Computer-assisted karyotyping with human interaction.

A system for machine assisted karyotyping and chromosome analysis has been developed. The system uses a drum- or TV-scanner as input device, runs provisionally in 32 K memory, and also allows human interaction on several stages. The accuracy with which banded chromosomes are karyotyped depends strongly on the type of classifier and varies from 40 up to 80%. The accuracy of the human assisted classifier (98%) comes close to that of a skilled technician (99.5%) using manual chromosomal analysis. Due to technical and memory limitations, the time necessary for the karyotyping of one cell is too long and depends on the interaction time; however karyotyping within 5 min, including human interaction, will be possible in the near future.

Model-based quantification of myocardial perfusion images from SPECT.

A system for quantitative analysis of myocardial perfusion tomograms is proposed. The system starts with an automated delineation of the total left ventricle, including possible perfusion defects, to determine the mass and shape of the myocardium. Next, polar maps or bulls-eyes are computed from the delineation, which can then be compared to reference bulls-eyes to detect perfusion defects. The proposed system differs in three main aspects from currently available bulls-eye algorithms. First, radial slices are used rather than short-axis slices. In this way three-dimensional gradient information is retained, in particular near the base and the apex of the left ventricle. Moreover, the reproducibility of this method is expected to be superior, since the interactive selection of short axis slices through the left ventricle is eliminated. Second, the left ventricle is automatically delineated using a flexible computer model in order to obtain higher reproducibility. The resulting delineation contains both mass and shape information. Third, in addition to the classic count rate bulls-eye, a mass bulls-eye is computed, which contains the myocardial mass corresponding to each bulls-eye pixel. Analysis of the count rate bulls-eye reveals perfusion defects, the quantification of the defects is carried out with the mass bulls-eye.

Delineation of ECT images using global constraints and dynamic programming.

A model-based delineation algorithm is presented. It is a flexible model fitting algorithm, approaching contour detection as an optimization problem. An objective function is introduced, which depends not only on local contour features, but also on a global shape constraint. The latter is implemented as the similarity to the instance of a parametric shape model. The algorithm optimizes both the contour points and the parameters of the model. As a result, both global and local characteristics of the contour are determined as a compromise between photometric data and prior knowledge. The method was applied to myocardial perfusion SPECT images, to delineate the entire left ventricle (endocardium and epicardium), including possible regions of reduced perfusion. By adapting the balance between the image data and the shape model, images with different characteristics can be processed, including Thallium-201 and MIBI scans.

Design of a special interpreter for the classification of human chromosomes.

The use of new staining methods and the large amount of investigations for human chromosomes has created a need for a useful automated chromosome analysis. Because of the lack of accuracy of the existing systems, a new approach is given. The problems in the different stages of the classification process are described. A comparison of the decision-statistical, syntactical, and interpretative approach is discussed. A system realization for the total karyotyping of chromosomes, based on the interpretative approach, is described in more detail. Guided by one of the models in the world model structure, a current description is recognized in a three-phase interpreter.

The plastic coupled map lattice: A novel image-processing paradigm.

Coupled map lattices (CML) can describe many relaxation and optimization algorithms currently used in image processing. We recently introduced the "plastic-CML" as a paradigm to extract (segment) objects in an image. Here, the image is applied by a set of forces to a metal sheet which is allowed to undergo plastic deformation parallel to the applied forces. In this paper we present an analysis of our "plastic-CML" in one and two dimensions, deriving the nature and stability of its stationary solutions. We also detail how to use the CML in image processing, how to set the system parameters and present examples of it at work. We conclude that the plastic-CML is able to segment images with large amounts of noise and large dynamic range of pixel values, and is suitable for a very large scale integration (VLSI) implementation.

Reconstruction of an arbitrary cross section from the serial drawings of a stereotaxic brain atlas.

A method is described for the reconstruction of arbitrary cross section from the serial line drawings of a stereotaxic brain atlas. Mathematically, the problem reduces to the intersection of a plane with a line pattern lying in another plane. However, the calculation yields a cloud of points, often confusing and unusable for the surgeon. Because it is impossible to link correctly all the calculated points in all cases [1,2], we propose a method where the number of points is drastically reduced: only regions of interest are depicted, i.e., the area where the electrode point is situated and the neighbouring regions. Instead of points, symbols are displayed, each symbol representing a different region. The efficiency of the method is shown using an atlas simulation of four intersecting spheres in the three dimensional space, Although the procedure is useful for all stereotaxic brain atlasses, a practical example is given where the poor quality of the reconstructed images does not allow good interpretation.

Angiographic localizer ring for the BRW stereotactic system.

An accessory locating device to the existing BRW stereotactic system is presented. It can be used as a reference device to locate angiographic data with respect to the BRW stereotactic system. Hence, the projection of target points onto angiograms, visible on CT scans, are easily calculated, as well as the stereotactic coordinates of a set of points (e.g., AVM) indicated on at least two angiograms. As a final result integrated images of cerebral blood vessels and an outline of tumor lesions can be generated using more sophisticated computer equipment.

Angiographic localizer for the BRW stereotactic system.

Preliminary experience with a newly constructed angiographic localizer system for use in stereotactic neurosurgery is reported. This localizer ring, mounted on the BRW head ring, allows for the transformation of target points with known stereotactic coordinates (e.g., visible on computerized tomography scans) onto angiograms, as well as the determination of stereotactic coordinates of a set of points (e.g., arteriovenous malformations) indicated on at least two angiograms.

An expert system for the labeling and 3D reconstruction of the coronary arteries from two projections.

In this paper we present a rule-based expert system for the automatic delineation and 3D reconstruction of the left coronary artery on standard RAO and LAO angiographic projections. The approach is based on the application of a general blood vessel model and on anatomical models which take into account the normal variations of the coronary artery structure. In a first step, the arteries are delineated by detecting the maximum intensity on the centerline of the vessels. Then, we label the blood vessel segments according to an anatomical model of the left coronary artery. In general, only 1-2 labels remain for each blood vessel segment. Finally, these results are used for an automatic 3D reconstruction of the left coronary artery from two projections. Results from clinical RAO and LAO angiograms will be presented.

Quantification of the degree of cell spreading of human fibroblasts by semi-automated analysis of the cell perimeter.

Cell flattening and spreading on a substratum is of major importance in cellular and developmental biology. To study the mechanisms of cell spreading, quantitative and reproducible measures of the degree of cell spreading must be available. Normal human fibroblasts, spreading on a substratum, were fixed with glutaraldehyde, stained with acridine orange and photographed (X 40) under a fluorescence microscope. The photonegatives (containing 10-30 cells) were scanned with a drum scanner and a complete picture containing 128 gray levels was constructed. Each cell contour was calculated with the use of a local threshold. The image and the superimposed cell contours were displayed on a television screen (16 gray levels) and errors were corrected interactively. With this system the spreading of normal human skin fibroblasts as a function of time could be quantified reproducibly. Compared to surface area or shape, the cell perimeter proved to be a very sensitive parameter of the degree of spreading. By using cell perimeter measurements, differences in the degree of spreading on various substrata could be quantified.

Multimedia E-mail systems for computer-assisted radiological communication.

In the film-based organization of communicating radiological results to the referring physician, the different media (text, images, graphics, voice) are separated. When using computer technology, multimedia reports containing links between these different media can be used. This changes the way radiological reports are generated, accessed, and possibly discussed. We performed experiments in a clinical setting using two different metaphors for communicating multimedia information. In the 'paper metaphor', labels in the report text are linked to annotations in selected images. In the 'slide presentation metaphor', annotated images are presented synchronously to a spoken report. With both systems additional interaction between radiologist and referring physician is supported using multimedia 'electronic mail'. The experiments indicate that multimedia does not only significantly increase the efficiency of information transfer, but also has the potential to make reporting itself more efficient. Given that the amount of image-related information keeps growing, multimedia links are a promising method to give efficient access to the most relevant information.

Design for user efficiency in a dedicated ICU viewing station.

The intensive care unit (ICU) is one application where significant benefit is expected from the use of digital technology in the acquisition, management and presentation of images. However, the potential benefits should not be outweighed by disadvantages of current digital technology. One of the bottlenecks is the efficiency of image viewing using a workstation, especially if this viewing station is implemented using affordable commonly available hardware. In this paper we describe the design concepts of a relatively low-cost but efficient viewing station for chest images, and discuss clinical experience with this system at an ICU ward. The user interface has been optimized towards the specific patterns of ICU image viewing. By anticipating user requests and preparing images during idle times of the computer, the mean image access time could be reduced by a factor of 4, while most images could be presented instantaneously. Information from the hospital information system (HIS) is exploited in the user interface, and a simplified PAC-HIS coupling has been implemented for the simultaneous presentation of images and reports.