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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69 巻, 6 号
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原著
  • 線量分布解析におけるラジオクロミックフィルムドジメトリーの正確性の向上に関する取り組み─フラットベッドスキャナの影響の補正法と色成分を利用した補正法の組み合わせ─
    上原 隆三, 橘 英伸, 伊藤 康, 吉野 慎一, 松林 史泰, 佐藤 智春
    2013 年 69 巻 6 号 p. 617-631
    発行日: 2013/06/20
    公開日: 2013/06/20
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.6.617
    ジャーナル フリー
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    It has been reported that the light scattering could worsen the accuracy of dose distribution measurement using a radiochromic film. The purpose of this study was to investigate the accuracy of two different films, EDR2 and EBT2, as film dosimetry tools. The effectiveness of a correction method for the non-uniformity caused from EBT2 film and the light scattering was also evaluated. In addition the efficacy of this correction method integrated with the red/blue correction method was assessed. EDR2 and EBT2 films were read using a flatbed charge-coupled device scanner (EPSON 10000G). Dose differences on the axis perpendicular to the scanner lamp movement axis were within 1% with EDR2, but exceeded 3% (Maximum: +8%) with EBT2. The non-uniformity correction method, after a single film exposure, was applied to the readout of the films. A corrected dose distribution data was subsequently created. The correction method showed more than 10%-better pass ratios in dose difference evaluation than when the correction method was not applied. The red/blue correction method resulted in 5%-improvement compared with the standard procedure that employed red color only. The correction method with EBT2 proved to be able to rapidly correct non-uniformity, and has potential for routine clinical IMRT dose verification if the accuracy of EBT2 is required to be similar to that of EDR2. The use of red/blue correction method may improve the accuracy, but we recommend we should use the red/blue correction method carefully and understand the characteristics of EBT2 for red color only and the red/blue correction method.
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  • MR画像における転移性脳腫瘍検出のコンピュータ支援診断
    竹永 智美, 内山 良一, 平井 俊範, 中村 英夫, 甲斐 豊, 桂川 茂彦, 白石 順二
    2013 年 69 巻 6 号 p. 632-640
    発行日: 2013/06/20
    公開日: 2013/06/20
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.6.632
    ジャーナル フリー
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    The fact that accurate detection of metastatic brain tumors is important for making decisions on the treatment course of patients prompted us to develop a computer-aided diagnostic scheme for detecting metastatic brain tumors. In this paper, we first describe how we extracted the cerebral parenchyma region using a standard deviation filter. Second, initial candidates for tumors were decided by sphericity and cross-correlation value with a simulated ring template. Third, we made true positive and false positive templates obtained from actual clinical images and applied the template matching technique to them. Finally, we detected metastatic tumors using these two characteristics. Our improved method was applied to 13 cases with 97 brain metastases. Sensitivity of detection of metastatic brain tumors was 80.4%, with 5.6 false positives per patient. Our proposed method has potential for detection of metastatic brain tumors in brain magnetic resonance (MR) images.
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ノート
  • 静磁場強度の異なる3機種を用いた脳定位放射線治療計画のためのMRI画像の歪み比較
    武村 哲浩, 笹本 耕平, 仲村 香織, 黒田 辰憲, 小路 佐織, 松浦 幸広, 松下 達彦
    2013 年 69 巻 6 号 p. 641-647
    発行日: 2013/06/20
    公開日: 2013/06/20
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.6.641
    ジャーナル フリー
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    In this study, we evaluated the image distortion of three magnetic resonance imaging (MRI) systems with magnetic field strengths of 0.4 T, 1.5 T and 3 T, during stereotactic irradiation of the brain. A quality assurance phantom for MRI image distortion in radiosurgery was used for these measurements of image distortion. Images were obtained from a 0.4-T MRI (APERTO Eterna, HITACHI), a 1.5-T MRI (Signa HDxt, GE Healthcare) and a 3-T MRI (Signa HDx 3.0 T, GE Healthcare) system. Imaging sequences for the 0.4-T and 3-T MRI were based on the 1.5-T MRI sequence used for stereotactic irradiation in the clinical setting. The same phantom was scanned using a computed tomography (CT) system (Aquilion L/B, Toshiba) as the standard. The results showed mean errors in the Z direction to be the least satisfactory of all the directions in all results. The mean error in the Z direction for 1.5-T MRI at －110 mm in the axial plane showed the largest error of 4.0 mm. The maximum errors for the 0.4-T and 3-T MRI were 1.7 mm and 2.8 mm, respectively. The errors in the plane were not uniform and did not show linearity, suggesting that simple distortion correction using outside markers is unlikely to be effective. The 0.4-T MRI showed the lowest image distortion of the three. However, other items, such as image noise, contrast and study duration need to be evaluated in MRI systems when applying frameless stereotactic irradiation.
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  • 二種類のFDG-PETガイドラインに対応した解析ソフトウェアパッケージの開発
    松本 圭一, 遠藤 啓吾
    2013 年 69 巻 6 号 p. 648-654
    発行日: 2013/06/20
    公開日: 2013/06/20
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.6.648
    ジャーナル フリー
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    Two kinds of Japanese guidelines for the data acquisition protocol of oncology fluoro-D-glucose-positron emission tomography (FDG-PET)/computed tomography (CT) scans were created by the joint task force of the Japanese Society of Nuclear Medicine Technology (JSNMT) and the Japanese Society of Nuclear Medicine (JSNM), and published in Kakuigaku-Gijutsu 27(5): 425-456, 2007 and 29(2): 195-235, 2009. These guidelines aim to standardize PET image quality among facilities and different PET/CT scanner models. The objective of this study was to develop a personal computer-based performance measurement and image quality processor for the two kinds of Japanese guidelines for oncology 18F-FDG PET/CT scans. We call this software package the “PET quality control tool” (PETquact). Microsoft Corporation’s Windows™ is used as the operating system for PETquact, which requires 1070×720 image resolution and includes 12 different applications. The accuracy was examined for numerous applications of PETquact. For example, in the sensitivity application, the system sensitivity measurement results were equivalent when comparing two PET sinograms obtained from the PETquact and the report. PETquact is suited for analysis of the two kinds of Japanese guideline, and it shows excellent spec to performance measurements and image quality analysis. PETquact can be used at any facility if the software package is installed on a laptop computer.
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臨床技術
  • Gd-EOB-DTPA造影後における STIR併用Low b Diffusion Weighted Imagingの有用性について
    中 孝文, 川口 征吾, 富山 岳明
    2013 年 69 巻 6 号 p. 655-662
    発行日: 2013/06/20
    公開日: 2013/06/20
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.6.655
    ジャーナル フリー
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    Diffusion weighted imaging (DWI) using a low b value for examination of the body is not common, so we examined its usefulness. Phantom experiments were performed in which I changed the length of the echo time (TE), with and without short inversion time inversion recovery (STIR). The signal intensity of each phantom was reduced by using a longer TE or by combination with STIR, but contrast was improved. We noted a similar pattern in clinical cases, and concluded that the results of the phantom study and clinical cases indicated the potential usefulness of TE with moderate STIR. Low-b DWI using appropriate imaging parameters gave better results than high-b DWI followed by visual assessment. The T1 value of normal liver cells is shortened by incorporating gadolinium-ethoxybenzyl-diethylene-triaminepentaacetic acid (Gd-EOB-DTPA). Normal liver cells are close to the null point in STIR-low-b DWI under these conditions. The signal-to-noise ratio (SNR) of normal liver cells thus decreases, unlike that for tumors containing no normal liver cells, giving improved contrast. At high SNRs, the use of low-b DWI provides several advantages: the anatomical location structure is easy to identify, and there is less left lateral division of liver signal degradation. We thus conclude STIR-low-b DWI after injection of Gd-EOB-DTPA to be a useful technique.
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  • 肺の定位放射線治療における計算アルゴリズムの線量計算精度の比較
    冨山 友希, 荒木 不次男, 兼武 渚, 下東 吉信, 富永 弘史, 坂田 潤一, 大野 剛, 河野 友宏, 日置 一成
    2013 年 69 巻 6 号 p. 663-668
    発行日: 2013/06/20
    公開日: 2013/06/20
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.6.663
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    Dose calculation algorithms in radiation treatment planning systems (RTPSs) play a crucial role in stereotactic body radiation therapy (SBRT) in the lung with heterogeneous media. This study investigated the performance and accuracy of dose calculation for three algorithms: analytical anisotropic algorithm (AAA), pencil beam convolution (PBC) and Acuros XB (AXB) in Eclipse (Varian Medical Systems), by comparison against the Voxel Monte Carlo algorithm (VMC) in iPlan (BrainLab). The dose calculations were performed with clinical lung treatments under identical planning conditions, and the dose distributions and the dose volume histogram (DVH) were compared among algorithms. AAA underestimated the dose in the planning target volume (PTV) compared to VMC and AXB in most clinical plans. In contrast, PBC overestimated the PTV dose. AXB tended to slightly overestimate the PTV dose compared to VMC but the discrepancy was within 3%. The discrepancy in the PTV dose between VMC and AXB appears to be due to differences in physical material assignments, material voxelization methods, and an energy cut-off for electron interactions. The dose distributions in lung treatments varied significantly according to the calculation accuracy of the algorithms. VMC and AXB are better algorithms than AAA for SBRT.
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特別企画　会員インタビュー～学会に貢献された人々～
教育講座—放射線技術学で必要な基礎統計学—
基礎講座—三次元コンピュータグラフィックス—
基礎講座—心臓病（特に虚血性心疾患）の診断から治療まで—
学術委員会報告
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