Systematic Review of fMRI Compatible Devices: Design and Testing Criteria.

Functional Magnetic Resonance Imaging (fMRI) is at present one of the most used methodologies for functional brain exploration, both in clinical and research settings. fMRI can noninvasively measure neural activity by using specific experimental paradigms. Often, these paradigms require the stimulation of the subject to perform sensorimotor tasks: in the past, the stimuli have been administered manually for investigating fundamental aspects of tactile perception and somatosensory processing. Nowadays, the use of mechatronic devices to stimulate the subject during fMRI studies is growing, also to assure reproducibility, control, and monitoring of task performances. For these reasons, researchers are interested in designing interfaces to be used inside the MRI environment during fMRI studies. For the design of every new device safety and compatibility constraints, imposed by the presence of high static magnetic field, switching magnetic gradients and radiofrequency electromagnetic pulses, must be satisfied. Moreover, it should be considered that functional imaging sequences are even more sensitive to perturbations of the magnetic field than MRI standard diagnostic sequences. Despite several existing devices for use in fMRI studies, an extensive review is still lacking. Our survey aims to introduce into the challenges imposed on the development of fMRI-compatible devices. The current state of the art of compatible devices in fMRI will be presented, pointing out the functionalities and peculiarities of various kinds of device. A particular emphasis will be placed on the tests for the evaluation of fMRI compatibility. This review will be useful both for designers of devices to be used in fMRI studies and for neuroscientists that are having to design fMRI experimental paradigm, and therefore require an overview of existing instruments, but also a knowledge of the benefits and criticism arising from their use.

Near infrared image processing to quantitate and visualize oxygen saturation during vascular occlusion.

The assessment of microcirculation spatial heterogeneity on the hand skin is the main objective of this work. Near-infrared spectroscopy based 2D imaging is a non-invasive technique for the assessment of tissue oxygenation. The haemoglobin oxygen saturation images were acquired by a dedicated camera (Kent Imaging) during baseline, ischaemia (brachial artery cuff occlusion) and reperfusion. Acquired images underwent a preliminary restoration process aimed at removing degradations occurring during signal capturing. Then, wavelet transform based multiscale analysis was applied to identify edges by detecting local maxima and minima across successive scales. Segmentation of test areas during different conditions was obtained by thresholding-based region growing approach. The method identifies the differences in microcirculatory control of blood flow in different regions of the hand skin. The obtained results demonstrate the potential use of NIRS images for the clinical evaluation of skin disease and microcirculatory dysfunction.

[Dirofilaria repens-infection in a dog in central Germany without any history of travel]. / Dirofilaria-repens-Befall bei einem Hund aus Mitteldeutschland ohne Reisevorbericht. Ein Fallbericht.

A mixed breed dog was presented with dyspnoea and fever. In the purulent thorax aspirate, a nematode larva was found during the cytological examination. Subsequent diagnostic tests revealed an infection with Dirofilaria repens, which was probably acquired autochthonously in central Germany. Moxidectin was administered every 4 weeks for 6 months and shown to be effective as indicated by subsequent blood examinations. This case report shows that infection with Dirofilaria repens is possible in Germany and can be treated successfully.

An electrodeless system for measurement of liquid sample dielectric properties in radio frequency band.

An electrodeless measurement system based on a resonant circuit is proposed for the measurement of dielectric properties of liquid samples at RF (radio frequency). Generally, properties as dielectric constant, loss factor and conductivity are measured by parallel plate capacitor cells: this method has several limitations in the case of particular liquid samples and in the range of radiofrequencies. Our method is based on the measurements of resonance frequency and quality factor of a LC resonant circuit in different measuring conditions, without and with the liquid sample placed inside a test tube around which the home made coil is wrapped. The measurement is performed using a network analyzer and a dual loop probe, inductively coupled with the resonant circuit. One of the advantages of this method is the contactless between the liquid sample and the measurement electrodes. In this paper the measurement system is described and test measurements of conventional liquids dielectric properties are reported.

A compatible electrocutaneous display for functional magnetic resonance imaging application.

In this paper we propose an MR (magnetic resonance) compatible electrocutaneous stimulator able to inject an electric current, variable in amplitude and frequency, into the fingertips in order to elicit tactile skin receptors (mechanoreceptors). The desired goal is to evoke specific tactile sensations selectively stimulating skin receptors by means of an electric current in place of mechanical stimuli. The field of application ranges from functional magnetic resonance imaging (fMRI) tactile studies to augmented reality technology. The device here proposed is designed using safety criteria in order to comply with the threshold of voltage and current permitted by regulations. Moreover, MR safety and compatibility criteria were considered in order to perform experiments inside the MR scanner during an fMRI acquisition for functional brain activation analysis. Psychophysical laboratory tests are performed in order to define the different evoked tactile sensation. After verifying the device MR safety and compatibility on a phantom, a test on a human subject during fMRI acquisition is performed to visualize the brain areas activated by the simulated tactile sensation.

Human blood monocytes: characterization of negatively selected human monocytes and their suspension cell culture derivatives.

Normal human monocytes were negatively selected from leucapheresis cell suspensions by countercurrent centrifugation-elutriation in high yield with a mean purity of 93.5%. The combination of the novel methods of negative cell selection and suspension cell culture has provided the opportunity to study serially over several days the morphologic and functional changes of monocytes from a single donor as they matured in culture to typical macrophages. Human monocytes nearly double in size during the first week of culture, experiencing near daily increases in cell volume. This was associated with changes in the ultrastructure of these cells, including the development of numerous small knob-like projections on the cell membrane and the proliferation of microtubules and filamentous structures within the cell cytoplasm during the first 6 days of culture. Peroxidase activity declined during the first 4 days of culture, whereas 5'-nucleotidase activity was acquired during the first 48 h of culture. Lysozyme activity in the cultures increased form day 2 to day 6 of culture. The phagocytic capacity of monocytes for igG-coated erythrocytes increased dramatically during the first week of culture, but the cytotoxic capability of monocytes against similar targets in an antibody-dependent cytotoxicity assay declined to nearly half of base-line levels by day 2 of culture and remained at this diminished level during subsequent days of culture.

Liquid preservation of canine granulocytes obtained by counterflow centrifugation-elutriation.

Granulocytes (PMN) were isolated from 120 ml of canine whole blood by a modification of the counterflow centrifugation-elutriation technique. Isolated cell suspensions of 96% granulocytes and 4% mononuclear leukocytes with a 21:1 PMN/RBC ratio were stored at 4 degrees C in 4:4:2 medium consisting of four parts HBSS minus Ca++ and Mg++, four parts MEM, twp parts autologous plasma, and 20 microgram/ml gentamicin for 15 days. Granulocytes were stored at concentrations of approximately 4 x 10(6) PMN/ml in polypropylene centrifuge tubes. The stored granulocyte suspensions were assayed in vitro 0, 1, 4, 8, and 15 days to monitor chemotaxis, bacterial growth inhibition, O2 consumption associated with phagocytosis, and enzyme activities. Cell volume analysis was used to evaluate cellular integrity of the liquid-stored granulocytes. Canine granulocytes isolated by the modified dilution technique of counterflow centrifugation-elutriation can be preserved for up to 15 days with 77 +/- 6% granulocyte survival with maintenance of morphological and organelle integrity, as well as retention of in vitro functions of recognition, migration, phagocytosis, and killing of gram-negative bacteria.

Improved technique for increased granulocyte recovery from canine whole blood samples by counterflow centrifugation-elutriation. I. In vitro analysis.

Granulocytes were isolated from 120 ml of canine whole blood by a modification in counterflow centrifugation-elutriation technique. The leukocytes were concentrated in a buffy coat fraction and diluted to a fixed RBC density prior to entry into the rotor. Overall recovery of granulocytes from canine whole blood averaged 82% with 96% purity from contaminating mononuclear leukocytes. The purified cellular fraction was assayed in vitro to monitor O2 consumption, chemotaxis, bacterial growth inhibition, and enzyme activities. Cellular integrity was monitored by scanning and transmission electron microscopy as well as by cell volume analysis. The data suggest that the granulocytes isolated by counterflow centrifugation-elutriation suffered no noticeable morphological damage or loss of function in terms of recognition of a toxic agent, migration, phagocytosis, or bactericidal capacity. Granulocytes isolated by counterflow centrifugation-elutriation may be physiologically more active than cells obtained by filtration leukapheresis, continuous-flow centrifugal leukapheresis or discontinuous flow centrifugation both in vitro and in vivo.