AUTOMATED SCORING OF MICRONUCLEI IN BINUCLEATED HUMAN-LYMPHOCYTES

Manual and automatic scoring of micronuclei (MN) in binucleated human lymphocytes (BNC) were compared after irradiation of whole blood sampl es. The blood samples were irradiated with X-ray doses (1, 2 or 3 Gy) and stained with Giemsa. The preparation technique was optimized in su ch a way that acceptable conditions (cell density, contrast) were obta ined for both scoring procedures. To estimate the quality of automatic micronucleus detection, two researchers who had different experience in scoring MN (6 months and 5 years) analysed the samples independentl y from each other. Automatic scoring was carried out with a digital im age analysis system and the recognition procedure was divided into two parts. The BNC positions were detected with low microscope magnificat ion (100x), and the recognition of micronuclei within the cytoplasm of the classified BNC was carried out at high magnification (630x). A fu zzy logic classification system as well as two different segmentation steps (preclassification and postclassification) made it possible that about 94% of all automatically recognized BNC were classified correct ly). On the other hand, the classification system was optimized in suc h a way that false positive decisions were minimized (95% of automatic ally recognized micronuclei were classified correctly). Failure to rec ognize micronuclei (8.5%-25% false negatives) was mainly due to extrem ely small micronuclei, poor contrast with respect to the cytoplasm, an d aggregation of micronuclei especially at higher doses.