著者

横町 和志 西丸 英治 藤岡 知加子 木口 雅夫 石風呂 実 船間 芳憲 粟井 和夫

出版者

公益社団法人 日本放射線技術学会

雑誌

日本放射線技術学会雑誌 (ISSN:03694305)

巻号頁・発行日

vol.70, no.10, pp.1166-1172, 2014 (Released:2014-10-20)

参考文献数

13

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Purpose: For emergency or pediatric head CT scans, a simplified pillow made of hard sponge instead of a dedicated head holder may be used if it is difficult to immobilize the head. However, the radiation dose when using a simplified head holder may be increased due to radiation absorption by the patient couch if the automatic exposure control (AEC) system is used. In this phantom study, we compared the radiation dose delivered when using a dedicated and a simplified head holder. Materials and Methods: We used a dedicated-type and a pillow-type head holder made of hard sponge (simplified head holder). We placed a 20 cm-diameter cylindrical phantom made of water-equivalent material and an anthropomorphic head phantom in the head holders and then scanned them five times with a 64-detector CT scanner (VCT, GE Healthcare). We performed step-and-shoot and helical scanning with AEC; the noise index was set to 2.8. We measured the radiation dose using fluorescent glass dosimeters in the head phantom and the image noise at five sites in the cylindrical phantom. All values were averaged. Results: With step-and-shoot scans, the mean image noise with the dedicated and the simplified head holder was 3.30 ± 0.05 [SD] and 3.20 ± 0.05, respectively. With helical scans they were 3.00 ± 0.09 and 2.88 ± 0.03, respectively. There was no statistically significant difference (p = 0.02 and 0.04, Student’s t-test). The radiation doses with the dedicated and the simplified head holder were 58.6 and 70.4 mGy, respectively, for step-and-shoot scanning and 41.8 and 49.0 mGy, respectively, for helical scanning. The doses were thus significantly higher with the simplified head holder for both step-and-shoot and helical scanning (p < 0.01 and < 0.01). Conclusion: We recommend the use of a dedicated head holder for head scanning with AEC since the radiation dose was lower than with the simplified head holder.

著者

船間 芳憲

出版者

日本放射線技術学会

雑誌

日本放射線技術学会雑誌 (ISSN:03694305)

巻号頁・発行日

vol.67, no.11, pp.1461-1467, 2011-11-20

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低線量で増加する画像ノイズ、X線量低減の有効策である低管電圧CTと逐次近似画像再構成法について概説する。

著者

永末 望 船間 芳憲 鬼木 里佳 瀬川 敦史 岩竹 聡 川内野 友彦 上谷 雅孝

出版者

公益社団法人 日本放射線技術学会

雑誌

日本放射線技術学会雑誌 (ISSN:03694305)

巻号頁・発行日

vol.65, no.6, pp.765-772, 2009-06-20 (Released:2009-07-14)

参考文献数

15

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We measured the contrast-to-noise ratio (CNR) and evaluated low-contrast images and streak artifacts to optimize abdominal C-arm CT imaging, and we investigated the view number, acquisition matrix, and pixel depth. To measure CNR, we filled 0.125–1.0-inch cavities in an American Association of Physicists in Medicine (AAPM) CT performance phantom with a sodium chloride solution. Five radiological technologists visually evaluated the noise, signal conspicuity at low-and high-signal density, and the overall image quality using paired comparisons based on Thurstone’s law. In a given acquisition matrix, the total view number had the greatest effect on the image noise, artifacts, and signal detectability on C-arm CT images. For a given incident dose per view on the flat-panel detector (FPD), fewer images with noise and streak artifacts resulted when a larger view number was selected.