An iterative approach to the beam hardening correction in cone beam CT

In computed tomography (CT), the beam hardening effect has been known to be one of the major sources of deterministic error that leads to inaccuracy and artifact in the reconstructed images. Because of the polychromatic nature of the x-ray source used in CT and the energy-dependent attenuation of most materials, Beer's law no longer holds. As a result, errors are present in the acquired line integrals or measurements of the attenuation coefficients of the scanned object. In the past, many studies have been conducted to combat image artifacts induced by beam hardening. In this paper, we present an iterative beam hardening correction approach for cone beam CT. An algorithm that utilizes a tilted parallel beam geometry is developed and subsequently employed to estimate the projection error and obtain an error estimation image, which is then subtracted from the initial reconstruction. A theoretical analysis is performed to investigate the accuracy of our methods. Phantom and animal experiments are conducted to demonstrate the effectiveness of our approach.     

Interleukin-1 (IL-1) production in a mouse tissue chamber model of inflammation. II. Identification of (tissue) macrophages as the IL-1 producing cells and the effect of anti-inflammatory drugs

We have used our newly described mouse tissue chamber model [1], to investigate the process of IL-1 production in more detail. The inflammatory reaction in the tissue surrounding the implanted chambers was investigated histologically and by using the polymerase chain reaction (PCR). The inflammatory response included influx of leucocytes into the granuloma surrounding the tissue chamber, expression of IL-1 on macrophages present in the inflamed tissue and an increase in the mRNA coding for IL-1 and IL-6 proteins in the granuloma. The effects of three anti-inflammatory or immunosuppressive drugs, prednisolone, indomethacin and cyclosporin A, on IL-1 and PGE₂ production in zymosan andBordetella-pertussis-vaccine (BPV)-challenged tissue chambers were also examined. Oral treatment with prednisolone and cyclosporin A of zymosan-challenged animals showed a dose-dependent reduction of IL-1 concentrations, but no effect of indomethacin. Both prednisolone and indomethacin dose-dependently reduced PGE₂ concentrations to control levels, while cyclosporin A was effective only at the highest dose tested (100 mg/kg/day p.o.). In drug-treated BPV-challenged animals, prednisolone and cyclosporin A also showed a dose-dependent reduction of IL-1, while indomethacin was again ineffective. Prednisolone and indomethacin also dose-dependently reduced the PGE₂ concentrations to control levels, whereas cyclosporin A was effective only at the highest dose tested (100 mg/kg/day p.o.).This model will be useful for investigating the mechanisms controlling the production of IL-1 from the mRNA level to the secretion of mature biologically active protein [1], and in the search for new drugs which could selectively interfere with this process.     

Fatality due to paraquat intoxication: confirmation by postmortem tissue analysis

A brief case report is presented describing a patient who unknowingly ingested a fatal amount of paraquat, presumably mixed in some illicit moonshine alcohol. Despite an initial clinical presentation typical of paraquat intoxication, the herbicide was absent upon analysis of multiple urine and blood specimens, and the diagnosis was confirmed only postmortem after determination of high paraquat tissue concentrations in all the major organs. Autopsy results are presented along with a discussion of the histopathologic changes observed in the lungs, liver, and kidneys. Because the combination of toxicologic sequelae attributable to acute paraquat poisoning is fairly unique to this agent, the diagnosis must be suspected highly early in the clinical course of such cases and appropriate therapy initiated, despite the inability to isolate paraquat on preliminary laboratory screening.     

The MMPI as a predictor of response to conservative treatment for low back pain.

Studies that used the MMPI to predict the response of chronic low back pain patients to standard medical treatment have not produced definitive results. Patients seen in a university hospital orthopedic back pain clinic were given the MMPI before treatment, and 6 to 12 months later 76 patients completed follow-up forms that indicated their level of intensity during the previous week and their ratings of the success of treatment in relieving their pain as well as in enabling them to return to normal activities. Predictions of poor response were made in terms of either single MMPI scales or code types. Patients with poor outcome on two of the three criteria (level of pain intensity and ability to return to normal activities) had significantly higher scores on the Hs scale. The predicted high risk code types very accurately identified patients with poor response on the same two criteria; however, the code-type procedure overpredicted poor response in the good outcome group.     

Development and Evaluation of a Tetraplex Flow Cytometric Assay for Quantitation of Serum Antibodies to Neisseria meningitidis Serogroups A, C, Y, and W-135

A rapid and simple method for the simultaneous quantitation of serum immunoglobulin G (IgG) antibodies specific for Neisseria meningitidis serogroups A, C, Y, and W-135 was developed and evaluated. Four bead sets were generated, each conjugated with one of the meningococcal capsular polysaccharides (A, C, Y, or W-135) and serologically assessed by the use of antimeningococcal international reference sera. Cross-reactivity studies demonstrated no inhibition between monoplex and multiplex assays, and the assay was linear over a 24-fold serum dilution range. Inhibition studies demonstrated that the assay is specific, with <25% heterologous inhibition occurring. The assay was also found to have low intra- and interassay variations and limits of detection ≤650 pg/ml. A comparison of the meningococcal bead assay with the standardized meningococcal enzyme-linked immunosorbent assay showed a good correlation between the IgG concentrations obtained by each assay. The tetraplex assay has the potential to be an important addition to the serologic evaluation of meningococcal capsular polysaccharide conjugate vaccines.     

Distribution of actin and myosin in a rat neuronal cell line infected with herpes simplex virus

Summary The indirect immunofluorescence technique was used to study alterations in the distribution of actin and myosin filaments in a rat B 103 neuronal cell line infected with herpes simplex virus type 1 (HSV-1). In uninfected cells, actin filaments were arranged in parallel and ran lengthwise from one end of the cell to the other; although myosin filaments were closely associated with actin filaments, additional myosin formed a netlike distribution which did not stain for actin. In infected cells, actin filaments became more randomly aligned and were concentrated along with myosin in close association with rosette-like formations of nuclei in syncytial cells; structural organization of actin and myosin within these intensely staining areas was no longer evident. The possible role of contractile proteins (actin and myosin) in viral infections of neural tissue is raised.With 3 Figures     

Identification of coagulase-negative staphylococci with the API staph system.

A kit for the identification of staphylococci based on the biochemical criteria proposed by Kloos and Schleifer (W.E. Kloos and K.H. Schleifer, J. Clin. Microbiol., 1:82-88, 1975) is now available commercially. The system was used to identify 100 strains of coagulase-negative staphylococci isolated from various body sites as the primary etiological agent of clinical infection. The increasing importance of staphylococci and their resistance to antibiotics provided the rationale for such an investigation. Over 90% of the Staphylococcus isolates were easily identified as to their species on the basis of their reaction profile to 19 biochemical tests included in the kit. The remainder, which showed minor variations, could also be assigned to the various species. Identification of the isolates was as follows: S. epidermidis, 54; S. haemolyticus, 5; S. simulans, 2; S. hominis, 1; S. capitis, 4; S. cohnii, 2; S. warneri, 2; S. xylosus, 8; and S. saprophyticus, 22. Antibiotic sensitivity patterns were determined for each of the isolates. Novobiocin resistance was detected in strains of S. saprophyticus and S. xylosus, a property hitherto recognized in Micrococcus sp. type 3 causing bacteriuria in young women. Resistance to penicillin was widespread among strains of several species, whereas resistance to tetracycline was mainly confined to strains of S. epidermidis. General resistance to sulfamethoxazole and nalidixic acid was found among all strains, with almost uniform sensitivity to the other drugs tested.