVS (chorionic villus sampling) or amniocentesis. Currently the analysis is done manually by a skilled operator and is a lengthy and fatiguing process. Applied Imaging is developing an automated procedure for counting FISH spots in these samples. Spot counting involves slide preparation, probe hybridization, filter selection, FISH image acquisition, image analysis, operator verification, and analysis of count distributions. We concentrate on the tasks starting with image acquisition. The following topics are covered: selection of appropriate cells, acquisition and processing of Z-stacks of FISH images for presentation and spot counting, background removal, formation of segmentation tree and selection of spot markers, growing of spot markers by means of constrained watershed, detection of irregular spots and flagging them for the user, time and accuracy compared with manual method, and applicability to a clinical research setting.