日本放射線技術学会雑誌
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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67 巻, 9 号
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巻頭言
第39回秋季学術大会プログラム
原著
  • 新規開発直接変換型ディジタルマンモグラフィ装置の最適な撮影条件の検討
    遠藤 登喜子, 白岩 美咲, 大岩 幹直, 西田 千嘉子, 森田 孝子, 吉川 和明, 佐藤 康幸, 林 孝子, 市原 周, 森谷 鈴子, ...
    2011 年 67 巻 9 号 p. 1151-1163
    発行日: 2011/09/20
    公開日: 2011/09/22
    DOIhttps://doi.org/10.6009/jjrt.67.1151
    ジャーナル フリー
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    A new direct-conversion detector for DR mammography has improved the detectability of microcalcifications and masses. Each optimized exposure condition (target/filter combination and tube voltage) was defined through comparison of physical values and visual evaluation on breast specimens using the innovative DR mammography. The contrast-to-noise-ratios (CNRs) of PMMA phantoms of various thicknesses were obtained under a variety of exposure conditions whose average glandular doses (AGDs) were made consistent. Fifty breast specimens were irradiated under these combinations. Visual evaluation was conducted on the images, whose histograms were controlled for consistency. In the phantoms with thicknesses of 20 mm or more, tungsten/rhodium had the highest CNRs of the targets/filters such as molybdenum/molybdenum and molybdenum/rhodium. For visualizing microcalcifications and masses on breast specimens of thicknesses of 35 mm and below, molybdenum/molybdenum was the best. Nevertheless, to obtain better image quality, molybdenum/rhodium was superior for 35–55 mm thickness, and tungsten/rhodium was superior for 55 mm and above under the same AGD, enabling accurate and efficient diagnosis. The study showed that the exposure conditions differ for obtaining the highest CNR using phantoms and those under which breast specimen images allow the most accurate and efficient diagnosis. In addition, image evaluations of the breast specimens allowed optimization of exposure conditions that are closer to those of the actual diagnosis using mammography.
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  • 外部放射線治療における腫瘍位置確認用金マーカからの散乱線による人体への影響の検討
    羽原 幸作, 下郷 智弘, 青山 裕一, 林 直樹, 安井 啓祐, 松浦 寛司, 古川 隆志, 川浪 亮太, 小幡 康範
    2011 年 67 巻 9 号 p. 1164-1173
    発行日: 2011/09/20
    公開日: 2011/09/22
    DOIhttps://doi.org/10.6009/jjrt.67.1164
    ジャーナル フリー
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    Image-guided radiation therapy using a gold marker-based tumor tracking technique provides precise patient setup and monitoring. However, the marker consists of high-Z material, and the resulting scattered rays tend to have adverse effects on the dose distribution of radiotherapy. The purpose of this study was to evaluate the dosimetric perturbation due to the use of a gold marker for radiotherapy in the lungs. The relative dose distributions were compared with film measurement, Monte Carlo simulation, and XiO calculation with the multi grid superposition algorithm using two types of virtual lung phantoms, which were composed of tough water phantoms, tough lung phantoms, cork boards, and a 2.0-mm-diameter gold ball. No dose increase and decrease in the vicinity of the gold ball was seen in the XiO calculations, although it was seen in the film measurements and the Monte Carlo simulation. The dose perturbation due to a gold marker cannot be evaluated using XiO calculation with the superposition algorithm when the tumor is near a gold marker (especially within 0.5 cm). To rule out the presence of such dose perturbations due to a gold marker, the distance between the gold marker and the tumor must therefore be greater than 0.5 cm.
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  • 高解像度ディジタルカメラを用いた高精度放射線治療用6軸寝台の位置精度測定法の検討
    武村 哲浩, 上田 伸一, 能登 公也, 倉田 雄一, 小路 佐織
    2011 年 67 巻 9 号 p. 1174-1182
    発行日: 2011/09/20
    公開日: 2011/09/22
    DOIhttps://doi.org/10.6009/jjrt.67.1174
    ジャーナル フリー
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    Purpose: In this study, we proposed and evaluated a positional accuracy assessment method with two high-resolution digital cameras for add-on six-degrees-of-freedom radiotherapy (6D) couches. Methods and Materials: Two high resolution digital cameras (D5000, Nikon Co.) were used in this accuracy assessment method. These cameras were placed on two orthogonal axes of a linear accelerator (LINAC) coordinate system and focused on the isocenter of the LINAC. Pictures of a needle that was fixed on the 6D couch were taken by the cameras during couch motions of translation and rotation of each axis. The coordinates of the needle in the pictures were obtained using manual measurement, and the coordinate error of the needle was calculated. The accuracy of a HexaPOD evo (Elekta AB, Sweden) was evaluated using this method. Results: All of the mean values of the X, Y, and Z coordinate errors in the translation tests were within ±0.1 mm. However, the standard deviation of the Z coordinate errors in the Z translation test was 0.24 mm, which is higher than the others. In the X rotation test, we found that the X coordinate of the rotational origin of the 6D couch was shifted. Conclusions: We proposed an accuracy assessment method for a 6D couch. The method was able to evaluate the accuracy of the motion of only the 6D couch and revealed the deviation of the origin of the couch rotation. This accuracy assessment method is effective for evaluating add-on 6D couch positioning.
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  • 銅製パイプ型吸収体を用いた新しい実効エネルギー測定法
    飯田 泰治, 能登 公也, 三井 渉, 高田 忠徳, 山本 友行, 松原 孝祐
    2011 年 67 巻 9 号 p. 1183-1191
    発行日: 2011/09/20
    公開日: 2011/09/22
    DOIhttps://doi.org/10.6009/jjrt.67.1183
    ジャーナル フリー
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    The general method of measuring the half-value layer (HVL) for X-ray computed tomography (CT) using square aluminum-sheet filters is inconvenient in that the X-ray tube has to be set to stationary mode. To avoid this inconvenience, we investigated a new method using copper-pipe filters that cover the ionization chamber (copper-pipe method). Using this method, the HVL can be measured at the isocenter in the rotation modes of CT. We examined the accuracy and reproducibility of the copper-pipe method compared with those of the general method. The effective energy measured using the copper-pipe method correlated well with the general method (y=1.064x, r=0.987), and its error was 1.81±1.38%. The results indicate that the copper-pipe method enables accurate measurement of the effective energy of X-ray CT and is a convenient method suited to all general X-ray equipment as well as all X-ray CT.
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ノート
  • Multi transmitにおける画像均一性とコントラストの基礎的検討
    渋川 周平, 堀江 朋彦, 西尾 広明, 室 伊三男
    2011 年 67 巻 9 号 p. 1192-1199
    発行日: 2011/09/20
    公開日: 2011/09/22
    DOIhttps://doi.org/10.6009/jjrt.67.1192
    ジャーナル フリー
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    In 3.0-T magnetic resonance imaging (MRI), shortened radio frequency (RF) wavelengths cause B1 inhomogeneity. Multi transmit (MT) has been reported as a method of solving this problem. We compared MT with single transmit (ST) and ST body-tuned CLEAR (BTC) in terms of basic performance because we got an opportunity to use MT. A phantom was used to evaluate the uniformity of the flip angles (FAs) of images, the phantom’s diameter, and the specific electric conductivity. To evaluate contrast, volunteers performed the significant difference test, and the changes in the FA of the phantom were measured. MT and BTC were better than ST in terms of the uniformity of the images. MT had the best contrast. The results showed that the uniformity of the images and the contrast were improved using MT compared with ST because MT can be uniformly irradiated to an object using two individual RF transmitters.
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  • 放射線技師教育用コーンビームCTシステムの開発
    寺本 篤司, 尾崎 香帆, 宮下 真梨子, 大野 智之, 津坂 昌利, 藤田 広志, 小原 健
    2011 年 67 巻 9 号 p. 1200-1208
    発行日: 2011/09/20
    公開日: 2011/09/22
    DOIhttps://doi.org/10.6009/jjrt.67.1200
    ジャーナル フリー
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    For radiological technologists, it is very important to understand the principle of computed tomography (CT) and CT artifacts derived from mechanical and electrical failure. In this study, a CT system for educating radiological technologists was developed. The system consisted of a cone-beam CT scanner and educational software. The cone-beam CT scanner has a simple structure, using a micro-focus X-ray tube and an indirect-conversion flat panel detector. For the educational software, we developed various educational functions of image reconstruction and reconstruction parameters as well as CT artifacts. In the experiments, the capabilities of the system were evaluated using an acrylic phantom. We verified that the system produced the expected results.
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臨床技術
第67回総会学術大会シンポジウム 1
JIRAトピックス
編集委員会特別企画
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