Identification of electron beam vibration sources by separation of magnetic distortion from electric distortion on scanning electron microscope imaging.

Different types of distortions in scanning electron microscopy require different methods of their elimination, and therefore influence of these types on particular elements of the SEM system should be known. The proposed method allows for separation of the direct influence of the magnetic field on the electron beam in the SEM chamber from its influence in the SEM column and from the distortions generated in the SEM scanning block. For this purpose, a series of distorted images is registered for several working distances (between the final aperture of the electron column and the specimen) and for several energies of the electrons. Magnitudes of the distortions are measured on these images. For each applied electron energy, the dependence of the results versus the working distance is approximated with the second-order polynomial function. The analysis of the polynomial coefficients allows for the separation of the above-mentioned kinds of distortions. The presented method enables a selection of the most efficient solution to the distortions reduction. It utilizes the SEM itself and does not need any additional equipment.

Elimination of scanning electron microscopy image periodic distortions with digital signal-processing methods.

Electromagnetic interference is one of the main distortion sources in scanning electron microscopy. Electromagnetic interference-generated scanning electron microscopy image distortions are usually visible as edge blur (at low scan rates) or vibration (at high scan rates). Hardware solutions to this problem, e.g. electrostatic and magnetic shielding, are expensive and, in some cases, difficult to implement. The current investigations led to a significant decrease in the periodic distortions by a novel adaptation of software-based digital signal processing to scanning electron microscopy problems, without any hardware modification.

Isolated intracranial infection with Mycobacterium avium complex.

UNLABELLED: Mycobacterium avium-M. complex (MAC) has been linked to devastating respiratory and systemic illnesses in patients, especially in those who are immunosuppressed. The purpose of this study is to describe a case of isolated central nervous system (CNS) infection with MAC. This is a single case report of a patient with isolated intracranial mycobacterial infection. SETTING: the patient was treated and the immunohistochemical investigations were undertaken at the National Institutes of Health in Bethesda, Maryland, USA. INTERVENTION: the patient initially was treated with a cocktail of antimycobacterial medications. However, because his disease was refractory, he underwent a suboccipital craniotomy and evacuation of his cerebellar mass. The patient was determined to have a low production of interferon-gamma (INF-gamma) and tumor necrosis factor-alpha (TNF-alpha) when compared to normal values. Despite extensive radiographic imaging studies and biopsies, there was no evidence of another focus of MAC infection in this patient. We conclude that intracranial infectious lesions in patients such as ours should be treated with conventional systemic antibiotic regimens as the first-line of therapy. We suggest neurosurgical intervention in medically refractory cases of intracranial infections.

Effects of nitric oxide on reactive oxygen species production and infarction size after brain reperfusion injury.

OBJECTIVE: Deleterious effects of strokes may be ameliorated when thrombolysis (i.e., with recombinant tissue plasminogen activator) restores circulation. However, reperfusion injury, mediated by oxygen free radicals (reactive oxygen species [ROS]), may limit the benefits of recombinant tissue plasminogen activator treatment. We hypothesized that, during reperfusion, exogenous nitric oxide (NO) would reduce stroke size by quenching ROS. METHODS: To investigate this hypothesis, we used two in vivo ischemia-reperfusion models, i.e., autologous cerebral embolism in rabbits and filament middle cerebral artery occlusion in rats. Using these models, we measured ROS levels (rabbit model) and stroke volumes (rat model) in response to transient ischemia, with and without intracarotid administration of ultrafast NO donor proline NO (proliNO). RESULTS: In the rabbit cerebral embolism model, intracarotid administration of proliNO (10(-6) mol/L) (n = 6) during reperfusion decreased free radical levels from 538 +/- 86 nmol/L in the vehicle-treated group (n = 7) to 186 +/- 31 nmol/L (2,3'-dihydroxybenzoic acid; P < 0.001) and from 521 +/- 86 nmol/L (n = 7) to 201 +/- 39 nmol/L (2,5'-dihydroxybenzoic acid; P < 0.002). In the rat middle cerebral artery occlusion model, intracarotid administration of proliNO (10(-5) mol/L) (n = 10) during reperfusion reduced the brain infarction volume from 256 +/- 48 mm3 in the vehicle-treated group (n = 8) to 187 +/- 41 mm3 (P < 0.005). In both experimental groups, intracarotid infusion of proliNO did not affect regional cerebral blood flow, mean arterial blood pressure, or brain and body temperatures. CONCLUSION: The beneficial effects of early restoration of cerebral circulation after cerebral ischemia were enhanced by intracarotid infusion of proliNO, most likely because of ROS scavenging by NO. These findings suggest the possibility of preventive treatment of reperfusion injury using NO donors.

Neuroprotection by the stable nitroxide Tempol during reperfusion in a rat model of transient focal ischemia.

OBJECT: The use of thrombolytic agents in the treatment of stroke has yielded surprisingly modest success, possibly because of reperfusion injury mediated by reactive oxygen species (ROS). Therefore, scavenging ROS may be of therapeutic value in the treatment of stroke. Nitroxides are low-weight superoxide dismutase mimics, which allows them to act as cell-permeable antioxidants. In this study the nitroxide 4-hydroxy-2,2,6,6,-tetramethylpiperidine-1-oxyl (Tempol) is investigated to determine its ability to reduce reperfusion injury. METHODS: Male Sprague-Dawley rats weighing between 280 g and 350 g underwent middle cerebral artery occlusion with an intraluminal suture for 60 minutes. Regional cerebral blood flow, blood pressure, cerebral temperature, and rectal temperature were monitored during the procedure. After reperfusion, the animals were randomized to groups receiving blinded intravenous administration of either Tempol (10 mg/kg; eight animals) or vehicle (eight animals) over the first 20 minutes of reperfusion (Study I). In a second study to determine dose dependency, animals were randomized to groups receiving Tempol (20 mg/kg; eight animals), low-dose Tempol (5 mg/kg; eight animals), or vehicle (eight animals; Study II). The rats were killed after 4 hours of reperfusion, and brain sections were stained with 2,3,5 triphenyltetrazolium chloride. Infarct volumes were measured using digital imaging. Animals receiving Tempol had significantly reduced infarct volumes at doses of 20 mg/kg and 10 mg/kg compared with controls (49.01+/-18.22% reduction [p = 0.003] and 47.47+/-34.57 [p = 0.02], respectively). No significant differences in the physiological variables measured were observed between groups. CONCLUSIONS: Tempol provides significant neuroprotection after reperfusion in a rat model of transient focal ischemia. These results support the importance of ROS in reperfusion injury and encourage further study of this molecule as a therapeutic agent following thrombolysis.

Improved investigation of portal-hepatic veins by echo-enhanced Doppler sonography.

Microbubbles of air released from a galactose vehicle (Levovist) amplify the intensity of Doppler signals. They survive both pulmonary and systemic capillary passage, leading to echo enhancement in the entire vascular system. The aim of this study was to investigate this agent in patients with liver disease and insufficient Doppler signals. A total of 275 Doppler examinations were performed in 176 patients; 20 of these patients could not be studied conventionally due to bowel gas, obesity or noncompliance. They received Levovist to examine portal or hepatic veins or TIPS patency. Angiography, computed tomography (CT) scan or magnetic resonance tomographic angiography (MRTA) was performed subsequently as a control. After administration of Levovist, portal or hepatic veins and TIPS patency could be unequivocally assessed in 18 of the 20 patients. In two patients, suspected occlusion of the portal vein was disproved because the diagnosis was not confirmed later. Only minor adverse effects were encountered. Echo-enhanced Doppler sonography with Levovist is well tolerated. Further study of the value of Levovist for the assessment of portal-hepatic vessels not amenable to conventional Doppler sonography is justified.

Balloon compression rhizolysis in the surgical management of trigeminal neuralgia.

To overcome some of the disadvantages of the current percutaneous surgical approaches to trigeminal neuralgia, we offer balloon compression rhizolysis (BCR) as an alternative. Guided by fluoroscopy, a 4 French Fogarty catheter is introduced into Meckl's cave, and its balloon is inflated tightly for a few minutes with soluble contrast agent to compress the gasserian ganglion and rootlets, under light endotracheal anesthesia. All patients experience immediate pain relief, with mild numbness in all three divisions, but with corneal sparing. Often, weakness of ipsilateral mastication appears transiently. In 33 procedures performed in 25 patients aged 48 to 86, with a follow-up period of 6 months to 7 years, there were 25 long-lasting cures (76%) and 8 recurrences. These results are fully comparable to those of other "destructive" procedures. There was no anesthetic complication and no mortality. The The advantages of this procedure, besides its efficacy and low rate of dysesthesia, include absence of discomfort for the patient, short operative time, technical ease for the neurosurgeon, minimal morbidity, and no risk to corneal sensation. We think that microvascular decompression (MVD) should be the first operation considered for trigeminal neuralgia, but we BCR as the procedure of choice in the aged and medically infirm, especially when V1 pain is present, in patients with multiple sclerosis, for recurrences after other procedures, and in virtually any situation in which MVD is, for some reason, not feasible.