Computed tomography (CT) has evolved remarkably through device improvement and advancement of peripherals, including computers. In 1999, multi detector row CT (MDCT) appeared and rapid high speed scanning became possible. However, usefulness of MDCT in actual clinical application cannot be assessed until the exposure doses are assessed appropriately. Since CT examinations need a comparatively high dose, it is necessary to evaluate patient exposure for introduction of MDCT.
Patient doses by three types of MDCTs were evaluated for cases of scanning of the chest and abdomen pelvis.
The examination conditions were the same as those in actual clinical examinations. The obtain ed effective doses were 9.4-28mSv for the chest examination and 13-28mSv for the abdomen pelvis. The average surface doses varied between 16-43mGy for the chest examination and 20-37mGy for the abdomen pelvis.
The highest surface dose was 57mGy for the abdomen pelvis examination. The exposed doses differed according to scanning method and imaging conditions such as tube current, slice thickness and so on. It seemed that there is room for dose reduction by proper adjustment of scan conditions in MDCT examinations.

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Measurement of the rate constant parameters of the tracer 18F-FDG, used with positron emission tomography (PET) to determine the cerebral metabolic rate of glucose (CMRG1c), can provide a clear understanding of the physiological processes in the human brain. At present, the methods that are widely used to obtain CMRG1c, such as nonlinear least squares (NLS), first require the reconstruction of a time sequence of images. The reconstruction of these images requires a large amount of computation, especially in 3D Depth -of Interaction PET (DOI-PET), and the nonlinear based methods also require a large amount of computation. In this paper, we propose a fast parametric image reconstruction method for 18F-FDG dynamic PET studies. In our method a deconvolving process is first employed on the time sequential projection data to remove the effect of the measured plasma time activity. The deconvolved terms are integrated over three different time intervals and the parameters for determining CMRG1c can be obtained analytically. Our method requires only three reconstructing processes and reduces the computational demand to estimate CMRG1c. The algorithm performance is evaluated using a digital phantom and a clinical data set and the results show that the proposed method produces images with the same or better quality as the images from the NLS method, with much less computation compared to the NLS method.

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Dry-processing leaser imager systems have become popular due to the advantages such as the elimination of the cost and labor associated with the wet chemical processing. In this paper, the stability of a dry-processing imager system Drypro 722/SD -P was studied using SMPTE pattern films processed by a dry-processing imager Drypro 722 and a wet-processing imager Li - 8/SRX -502 at three different times of the day over a period of five consecutive working days. The dry system is inferior to the wet system on the stability and the spatial uniformity, so that the problems assess the necessity of QC for Drypro 722 Laser Imagers. The instability of the post-processing dry and wet films is also studied. The dry film is very instable compared with the wet film. Accordingly the wet film must be handled with the care.

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