The impact of the condenser on cytogenetic image quality in digital microscope system.

BACKGROUND: Optimizing operational parameters of the digital microscope system is an important technique to acquire high quality cytogenetic images and facilitate the process of karyotyping so that the efficiency and accuracy of diagnosis can be improved. OBJECTIVE: This study investigated the impact of the condenser on cytogenetic image quality and system working performance using a prototype digital microscope image scanning system. METHODS: Both theoretical analysis and experimental validations through objectively evaluating a resolution test chart and subjectively observing large numbers of specimen were conducted. RESULTS: The results show that the optimal image quality and large depth of field (DOF) are simultaneously obtained when the numerical aperture of condenser is set as 60%-70% of the corresponding objective. Under this condition, more analyzable chromosomes and diagnostic information are obtained. As a result, the system shows higher working stability and less restriction for the implementation of algorithms such as autofocusing especially when the system is designed to achieve high throughput continuous image scanning. CONCLUSIONS: Although the above quantitative results were obtained using a specific prototype system under the experimental conditions reported in this paper, the presented evaluation methodologies can provide valuable guidelines for optimizing operational parameters in cytogenetic imaging using the high throughput continuous scanning microscopes in clinical practice.

A simple method for enhancing hybridization efficiency in chromosome and array comparative genomic hybridization.

The accuracy of comparative genomic hybridization (CGH) analysis is affected by hybridization efficiency. We describe here a simple method for enhancing hybridization efficiency. The hybridization procedure is essentially the same as that of conventional methods. Hybridization solution containing denatured DNA probe mixture was applied to a metaphase chromosome slide or DNA chip slide and covered with a coverslip. In the new method, however, the slide was inverted by turning the coverslip downward prior to hybridization. We termed this method the inverted slide method. To estimate the efficiency of the new method, metaphase chromosome slides and DNA chip slides were treated by both the conventional and inverted slide methods and incubated in a moist chamber at 37°C for 12, 24, 48, and 72 h. Hybridization signals were approximately 1.5 to 2 times brighter on the slides using the inverted slide method than those using the conventional method after 48 and 72 h of incubation. Furthermore, topographical differences in fluorescence intensity were smaller in slides using the inverted-slide method than in those prepared by the conventional method. The inverted slide method is methodologically very simple and improves the resolution of CGH.

Refined characterisation of chromosome aberrations in tumours by multicolour banding and electronic mapping resources.

Acquired chromosome abnormalities in tumours often reflect pathogenetic events at the gene level. Multicolour fluorescence in situ hybridisation (FISH) with single-copy probes offers extensive possibilities to characterise chromosome breakpoints in relation to the physical map of the human genome. This approach is based on the construction of comprehensive EST- based maps, combinatorial labelling of probes, and tumour cell preparations optimised for metaphase FISH. Information from several electronically available databases is combined into an integrated physical map, to which clones carrying yeast and bacterial artificial chromosomes are anchored. Extracted DNA or PCR products from these clones are then fluorescently labelled by one or several fluors, allowing simultaneous FISH detection of multiple loci. To improve hybridisation efficiency and reduce background fluorescence, standard methods for chromosome preparation from cultured tumour cells are complemented with a prolonged trypsin treatment to obtain complete disaggregation of cells, and exposure of the metaphase spreads to detergent and saline at high temperature, followed by pepsin digestion to remove extracellular matrix and cytoplasmic debris. The resulting colour-banding allows the characterisation of chromosome abnormalities in relation to expressed sequences, even in tumours exhibiting highly complex rearrangements.

MicroMeasure: a new computer program for the collection and analysis of cytogenetic data.

The ability to identify individual chromosomes in cytological preparations is an essential component of many investigations. While several computer software applications have been used to facilitate such quantitative karyotype analysis, most of these programs are limited by design for specific types of analyses, or can be used only with specific hardware configurations. MicroMeasure is a new image analysis application that may be used to collect data for a wide variety of chromosomal parameters from electronically captured or scanned images. Unlike similar applications, MicroMeasure may be individually configured by the end user to suit a wide variety of research needs. This program can be used with most common personal computers, and requires no unusual or specific hardware. MicroMeasure is made available to the research community without cost by the Department of Biology at Colorado State University via the World Wide Web at http://www.biology.colostate.edu/MicroMeasure.

Improvements in cytogenetic slide preparation: controlled chromosome spreading, chemical aging and gradual denaturing.

BACKGROUND: Metaphase spreading is an essential technique for clinical and molecular cytogenetics. Results of classical banding techniques as well as complex fluorescent in situ hybridization (FISH) applications, such as comparative genomic hybridization (CGH) or multiplex FISH (M-FISH), are greatly influenced by the quality of chromosome spreading and pretreatment of the slide prior to hybridization. Materials and Methods Using hot steam and a metal plate with a temperature gradient across its surface, a reproducible protocol for slide preparation, aging, and hybridization was developed. RESULTS: This protocol yields good chromosome spreads from even the most difficult cell suspensions and is unaffected by the environmental conditions. Chromosome spreads were suitable for both banding and FISH techniques common to the cytogenetic laboratory. Chemical aging is a rapid slide pretreatment procedure for FISH applications, which allows freshly prepared cytogenetic slides to be used for in situ hybridization within 30 min, thus increasing analytical throughput and reducing benchwork. Furthermore, the gradually denaturing process described allows the use of fresh biologic material with optimal FISH results while protecting chromosomal integrity during denaturing. CONCLUSION: The slide preparation and slide pretreatment protocols can be performed in any laboratory, do not require specialized equipment, and provide robust results.

Image quality in digital chromosome analysis systems.

This paper reports on an investigation into the differences in image quality of different components used in a digital image processing system for chromosome analysis. As chromosome aberrations are important tools in the cloning of genes, it is important to know if the introduction of computerized analysis systems increases the risk of missing small aberrations. In this investigation the number of visible bands on a number of chromosomes has been used as a measure of quality. The images compared are microscope ocular images, photographs from a microscope built-in camera, digital images from a high and from a standard resolution camera, presented both on screen and print-out on paper. The main conclusions are that: (1) the view in the microscope ocular gives the best resolution, (2) there are risks of losing vital information using the digital image processing system for chromosome analysis, and (3) this risk is significantly reduced when using a high resolution camera.