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At least 883 records · Page 49Linked to original sources
PubMed2003

Modified renal morcellation for renal cell carcinoma: laboratory experience and early clinical application.

OBJECTIVES: To present our modified technique to expedite the entrapment and morcellation process. Standard renal morcellation is typically performed using a 12-mm incision, with the specimen entrapped within a durable LapSac. Because the LapSac does not have a deployment mechanism, its application is technically demanding and time consuming. The recent elimination of the electrical morcellator has also made the morcellation process time consuming and tedious. METHODS: Using an in vitro porcine kidney morcellation model, we compared traditional morcellation (n = 10) with our modified morcellation technique (n = 10). The modified morcellation technique incorporated an EndoCatch entrapment sac and used standard manual morcellation through a 3-cm incision. The 3-cm incision allowed for extracorporeal morcellation, because the specimen could be seen through the abdominal wall defect. Subsequently, we performed 11 laparoscopic radical/total nephrectomies for renal masses using the modified morcellation technique through a 3-cm incision. RESULTS: In this in vitro model, renal specimen morcellation with the standard technique required a mean of 9.4 minutes (16.5 g/min) and modified morcellation required 3.24 minutes (51.24 g/min; P <0.0001). The mean fragment size with standard and modified morcellation was 1.47 and 4.46 g, respectively (P <0.0001). EndoCatch entrapment sack integrity was confirmed in all 10 cases (100%). Clinically, 12 patients underwent modified morcellation of radical nephrectomy specimens. All specimens were renal cell carcinoma, with a mean specimen weight of 724 g. The mean entrapment time was 2 minutes, 40 seconds, and the mean morcellation time was 11 minutes. EndoCatch entrapment sack integrity was confirmed in all cases. At a mean follow-up of 8 months, no trocar site or local recurrences have developed. CONCLUSIONS: Preliminary laboratory and clinical data have demonstrated that the modified morcellation technique is safe and expeditious. The larger fragments that result from the modified technique may facilitate tumor staging. The technique must be performed with great care to prevent sack perforation. Prospective randomized comparison of the modified and standard morcellation techniques and long-term follow-up are required before routine application of this technique.

Animals↗
PubMed2004

Mammalian prion biology: one century of evolving concepts.

Prions have been responsible for an entire century of tragic episodes. Fifty years ago, kuru decimated the population of Papua New Guinea. Then, iatrogenic transmission of prions caused more than 250 cases of Creutzfeldt-Jakob disease. More recently, transmission of bovine spongiform encephalopathy to humans caused a widespread health scare. On the other hand, the biology of prions represents a fascinating and poorly understood phenomenon, which may account for more than just diseases and may represent a fundamental mechanism of crosstalk between proteins. The two decades since Stanley Prusiner's formulation of the protein-only hypothesis have witnessed spectacular advances, and yet some of the most basic questions in prion science have remained unanswered.

Animals↗
PubMed1999

Comparison of the obturation of lateral canals by six techniques.

The following obturation techniques were compared on their ability to obturate lateral canals in vitro, lateral condensation (LC), continuous wave of condensation (CW), warm vertical condensation (WV), carrier-based thermoplasticized gutta-percha (CB), warm lateral condensation (WL), and vertically condensed high-temperature gutta-percha (HT). A root canal system with lateral canals in the coronal, middle, and apical thirds was prepared in resin blocks. Each block was obturated using each technique (n = 30, 15 each, with and without sealer). The length of gutta-percha and sealer in each of the lateral canals was measured with a measuring microscope and statistically compared. All techniques obturated all three levels of lateral canals with sealer. WV, CB, and CW were able to fill the lateral canals with gutta-percha significantly better when root canal sealer was used. WV, CB, CW, and HT filled the coronal and middle lateral canals significantly better with gutta-percha than LC or WL condensation. CB and CW filled the apical lateral canal significantly better with gutta-percha than HT, WV, WL, or LC.

Analysis of Variance↗
PubMed1975

The effect of preparation procedures on original canal shape and on apical foramen shape.

With the use of clear casting resin, simulated curved canals were created so that canal preparation procedures could be directly visualized and compared. Regardless of the type of enlarging instrument or the technique used, undesirable characteristics were produced in all preparations that would make canal filling difficult. To modify the typical preparations, alteration of the enlarging flutes, use of rasping rather than rotation of the instruments, and a flaring technique are recommended.

Dental Pulp Cavity↗
PubMed1999

Comparison of cutting efficiency and instrumentation of curved canals with nickel-titanium and stainless-steel instruments.

The cutting efficiency and the effects of instrumentation on curved canal shape of both stainless-steel and nickel-titanium nonstandardized ProFile Series 29 hand instruments and stainless-steel Flexoreamer were investigated under standardized conditions. Concerning cutting efficiency in rotary motion, the Flexoreamer had significantly (p < 0.01) greater cutting efficiency than stainless-steel ProFiles and nickel-titanium ProFiles. Changes in the canal shape differed significantly between the different instruments at all measuring points (p < 0.001). After instrumentation with Flexoreamers with inclusion of two half-sizes (#17 and #22), there were fewer undesirable changes in canal shape compared with both stainless-steel and nickel-titanium ProFile Series 29 instruments. In this study, it seemed that flexible stainless-steel instruments with noncutting tips were superior to the nonstandardized ProFile Series 29 instruments with regard to cutting efficiency and instrumentation of curved canals.

Analysis of Variance↗
PubMed1999

Dynamic and cyclic fatigue of engine-driven rotary nickel-titanium endodontic instruments.

The absence of adequate testing standards for engine-driven nickel-titanium (NiTi) instruments necessitates further study of these instruments in all areas. This study examined three groups of engine-driven rotary NiTi endodontic instruments (Profile, Hero, and Quantec) and assessed the times for dynamic fracture in relation to the radius of curvature to which the instruments were subjected during preparation, with the instrument diameter determined by size and taper and the mode by which the fracture occurred. Ten instruments were randomly selected representing each size and taper for each group and for each radius of curvature: 600 in total. The instruments were rotated at 350 rpm and introduced into a tempered steel curve that simulated a canal. Two radii of curvature of canals were used: 5 and 10 mm. Time at fracture was noted for all files, and the fracture faces of each file were analyzed with scanning electron microscopy. Radius of curvature was found to be the most significant factor in determining the fatigue resistance of the files. As radius of curvature decreased, fracture time decreased. Taper of files was found to be significant in determining fracture time. As diameter increased, fracture time decreased. In all cases, fracture was found to be of a ductile nature, thus implicating cyclic fatigue as a major cause of failure and necessitating further analyses and setting of standards in this area.

Dental High-Speed Technique↗
PubMed2002

Guide for the practical application of the ICRP Human Respiratory Tract Model. A report of ICRP supporting guidance 3: approved by ICRP committee 2 in October 2000.

The ICRP Publication 66 Human Respiratory Tract Model for Radiological Protection (HRTM) has been applied to calculate dose coefficients (doses per unit intake) and bioassay functions in ICRP Publications 68, 71, 72 and 78. For these purposes, ICRP assigned numerical values to a range of model parameters, such as the size of the inhaled particles and the breathing rate of the subjects. These are known as 'default' or 'reference' values, and were chosen to be typical, representative values. In any particular situation the actual values of many parameters can be considerably different from the reference values. Usually, doses from intakes of radionuclides are low compared with the relevant limit or constraint, and the resulting difference is unimportant. There are, however, circumstances where more reliable assessments of intake and dose are desirable. This Guidance Document therefore gives advice on applying specific information within the framework of the HRTM for assessing occupational and environmental exposures and for interpreting bioassay data. Chapters on each aspect of the model (morphometry, physiology, deposition, clearance, gases and vapours, dosimetry) provide: A summary of how the HRTM treats that topic;Information on the reference values of relevant parameters;Guidance on choosing between default values;Information on how doses and bioassay quantities (lung retention, urine, and faecal excretion) vary with the values of selected parameters, giving guidance on the importance of obtaining specific information;Simple examples of the use of specific information relating to the topic.Annexes give additional information for those directly involved in applying the HRTM to specific situations, including guidance on obtaining parameter values. A brief overview is given of the deposition, characterisation, and sampling of aerosols, with references to further information, as there are relevant text books already available. Issues specific to radioactive aerosols, such as low particle number concentrations for high specific activity materials are, however, addressed. Guidance on obtaining information about absorption of inhaled radionuclides into blood is given in greater detail, because this is a topic on which ICRP has traditionally given guidance, and because a compilation of such information is not readily available elsewhere. Several detailed examples are also provided. One involves assessment of an individual's intake and committed dose from comprehensive bioassay monitoring data. The others deal with the derivation of HRTM absorption parameter values from experimental data, and their application, with additional information on e.g. size distribution, to calculate dose coefficients and interpret bioassay data.

Adolescent↗
PubMed1998

An on-line archive of reconstructed hippocampal neurons.

We have developed an on-line archive of neuronal geometry to encourage the use of realistic dendritic structures in morphometry and for neuronal modeling, located at web address www.neuro.soton.ac.uk. Initially we have included full three-dimensional representations of 87 neurons from the hippocampus, obtained following intracellular staining with biocytin and reconstruction using Neurolucida. The archive system includes a structure editor for correcting any departures from valid branching geometry and which allows simple errors in the digitisation to be corrected. The editor employs a platform-independent file format which enforces the constraints that there should be no isolated branches and no closed loops. It also incorporates software for interconversion between the archive format and those used by various neuronal reconstruction and modelling packages. The raw data from digitisation software can be included in the archive as well as edited reconstructions and any further information available. Cross-referenced tables and indexes are updated automatically and are sorted according to a number of fields including the cell type, contributor, submission date and published reference. Both the archive and the structure editor should facilitate the quantitative use of full three-dimensional reconstructions of neurons from the hippocampus and other brain regions.

Animals↗
PubMed1996

Nuclear architecture and the induction of chromosomal aberrations.

Progress in fluorescence in situ hybridization, three dimensional microscopy and image analysis has provided the means to study the three-dimensional structure and distribution of chromosome territories within the cell nucleus. In this contribution, we summarize the present state of knowledge of the territorial organization of interphase chromosomes and their topological relationships with other macromolecular domains in the human cell nucleus, and present data from computer simulations of chromosome territory distributions. On this basis, we discuss models of chromosome territory and nuclear architecture and topological consequences for the formation of chromosome exchanges.

Animals↗
PubMed2003

Localization of auditory N1 in children using MEG: source modeling issues.

Techniques for localizing auditory (AEF) sources are a topic of on-going discussion and this is particularly pertinent in pediatric research. Smaller head sizes are: (1) subject to bilateral temporal lobe source interference from both temporal lobes; and (2) further from MEG sensors resulting in poorer signal-to-noise ratios. An additional consideration in children is that the components of the AEF have distinct contributions along the development spectrum resulting in an ever-changing morphology for the pediatric AEF. These factors present a complicated picture for dipole fitting and raise the question of the most effective fitting strategy. We examined the AEF localizations in five children from 151, 70 and 47 MEG channels of data. We found evidence that bilateral source interaction could result in localization errors along the medial-lateral axis of up to 1 cm. We suggest that any modeling strategy needs to sufficiently account for this interaction and more precise models allowing for multiple sources need to be developed.

Acoustic Stimulation↗
PubMed2003

Fast algorithm for 3-D vascular tree modeling.

In this short paper, accelerated three-dimensional computer simulations of vascular trees development, preserving physiological and haemodynamic features, are reported. The new computation schemes deal: (i). with the geometrical optimization of each newly created bifurcation; and (ii). with the recalculation of blood pressures and radii of vessels in the whole tree. A significant decrease of the computation time is obtained by replacing the global optimization by the fast updating algorithm allowing more complex structure to be simulated. A comparison between the new algorithms and the previous one is illustrated through the hepatic arterial tree.

Algorithms↗
PubMed1997

An algorithm for real-time vessel enhancement and detection.

In this paper we present an algorithm for the real-time enhancement and detection of blood vessels in medical images. The algorithm is based on a set of linear filters sensitive to vessels of different orientation and thickness. Such filters are obtained as linear combinations of properly shifted Gaussian kernels. The output of multiple oriented vessel-enhancing filters can be integrated to obtain images in which vessels are highly enhanced independently of their direction and thickness. To avoid spurious responses in the presence of step edges or to enhance the skeletons of vessels, the output of directional filters can be validated before integration. Skeleton detection and vessel segmentation can be performed via thresholding with hysteresis. Experimental results on synthetic images and real coronary arteriograms are reported.

Algorithms↗