The effect of surface tension reduction on the clinical performance of sodium hypochlorite in endodontics.

Sodium hypochlorite (NaOCl) is recommended as an endodontic irrigant in view of its broad antimicrobial and tissue dissolution capacities. To enhance its penetration into inaccessible areas of root canals and to improve its overall effect, the addition of surface-active agents has been suggested. The aim of this investigation was to review the effect of the reduction of the surface tension on the performance of NaOCl in endodontics. A search was performed in the Medline electronic database (articles published up to 28 July 2012, in English) with the search terms and combinations as follows: 'sodium hypochlorite AND surface tension or interfacial force or interfacial tension or surface-active agent or amphiphilic agent or surface active agent or surfactant or tenside or detergent'. The purpose of this search was to identify publications that compared NaOCl alone and NaOCl modified with the addition of a surface-active agent in endodontics. A hand search of articles published online ('in-press' and 'early view'), and appearing in the reference list of the articles included, was further performed, using the same search criteria as the electronic search. The search identified 302 publications, of which 11 fulfilled the inclusion/exclusion criteria of the review. The evidence available suggests that surface-active agents improve the penetration of NaOCl in the main canal and have no effect on its pulp tissue dissolution ability. There are, however, insufficient data to enable a sound conclusion to be drawn regarding the effect of modifying NaOCl's surface tension on lubrication, antimicrobial and smear layer or debris removal abilities.

Cutaneous wound analysis using hyperspectral imaging.

A correlative bright-field and hyperspectral analysis of full-thickness, cutaneous wounds in a porcine model was undertaken to investigate the efficacy of hyperspectral imaging as an alternate method for wound identification. Analysis of a randomly selected specimen yielded distinct spectral signatures for cutaneous regions of interest including the epidermis, injured dermis, and normal dermis. The scanning of the entire specimen group using these hyperspectral signatures revealed an exclusionary, pseudo-color pattern whereby a central wound region was consistently defined by a unique spectral signature. An algorithm was derived as an objective tool for the comparison of the wound regions defined by the hyperspectral classification versus the pathologists' manual tracings. The dimensions of the wound identified in the hyperspectral assay did not differ significantly from the wound region identified by the pathologists using standard bright-field microscopy. These data indicate that hyperspectral analysis may provide a high-throughput alternative for wound estimation that approximates standard bright-field imaging and pathologist evaluation.

Spectroscopic assessment of alterations in macromolecule and small-molecule metabolites in human brain after stroke.

BACKGROUND AND PURPOSE: We sought to measure the temporal evolution and spatial distribution of lesion macromolecules and small molecules (lactate, N-acetyl compounds, creatine, and choline) in stroke patients by using short echo time in vivo proton MR spectroscopy. METHODS: Single-voxel spectra with TE=22 ms were obtained with and without inversion recovery suppression of small-molecule resonances from 30 examinations of 24 patients 3 to 214 days after stroke. Subtraction of the suppressed from the unsuppressed spectra yielded metabolite spectra without overlap from macromolecules. Two-dimensional spectroscopic images were acquired with macromolecule and small-molecule suppression from 5 additional patients. RESULTS: Macromolecule signals were elevated in lesions relative to normal brain and tended to increase in the subacute period, even as lactate peaks declined. Regions of increased lactate, increased macromolecule signal at 1.3 ppm, and decreased N-acetyl compounds were closely correlated in the 2D spectroscopic images. CONCLUSIONS: Short echo time spectra can be acquired in vivo in a manner that improves signal-to-noise ratio over long echo experiments and resolves overlapping macromolecule and small-molecule signals. The prominent macromolecule signals seen in the subacute period in association with persistently elevated lactate may represent mobile lipids in macrophages or other cells.

Rectal pulse granuloma.

Pulse granuloma is a rare benign entity, most likely representing a foreign body reaction to vegetable particles. We report a case of a pulse granuloma involving the rectum. The patient presented with a submucosal and intramuscular mass lesion found at routine rectal examination and subsequent colonoscopy. The mass was excised and the microscopic examination revealed acute and chronic inflammatory cells, foreign-body giant cells, vegetable matter, and convoluted hyaline rings and scattered circular structures containing basophilic granules, consistent with pulse granuloma. There are a few reports in the literature of pulse granulomas, with most occurring in the oral cavity or lungs. To the best of our knowledge, this is the first reported example of pulse granuloma in the rectum. Although rare, familiarity with this entity's distinctive histopathologic features may avoid a delay in diagnosis and prevent the expense of distinguishing it from its histologic lookalikes.

Characterization of signal properties in atherosclerotic plaque components by intravascular MRI.

Magnetic resonance imaging (MRI) is capable of distinguishing between atherosclerotic plaque components solely on the basis of biochemical differences. However, to date, the majority of plaque characterization has been performed by using high-field strength units or special coils, which are not clinically applicable. Thus, the purpose of the present study was to evaluate MRI properties in histologically verified plaque components in excised human carotid endarterectomy specimens with the use of a 5F catheter-based imaging coil, standard acquisition software, and a clinical scanner operating at 0.5 T. Human carotid endarterectomy specimens from 17 patients were imaged at 37 degrees C by use of an opposed solenoid intravascular radiofrequency coil integrated into a 5F double-lumen catheter interfaced to a 0.5-T General Electric interventional scanner. Cross-sectional intravascular MRI (156x250 microm in-plane resolution) that used different imaging parameters permitted the calculation of absolute T1and T2, the magnetization transfer contrast ratio, the magnitude of regional signal loss associated with an inversion recovery sequence (inversion ratio), and regional signal loss in gradient echo (gradient echo-to-spin echo ratio) in plaque components. Histological staining included hematoxylin and eosin, Masson's trichrome, Kossa, oil red O, and Gomori's iron stain. X-ray micrographs were also used to identify regions of calcium. Seven plaque components were evaluated: fibrous cap, smooth muscle cells, organizing thrombus, fresh thrombus, lipid, edema, and calcium. The magnetization transfer contrast ratio was significantly less in the fibrous cap (0.62+/-13) than in all other components (P<0.05) The inversion ratio was greater in lipid (0.91+/-0.09) than all other components (P<0.05). Calcium was best distinguished by using the gradient echo-to-spin echo ratio, which was lower in calcium (0.36+/-0.2) than in all plaque components, except for the organizing thrombus (P<0.04). Absolute T1 (range 300+/-140 ms for lipid to 630+/-321 ms for calcium) and T2 (range 40+/-12 ms for fresh thrombus to 59+/-21 ms for smooth muscle cells) were not significantly different between groups. In vitro intravascular MRI with catheter-based coils and standard software permits sufficient spatial resolution to visualize major plaque components. Pulse sequences that take advantage of differences in biochemical structure of individual plaque components show quantitative differences in signal properties between fibrous cap, lipid, and calcium. Therefore, catheter-based imaging coils may have the potential to identify and characterize those intraplaque components associated with plaque stability by use of existing whole-body scanners.

Homocarnosine and the measurement of neuronal pH in patients with epilepsy.

Homocarnosine is a dipeptide of gamma-aminobutyric acid (GABA) and histidine found uniquely in the brain, most likely in a subclass of GABAergic neurons. By comparison of spectra from the occipital lobe of patients receiving a homocarnosine elevation drug to normal subjects we have assigned two elevated resonances in the short TE 1H MRS spectrum to homocarnosine. These resonances are partially resolved at 7.05 and 8.02 ppm in a short TE spectrum at 2.1 T when macromolecule resonances are removed by subtraction of a spectrum in which the metabolite resonances are nulled by inversion recovery. The chemical shift of both of these resonances is sensitive to pHi. By comparison with a titration curve the pHi was calculated from the downfield resonance to be 7.06 in the patient group which is similar to values reported using the P(i) resonance. Based on the in vivo results and theoretical considerations the potential sensitivity for using nonelevated homocarnosine to measure pH is similar to that of P(i) under physiological conditions.

New nuclear magnetic resonance data in epilepsy.

Nuclear magnetic resonance methods as a whole have contributed as much to the study and treatment of epilepsy as to any branch of medicine. The pace of the progress in this field increases as recently developed nuclear magnetic resonance techniques mature into practical tools for epilepsy research and management. Recent examples of such progress include new data on seizure-related brain water diffusion changes, brain metabolic abnormalities in epileptic patients, and pharmacologic manipulation of brain gamma-aminobutyric acid.

Reversible, reproducible reduction of brain water apparent diffusion coefficient by cortical electroshocks.

Rat brains were imaged after cortical electroshock pulse trains (1 ms pulses at 100 Hz) of varying durations (0.1-10 s), with diffusion-weighted echo planar imaging sequences at 2.0 T. The apparent water diffusion coefficient (ADC) decreased after either single or repeat electroshock trains. ADC reductions were observed within 6 s after the first shock. The size of the affected area of the brain increased in subsequent images during the 1st min after a 10-pulse (0.1 s) train, and also increased with the duration of electroshock trains. ADC reduction was reproducible in extent and time course after single 10-shock trains and was reversible. In the affected pixels the mean ADC reduction was 4% for a single shock train (0.1 s), and 7-8% for trains repeated once a minute, independent of electroshock train duration. The results indicate that neuronal activity associated with electrostimulation may be monitored with water diffusion measurements, and they may be useful for measuring the severity of seizure activity in patients with medically intractable epilepsy.

Short echo time proton magnetic resonance spectroscopic imaging of macromolecule and metabolite signal intensities in the human brain.

A novel approach is presented for imaging macromolecule and metabolite signals in brain by proton magnetic resonance spectroscopic imaging. The method differentiates between metabolites and macromolecules by T1 weighting using an inversion pulse followed by a variable inversion recovery time before localization and spectroscopic imaging. In healthy subjects, the major macromolecule resonances at 2.05 and 0.9 ppm were mapped at a nominal spatial resolution of 1 x 1 x 1.5 cm3 and were demonstrated to be highly reproducible between subjects. In subacute stroke patients, a highly elevated macromolecule resonance at 1.3 ppm was mapped to infarcted brain regions, suggesting potential applications for studying pathological conditions.

Effects of osmotically driven cell volume changes on diffusion-weighted imaging of the rat optic nerve.

The apparent diffusion coefficient (ADC) of the rat optic nerve was measured in vitro, using magnetic resonance imaging, to determine the effects of changes in cellular volume fraction on the diffusion of tissue water. Nerve ADC was determined under conditions of cell membrane depolarization and (i) increased intracellular volume, (ii) decreased intracellular volume, and (iii) negligible volume change. Depolarization alone had little affect on ADC, whereas volume changes produced strong, reversible effects. Increased cell volume decreased ADC and vice versa. These results are consistent with the view that changes in the extracellular space are the major source of ADC changes in brain tissue.

Diffusion-weighted NMR imaging changes caused by electrical activation of the brain.

The apparent diffusion coefficient of brain water was decreased by frontal cortical electroshock, usually but not always associated with brief epileptic afterdischarge detectable at the parietal cortex. Previous studies have shown that status epilepticus causes similar larger decreases, which are largely reversible by the termination of seizure discharge with pentobarbital. Cerebral blood flow is elevated in these conditions, and biochemical energy failure does not occur. The brain water diffusion coefficient also decreases in spreading depression, without depletion of energy stores. All of these findings may be due in part to the reduction of brain extracellular space caused by cell swelling, which occurs to some degree in all three conditions. However, major biological differences between brain activation and brain ischemia and new evidence for increased cytosolic viscosity in the latter both suggest that other mechanisms deserve further investigation. Use-dependent motility of dendritic spines and other phenomena that may allow direct detection of neural activity by diffusion-weighted NMR imaging are of special interest.

New magnetic resonance techniques for acute ischemic stroke.

Neuroimaging was revolutionized by the development of computed tomography (CT) and standard T1- and T2-weighted magnetic resonance imaging (MRI). Magnetic resonance imaging and CT can adequately distinguish hemorrhage from infarction and depict ischemic stroke 12 to 24 hours after onset. However, during the critical initial hours after the onset of ischemic stroke, these imaging technologies do not adequately demonstrate the location and extent of infarction. Diffusion-weighted MRI and perfusion imaging, as well as advances in magnetic resonance spectroscopy, will enhance our ability to evaluate ischemic stroke shortly after onset. Some of the uses of MRI techniques are as follows: (1) Diffusion-weighted imaging can depict the location and extent of the ischemic lesion as soon as a stroke patient is available for examination. (2) Perfusion imaging evaluates blood flow within the brain's microvasculature and can reveal regions of perfusion deficits corresponding to major vascular territories. (3) Magnetic resonance spectroscopy evaluates metabolic abnormalities associated with focal brain ischemia by specific biochemical measurements. These MRI techniques will rapidly provide important information to clinicians about ischemia, guiding diagnosis and helping in the development of acute stroke interventions to improve outcome.