Endovascular treatment of wide-necked aneurysms by using two microcatheters: techniques and outcomes in 25 patients.
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BACKGROUND AND PURPOSE: The endovascular occlusion of aneurysms with unfavorable configurations such as a broad neck and an important branch from the fundus remains a technical challenge. The purpose of this study was to evaluate the radiologic and clinical results of complicated aneurysm treatment by using two microcatheters. METHODS: Twenty-five aneurysms in 25 patients were treated by using two microcatheters, from August 2001 to February 2004. Fourteen patients presented with a subarachnoid hemorrhage (SAH) and 11 had unruptured aneurysms. The aneurysms were of the basilar top (7), middle cerebral artery bifurcation (4), posterior communicating artery (4), anterior communicating artery (3), superior cerebellar artery (2), ophthalmic artery (2), and one aneurysm of each of cavernous internal carotid artery (ICA), dorsal ICA, and midbasilar artery. In 16 aneurysms (64%), the width of the aneurysm was the same or longer than the height. In 19 (76%), important branches arose from the aneurysm base, and some were even incorporated with the aneurysm fundus. The mean dome (height)-to-neck ratio was 1.23 +/- 0.37 (range, 0.65-2.33), and this was greater than or equal to 1.0 in 19 aneurysms (76%). RESULTS: All aneurysms were successfully embolized. Immediate postembolization angiography showed no residual contrast filling in eight aneurysms (32%), and some residual contrast filling in 16. The aneurysm remnants, however, were intentionally left to preserve important branches in 12 of the 16 aneurysms with incomplete occlusion. Two complications occurred, including one thromboembolic and one coil protrusion, but they were successfully resolved and produced no clinical symptoms. All patients except one showed excellent clinical outcomes. One patient revealed moderate cognitive dysfunction. During the follow-up period, no new bleeding occurred. CONCLUSION: Our experience with 25 cerebral aneurysm patients shows that the technique of using two microcatheters is feasible and safe for coil embolization of aneurysms with unfavorable configurations. Although the lack of angiographic follow-up prevents us from drawing conclusions about its effectiveness as compared with other techniques such as stent placement and balloon-neck protection, we believe that this technique offers a reliable alternative for endovascular therapy of complicated aneurysms. (+info)
Quantification of trabecular bone structure using magnetic resonance imaging at 3 Tesla--calibration studies using microcomputed tomography as a standard of reference.
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The purpose of this study is to use high-resolution magnetic resonance (MR) imaging at 3 Tesla (3T) to quantify trabecular bone structure in vitro using femoral head specimens, and to correlate the calculated structure measures with those that were determined using microcomputed tomography (microCT), the standard of reference. Fifteen cylindrical cores were obtained from fresh femoral heads after total hip arthroplasty. MR images were obtained at 3T using a transmit-receive wrist coil. High-resolution coronal images were acquired using a modified three-dimensional (3D) fast-gradient echo sequence. From these data sets two-dimensional (2D) structural parameters analogous to bone histomorphometry were derived by using both mean intercept length (MIL) methods based on the plate model and the more recent model-assumption free 3D distance-transformation (DT) methods. The parameters measured by the 2D plate model-based MIL method and the DT method included apparent (App). BV/TV (bone volume/total volume), App. Tb.Th (trabecular thickness), App. Tb.Sp (trabecular separation), and App. Tb.N (trabecular number). Identical regions of interest were analyzed in the MR images and the microCT data sets, and similar structure measures were derived. The means and standard deviations of the parameters over all slices were calculated and MR-derived measures were correlated with those derived from the microCT data sets using linear regression analyses. Structure measures were overestimated with MRI, for example, the mean App. BV/TV was 0.45 for MRI and 0.20 for microT, and the slope of the graph was 1.45. App. Tb.Th was overestimated by a factor of 1.9, whereas App. Tb.Sp was underestimated; Tb.N showed the smallest effect. Correlations between the individual parameters were excellent (App. BV/TV, r2 = 0.82; App. Tb.Sp, r2 = 0.84; App. Tb.N, r2 = 0.81), except for App.Tb.Th (r2 = 0.67). The results of this study show that trabecular bone structure measures may be obtained using 3T MR imaging. These measures, although higher than the standard of reference, show a highly significant correlation with true structure measures obtained by microCT. (+info)
A modular microfluidic architecture for integrated biochemical analysis.
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Microfluidic laboratory-on-a-chip (LOC) systems based on a modular architecture are presented. The architecture is conceptualized on two levels: a single-chip level and a multiple-chip module (MCM) system level. At the individual chip level, a multilayer approach segregates components belonging to two fundamental categories: passive fluidic components (channels and reaction chambers) and active electromechanical control structures (sensors and actuators). This distinction is explicitly made to simplify the development process and minimize cost. Components belonging to these two categories are built separately on different physical layers and can communicate fluidically via cross-layer interconnects. The chip that hosts the electromechanical control structures is called the microfluidic breadboard (FBB). A single LOC module is constructed by attaching a chip comprised of a custom arrangement of fluid routing channels and reactors (passive chip) to the FBB. Many different LOC functions can be achieved by using different passive chips on an FBB with a standard resource configuration. Multiple modules can be interconnected to form a larger LOC system (MCM level). We demonstrated the utility of this architecture by developing systems for two separate biochemical applications: one for detection of protein markers of cancer and another for detection of metal ions. In the first case, free prostate-specific antigen was detected at 500 aM concentration by using a nanoparticle-based bio-bar-code protocol on a parallel MCM system. In the second case, we used a DNAzyme-based biosensor to identify the presence of Pb(2+) (lead) at a sensitivity of 500 nM in <1 nl of solution. (+info)
Blood-on-a-chip.
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Accurate, fast, and affordable analysis of the cellular component of blood is of prime interest for medicine and research. Yet, most often sample preparation procedures for blood analysis involve handling steps prone to introducing artifacts, whereas analysis methods commonly require skilled technicians and well-equipped, expensive laboratories. Developing more gentle protocols and affordable instruments for specific blood analysis tasks is becoming possible through the recent progress in the area of microfluidics and lab-on-a-chip-type devices. Precise control over the cell microenvironment during separation procedures and the ability to scale down the analysis to very small volumes of blood are among the most attractive capabilities of the new approaches. Here we review some of the emerging principles for manipulating blood cells at microscale and promising high-throughput approaches to blood cell separation using microdevices. Examples of specific single-purpose devices are described together with integration strategies for blood cell separation and analysis modules. (+info)
Direct observation of thitherto unobservable quantum phenomena by using electrons.
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Fundamental aspects of quantum mechanics, which were discussed only theoretically as "thought experiments" in the 1920s and 1930s, have begun to frequently show up in nanoscopic regions owing to recent rapid progress in advanced technologies. Quantum phenomena were once regarded as the ultimate factors limiting further miniaturization trends of microstructured electronic devices, but now they have begun to be actively used as the principles for new devices such as quantum computers. To directly observe what had been unobservable quantum phenomena, we have tried to develop bright and monochromatic electron beams for the last 35 years. Every time the brightness of an electron beam improved, fundamental experiments in quantum mechanics became possible, and quantum phenomena became observable by using the wave nature of electrons. (+info)
A novel miniaturized flame ionization detector for portable gas chromatography.
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A novel miniaturized flame ionization detector (FID) operated by battery, which can be used as a detector in portable gas chromatography (GC) is devised and manufactured. It is characterized by the structure of building blocks, small volume, low energy consumption, and needing only two gases, which can be used for detection of hydrocarbons in portable GC. The miniaturized detector mainly includes a porous metallic diffuser plate, bugle-figuration collector, quartz capillary flame tip, and self-heated system. The miniaturized FID is easy to fabricate and assemble because of its structure of building blocks. The FID response is linear over six orders of magnitude and the detection limit of 0.518 ng for benzene, 0.430 ng for n-dodecane, 0.473 ng for naphthalene, and 0.509 ng for n-tetradecane. (+info)
IVF within microfluidic channels requires lower total numbers and lower concentrations of sperm.
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BACKGROUND: Microfluidic technology has been utilized in numerous biological applications specifically for miniaturization and simplification of laboratory techniques. We sought to apply microfluidic technology to murine IVF. METHODS: Microfluidic devices measuring 500 microm wide, 180 microm deep, and 2.25 cm in length were designed and fabricated using poly(dimethylsiloxane) (PDMS). Controls were standard centre-well culture dishes with 500 microl of media, half of which also contained PDMS as a material control. Denuded mouse oocytes were placed into microchannels or centre-well dish controls in groups of 10, then co-incubated overnight with epididymal mouse sperm at various concentrations. Fertilization was assessed and Fisher's exact test was used for statistical analysis (P < 0.05 significant). RESULTS: Fertilization rates between the two control groups (42%, no PDMS; 41%, with PDMS; not significant) were similar. Fertilization rates for denuded oocytes at standard mouse insemination sperm concentration (1 degrees 10(6) sperm/ml) was poorer in microchannels (12%) than controls (43%; P < 0.001). As insemination concentrations decreased, fertilization rates improved in microchannels with a plateau between 8 degrees 10(4) and 2 degrees 10(4) sperm/ml (4000-1000 total sperm). At these concentrations, combined fertilization rate for denuded oocytes was significantly higher in microchannels than centre-well dishes (27 versus 10%, respectively; P < 0.001), and was not significantly different from corresponding controls with a sperm concentration of 1 degrees 10(6) (37%; P = 0.06). CONCLUSIONS: Murine IVF can be conducted successfully within microfluidic channels. Lower total numbers and concentrations of sperm are required. Microfluidic devices may ultimately be useful in clinical IVF. (+info)
Electrostatic microactuators for precise positioning of neural microelectrodes.
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Microelectrode arrays used for monitoring single and multineuronal action potentials often fail to record from the same population of neurons over a period of time likely due to micromotion of neurons away from the microelectrode, gliosis around the recording site and also brain movement due to behavior. We report here novel electrostatic microactuated microelectrodes that will enable precise repositioning of the microelectrodes within the brain tissue. Electrostatic comb-drive microactuators and associated microelectrodes are fabricated using the SUMMiT V (Sandia's Ultraplanar Multilevel MEMS Technology) process, a five-layer polysilicon micromachining technology of the Sandia National labs, NM. The microfabricated microactuators enable precise bidirectional positioning of the microelectrodes in the brain with accuracy in the order of 1 microm. The microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multiunit activity. The microactuators are capable of driving the microelectrodes in the brain tissue with forces in the order of several micro-Newtons. Single unit recordings were obtained from the somatosensory cortex of adult rats in acute experiments demonstrating the feasibility of this technology. Further optimization of the insulation, packaging and interconnect issues will be necessary before this technology can be validated in long-term experiments. (+info)