Chest radiograms obtained by using Fuji Computed Radiography(FCR) system were compared to conventional film/screen radiograms. The FCR images showed better image quality in diagnostic informations than the conventional chest images. In FCR, the radiation exposure to patient for chest examination could be reduced up to one tenths of conventional chest examination. The main advantages or FCR were considered to depend on the contrast processing and frequency processing properties. The use of FCR in clinical work may improve both diagnostic quality and radiation exposure.

Experiment was conducted on the image quality and exposure dose following replacement of $CaWO_4$ system screen BH-III and BX-III which have so far been used for high-voltage hard-radiation quality radiography, with rare earth system screen KO750, combined with high contrast film SRH, while additional filter was altered, Cu 0.8 mm+Al 1.4 mm(HVL : Al 8.8 mm), Cu 1.3 mm+Al 1.0 mm(HVL : Al 10.6 mm) and Cu 1.8 mm+Al 1.5 mm(HVL : Al 11.4 mm). AS a result, visual evaluation did not detect extreme changes in image quality under the respective condition(HVL : $Al\;8.8\;mm{\sim}Al\;11.4\;mm$). It was noted, however, that surface exposure dose declined with an increase in the thickness of the additional filter, as it was $18.9\;{\mu}Gy$ at HVL Al 8.8 mm, $17.5\;{\mu}Gy$ at Al 10.6 mm and $15.7\;{\mu}Gy$ at Al 11.4 mm. Considering the limited rating of X-ray equipment and wear of machinery, however, the range of $Cu\;1.3\;mm{\sim}1.8\;mm+Al\;1.0\;mm{\sim}1.5\;mm(1/16\;VL{\sim}1/32\;VL)$ seemed to be a limit.

The combined effect of radiation and ultrasound has been studied in mouse embryos. Radiation and/or ultrasound were adminstered to ICR mice on day 8 of gestation. Intrauterine death, gross malformation, and fetal body weight were selected as indicators of effects. Does of whole-body ${\gamma}-irradiation$ were 0.5 to 2.5 Gy and those of ultrasound were $0.5\;W/cm^2$ to $3\;W/cm^2$. Intrautrine mortality increased with increasing radiation dose ; this trend was more remarkable in combination with ultrasound. Gross malformations such as exencephaly and anophthalmia/microphthalmia appeared frequently in the fetuses treated with both radiation and ultrasound. Decreased fetal weight was observed even in mice treated with 1.5 Gy of radiation or $1\;W/cm^2$ of ultrasound. There was a linear relationship between dose and reduction of fetal weight. The fetal weight was sensitive, precise and easy-to-handle indicator for the effects of growth retardation. Intrauterine mortality and frequencies of exencephaly and anophthalmia/microphthalmia were higher than the sum of those induced by radiation and by ultrasound. The results indicatied that the combined action of radiation and ultrasound on intrauterine death and malformations was synergistic.

SPECT 영상에서 콤프톤 산란 광자는 공간분해능의 감소와 그 양을 측정하는데 있어 정확성과 정밀성을 감소시킨다. 이와같은 콤프톤 산란의 영향을 감소시키기 위하여 사용하는 대부분의 보정방법은 선원의 위치로부터 거리의 단일지수함수로 대칭인 산란분포함수를 고려하게 된다. 본 연구는 균등 및 불균등 산란에 대한 산란분포함수를 얻기 위하여 보다 현실적인 접근방법을 시도하였다. 산란 및 비산란광자의 공간분포와 에너지분포를 얻기 위하여 뼈, 폐, 물의 균등 및 불균등 분포로 된 원통형의 팬톰 속에 $^{99m}Tc$의 선선원 및 점선원을 놓고 Monte Carlo Simulation을 하였으며, 깊이의 함수, media의 접촉영역으로부터 선원거리 및 산란체의 밀도의 변화로 표현한 산란분포함수(SDF)를 얻었다. 산란분포함수는 균등한 뼈, 폐, 물에서는 선원위치로부터 거리의 단일지수함수(single exponential functions)로 대칭으로 나타났으며, 두 물체의 조합에서는 2중지수함수(dual exponential functions)로 비대칭으로 나타났다. 산란분율은 20% window photopeak에서 총 계수의 8%에서 53%까지 다양한 변화가 있었으며, 지수함수의 기울기는 $0.1{\sim}0.9\;cm^{-1}$의 범위로 나타났다. 불균등 산란체에서 얻은 산란분포함수는 SPECT 영상에 있어 콤프톤 산란의 감소에 대한 보다 정확한 보정방법의 개발에 필요한 정보를 제공할 것이다.

I reduced overexposed X-Ray film image with farmer reduction method and $KMnO_4$ reduction method. The results are as follows : 1. In farmer reduction method, there appears linear decreasing film image density. 2. In $KMnO_4$ reduction method, there appears over proportional reduction. 3. When red prussiate is compared with $KMnO_4$ reduction method, the latter shows more intense reduction. 4. If the reduction solution isn't used within 10 minutes after dilution, it becomes oxidized and the ability is decreased remarkably.