EVALUATION OF INTERNAL EXPOSURE TO RADIOACTIVE AEROSOL GENERATED FROM PLASMA MELTING SYSTEM USING THE BIDAS CODE.

The radioactive aerosol generated by the Nuclear Power Plant (NPP) decommissioning process can be inhaled by workers and deposited inside the human body, resulting in internal exposure. Because internal exposure, unlike external exposure, is difficult to measure directly, it is all the more necessary to assess the dose workers receive as a result of internal exposure. Precise assessment of the internal exposure necessitates actual measurements in the work environment such as the workers' respiration rate, kind of nuclide and amount of captured nuclide. However, in the event of difficulties in securing these measurements, the internal exposure dose can be estimated based upon the recommended values by the ICRP (International Commission on Radiological Protection) such as the intake fraction and particle size. In this study, 5 µm was selected as the particle size as recommended by the ICRP, and both heavy and light respiratory rates were used in the calculation. With respect to the nuclides contained in the radioactive aerosol and their concentrations, the data captured for the aerosol in the melting facility on the Kozloduy NPP premises in Bulgaria were applied to estimate workers' internal exposure. As a result, each worker was found not to have received more than 20 mSv/yr, which is the maximum annual permissible dose for workers.

Objective assessment of image quality and dose reduction in CT iterative reconstruction.

PURPOSE: Iterative reconstruction (IR) algorithms have the potential to reduce radiation dose in CT diagnostic imaging. As these algorithms become available on the market, a standardizable method of quantifying the dose reduction that a particular IR method can achieve would be valuable. Such a method would assist manufacturers in making promotional claims about dose reduction, buyers in comparing different devices, physicists in independently validating the claims, and the United States Food and Drug Administration in regulating the labeling of CT devices. However, the nonlinear nature of commercially available IR algorithms poses challenges to objectively assessing image quality, a necessary step in establishing the amount of dose reduction that a given IR algorithm can achieve without compromising that image quality. This review paper seeks to consolidate information relevant to objectively assessing the quality of CT IR images, and thereby measuring the level of dose reduction that a given IR algorithm can achieve. METHODS: The authors discuss task-based methods for assessing the quality of CT IR images and evaluating dose reduction. RESULTS: The authors explain and review recent literature on signal detection and localization tasks in CT IR image quality assessment, the design of an appropriate phantom for these tasks, possible choices of observers (including human and model observers), and methods of evaluating observer performance. CONCLUSIONS: Standardizing the measurement of dose reduction is a problem of broad interest to the CT community and to public health. A necessary step in the process is the objective assessment of CT image quality, for which various task-based methods may be suitable. This paper attempts to consolidate recent literature that is relevant to the development and implementation of task-based methods for the assessment of CT IR image quality.

Color image detection by biomolecular photoreceptor using bacteriorhodopsin-based complex LB films.

A biomolecular photoreceptor consisting of bacteriorhodopsin (bR)-based complex Langmuir-Blodgett (LB) films was developed for color image detection. By mimicking the functions of the pigments in retina of human visual system, biomolecules with photoelectric conversion function were chosen and used as constituents for an artificial photoreceptor. bR and flavin were deposited onto the patterned (9-pixelized) ITO glass by LB technique. A 9-pixel biomolecular photoreceptor was fabricated with a sandwich-type structure of ITO/LB films/electrolyte gel/Pt. Since each functional molecule shows its own response characteristic according to the light illumination in the visible region, the simplified knowledge-based algorithm for interpretation of the incident light wavelength (color) was proposed based on the basic rule describing the relationship between the photoelectric response characteristics and the incident light wavelength. When simple color images were projected onto the photoreceptor, the primary colors in visible light region, red, green, and blue were clearly recognized, and the projected color images were fairly well reproduced onto the color monitor by the proposed photoreceptor with the knowledge-based algorithm. It is concluded that the proposed device has a capability of recognizing the color images and can be used as a model system to simulate the information processing function of the human visual system.

Digital optical imaging of green fluorescent proteins for tracking vascular gene expression: feasibility study in rabbit and human cell models.

PURPOSE: To investigate the feasibility of using a sensitive digital optical imaging technique to detect green fluorescent protein (GFP) expressed in rabbit vasculature and human arterial smooth muscle cells. MATERIALS AND METHODS: A GFP plasmid was transfected into human arterial smooth muscle cells to obtain a GFP-smooth muscle cell solution. This solution was imaged in cell phantoms by using a prototype digital optical imaging system. For in vivo validation, a GFP-lentivirus vector was transfected during surgery into the carotid arteries of two rabbits, and GFP-targeted vessels were harvested for digital optical imaging ex vivo. RESULTS: Optical imaging of cell phantoms resulted in a spatial resolution of 25 microm/pixel. Fluorescent signals were detected as diffusely distributed bright spots. At ex vivo optical imaging of arterial tissues, the average fluorescent signal was significantly higher (P <.05) in GFP-targeted tissues (mean +/- SD, 9,357.3 absolute units of density +/- 1,001.3) than in control tissues (5,633.7 absolute units of density +/- 985.2). Both fluorescence microscopic and immunohistochemical findings confirmed these differences between GFP-targeted and control vessels. CONCLUSION: The digital optical imaging system was sensitive to GFPs and may potentially provide an in vivo imaging tool to monitor and track vascular gene transfer and expression in experimental investigations.

Naturally acquired antibody responses to the C-terminal region of merozoite surface protein 1 of Plasmodium vivax in Korea.

We expressed a protein in Saccharomyces cerevisiae in order to evaluate the humoral immune responses to the C-terminal region of the merozoite surface protein 1 of Plasmodium vivax. This protein (Pv200(18)) had a molecular mass of 18 kDa and was reactive with the sera of individuals with patent vivax malaria on immunoblotting analysis. The levels of immunoglobulin M (IgM) and IgG antibodies against Pv200(18) were measured in 421 patients with vivax malaria (patient group), 528 healthy individuals from areas of nonendemicity (control group 1), and 470 healthy individuals from areas of endemicity (control group 2), using the indirect enzyme-linked immunosorbent assay (ELISA) method. To study the longevity of the antibodies, 20 subjects from the patient group were also tested for the antibody levels once a month for 1 year. When the cutoff values for seropositivity were determined as the mean + 3 x standard deviation of the antibody levels in control group 1, both IgG and IgM antibody levels were negative in 98.5% (465 of 472) of control group 2. The IgG and IgM antibodies were positive in 88.1% (371 of 421) and 94.5% (398 of 421) of the patient group, respectively. The IgM antibody became negative 2 to 4 months after the onset of symptoms, whereas the IgG antibody usually remained positive for more than 5 months. In conclusion, indirect ELISA using Pv200(18) expressed in S. cerevisiae may be a useful diagnostic method for vivax malaria.