Nicolaos A. Mouravliansky

Automatic retinal image registration scheme using global optimization techniques

Retinal image registration is commonly required in order to combine the complementary information in different retinal modalities. In this paper, a new automatic scheme to register retinal images is presented and is currently tested in a clinical environment. The scheme considers the suitability and efficiency of different image transformation models and function optimization techniques, following an initial preprocessing stage. Three different transformation models-affine, bilinear and projective-as well as three optimization techniques-downhill simplex method, simulated annealing and genetic algorithms-are investigated and compared in terms of accuracy and efficiency. The registration of 26 pairs of fluoroscein angiography and indocyanine green chorioangiography images with the corresponding red-free retinal images, showed the superiority of combining genetic algorithms with the affine and bilinear transformation models. A comparative study of the proposed automatic registration scheme against the manual method, commonly used in clinical practice, is finally presented showing the advantage of the proposed automatic scheme in terms of accuracy and consistency.

DIAGNOSIS: A Telematics-Enabled System for Medical Image Archiving, Management, and Diagnosis Assistance

In this paper, a modular system for medical image archiving, management, diagnosis support, and telematic cooperation is presented. The system provides digital imaging and communications in medicine (DICOM)-compatible tools for digital image processing and database management of medical images. The software features algorithms for preprocessing, manual or semi-automatic segmentation, automatic calculation of geometrical/size characteristics, and 3-D visualization of organs or selected regions of interest. Additionally, the system incorporates a database where patient data and information can be stored and retrieved. Access to the database is only permitted to authorized users. The user-friendly interface makes the software handy and accessible to clinicians, whereas the telematic components allow collaboration with remote experts. The pilot system incorporates a computer-aided diagnosis module aiming at providing support in the diagnosis of focal liver lesions from computed tomography images.

MR functional cardiac imaging: segmentation, measurement and WWW based visualisation of 4D data

Abstract This paper considers the problem of ventricular segmentation and visualisation from dynamic (4D) MR cardiac data covering an entire patient cardiac cycle, in a format that is compatible with the web. Four different methods are evaluated for the process of segmentation of the objects of interest: The K-means clustering algorithm, the fuzzy K-means (FKM) algorithm, self-organizing maps (SOMs) and seeded region growing algorithm. The technique of active surface is then subsequently applied to refine the segmentation results, employing a deformable generalised cylinder as geometric primitive. The final ventricular models are presented in VRML 2.0 format. The same process is repeated for all the 3D volumes of the cardiac cycle. The radial displacement between end systole and end diastole is calculated for each point of the active surface and is encoded in colour on the VRML vertex, using the RGB colour model. Using the VRML 2.0 specifications, morphing is performed showing all cardiac phases in real time. The expert has the ability to view the objects and interact with them using a simple internet browser. Preliminary results of normal and abnormal cases indicate that very important pathological situations (such as infarction) can be visualised and thus easily diagnosed and localised with the assistance of the proposed technique.

DIAGNOSIS: A Telematics Enabled System for Medical Image Archiving, Management and Diagnosis Assistance

In this paper, a modular system for medical image archiving, management, diagnosis support, and telematic cooper- ation is presented. The system provides digital imaging and com- munications in medicine (DICOM)-compatible tools for digital image processing and database management of medical images. The software features algorithms for preprocessing, manual or semi-automatic segmentation, automatic calculation of geomet- rical/size characteristics, and 3-D visualization of organs or se- lected regions of interest. Additionally, the system incorporates a database where patient data and information can be stored and retrieved. Access to the database is only permitted to authorized users. The user-friendly interface makes the software handy and accessible to clinicians, whereas the telematic components allow collaboration with remote experts. The pilot system incorporates a computer-aided diagnosis module aiming at providing support in the diagnosis of focal liver lesions from computed tomography images.

Combining a morphological interpolation approach with a surface reconstruction method for the 3-D representation of tomographic data

Abstract In this paper, a new interpolation scheme, based on Mathematical Morphology and a modified Marching Cubes (MC) Algorithm to reconstruct 3-D anatomical structures is presented. The proposed interpolation technique is implemented using morphological operations and incorporates a distance function to improve the computational effectiveness of the technique. The morphological interpolation technique is compared to an existing shape based interpolation method and its advantages include superiority capability on handling various cases such as the branching and holes problem (appearance and disappearance of information) and more accurate volume estimation. Furthermore, the morphological technique is companied with a 3-D reconstruction algorithm capable of representing any anatomical structure from real 3-D medical data. Introducing a novel general rule, the algorithm triangulates all standard cube configurations introduced from the standard MC algorithm, without producing topologically incoherent surfaces or holes. Finally, the technique is implemented in JAVA and its output is in VRML 1.0 format; therefore it can be executed over the internet and implemented for telemedicine applications.

A simplified simulation model and virtual reality visualization of tumour growth in vitro

Abstract The aim of this paper is to demonstrate the impact that modern visualization techniques can have on the simulation of biological processes such as tumour growth. Therefore, a simplified three-dimensional cytokinetic simulation model of tumour growth in vitro has been developed. Results concerning the development of a small cell lung cancer (SCLC) tumour spheroid in cell culture have been obtained and their behaviour has been compared with both published data and laboratory experience. A special visualization system allowing real time surface and volume rendering on inexpensive computer hardware has been proposed. Its application to the model has led to a spectacular three-dimensional visualization of both the external and the internal structure of a growing tumour spheroid.

Image Registration Based on Lifting Process: An Application to Digital Subtraction Radiography

In this paper, a digital subtraction radiology scheme is presented based on a new method for the automatic registration of dental radiographs acquired with or without rigorous a priori standardization. The scheme is comprised of an automatic registration method and a subtraction process. The proposed registration method can be considered as an object-based registration method without imposing the prerequisite of image segmentation in order to detect the boundary of the objects of interest or the automatic detection of matching landmarks. This is achieved by augmenting the dimensionality of the problem from two-dimensional gray-level matching to three-dimensional surface matching using the process of lifting in combination with a surface-matching technique. The pseudo three-dimensional affine transformation that matches the lifted images incorporates advantageous characteristics including spatial alignment of the surfaces, anisotropic correction of brightness/contrast differences, and stable convergence of the similarity function to its optimal value. The performance of the proposed automatic registration method is assessed against a manual method based on the projective transformation. The qualitative and quantitative assessments of the experiments have shown advantageous performance of the proposed automatic registration method against the manual one. Finally, the proposed registration method has been further improved in terms of execution time by the implementation of a surface decimation process

From raw data to WWW compatible visualization and manipulation: imaging human electric potentials

Abstract This paper describes a pilot system that acquires images of the electric potentials within the human body and stores the results in a format accessible and visualizable through the WWW. The proposed system uses a system of external electrodes to acquire measurements of electric potentials at the level of the skin, followed by an algorithm that reconstructs the value of the electric potential in the interior of the human body, thus producing a three-dimensional (3D) image. The main aspects of the reported work is the visualization of the results in such a way that the acquired information can be imaged through the WWW so that the diagnostically useful information can be maximized. For this reason, the voxels of the acquired electric image are labeled using a conventional CT image from the same patient whereas a triangulation algorithm (marching cubes — MC) is used to create the VRML output for information visualization.