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, 5 号
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巻頭言
原著
  • 放射線治療計画装置を用いたkV-CBCT吸収線量評価～前立腺がん放射線治療に及ぼす影響～
    川村 哲朗, 村上 直基, 岡村 佳明, 西村 英輝, 宮脇 大輔, 木村 邦彦, 土師 守, 佐々木 良平
    2013 年 69 巻 5 号 p. 491-499
    発行日: 2013/05/20
    公開日: 2013/05/24
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.5.491
    ジャーナル フリー
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    Image-guided radiation therapy (IGRT) is increasingly being used in modern radiation therapy, and it is now possible to verify a patient’s position using kilo-voltage cone-beam computed tomography (kV-CBCT). However, if kV-CBCT is used frequently, the dose absorbed by the body cannot be disregarded. A number of studies have been made on the absorbed dose of kV-CBCT, in which absorbed dose measurements were made using a computed tomography dose index (CTDI) or a thermoluminescent dosimeter (TLD). Other methods include comparison of the absorbed dose between a kV-CBCT and other modalities. These techniques are now in common use. However, dose distribution within the patient varies with the patient’s size, posture and the part of the body to which radiation therapy is applied. The chief purpose of this study was to evaluate the dose distribution of kV-CBCT by employing a radiotherapy planning system (RTPS); a secondary aim was to examine the influence of a dose of kV-CBCT radiation when used to treat prostate cancer. The beam data of an on-board imager (OBI) was registered in the RTPS, after which modeling was performed. The radiation dosimetry was arranged by the dosimeter in an elliptical phantom. Rotational radiation treatment was used to obtain the dose distribution of the kV-CBCT within the patient, and the patient dose was evaluated based on the simulation of the dose distribution. In radiation therapy for prostate cancer, if kV-CBCT was applied daily, the dose increment within the planning target volume (PTV) and the organ in question was about 1 Gy.
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  • 診断領域における散乱X線の可視化装置の製作と実習の提案
    岸田 弥奈, 林 裕晃, 窪薮 友美, 竹上 和希, 井上 直, 花光 宏樹, 西原 貞光
    2013 年 69 巻 5 号 p. 500-507
    発行日: 2013/05/20
    公開日: 2013/05/24
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.5.500
    ジャーナル フリー
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    We have built equipment that can visualize the angle distributions of scattered X-rays. The main body of the equipment is made of a lead-shielded box 340 mm long, 300 mm wide and 270 mm high. The collimated X-rays are introduced into the equipment from the front face, then scattered by the sample located in the center of the equipment. The X-rays scattering toward the upper side are detected by the phosphor plate. To verify the usability of the equipment, an experiment using diagnostic X-rays was carried out. X-rays with a tube voltage of 100 kV were narrowed down to 6 mmφ and a 2 mm-thick acrylic sample was irradiated. The experimental conditions with a tube current-time product of 300 mAs to 1500 mAs proved appropriate for obtaining suitable images on a 10 inch×12 inch phosphor plate. The obtained images were analyzed using ImageJ. The experimental values were in good agreement with the theoretical distribution calculated by Klein and Nishina. Because the distribution of the scattered X-rays can be visualized in relatively simple experiments using the developed equipment, it is hoped that it will be of use for the practical training of beginners.
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ノート
  • CT-AECを用いた胸部単純CTから推定した心臓CT検査における個別管電流設定の検討
    岸本 淳一, 酒匂 敏雄, 太田 靖利
    2013 年 69 巻 5 号 p. 508-513
    発行日: 2013/05/20
    公開日: 2013/05/24
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.5.508
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    The aim of this study was to estimate the tube current on a cardiac computed tomography (CT) from a plain chest CT using CT-automatic exposure control (CT-AEC), to obtain consistent image noise, and to optimize the scan tube current by individualizing the tube current. Sixty-five patients (Group A) underwent cardiac CT at fixed tube current. The mAs value for plain chest CT using CT-AEC (AEC value) and cardiac CT image noise were measured. The tube current needed to obtain the intended level of image noise in the cardiac CT was determined from their correlation. Another 65 patients (Group B) underwent cardiac CT with tube currents individually determined from the AEC value. Image noise was compared among Group A and B. Image noise of cardiac CT in Group B was 24.4±3.1 HU and was more uniform than in Group A (21.2±6.1 HU). The error with the desired image noise of 25 HU was lower in Group B (2.4%) than in Group A (15.2%). Individualized tube current selection based on AEC value thus provided consistent image noise and a scan tube current optimized for cardiac CT.
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  • 造影タイミングの変化におけるパワースペクトル解析の試み
    高津 安男, 井上 泰吉, 宮地 利明, 中塚 隆之
    2013 年 69 巻 5 号 p. 514-520
    発行日: 2013/05/20
    公開日: 2013/05/24
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.5.514
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    Frequency analysis is a method of measuring the spatial frequency component in images. We attempted to analyze and assess frequency analyses of images of various contrast medium injection timings using a normalized integral power spectrum. In magnetic resonance imaging, the k-space order was linear and sequential. During the twenty-second scanning time, we injected contrast medium at 3 ml/s and varied the duration of the injection from zero to four seconds, four to eight seconds, eight to twelve seconds, twelve to sixteen seconds, and sixteen to twenty seconds. We then analyzed the images. The rates of change and area values were calculated, and a dendrogram of area value by cluster analysis was made. The element of high frequency area’s power values rose when the contrast medium was in the high-frequency area, and the element of low frequency area’s power values rose when the contrast medium was in the low-frequency area. These data lines crossed at 0.092–0.115 cycles/mm. Five time durations were identified: these were a function of rate of change and area value. Frequency analysis of injection timing for contrast medium using the normalized integral power spectrum can thus be applied; this method can thus be employed as a method of examining injection timing for contrast medium and choosing a k-space order of optimization.
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  • 1.5 Tおよび3.0 T-MRI検査における歯科用チタン(Ti)製インプラントのRF発熱に関する検討─人体等価ファントムを用いた温度測定─
    出田 貴裕, 山﨑 勝, 工藤 禎宏, 東田 満治, 森 進太郎, 金田 隆, 中澤 雅美
    2013 年 69 巻 5 号 p. 521-528
    発行日: 2013/05/20
    公開日: 2013/05/24
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.5.521
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    Titanium (Ti) implants are increasingly being used for dental parts. There is no problem with the attraction of a static magnetic field for Ti in magnetic resonance imaging (MRI), since Ti is paramagnetic. However, there is a risk of radio frequency (RF) heat generation within Ti. 3.0 T-MRI scanners are becoming increasingly common. The specific absorption rate (SAR) of 3.0 T-MRI is quadruple that of SAR compared with 1.5 T-MRI due to its being proportional to the square of the strength of a static magnetic field. The effect of heat generation in 3.0 T-MRI can thus be greater than in 1.5 T-MRI. So, using 1.5 T and 3.0 T-MRI scanners, we measured the temperature of several Ti implants using the same scanning parameters during MRI scanning. Our measurements showed the rise in temperature of the Ti implants to be a maximum of 0.4°C. In this study, however, Ti in a human mouth was not directly measured, so we need to attempt to perform MRI carefully on patients with Ti implants.
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臨床技術
  • 3T-MR装置を用いた根治的前立腺全摘除術における手術支援用3D画像作成のための適切なMR撮像シーケンスと撮像条件の検討
    白勢 竜二, 櫻井 佑樹, 長濱 宏史, 原田 邦明, 高島 弘幸, 中西 光広, 原田 耕平, 宍戸 博紀, 今村 塁, 坂田 元道, 畠 ...
    2013 年 69 巻 5 号 p. 529-534
    発行日: 2013/05/20
    公開日: 2013/05/24
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.5.529
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    The objective of our study was to optimize magnetic resonance image (MRI) sequences and parameters using operative assisted images (three-dimensional images) for radical prostatectomy at 3 tesla (T) MRI. Five healthy volunteers underwent MRI on the 3.0 T scanner. Various sequences and parameters [Cube (TE/TR=18, 50, 90 ms/2000 ms), FIESTA (TE/TR/FA=2.4 ms/5 ms/40°, 90°), fSPGR (TE/TR/FA=2.3 ms/11.2 ms/20°), slice thickness=1.2 mm, matrix=192×160] were respectively compared. Several structures of the pelvis (the central zones and transition zones of the prostate, the peripheral zones of the prostate, seminal vesicles, rectum wall, bladder, muscle and fat) were determined. The signal intensities of these structures were measured on reformatted axial images and compared against several structures of the pelvis. Correlation with various sequences and parameters was based on the signal-to-noise ratio (SNR), the contrast ratio (CR) and the presence of artifacts. Student’s t-test was used for statistical analysis. With Cube (TE/TR=50 ms/2000 ms), the average value of visual evaluation with artifacts was high, and SNR and CR were higher than for other sequence and parameters. Optimized MRI sequences and parameters were Cube (TE/TR=50 ms/2000 ms) which provides improved SNR and CR and the presence of artifacts with operative assisted images for radical prostatectomy. These operative assisted images obtained from Cube (TE/TR=50 ms/2000 ms) are likely to be useful for surgery.
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  • 逐次近似SPECT再構成法の123I-IMP局所脳血流量定量への応用─最適な再構成法と前処理フィルタの遮断周波数に関する検討─
    浅津 輝, 林 万寿夫, 新井 真美, 熊井 由昌, 赤木 弘之, 岡山 勝良, 鳴海 善文
    2013 年 69 巻 5 号 p. 535-544
    発行日: 2013/05/20
    公開日: 2013/05/24
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.5.535
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    In cerebral blood flow tests using N-Isopropyl-p-[123I] Iodoamphetamine 123I-IMP, quantitative results of greater accuracy than possible using the autoradiography (ARG) method can be obtained with attenuation and scatter correction and image reconstruction by filtered back projection (FBP). However, the cutoff frequency of the preprocessing Butterworth filter affects the quantitative value; hence, we sought an optimal cutoff frequency, derived from the correlation between the FBP method and Xenon-enhanced computed tomography (XeCT)/cerebral blood flow (CBF). In this study, we reconstructed images using ordered subsets expectation maximization (OSEM), a method of successive approximation which has recently come into wide use, and also three-dimensional (3D)-OSEM, a method by which the resolution can be corrected with the addition of collimator broad correction, to examine the effects on the regional cerebral blood flow (rCBF) quantitative value of changing the cutoff frequency, and to determine whether successive approximation is applicable to cerebral blood flow quantification. Our results showed that quantification of greater accuracy was obtained with reconstruction employing the 3D-OSEM method and using a cutoff frequency set near 0.75–0.85 cycles/cm, which is higher than the frequency used in image reconstruction by the ordinary FBP method.
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第68回総会学術大会シンポジウム
第68回総会学術大会教育講演
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–
JIRAトピックス
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