Design of a virtual data shelf to effectively explore a large database of 3D medical surface models in VR.

PURPOSE: Medical researchers deal with a large amount of patient data to improve future treatment decisions and come up with new hypotheses. To facilitate working with a large database containing many patients and parameters, we propose a virtual data shelf, displaying the 3D anatomical surface models in an immersive VR environment. METHODS: Thereby, different functionalities such as sorting, filtering and finding similar cases are included. To provide an appropriate layout and arrangement of 3D models that optimally supports working with the database, three layouts (flat, curved and spherical) and two distances are evaluated. A broad audience study with 61 participants was conducted to compare the different layouts based on their ease of interaction, to get an overview and to explore single cases. Medical experts additionally evaluated medical use cases. RESULTS: The study revealed that the flat layout with small distance is significantly faster in providing an overview. Applying the virtual data shelf to the medical use case intracranial aneurysms, qualitative expert feedback with two neuroradiologists and two neurosurgeons was gathered. Most of the surgeons preferred the curved and spherical layouts. CONCLUSION: Our tool combines benefits of two data management metaphors, resulting in an efficient way to work with a large database of 3D models in VR. The evaluation gives insight into benefits of layouts as well as possible use cases in medical research.

A two-step risk assessment method for radiofrequency ablations of spine metastases.

BACKGROUND: Spine metastases (MTS) can be treated via Radiofrequency Ablation (RFA) electrodes. To bring these electrodes into vertebral MTS, pathways have to be created. This can be done via transpedicular hammering or drilling. However, this is challenging due to spatial constraints, and because MTS can alter bone density considerably. METHOD: In this work a two-step method is presented that intends to offer cognitive and physical assistance. Step 1 comprises two visualization methods that depict safety margins between and in risk structures. For Step 2, the correlation between Hounsfield Units (HUs) and drilling forces was analyzed to support manual and robot-assisted RFAs. RESULTS: In-depth descriptions of two clinical cases and detailed feedback from the local clinic of neuroradiology are used to present the capabilities of the proposed method. Furthermore, a stiffness criterion is presented to predict drilling force changes from the local distribution and homogeneity of HUs with an inaccuracy of less than 1 mm. CONCLUSIONS: The combination of visualization and drilling force prediction shows potential to support manual and robot-assisted spine RFAs. However, limitations have to be addressed in the future. For example, it has to be carefully evaluated to which extent the proposed method can speed up the planning process and increase intervention safety.

Does the DSA reconstruction kernel affect hemodynamic predictions in intracranial aneurysms? An analysis of geometry and blood flow variations.

BACKGROUND: Computational fluid dynamics (CFD) blood flow predictions in intracranial aneurysms promise great potential to reveal patient-specific flow structures. Since the workflow from image acquisition to the final result includes various processing steps, quantifications of the individual introduced potential error sources are required. METHODS: Three-dimensional (3D) reconstruction of the acquired imaging data as input to 3D model generation was evaluated. Six different reconstruction modes for 3D digital subtraction angiography (DSA) acquisitions were applied to eight patient-specific aneurysms. Segmentations were extracted to compare the 3D luminal surfaces. Time-dependent CFD simulations were carried out in all 48 configurations to assess the velocity and wall shear stress (WSS) variability due to the choice of reconstruction kernel. RESULTS: All kernels yielded good segmentation agreement in the parent artery; deviations of the luminal surface were present at the aneurysm neck (up to 34.18%) and in distal or perforating arteries. Observations included pseudostenoses as well as noisy surfaces, depending on the selected reconstruction kernel. Consequently, the hemodynamic predictions show a mean SD of 11.09% for the aneurysm neck inflow rate, 5.07% for the centerline-based velocity magnitude, and 17.83%/9.53% for the mean/max aneurysmal WSS, respectively. In particular, vessel sections distal to the aneurysms yielded stronger variations of the CFD values. CONCLUSIONS: The choice of reconstruction kernel for DSA data influences the segmentation result, especially for small arteries. Therefore, if precise morphology measurements or blood flow descriptions are desired, a specific reconstruction setting is required. Furthermore, research groups should be encouraged to denominate the kernel types used in future hemodynamic studies.

Evolution of antimicrobial resistance of Acinetobacter baumannii in a university hospital.

AIMS: To investigate the susceptibility pattern and the molecular epidemiology of Acinetobacter baumannii isolates in two periods (1994-1996 and 2004-2007) in Londrina University Hospital. METHODS AND RESULTS: Antimicrobial susceptibility of 150 A. baumannii isolates was assessed by disc diffusion and agar dilution methods. Genetic similarity amongst the isolates was evaluated by ERIC-PCR. Resistance of A. baumannii to carbapenems increased from 2% (1994-1996) to 73% (2004-2007). Thirty-eight clones were detected. CONCLUSIONS: The results of the study suggest that the high prevalence of carbapenem resistance amongst Acinetobacter baumannii organisms in this institution is not caused by the spread of a predominant clone. SIGNIFICANCE AND IMPACT OF THE STUDY: This work reinforces the importance monitoring antimicrobial susceptibility rates.

Drosophila brain development: closing the gap between a macroarchitectural and microarchitectural approach.

Neurobiologists address neural structure, development, and function at the level of "macrocircuits" (how different brain compartments are interconnected; what overall pattern of activity they produce) and at the level of "microcircuits" (how connectivity and physiology of individual neurons and their processes within a compartment determine the functional output of this compartment). Work in our lab aims at reconstructing the developing Drosophila brain at both levels. Macrocircuits can be approached conveniently by reconstructing the pattern of brain lineages, which form groups of neurons whose projections form cohesive fascicles interconnecting the compartments of the larval and adult brain. The reconstruction of microcircuits requires serial section electron microscopy, due to the small size of terminal neuronal processes and their synaptic contacts. Because of the amount of labor that traditionally comes with this approach, very little is known about microcircuitry in brains across the animal kingdom. Many of the problems of serial electron microscopy reconstruction are now solvable with digital image recording and specialized software for both image acquisition and postprocessing. In this chapter, we introduce our efforts to reconstruct the small Drosophila larval brain and discuss our results in light of the published data on neuropile ultrastructure in other animal taxa.

[BiPAP therapy of respiratory disorders in patients with congenital neuromuscular diseases]. / BiPAP-Therapie von Atmungsstörungen bei Patienten mit angeborenen neuromuskulären Erkrankungen.

BACKGROUND: Patients with hereditary generalized neuromuscular diseases develop respiratory failure and decreased maximal inspiratory pressure (Pi max) due to both, involvement of respiratory muscles in the disease and secondary spine- and thorax-deformity. In recent years mechanical respiratory support was done mostly by hyperbaric pressure ventilation when the patients become hypercapnic during daytime. However, polysomnographic investigations have shown that despite normal ventilation during daytime, severe respiratory failure might be detectable only during sleep. PATIENTS AND METHODS: Fourty patients with hereditary generalized neuromuscular diseases were analyzed using polysomnographic analyses and lung function tests (4-channel-ECG,2-channel-ECG, EOG, respiratory parameters, continuous oxygen saturation measurement and capillary blood gas analyses during sleep). Patients with need of ventilatory support during sleep were treated using bilevel positive airway pressure ventilation (BiPAP). RESULTS: Twenty patients revealed severe sleep related breathing disorders and were therefore treated by BiPAP. All showed normalisation or substantial improvement during BiPAP-therapy except two patients with persistent daytime symptoms. During follow-up (6 to 38 months) 3 patients died (cardiomyopathy, pulmonary embolism, pneumonia). The most important side effect of BiPAP-therapy was pressure marks due to the masks. CONCLUSIONS: BiPAP is useful for treatment of sleep related respiratory failure in patients with hereditary generalized neuromuscular diseases.

[Use of microcomputers in polysomnography]. / Einsatz von Mikrocomputern bei der Polysomnographie.

Constantly falling prices and increasing power combine to make the personal computer an attractive alternative to established recording devices for use in polysomnography. Apart from its price advantage, digital recording of psychophysiological signals offers the possibility of selective display (compression and zooming to parts of special interest), and also semi-automatic evaluation. In order to be able to feed the data acquired in the sleep laboratory into the computer, an interface for signal matching, an analog/digital converter, and suitable software, are required. In order to reduce the wealth of data to the clinically relevant (and, in the last resort, also manageable) amount, preprocessing hardware, such as EEG filters, snore detectors, etc., are required. The system we recommend comprises individual hardware, modules for the pickup of physiological signals, and flexibly combinable software routines that permit adaptation to any future expansions of changing medical problems.