Nationwide survey of fluoroscopy: radiation dose and image quality

PURPOSE: To determine the average abdominal entrance air kerma, low-contrast sensitivity, and spatial resolution in upper gastrointestinal tract fluoroscopy in the United States. MATERIALS AND METHODS: A random sample of fluoroscopic facilities was selected to be surveyed for the Nationwide Evaluation of X-ray Trends program. Measurements were performed by using a newly developed fluoroscopic phantom. The surveys were conducted by state radiation control personnel. RESULTS: Average air kerma rates 1 cm above the tabletop, free in air, were 43 mGy/min (n = 340). The rate increased to 64 mGy/min when a 1.6-mm-thick copper filter, which simulated the use of barium contrast medium, was added to increase attenuation. The average entrance air kerma, free in air, for radiographs was 3.4 mGy, and an average of 12 radiographs were obtained per examination. Of 352 facilities surveyed, 306 (87%) were able to resolve wire mesh with 20 or more lines per inch. Of 339 facilities for which percentage contrast could be calculated, 192 (57%) had minimum percentage contrast values of 4% or more. CONCLUSION: Spatial resolution for fluoroscopy is adequate for most of the facilities surveyed, but a substantial proportion of facilities could not visualize low-contrast test objects, which strongly suggests image quality problems.     

Relationship between prothrombin activation fragment F1.2 and international normalized ratio in patients with atrial fibrillation. Stroke Prevention in Atrial Fibrillation Investigators

BACKGROUND AND PURPOSE: The prothrombin time (expressed as the international normalized ratio [INR]) is the standard method of monitoring warfarin therapy in patients with atrial fibrillation. Prothrombin activation fragment F1.2 provides an index of in vivo thrombin generation and might provide a better index of the effective intensity of anticoagulation. We examined the relationship between F1.2 and INR in patients with atrial fibrillation. METHODS: We measured INR and F1.2 levels in 846 patients with atrial fibrillation participating in the Stroke Prevention in Atrial Fibrillation III study. Two hundred nineteen (26%) were taking aspirin alone, 326 (39%) were taking adjusted-dose warfarin, and 301 (36%) were taking a low fixed dose of warfarin (1 to 3 mg) plus aspirin (combination therapy). F1.2 levels were measured with an enzyme-linked immunosorbent assay. RESULTS: Patients receiving adjusted-dose warfarin or combination therapy had significantly higher INR and significantly lower F1.2 values than those on aspirin alone (P < or = .0001 for each of the four comparisons). F1.2 values (nanomolar) were inversely correlated with INR (F1.2 = -0.1 + 2.3[1/INR]; R2 = .37; P < .0001; simple linear regression). However, significant variability remained. Among patients receiving warfarin, older patients had higher F1.2 values than younger patients after adjustment for INR intensity (P < .001) in the model. There was no difference in the relationship between F1.2 and INR between men and women. CONCLUSIONS: Increasing intensity of anticoagulation, as measured by the INR, is associated with decreasing thrombin generation as measured by the F1.2 level, but significant variability exists in this relationship. Older anticoagulated patients have higher F1.2 values than younger patients at equivalent INR values. The clinical significance of these differences is not clear. F1.2 measurement might provide information regarding anticoagulation intensity in addition to that reflected by the INR.     

Effect of ectoparasite removal procedures on recapture of Microtus californicus

We tested the null hypothesis that anesthetizing meadow voles (Microtus californicus) and brushing them vigorously for ectoparasites would have no effect on the later recapture of these voles. Voles were trapped from 6 December 1993 to 10 January 1994 at Faye Slough Wildlife Area near Eureka, Humboldt County, California (USA). Alternate trapped voles were anesthetized with ethyl ether and brushed vigorously for ectoparasites. There was no significant difference in the frequency of recapture nor in the time to first recapture between those voles anesthetized and brushed, compared to control animals.     

Hepatic hemangioma. Analysis of 103 cases. Clinical considerations and imaging methods

Hemangiomas are the most common benign vascular tumor found in the liver. In this study, 103 cases of hepatic hemangiomas were analysed in a retrospective manner. Image aspects such as those seen in ultrassonography, computed tomography, nuclear magnetic resonance and arteriography are discussed. The incidence was higher amongst the female sex, between individuals from 40 to 60 years old, which presented predominantly without symptoms (66%) and localized mainly in the right hepatic lobe (74%). The meaning of those aspects, when adopted, permits the clinicians to differentiate benign from malignant nodular lesions in the liver.     

Escherichia coli purine repressor: key residues for the allosteric transition between active and inactive conformations and for interdomain signaling

The Escherichia coli purine repressor, PurR, exists in an equilibrium between open and closed conformations. Binding of a corepressor, hypoxanthine or guanine, shifts the allosteric equilibrium in favor of the closed conformation and increases the operator DNA binding affinity by 40-fold compared to aporepressor. Glu70 and Trp147 PurR mutations were isolated which perturb the allosteric equilibrium. Three lines of evidence indicate that the allosteric equilibrium of E70A and W147A aporepressors was shifted toward the closed conformation. First, compared to wild-type PurR, these mutant repressors had a 10-30-fold higher corepressor binding affinity. Second, the mutant aporepressors bound to operator DNA with an affinity that is characteristic of the wild-type PurR holorepressor. Third, binding of guanine to wild-type PurR resulted in a near-UV circular dichroism spectral change at 297-305 nm that is attributed to the closed conformation. The circular dichroism spectrum of the E70A aporepressor at 297-305 nm was that expected for the closed conformation, and it was not appreciably altered by corepressor binding. Mutational analysis was used to identify an Arg115-Ser46' interdomain intersubunit hydrogen bond that is necessary for transmitting the allosteric transition in the corepressor binding domain to the DNA binding domain. R115A and S46G PurR mutants were defective in DNA binding in vitro and repressor function in vivo although corepressor binding was identical to the wild type. These results establish that the hydrogen bond between the side chain NH2 of Arg115 and the main chain CO of Ser46' plays a critical role in interdomain signaling.     

Properties and functions of the thiamin diphosphate dependent enzyme transketolase

This review highlights recent research on the properties and functions of the enzyme transketolase, which requires thiamin diphosphate and a divalent metal ion for its activity. The transketolase-catalysed reaction is part of the pentose phosphate pathway, where transketolase appears to control the non-oxidative branch of this pathway, although the overall flux of labelled substrates remains controversial. Yeast transketolase is one of several thiamin diphosphate dependent enzymes whose three-dimensional structures have been determined. Together with mutational analysis these structural data have led to detailed understanding of thiamin diphosphate catalysed reactions. In the homodimer transketolase the two catalytic sites, where dihydroxyethyl groups are transferred from ketose donors to aldose acceptors, are formed at the interface between the two subunits, where the thiazole and pyrimidine rings of thiamin diphosphate are bound. Transketolase is ubiquitous and more than 30 full-length sequences are known. The encoded protein sequences contain two motifs of high homology; one common to all thiamin diphosphate-dependent enzymes and the other a unique transketolase motif. All characterised transketolases have similar kinetic and physical properties, but the mammalian enzymes are more selective in substrate utilisation than the nonmammalian representatives. Since products of the transketolase-catalysed reaction serve as precursors for a number of synthetic compounds this enzyme has been exploited for industrial applications. Putative mutant forms of transketolase, once believed to predispose to disease, have not stood up to scrutiny. However, a modification of transketolase is a marker for Alzheimer's disease, and transketolase activity in erythrocytes is a measure of thiamin nutrition. The cornea contains a particularly high transketolase concentration, consistent with the proposal that pentose phosphate pathway activity has a role in the removal of light-generated radicals.     

Human polymorphonuclear leukocytes adhere to complement factor H through an interaction that involves alphaMbeta2 (CD11b/CD18)

The work presented here demonstrates that human complement factor H is an adhesion ligand for human neutrophils but not for eosinophils. The adherence of polymorphonuclear leukocytes (PMNs) to plastic wells coated with factor H depended on divalent metal ions and was augmented by C5a and TNF-alpha. PMN adhesion to factor H in the presence or absence of C5a was blocked specifically by mAbs against CD11b or CD18. Affinity purification using factor H Sepharose followed by immunoprecipitation using mAbs to various integrin chains identified Mac-1 (CD11b/CD18) as a factor H binding receptor. The presence of surface bound factor H enhanced neutrophil activation resulting in a two- to fivefold increase in the generation of hydrogen peroxide by PMNs stimulated by C5a or TNF-alpha. When factor H was mixed with PMNs, 1.4 to 3.8-fold more cells adhered to immobilized heparin or chondroitin A. In addition, augmented adhesion of PMNs was measured when factor H, but not HSA or C9, was absorbed to wells that were first coated with heparin or chondroitin A. The adhesion of PMNs to glycosaminoglycan-factor H was blocked by mAbs to CD11b and CD18. These studies demonstrate that factor H is an adhesion molecule for human neutrophils and suggest that the interaction of factor H with glycosaminoglycans may facilitate the tethering of this protein in tissues allowing factor H to serve as a neutrophil adhesion ligand in vivo.     

A survey of current clinical practice of permanent prostate brachytherapy in the United States

PURPOSE: To help establish standards of care for transperineal interstitial permanent prostate brachytherapy (TIPPB) by obtaining data regarding current clinical practice among the most experienced TIPPB brachytherapists in the United States. METHODS AND MATERIALS: The 70 brachytherapists who performed the greatest number of TIPPB cases in 1995 in the U.S. were surveyed. Each received a comprehensive four page questionnaire that included sections on training and experience, patient and isotope selection criteria, manpower, technique, and follow-up. Thirty-five (50%) surveys were ultimately returned after three mailings and follow-up phone calls. The cumulative experience of the 35 respondents represented approximately 45% of the total TIPPB volume in the U.S. for 1995. Respondents included 29 from the private sector and six from academic programs. RESULTS: The median physician experience with TIPPB was reported as 4.9 years. Each performed an average of 73 TIPPB procedures in 1995 (range 40-300). This represented an increase in volume for most (74%) of the respondents. Sixty-three percent of the respondents attended a formal training course, 54% had TIPPB-specific residency training, and 31% had been proctored (16 had received two or more types of training experience). The most commonly reported selection criteria for implant alone was on Gleason score < or = 7, PSA < 15, < or = Stage T2a, and gland size < or = 60 cc, although no clear consensus was found. Fifty-four percent considered a history of TURP to be a relative contraindication, while 34% considered TURP to have no impact on patient selection. Eighty-six percent of respondents combine brachytherapy with external beam radiation in an average of 32% of their patients. Boosts were given with both 125I prescribed to 120 Gy (75%) or 103Pd to 90 Gy (50%). Sixty percent reported using a Mick applicator, 46% prefer using preloaded needles, and (11%) use both techniques. Real-time imaging was usually performed with ultrasound (94%); most included fluoroscopy (60%). Definitions of PSA control varied widely. CONCLUSIONS: TIPPB clinical practice in the U.S. demonstrates similarities in technique, but differences in patient selection and definitions of biochemical control. It is, therefore, incumbent on those beginning TIPPB programs to carefully review the specific practice details of those institutions with a broad experience.     

Diagnosis of natural rubber latex allergy: multicenter latex skin testing efficacy study. Multicenter Latex Skin Testing Study Task Force

BACKGROUND: No characterized diagnostic natural rubber latex skin testing material is licensed for use in the United States. OBJECTIVE: We have conducted a multicenter clinical skin testing study to document the safety and diagnostic sensitivity and specificity of a candidate Hevea brasiliensis nonammoniated latex (NAL) extract. These data are intended to support the licensing of this reagent for the diagnosis of latex allergy in high-risk populations. METHODS: Three hundred twenty-four subjects (304 adults and 20 children) were classified by their clinical history as having latex allergy (LA group, 124 adults and 10 children) or having no latex allergy (NLA group, 180 adults and 10 children). All subjects provided blood samples and then received sequential puncture skin tests (PSTs) at 1, 100, or 1000 microg/mL protein with a bifurcated needle and NAL (Greer Laboratories) from Malaysian Hevea brasiliensis (clone 600) sap. A 2-stage glove provocation test was used to clarify latex allergy status of individuals with positive history/negative PST result and negative history/positive PST result mismatches. RESULTS: Twenty-four subjects (15%) originally designated as having LA on the basis of their initial clinical history were reclassified to the NLA group on the basis of a negative glove provocation test result. Of the 134 subjects with LA, 54 (40%) were highly sensitive to latex, with a positive PST result at 1 microg/mL NAL. The Greer NAL reagent produced a positive PST rate (sensitivity) of 95% and 99% in subjects with LA at 100 microg/mL and 1 mg/mL, respectively. The negative PST rate (specificity) in 190 subjects with a negative history with the NAL extract at 100 microg/mL and 1 mg/mL, was 100% and 96%, respectively. Immediately after the PST, mild systemic reactions (mainly pruritus) were recorded in 16.1 % of the adults in the LA group and 4.4% of the adults in the NLA group. No reactions required treatment with epinephrine. Only mild delayed reactions were observed in 9.6% (LA group) and 2.8% (NLA group) of subjects 24 to 48 hours after PST. Mean wheal and erythema diameters measured in the 10 children in the LA group with spina bifida at 100 microg/mL and 1 mg/mL were similar to those observed in the adults in the LA group, suggesting that children are not at increased risk for systemic reactions compared with adults. CONCLUSIONS: A suggestive clinical history is necessary but not sufficient for a definitive diagnosis of IgE-dependent latex allergy. These data support the safety and diagnostic efficacy of the Greer NAL, skin test reagent at 100 micro/mL and 1 mg/mL for confirmatory PSTs.