Operation planning of correction osteotomies in 3D.

This paper discusses an operation planning system for correction osteotomies. It is based on 3D data obtained from CT/MR of the bone and it allows to perform a 3D planning. The physician can individually determine anatomical landmarks for measuring geometric parameters of the bone like length, angle and torsion angle. In a virtual scene he or she can set a single cut or can remove/insert a wedge, dissecting the bones. The bone parts can be rearranged in 3D space. Optimization routines allow that the physician only defines the position of the cut, the orientation of the cut plane, the rearrangement of the bone and the optimization for the maximal overlap of the cortical bone can be processed automatically. The system is currently in use at the Trauma department at the University of Ulm. A case study shows the results by applying this system.

[Cathi-training on virtual patients for catheter interventions]. / Cathi-training on virtual patients for catheter interventions.

In this paper we present a trainings system for catheter interventions, especially PCTAs also called ballon dilatation. Despite the large number of such interventions the education of the cardiologist is still based on learning on the patient. This means risk to the patient and additional cost. To overcome these problems we developed the CathI system (Catheter Instruction System), a realistic computerbased training system. It provides the physician with the same equipment found in a catheter laboratory, e.g. original control instruments for the flouroscopy system, syringes, catheters, and guide wires. CathI only replaces patient and C-arm by a virtual patient and a virtual x-ray system.

[Virtual reality in ophthalmological education]. / Virtuelle Realitäten für die augenchirurgische Ausbildung.

We present a computer-based medical training workstation for the simulation of intraocular eye surgery. The surgeon manipulates two original instruments inside a mechanical model of the eye. The instrument positions are tracked by CCD cameras and monitored by a PC which renders the scenery using a computer-graphic model of the eye and the instruments. The simulator incorporates a model of the operation table, a mechanical eye, three CCD cameras for the position tracking, the stereo display, and a computer. The three cameras are mounted under the operation table from where they can observe the interior of the mechanical eye. Using small markers the cameras recognize the instruments and the eye. Their position and orientation in space is determined by stereoscopic back projection. The simulation runs with more than 20 frames per second and provides a realistic impression of the surgery. It includes the cold light source which can be moved inside the eye and the shadow of the instruments on the retina which is important for navigational purposes.

Computer assisted treatment of pelvis fractures.

The presented approach is the realization of a minimal invasive treatment of pelvis fractures using the computer aided surgery (CAS). Main problem of tracking of major bone fragments after reposition is solved by implementing of 3D ultrasound to obtain intraoperative bone surfaces. Preoperative and intraoperative data sets are matched. Major fragments are tracked. The real time navigation is possible.

Computer simulation of osteotomy correction.

This paper describes a novel approach to correct osteotomy deformities of long bones using virtual reality and image processing techniques on personal computers. The discussed method allows to simulate osteotomy corrections by implementing a single cut and a rearrangement of the dissected bone parts. It allows the surgeon to directly control the pre-operative situation and the post-operative result of the simulation by comparing bone-length, angles, and torsion of the bone. In addition, he or she obtains the coordinates and angles of the planned cut relative to anatomical landmarks.

Real-time direct volume rendering in functional magnetic resonance imaging.

Direct volume rendering is a visualization method that allows display of all information hidden in three-dimensional data sets of, for example, computed tomography or magnetic resonance imaging (MRI). In contrast to commonly used surface rendering methods, these algorithms need no preprocessing but suffer from a high computational complexity. A real-time rendering system, VIRIM (Vitec: Visualization Technology GmbH, Mannheim, Germany), cuts down rendering times of minutes on normal workstations to an interactive rate of 1 second or less. The immediate visual feedback allows interactive steering of the visualization process to achieve insight into the internal three-dimensional structure of objects. Additional information is obtained by using an interactive gray-value segmentation tool that both allows segmentation of the data set according to bone, tissue, and liquor and display of multifunctional data sets (e.g., functional MRI [fMRI] data sets). Thus, real-time direct volume rendering allows segmentation and volume data processing of functional and anatomical MR data sets simultaneously. As this method can be integrated in the clinical routine, it is of great importance for real-time motion artifact detection and the interpretation of fMRI data acquired during cognitive experiments with normal subjects and psychiatric patients. Because of the free programmability of VIRIM, more complex matching procedures are currently being investigated for future implementation.

A hybrid neural and statistical classifier system for histopathologic grading of prostatic lesions.

Neural network and statistical classification methods were applied to derive an objective grading for moderately and poorly differentiated lesions of the prostate, based on characteristics of the nuclear placement patterns. A partly trained multilayer neural network was used as a feature extractor. A hybrid classifier system using a quadratic Bayesian classifier applied to these features allowed grade assignment consensus with visual diagnosis in 96% of fields from a training set of 500 fields and in 77% of 130 fields of a test set.

Gradual and random binarization of gray-scale holograms.

A new method called gradual and random binarization to binarize gray-scale holograms, based on an iterative algorithm, is proposed. The binarization process is performed gradually, and the pixels to be binarized are chosen randomly. Errors caused by this operation are spatially diffused. A comparison with other established methods based on error diffusion, direct binary search, and iterative stepwise quantization shows that the gradual and random binarization method achieves a very good compromise between computational complexity and reconstruction quality. Optical reconstructions are presented.

Multiprocessor and memory architecture of the neurocomputer SYNAPSE-1.

A general purpose neurocomputer, SYNAPSE-1, which exhibits a multiprocessor and memory architecture is presented. It offers wide flexibility with respect to neural algorithms and a speed-up factor of several orders of magnitude--including learning. The computational power is provided by a 2-dimensional systolic array of neural signal processors. Since the weights are stored outside these NSPs, memory size and processing power can be adapted individually to the application needs. A neural algorithms programming language, embedded in C(+2) has been defined for the user to cope with the neurocomputer. In a benchmark test, the prototype of SYNAPSE-1 was 8000 times as fast as a standard workstation.

Radiographic pulmonary changes of gastro-oesophageal reflux disease in elderly patients.

The aim of this study was to investigate the association of gastro-oesophageal reflux disease (GORD) with radiographic pulmonary changes. One hundred and thirty-seven patients aged over 60 years referred for endoscopy for abdominal symptoms were included in the study. In patients with any suspicion of GORD (n = 95), 24-hour oesophageal pH monitoring was carried out. All the patients were interviewed before the examinations. Chest radiography was performed in all patients. Odds ratio of respiratory symptoms was 8.7 (95% confidence interval 3.4-22.4) in patients with total reflux time of more than 10% compared with those who had total reflux time of less than 10%. In chest radiography, bilateral pleural adhesions and thickenings and bilateral parenchymal scars were significantly more common in patients with, than in those without, regurgitation or large hiatal openings. The occurrence of bilateral scars and pleural thickenings increased with the extent of gastro-oesophageal reflux in pH monitoring. Odds ratios of bilateral pleural thickening and pulmonary scars were 3.1 (95% confidence interval 0.8-11.5) and 5.8 (1.1-29.6) in patients with total reflux time over 10%, compared with patients who had normal total reflux time. The findings indicate that respiratory involvement is a characteristic feature of GORD in elderly patients.

Real-time multiprocessing of slit scan chromosome profiles.

The multiprocessor NERV and its application to slit scan flow cytometry is described. Up to 320 processors and 640 MBytes of RAM may be used in one VME crate, providing a computing power of less than or equal to 1300 MIPS. The multiprocessor is controlled by a host computer that provides a friendly user interface and comfortable program development tools. All hardware and software has been tested on a prototype NERV system with 5 processors. For a real-time classification/detection of normal and aberrant chromosomes, the centromeric index or the number of centromeres are computed or specifically labeled DNA sequences are detected. The program is partitioned into 60 tasks that can be executed concurrently. A total analysis time of less than 600 microseconds including system overhead will be achieved according to timing measurements which have been done for all individual tasks.

Biological dosimetry by chromosome aberration scoring with parallel image processing with the Heidelberg POLYP Polyprocessor system.

Chromosome aberrations in human peripheral blood are recognized parameters of cellular damage and are used as indicators of exposure to ionizing radiation. In order to reach the low dose range, up to 10,000 metaphase cells each consisting of 46 chromosomes have to be analysed for each radiation exposed person. In order to perform this task within reasonable time limits the application of the Heidelberg POLYP Polyprocessor is considered. The POLYP consists of a number of processor modules and several global memory modules which are interconnected by a multi-common-bus for parallel data transfers and a multiple synchronization bus for processor/task-scheduling. The system is designed for handling large amounts of data in real time as is typical for image processing applications.

Potassium chloride preparations and fecal blood loss. A parallel study with a 10 percent solution and a non-enteric-coated waxy-matrix tablet.

Concentrated potassium chloride produces ulceration of the gastrointestinal mucosa. Dilute solutions are frequently not acceptable to the patient. A tablet containing potassium chloride crystals suspended in a waxy matrix has been developed to avoid these drawbacks. We measured fecal blood loss by a radioactive chromium technique on 20 subjects during five days while they were given potassium chloride, 40mEq/day; ten subjects took a 10% solution; the others the waxy-matrix tablet. Fecal blood loss did not differ significantly between these groups. Mean fecal blood losses in both groups were slightly increased during the potassium chloride administration but never exceeded acceptable normal limits.