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PubMed1990

Carbohydrate characterization of recombinant glycoproteins of pharmaceutical interest.

Carbohydrate characterization of recombinant glycoproteins entails determination of the primary structures and points of attachment of the oligosaccharide moieties. This article reviews several methods for oligosaccharide- and glycosylation-site characterization. A major recent advance in carbohydrate analysis has been the use of high-pH anion exchange (HPAE) chromatography for separation of glycoprotein-derived oligosaccharides. These separations are sensitive to molecular size, carbohydrate composition, linkage positions, and anomeric configurations. As a result, HPAE chromatography is a powerful technique for glycoprotein characterization and can serve as the basis of an "oligosaccharide map." Characterization of potential N-glycosylation sites involves determining whether each potential site is glycosylated, the extent of oligosaccharide processing at each site, and ideally, a detailed description of the distribution of oligosaccharides at each site. Several approaches to characterizing glycosylation sites are described, including peptide mapping and mass spectrometry. Treatment of a glycoprotein with endo-beta-N-acetylglucosaminidase H (endo H) followed by peptide:N-glycosidase F (PNGase F) can be used to distinguish sites that are not glycosylated from those carrying high-mannose structures and from those containing attached complex oligosaccharides. After individual glycosylation sites have been labeled by this series of reaction, the resulting peptides are characterized by automated Edman degradation. This technique is particularly valuable for characterizing peptides that contain more than one potential N-glycosylation site. An example is also given in which HPAE chromatography is used in conjunction with reversed-phase high-performance liquid chromatography tryptic mapping to obtain detailed information on the distribution of oligosaccharides at individual glycosylation sites.

Carbohydrate Sequence↗

PubMedDate not supplied

Liver lesion detection, characterization, and effect on patient management: comparison of single-phase spiral CT and current MR techniques.

This study compares liver lesion detection, characterization, and effect on patient management between single-phase spiral CT and MRI using spoiled gradient echo (SGE), T2-weighted fat-suppressed spin echo, and serial post gadolinium SGE. All patients with suspected liver lesions who underwent spiral CT and MRI within a 1-month period between January 1993 and September 1996 were included in the study. Spiral CT and MRI were interpreted prospectively in a blinded fashion by separate individual experienced investigators, and lesion detection and characterization were determined. Confirmation was obtained by surgery (6 patients), biopsy (18 patients), imaging follow-up (36 patients), or combined reading of all imaging studies and clinical follow-up (29 patients). Effect on patient management was determined by combined chart review and interview of the patients' physicians and by retrospective clinical assessment performed by a surgical oncologist and medical oncologist separately. Eighty-nine patients were included in the study. Regarding true positive lesion detection, 295 and 519 lesions were detected on spiral CT and MR images, respectively, which was significantly different on a patient-by-patient basis (P < .001). More lesions were detected on MR than on spiral CT in 44 of 89 patients (49.4%), and 11 of these 44 patients had lesions shown on MRI in whom no lesions were apparent on CT images. No patients had true positive lesions shown on spiral CT that were not shown on MRI. Regarding lesion characterization, 129 and 466 lesions were characterized on spiral CT and MRI images, respectively, which was significantly different on a patient-by-patient basis (P < .001). More lesions were characterized on MR than CT images in 67 patients (75.3%). Regarding effect on patient management, chart review with physician interview demonstrated that findings on MRI provided information that altered patient management as compared with findings on spiral CT in 57 patients. Retrospective clinical evaluation by the surgical and medical oncologist showed that MRI was considered to have a greater effect on patient management than spiral CT in 58 and 55 patients, respectively. Comparing current MRI technique to single-phase spiral CT, MRI detected more lesions in 49.4% and characterized more lesions in 75.3% of patients investigated for focal liver disease. MRI had a greater effect on patient management in each of the three methods than single-phase spiral CT in more than 61% of patients.

Adolescent↗

PubMedDate not supplied

Time series characterization of simulated microtubule dynamics in the nerve growth cone.

The process of neurite outgrowth is critically dependent on proper microtubule assembly. However, characterizing the dynamics of microtubule assembly and their quantitative relationship to neurite outgrowth is a difficult task. The difficulty can be reduced by using time series analysis which has broad application in characterizing the dynamics of stochastic, or "noisy," behaviors. Here we apply time series analysis to quantitatively compare simulated microtubule assembly and neurite outgrowth in vitro. Microtubule length life histories were simulated assuming constant growth and shrinkage rates coupled with random selection of growth and shrinkage times, a formulation based on the dynamic instability model of microtubule assembly. Net length displacements of simulated microtubules were calculated at discrete, evenly spaced times, and the resulting time series were characterized by both spectral and autocorrelation analysis. Depending on the sampling rate and the dynamic parameters, simulated microtubules exhibited significant autocorrelation and periodicity. To make a comparison to neurite outgrowth, we characterized the dynamic behavior of simulated microtubule populations and found it was not significantly different from that of single microtubules. The net displacements of rat superior cervical ganglion neurite tips were measured and characterized using time series methods. Their behavior was consistent with the microtubule dynamics for appropriate simulation parameters and sampling rates. Our results show that time series analysis can provide a useful tool for quantitative characterization of microtubule dynamics and neurite outgrowth and for assessing the relationship between them.

Animals↗

PubMed1997

Characterization of human serotonin 1D and 1B receptors using [3H]-GR-125743, a novel radiolabelled serotonin 5HT1D/1B receptor antagonist.

The study of serotonin (5-HT) receptors from the points of view of their anatomical localization and pharmacological characterization has been linked to the availability of highly selective radioligands exhibiting high affinity for their targets. This is particularly so in the case of serotonin receptors, since many different subtypes with overlapping pharmacological profiles have been described. Of these, the serotonin 5-HT1 receptor family appears to be the most complex in terms of molecular diversity and pharmacological properties. The lack of appropriate tools to characterize the different receptor subtypes included in this family has hampered progress in the understanding of biological function. In the case of serotonin 5-HT1D receptors all the radioligands used so far in their characterization behave as agonists from the functional point of view. This agonistic character is regarded as a disadvantage for radioligands since their interaction with the receptors under study depends on factors other than the abundance of the receptor, such as the coupling of the receptors with G-proteins. We describe here the binding properties of [3H]-GR-125743, a new radiolabelled derivative of a compound that exhibits selective antagonistic properties with respect to the serotonin human (h5-HT1D) and human (h5-HT1B) receptors. The compound has been characterized for its ability to label the cloned h5-HT1D and h5-HT1B receptors. The binding obtained in both cases was specific, saturable and reversible, whereas the percentage of specific binding depended on the level of expression of the receptors. Using saturation analysis we have found that, on the specific clones used in this study, the compound labels a receptor population 5 to 10-fold higher that the one revealed using [3H]-5-carboxamidotryptamine, a compound with agonist properties for these receptors in functional assays. Using [3H]-GR-125743 as a radioligand we have characterized the pharmacological profile of the same cloned h5-HT1D and h5-HT1B receptor preparations for a range of serotonin reference compounds by means of displacement assays. The affinities found have been compared, using regression analysis, with those obtained for the same radioligand and compounds in membranes obtained from human substantia nigra, a tissue known to be rich in hS-HT(1B/1D) receptors. We have found a better correlation, both in terms of correlation coefficient and of slope, between the substantia nigra data and the h5-HT1B data compared with the h5-HT1D data (0.94 and 1.05 vs. 0.86 and 0.64 respectively). Finally, the addition of 100 microM GTP reduced the binding of [3H]-GR-125743 to h5-HT1D and h5-HT1B receptor subtypes by approximately 20% without affecting the affinities obtained for different displacers. Therefore, [3H]-GR-125743 appears to be a suitable radioligand for the characterization of h5-HT1D and h5-HT1B receptor subtypes, being potentially more useful than previously existing compounds.

Benzamides↗

PubMed1997

ENVIRONMENTAL AUDITING: An Approach for Characterizing Tropospheric Ozone Risk to Forests

/ The risk tropospheric ozone poses to forests in the United States is dependent on the variation in ozone exposure across the distribution of the forests in question and the various environmental and climate factors predominant in the region. All these factors have a spatial nature, and consequently an approach to characterization of ozone risk is presented that places ozone exposure-response functions for species as seedlings and model-simulated tree and stand responses in a spatial context using a geographical information systems (GIS). The GIS is used to aggregate factors considered important in a risk characterization, including: (1) estimated ozone exposures over forested regions, (2) measures of ozone effects on species' and stand growth, and (3) spatially distributed environmental, genetic, and exposure influences on species' response to ozone. The GIS-based risk characterization provides an estimation of the extent and magnitude of the potential ozone impact on forests. A preliminary risk characterization demonstrating this approach considered only the eastern United States and only the limited empirical data quantifying the effect of ozone exposures on forest tree species as seedlings. The area-weighted response of the annual seedling biomass loss formed the basis for a sensitivity ranking: sensitive-aspen and black cherry (14%-33% biomass loss over 50% of their distribution); moderately sensitive-tulip popular, loblolly pine, eastern white pine, and sugar maple (5%-13% biomass loss); insensitive-Virginia pine and red maple (0%-1% loss). In the future, the GIS-based risk characterization will include process-based model simulations of the three- to 5-year growth response of individual species as large trees with relevant environmental interactions and model simulated response of mixed stands. The interactive nature of GIS provides a tool to explore consequences of the range of climate conditions across a species' distribution, forest management practices, changing ozone precursors, regulatory control strategies, and other factors influencing the spatial distribution of ozone over time as more information becomes available.KEY WORDS: Ecological risk assessment; GIS; Ozone; Risk characterization; Forests; Trees

Journal Article↗

PubMed1981

Immunofixation as an adjunct to immunoelectrophoresis in characterization of serum monoclonal immunoglobulins.

We evaluated quantitatively the usefulness of immunofixation (IF) as an adjunct to immunoelectrophoresis (IEP) in characterizing serum monoclonal proteins. In 33 out of 97 consecutive patients with one or more homogeneous bands on cellulose acetate serum protein electrophoresis, a monoclonal immunoglobulin could not be characterized with certainty by IEP. Of these 33 cases, in 76% a monoclonal immunoglobulin was subsequently characterized by IF on agarose gel. In 18% IF provided additional suggestive information, and in 6% it provided no additional or less information than IEP. The mean concentration of monoclonal proteins (other than free light chains) that could be characterized by IEP was 25 g/l. The monoclonal proteins that required IF for characterization were all less than 10 g/l. Of all monoclonal proteins below 10 g/l, 53% required IF for complete characterization. IF is a useful adjunct to IEP, primarily in cases where the concentration of monoclonal immunoglobulin is less than 10 g/l.

Humans↗

PubMed2005

Probabilistic risk characterization: an example with di(2-ethylhexyl) phthalate.

While probabilistic methods gain attention in hazard characterization and are increasingly used in exposure assessment, full use of the available probabilistic information in risk characterization is still uncommon. Usually, after probabilistic hazard characterization and/or exposure assessment, percentiles from the obtained distributions are used as point estimates in risk characterization. In this way, all information on variability and uncertainty is lost, while these aspects are crucial in any risk assessment. In this paper, we present a method to integrate the entire distributions from probabilistic hazard characterization and exposure assessment into one risk characterization plot. This method is illustrated using di(2-ethylhexyl) phthalate as an example. The final result of this probabilistic risk assessment is summarized in a single plot, containing two pieces of information: the confidence we may have in concluding there is no risk, and the fraction of the population this conclusion applies to. This information leads to a better informed conclusion on the risk of a substance, and may be very useful to define the necessary measures for risk reduction.

Adult↗

PubMedDate not supplied

On graphical and numerical characterization of proteomics maps.

We outlined a mathematical approach suitable for characterization of experimental data given by 2-D densitograms. In particular we consider numerical characterization of proteomics maps. The basis of our approach is to order "spots" of a 2-D map and assign them unique labels (that in general will depend on the criteria used for ordering). In this way a map is "translated" into a sequence. In the next step one associates with the generated sequence a geometrical path and views such a path as a mathematical object that needs characterization. We have ordered spots representing proteins in 2-D gel plates according to their relative intensities which results in a zigzag path that produces a complicated "fingerprint" pattern. Mathematical characterization of zigzag pattern follows similar mathematical characterizations of embedded patterns based on matrices, the elements of which are given as quotients of Euclidean distance between spots and the distance along the zigzag path. The leading eigenvalue of constructed matrices is taken to represent characterization of the original 2-D map. Comparison of different 2-D maps (simulated by using random generator) allows one to construct partial order, which although qualitative in nature gives some insight into perturbation induced by foreign agents to the proteome of the control cell.

Computer Graphics↗

PubMed2002

Top down characterization of larger proteins (45 kDa) by electron capture dissociation mass spectrometry.

The structural characterization of proteins expressed from the genome is a major problem in proteomics. The solution to this problem requires the separation of the protein of interest from a complex mixture, the identification of its DNA-predicted sequence, and the characterization of sequencing errors and posttranslational modifications. For this, the "top down" mass spectrometry (MS) approach, extended by the greatly increased protein fragmentation from electron capture dissociation (ECD), has been applied to characterize proteins involved in the biosynthesis of thiamin, Coenzyme A, and the hydroxylation of proline residues in proteins. With Fourier transform (FT) MS, electrospray ionization (ESI) of a complex mixture from an E. coli cell extract gave 102 accurate molecular weight values (2-30 kDa), but none corresponding to the predicted masses of the four desired enzymes for thiamin biosynthesis (GoxB, ThiS, ThiG, and ThiF). MS/MS of one ion species (representing approximately 1% of the mixture) identified it with the DNA-predicted sequence of ThiS, although the predicted and measured molecular weights were different. Further purification yielded a 2-component mixture whose ECD spectrum characterized both proteins simultaneously as ThiS and ThiG, showing an additional N-terminal Met on the 8 kDa ThiS and removal of an N-terminal Met and Ser from the 27 kDa ThiG. For a second system, the molecular weight of the 45 kDa phosphopantothenoylcysteine synthetase/decarboxylase (CoaBC), an enzyme involved in Coenzyme A biosynthesis, was 131 Da lower than that of the DNA prediction; the ECD spectrum showed that this is due to the removal of the N-terminal Met. For a third system, viral prolyl 4-hydroxylase (26 kDa), ECD showed that multiple molecular ions (+98, +178, etc.) are due to phosphate noncovalent adducts, and MS/MS pinpointed the overall mass discrepancy of 135 Da to removal of the initiation Met (131 Da) and to formation of disulfide bonds (2 x 2 Da) at C32-C49 and C143-C147, although 10 S-S positions were possible. In contrast, "bottom up" proteolysis characterization of the CoaBC and the P4H proteins was relatively unsuccessful. The addition of ECD substantially increases the capabilities of top down FTMS for the detailed structural characterization of large proteins.

Amino Acid Sequence↗

PubMed2003

Phylogenetic analysis by 16S rDNA gene sequence comparison of avian taxa of Bisgaard and characterization and description of two new taxa of Pasteurellaceae.

AIMS: Characterization and classification of members of Pasteurellaceae isolated from birds by extended phenotypic characterization and 16S rDNA gene sequence comparison. METHODS AND RESULTS: A total of 95 avian isolates were subjected to extended phenotypic characterization. Thirteen bacterial strains selected from main phenotypic clusters and isolated from parrot, parakeet, budgerigar, partridge, pheasant, chicken, duck, hawk and gull were subsequently characterized by 16S rDNA gene sequencing. Eight of the sequenced strains were classified with six taxa of Bisgaard of which two (34 and 40) have not been published before, and the properties of four others (14, 22, 26 and 32) changed upon the characterization of these new isolates. Of the remaining strains, one was identified as a phenotypic variant in maltose and dextrin of Pasteurella gallinarum another as a trehalose positive variant of taxon 3 of Bisgaard. The remaining three strains sequenced were not closely related to existing taxa of Pasteurellaceae. However, they were found to belong to the Avian cluster with 92-97% 16S rDNA gene sequence similarity. CONCLUSION: The study allowed the classification of bacteria isolated from birds by the integrated use of extended phenotypic characterization and 16S rDNA gene sequence analysis. Only the application of 16S rDNA gene sequencing allows a correct identification of variant strains. SIGNIFICANCE AND IMPACT OF THE STUDY: The description of new taxa within the bacterial family Pasteurellaceae will subsequently allow additional isolates of these taxa to be identified and improve the diagnosis and epidemiological understanding of bacteria causing disease in birds.

Animals↗

PubMed1993

Age determination of experimental venous thrombi by ultrasonic tissue characterization.

PURPOSE: The ability of ultrasonic tissue characterization based on radiofrequency signal processing to detect compositional differences in thrombi of varying ages was evaluated in vivo. METHODS: Thrombi were produced in 49 jugular veins of 26 anesthetized 18 to 20 kg pigs by partial ligation and application of direct electric current. Thrombi were imaged 30 minutes after formation and 1, 7, and 14 days later with a color Doppler ultrasound scanner that identified the thrombi, and acquired radio frequency data for ultrasonic tissue characterization analysis. Ultrasonic tissue characterization used two parameters from the normalized power spectrum, slope, and intercept, which are related to scatterer size, scatterer concentration, and acoustic-impedance differences between scatterers and surrounding medium. Previous in vitro studies demonstrated that lower slope and higher intercept values correlated with greater cellularity and more-dense fibrin mesh. Histologic examination was performed for each time period. The values of slope and intercept for each timed observation were compared by a multilinear discriminant analysis. RESULTS: There were no statistical differences between day 0 and day 1. Statistically-significant differences in ultrasonic tissue characterization parameters were seen between all other time intervals with p values < 0.01. Older thrombi tended to demonstrate higher slope and lower intercept values. These ultrasonic tissue characterization changes correlated with a red cell and fibrin-mesh density reduction, which was confirmed by histologic findings and was indicative of partial spontaneous thrombolysis. The degree of spontaneous thrombolysis provides an estimate of the age of thrombi. CONCLUSION: Ultrasonic tissue characterization is capable of distinguishing age differences in thrombi in an animal model and has the potential for noninvasive application in clinical diagnosis.

Animals↗

PubMed2006

Identification and chemical characterization of industrial particulate matter sources in southwest Spain.

A detailed physical and chemical characterization of coarse particulate matter (PM10) and fine particulate matter (PM2.5) in the city of Huelva (in Southwestern Spain) was carried out during 2001 and 2002. To identify the major emission sources with a significant influence on PM10 and PM2.5, a methodology was developed based on the combination of: (1) real-time measurements of levels of PM10, PM2.5, and very fine particulate matter (PM1); (2) chemical characterization and source apportionment analysis of PM10 and PM2.5; and (3) intensive measurements in field campaigns to characterize the emission plumes of several point sources. Annual means of 37, 19, and 16 microg/m3 were obtained for the study period for PM10, PM2.5, and PM1, respectively. High PM episodes, characterized by a very fine grain size distribution, are frequently detected in Huelva mainly in the winter as the result of the impact of the industrial emission plumes on the city. Chemical analysis showed that PM at Huelva is characterized by high PO4(3-) and As levels, as expected from the industrial activities. Source apportionment analyses identified a crustal source (36% of PM10 and 31% of PM2.5); a traffic-related source (33% of PM10 and 29% of PM2.5), and a marine aerosol contribution (only in PM10, 4%). In addition, two industrial emission sources were identified in PM10 and PM2.5: (1) a petrochemical source, 13% in PM10 and 8% in PM2.5; and (2) a mixed metallurgical-phosphate source, which accounts for 11-12% of PM10 and PM2.5. In PM2.5 a secondary source has been also identified, which contributed to 17% of the mass. A complete characterization of industrial emission plumes during their impact on the ground allowed for the identification of tracer species for specific point sources, such as petrochemical, metallurgic, and fertilizer and phosphate production industries.

Air Pollutants↗

PubMed2006

Mechanical characterization of anisotropic planar biological soft tissues using large indentation: a computational feasibility study.

Traditionally, the complex mechanical behavior of planar soft biological tissues is characterized by (multi)axial tensile testing. While uniaxial tests do not provide sufficient information for a full characterization of the material anisotropy, biaxial tensile tests are difficult to perform and tethering effects limit the analyses to a small central portion of the test sample. In both cases, determination of local mechanical properties is not trivial. Local mechanical characterization may be performed by indentation testing. Conventional indentation tests, however, often assume linear elastic and isotropic material properties, and therefore these tests are of limited use in characterizing the nonlinear, anisotropic material behavior typical for planar soft biological tissues. In this study, a spherical indentation experiment assuming large deformations is proposed. A finite element model of the aortic valve leaflet demonstrates that combining force and deformation gradient data, one single indentation test provides sufficient information to characterize the local material behavior. Parameter estimation is used to fit the computational model to simulated experimental data. The aortic valve leaflet is chosen as a typical example. However, the proposed method is expected to apply for the mechanical characterization of planar soft biological materials in general.

Animals↗

PubMed2006

Can the fliC PCR-restriction fragment length polymorphism technique replace classic serotyping methods for characterizing the H antigen of enterotoxigenic Escherichia coli strains?

In this study, we performed fliC PCR-restriction fragment length polymorphism (RFLP) to investigate whether this technique would be better than classic serotyping for the characterization of the H antigen in enterotoxigenic Escherichia coli (ETEC) strains. We showed that the fliC genes from ETEC strains can be characterized by restriction analysis of their polymorphism. Only one allele of the fliC gene from ETEC strains was found for each flagellar antigen, with the exception of H21. Nonmotile strains could also be characterized using this molecular technique. Moreover, determination of the somatic antigen was guided by the identification of the flagellar antigen from previously unknown serotypes of ETEC strains by PCR-RFLP, thus reducing the number of anti-antigen O sera used. The PCR-RFLP technique proved to be faster than classic serotyping for the characterization of the E. coli H antigen, taking 2 days to complete instead of the 7 or more days using classic serotyping. In conclusion, the H molecular typing for Enterobacteriaceae members may become an important epidemiological tool for the characterization of the H antigen of E. coli pathotypes. The PCR-RFLP technique is capable of guiding the determination of the H antigen and could partially replace seroagglutination. With the determination of the molecular profiles of alleles from strains obtained in epidemiological studies, new patterns will be described for ETEC strains or other E. coli pathotypes, thus permitting widespread use of this technique to characterize fliC genes and determine the H antigen of E. coli strains.

Antigens, Bacterial↗

PubMed2005

Use of ultrasound for characterizing dairy products.

It has been known for a long time that acoustic measurements offer some unique features for characterizing liquid food products in their intact state, without any preparation or destruction of the product sample. Acoustic characterization can yield information about fat content, droplet size distribution, and kinetics of product variation with time. Furthermore, acoustic methods are very attractive for on-line process control. This paper addresses several questions: Why does ultrasound attenuate when propagating through a heterogeneous system? What properties of dairy products can be extracted from such ultrasound measurements? Which measurement is better for product characterization: attenuation or sound speed? What measurement precision is required to adequately characterize product properties? What frequency range is of most value for determining these product properties?It is possible to provide answers to many of these questions using experimental data, thereby avoiding, for the moment, any complex mathematical analysis. We present several applications of acoustic spectroscopy for characterizing dairy products, including characterization of the fat content in a wide variety of dairy products; calculation of the fat droplet size distribution in milk without dilution; and calculation of water droplet size in butter, without dilution or melting.

Acoustics↗

PubMed1999

[The identification of the criteria of malignancy and the tissue characterization of expansive processes in periskeletal soft tissues. The current role of magnetic resonance].

INTRODUCTION: Expansive masses arising from periskeletal soft tissues are a frequent challenge for the imaging specialist. Lesion diagnosis and characterization, and the assessment of benign/malignant nature are very important factors for treatment planning. We investigated MR capabilities in distinguishing benign from malignant masses and for histopathologic lesion characterization, also in the light of the latest most authoritative literature reports. MATERIAL AND METHODS: February 1995 to November 1997, we examined 237 patients with known space-occupying lesions arising from periskeletal soft tissues. T1- and PD/T2-weighted SE images were acquired on the most suitable planes. The findings were independently evaluated by two groups of radiologists who were asked a benignity/malignancy judgment based on specific morphological criteria and then a presumptive histopathologic characterization. The results were then compared with pathologic findings. RESULTS: We had high agreement rates for benignity/malignancy judgements, with only < or = 3.8% error rates. In contrast, rates were quite variable for histopathologic characterization and differed greatly by lesion type. The lesions, defined as malignant, could not be characterized histologically in approximately 18% of cases by both groups. DISCUSSION AND CONCLUSIONS: Our results, which are in substantial agreement with the recent authoritative literature, confirm MRI as an extremely reliable tool for distinguishing benign from malignant expansive masses arising from periskeletal soft tissues. On the contrary, MRI exhibits good specificity in histopathologic characterization only for the masses with such development as to permit identification of the anatomical compartment of origin, which are usually benign, as well as the masses with typical or pathognomonic tissue signal.

Adolescent↗

PubMed2006

Tissue characterization of solitary pulmonary nodule: comparative study between helical dynamic CT and integrated PET/CT.

UNLABELLED: Recent advances in the technology of helical multidetector CT allow precise evaluations of nodule hemodynamics. In addition, the efficacy of tissue characterization has improved, and now sensitivity and specificity of >90% are achieved. Moreover, the efficacy of PET for the tissue characterization of solitary pulmonary nodules (SPNs) has also become of importance. The purpose of this study was to compare the diagnostic accuracy of helical dynamic (HD) CT (HDCT) and integrated PET/CT for pulmonary nodule characterization. METHODS: One hundred nineteen patients with an SPN underwent both HDCT (unenhanced scans, followed by series of images at 30, 60, 90, 120 s and at 5 and 15 min after intravenous injection of contrast medium) and integrated PET/CT. On HDCT, a nodule was regarded as malignant with a net enhancement of > or =25 Hounsfield units (HU) and a washout of 5-31 HU. On integrated PET/CT, nodules were considered malignant with a > or =3.5 maximum standardized uptake value and an 18F-FDG uptake greater than that of mediastinal structures. The sensitivity, specificity, and accuracy of the 2 modalities for malignancy were compared using the McNemar test. RESULTS: There were 79 malignant and 40 benign nodules. The sensitivity, specificity, and accuracy for malignancy on HDCT were 81% (64/79 nodules), 93% (37/40), and 85% (101/119), respectively, whereas those on integrated PET/CT were 96% (76/79), 88% (35/40), and 93% (111/119), respectively (P = 0.008, 0.727, and 0.011, respectively). All malignant nodules were interpreted correctly on either HDCT or PET/CT. CONCLUSION: Integrated PET/CT is more sensitive and accurate than HDCT for the malignant nodule characterization; therefore, PET/CT may be performed as the first-line evaluation tool for SPN characterization. Because HDCT has high specificity and acceptable sensitivity and accuracy, it may be a reasonable alternative for nodule characterization when PET/CT is unavailable.

Adult↗

PubMed1997

Risk characterization: A bridge to informed decision making.

Regulatory decisions should be made in the most expert and informed way since they are precipitated by real and perceived threats to human health, under the glare of public scrutiny. In 1994, the National Research Council (NRC) reported that the U.S. Environmental Protection Agency's (USEPA's) overall approach to assessing risks is fundamentally sound, but the Agency must more clearly establish the scientific and policy basis for risk estimates and better communicate the associated uncertainties. On March 21, 1995, USEPA issued a risk characterization policy and guidance. In this policy, an effective risk characterization must fully and clearly characterize risks and disclose the scientific analysis, uncertainties, assumptions, and science policy that underlie decisions throughout the risk assessment process. A number of regulatory reform bills which required risk characterization as part of all Federal risk assessments were introduced by the 104th Congress. The purpose of this workshop was to familiarize Society of Toxicology members with: (1) key elements to be considered in risk characterization and (2) new advances in risk characterization addressed by Federal and State agencies, industry, academia, NRC, and Presidential/Congressional Commission on Risk Assessment and Risk Management. Furthermore, the main objective was to engage the audience in discussing the proper role of science in risk assessment-risk management interface to make informed decisions in the face of scientific uncertainty.

Decision Making↗