나선형 CT와 16 Slice MDCT의 Brain과 Abdome 검사 시 산란선에 관한 연구

Study on Scattered Ray in Spiral CT and 16-Slice MDCT of Brain and Abdomen

Purpose The present study purposed to measure the degree of scattered ray of radiation in spiral CT and 16-Slice MDCT of brain and abdomen using Rando phantom and to examine the change in non-patients’ exposure to scattered ray according to distance between the central beam and the patient and the reduction of exposure according to the thickness of a protection outfit for shielding from radiation. Materials and methods We measured the change of scattered ray on non-patients according to distance between the brain beam of CT and the patient and the change of scattered ray according to the thickness of an apron for shielding from scattered ray, assuming a critically ill patient and an infant on Somatom Plus 4 and MDCT table at the present hospital using Rando phantom under the same setting of cerebral and abdominal CT scan parameters. In order to reduce errors in measurements, each factor was measured three times and the mean value was obtained. The height of the survey meter probe was 111.5cm, which is ordinary adults’ iliac crest level. Results A. In the result of brain test with Plus 4, the reduction rate of scattered ray at a distance of 50cm according to distance from the central beam without an apron (15.5mR) and with an apron on: 1. When Pb equivalent was 2.5mm, the reduction rate of scattered ray was 91.55% at 50cm, 94.82% at 100cm, 98.64% at 150cm, and 99.38% at 200cm. 2. When Pb equivalent was 5.0mm, the reduction rate of scattered ray was 98.50% at 50cm, 99.26% at 100cm, 99.58% at 150cm, and 99.70% at 200cm. 3. When Pb equivalent was 7.5mm, the reduction rate of scattered ray was 98.87% at 50cm, 99.37% at 100cm, 99.79% at 150cm, and 99.80% at 200cm. B. In the result of brain test with 16-Slice MDCT, the reduction rate of scattered ray at a distance of 50cm according to distance from the central beam without an apron (16.47mR) and with an apron on: 1. When Pb equivalent was 2.5mm, the reduction rate of scattered ray was 95.40% at 50cm, 97.69% at 100cm, 98.84% at 150cm, and 99.33% at 200cm. 2. When Pb equivalent was 5.0mm, the reduction rate of scattered ray was 98.54% at 50cm, 99.18% at 100cm, 98.54% at 150cm, and 99.66% at 200cm. 3. When Pb equivalent was 7.5mm, the reduction rate of scattered ray was 98.10% at 50cm, 99.55% at 100cm, 99.86% at 150cm, and 99.78% at 200cm. C. In the result of abdomen test with Plus 4, the reduction rate of scattered ray at a distance of 50cm according to distance from the central beam without an apron (61.47mR) and with an apron on: 1. When Pb equivalent was 2.5mm, the reduction rate of scattered ray was 91.52% at 50cm, 97.15% at 100cm, 98.74% at 150cm, and 99.40% at 200cm. 2. When Pb equivalent was 5.0mm, the reduction rate of scattered ray was 98.48% at 50cm, 99.19% at 100cm, 99.60% at 150cm, and 99.72% at 200cm. 3. When Pb equivalent was 7.5mm, the reduction rate of scattered ray was 98.81% at 50cm, 99.49% at 100cm, 99.71% at 150cm, and 99.82% at 200cm. D. In the result of abdomen test with 16-Slice MDCT, the reduction rate of scattered ray at a distance of 50cm according to distance from the central beam without an apron (79.47mR) and with an apron on: 1. When Pb equivalent was 2.5mm, the reduction rate of scattered ray was 96.56% at 50cm, 98.64% at 100cm, 99.34% at 150cm, and 99.69% at 200cm. 2. When Pb equivalent was 5.0mm, the reduction rate of scattered ray was 98.96% at 50cm, 99.45% at 100cm, 99.72% at 150cm, and 99.85% at 200cm. 3. When Pb equivalent was 7.5mm, the reduction rate of scattered ray was 99.56% at 50cm, 99.75% at 100cm, 99.86% at 150cm, and 99.94% at 200cm. Conclusion According to the results of this study, scattered ray decreased with the increase of distance. The scattered ray shielding effect was highest when the Pb equivalent of the radiation shielding outfit was 7.5mm. However, the reduction rate of scattered ray with a radiation shielding outfit at thickness of 5.0mm was higher (+4% on the average) than that with an outfit a