Extending the dynamic range of biomedical micro-computed tomography for application to geomaterials.

BACKGROUND: X-ray computed tomography (CT) can non-destructively examine objects by producing three-dimensional images of their internal structure. Although the availability of biomedical micro-CT offers the increased access to scanners, CT images of dense objects are susceptible to artifacts particularly due to beam hardening. OBJECTIVE: This study proposes and evaluates a simple semi-empirical correction method for beam hardening and scatter that can be applied to biomedical scanners. METHODS: Novel calibration phantoms of varying diameters were designed and built from aluminum and poly[methyl-methacrylate]. They were imaged using two biomedical micro-CT scanners. Absorbance measurements made through different phantom sections were fit to polynomial and inversely exponential functions and used to determine linearization parameters. Corrections based on the linearization equations were applied to the projection data before reconstruction. RESULTS: Correction for beam hardening was achieved when applying both scanners with the correction methods to all test objects. Among them, applying polynomial correction method based on the aluminum phantom provided the best improvement. Correction of sample data demonstrated a high agreement of percent-volume composition of dense metallic inclusions between using the Bassikounou meteorite from the micro-CT images (13.7%) and previously published results using the petrographic thin sections (14.6% 8% metal and 6.6% troilite). CONCLUSIONS: Semi-empirical linearization of X-ray projection data with custom calibration phantoms allows accurate measurements to be obtained on the radiodense samples after applying the proposed correction method on biomedical micro-CT images.

Inactivated influenza virus vaccines in man: a comparative study of subunit and split vaccines using two methods for assessment of antibody responses.

The serum antibody responses and reactions of volunteers to a trivalent subunit influenza virus vaccine prepared using cetyl trimethyl ammonium bromide (CTAB) or trivalent split vaccine prepared by ether-extraction, were essentially similar, although the antibody levels to the A/Brazil/78 (H1N1) components of the vaccine were greater in volunteers receiving the subunit preparation. Antibody responses to the vaccines were assessed using both the haemagglutination-inhibition (HI) and single radial haemolysis (SRH) tests. Although good correlation was found between the tests with respect to both antibody titres in individual sera and antibody responses in serum pairs to both A(H3N2 and H1N1) and B influenza viruses, the greater reliability of SRH, indicates this test should supplant the HI test for the routine measurement of antibody responses to influenza viruses.

A new surface-antigen-adsorbed influenza virus vaccine. II. Studies in a volunteer group.

A group of 23 volunteers were each inoculated with 600 CCA of a new form of influenza virus A/England/42/72 vaccine; this vaccine consisted of purified haemagglutinin and neuraminidase antigens adsorbed to alhydrogel. No significant reactions to the vaccine were reported. Twenty-two volunteers produced increased titres of serum HI antibody, and all showed increased titres of NI antibody after immunization. Thus, for volunteers with no pre-immunization serum HI antibody, the geometric mean titre of serum antibody increased from 1/5 to 1/196 after immunization. Ten volunteers developed local neutralizing antibody after immunization; this antibody response was detected most frequently in volunteers who showed the greater serum antibody response to immunization, and in nasal washings with the higher concentrations of protein and IgA. Ten weeks after immunization, the vaccinees and a group of matched controls were inoculated intranasally with attenuated A/England/42/72 virus. Evidence of infection with the challenge virus was found in 14 of the control subjects and in one of the vaccinees. The results indicate that the surface-antigen-adsorbed vaccine induced high titres of serum antibody, and gave significant protection against challenge infection.