著者
福永 正明 大西 英雄 松友 紀和 山本 浩之
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.72, no.6, pp.489-495, 2016 (Released:2016-06-20)
参考文献数
12
被引用文献数
1

Purpose: The purpose of this study was to evaluate the effects of target diameter and display-field of view (D-FOV) in modulation transfer function (MTF) by circular edge strategy using the computed tomography (CT) image measurement program “CTmeasure”. Methods: We calculated the MTF (MTFedge) using the circular edge strategy applied to cylindrical phantom (200 mmφ) that inserted with cylinders have 10, 20, 30, and 40 mm diameters. The phantom images were reconstructed using filtered back projection method varied with D-FOV (240, 320, 400, and 500 mm). The study compared both MTFedge and MTFwire at MTF50% and MTF10% for target diameter and D-FOV, respectively. Results: The MTFedge by the different of target diameter indicated in rough compatibility. However, MTFedge of D-FOV diameters (320, 400, and 500 mm) decreased in the high frequency range. Conclusions: The circular edge strategy for MTF depended on the D-FOV, however, it was little dependent on target diameter using the CT image measurement program “CTmeasure”.
著者
土橋 俊男 藤田 功 岩崎 淳 森 克彦 鈴木 健
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.58, no.3, pp.406-412, 2002-03-20 (Released:2017-06-30)
参考文献数
8
被引用文献数
1 1

During this project, we evaluated methods to prevent high-signal artifact (marching metal artifact) that are caused by magnetic substance. Marching metal artifact is caused by the resonance frequency created by magnetic substance. Phase encoding and frequency encoding are often switched to minimize the influence that marching metal artifact have on the image. However, this method will only change the position at which marching metal artifact occur. It does not have the ability to completely prevent marching metal artifact. Our research illustrated that marching metal artifact can be prevented by changing the strength of the slice selective gradient field at the 90° RF pulse and 180° RF pulse. In other words, marching metal artifact can be prevented by changing the frequency bandwidth for the 90° RF pulse and 180° RF pulse. The incorporation of the phase correct option in the device used for our research (SIGNA LX and SIGNA CV/i) results in different slice selective gradient field strengths at the 90° RF pulse and the 180° RF pulse. This indicates that the use of phase correction enables marching metal artifact to be prevented.
著者
村山 大知 坂井 上之 米山 正己 能勢 毅一 畠山 英久 渡邉 一寿 越智 茂博
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.77, no.6, pp.572-580, 2021 (Released:2021-06-20)
参考文献数
17

Magnetic resonance angiography (MRA) using ultra-short TE (uTE) is known to be used for the evaluation of cerebral aneurysm after treatment such as clipping and coiling. However, conventional uTE sequences are not appropriate as an additional imaging sequence for 3D time-of-flight (TOF)-MRA because it is not possible to shorten scan time and acquire selective-volume imaging. To solve the problem, we focused on the combination of uTE sampling and 3D radial scan sequences. In this study, we examined the optimal imaging parameters of the proposed uTE-MRA. A simulated blood flow phantom with stents (Enterprise) and titanium clips (YASARGIL) was used for optimizing the TR, flip angle (FA), and radial percentage. The signal intensity in the simulated vessel was measured in each imaging condition, and the ratio of the presence or absence of a stent was evaluated as a relative in-stent signal (RIS). In addition, the diameter of the signal loss of the simulated artery was measured for each imaging condition, and signal loss length (SLL) of a clip was calculated from the average value. The RIS improved with increasing the FA and shortening the TR, but it did not change by changing the radial percentage. The SLL became smaller at the coil as the FA increased, but there was no significant difference between the intersection and the blade. There was also no significant difference between TR and radial percentage. The effective imaging conditions for uTE-MRA to improve the vascular description of the evaluation after treatment of cerebral aneurysms with metallic devices were those with large FA and short TR.
著者
山谷 裕哉
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.75, no.11, pp.1337-1346, 2019 (Released:2019-11-20)
参考文献数
22
被引用文献数
1

We conducted a questionnaire survey (situation, patient factor, environmental factor, operator factor, degree of disability, countermeasure etc.) on cases that occurred up to the present to investigate the actual situation of the medical accidents that occur in the radiological examination department of medical institutions. There were 373 questionnaires collected. Among them, there were 197 cases of falls. In this study, we examined the age of patients who fell, the background of the accident, and factors. As for the accident, 11.7% of accidents with risk impact level 3b or higher occurred including the fatal accident. Of the accidents, 44.2% were foreseeable and 55.8% were unforeseeable. The most accident-prone age was elderly in their 60s to 80s. As the causative factor for the accident, the patient factor was the largest at 63.5%. We can prevent about 30% of the accident by improving the operator factor and the environmental factor which are parts other than patient factor. It is important for us to understand what kind of people tend to fall. Among foreseeable accidents, the causes of patient factors can be reduced.
著者
福永 晃太 圓﨑 将大 小味 昌憲 東 美菜子 平井 俊範 藤原 康博
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.79, no.7, pp.663-673, 2023 (Released:2023-07-20)
参考文献数
29

【目的】Three-dimensional (3D) quantification using an interleaved Look-Locker acquisition sequence with T2 preparation pulse(QALAS)は,緩和時間を測定可能なシーケンスの一つである.3D-QALASは短時間に高い空間分解能で撮像可能な特徴があるが,3.0 Tにおける3D-QALASの緩和時間の測定精度や従来法とのバイアスは明らかになっていない.本研究の目的は,3.0 Tにおける3D-QALASの緩和時間を従来法と比較し,明らかにすることである.【方法】3D-QALASでファントムのT1値とT2値を測定し,それらの精度を評価した.次に,健常者の脳組織のT1値,T2値,プロトン密度を2D multi-dynamic multi-echo(MDME)と3D-QALASで測定し,それらの差を評価した.【結果】ファントムによる評価において,3D-QALASのT1値は,inversion recovery spin-echoのT1値より平均8.3%延長した.3D-QALASのT2値は,multi-echo spin-echoのT2値より平均18.4%短縮した.生体による評価では,3D-QALASの平均のT1値とT2値とPDは,2D-MDMEと比較して,それぞれ5.3%延長,9.6%短縮,7.0%増加した.【結語】3.0 Tの3D-QALASはT1値が1000 ms未満では測定精度が高いが,それ以上では過大評価される.また,3D-QALASのT2値は過小評価され,T2値が長いほどその傾向は大きくなる.
著者
有谷 航 中山 寛介
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.79, no.7, pp.708-716, 2023 (Released:2023-07-20)
参考文献数
16

Magnetic resonance cholangiopancreatography(MRCP)は低侵襲に胆汁や膵液を直接画像化できる方法であり,Heavily T2強調3Dマルチスライス法では自由呼吸下で呼吸同期撮像を行うことで高画質な膵胆管の全体像が得られる.1回のデータ収集時間(echo train duration: ETD)を被検者の呼吸状態に合わせることで撮像時間が調整できるが,高速スピンエコー法におけるETDの変化は,画像コントラストや空間分解能に影響を与える.本研究では,ETDが画質に及ぼす影響について,ファントムを用いて評価した.いずれの条件でも模擬膵臓と模擬膵管は高い画像コントラストを示した.また,ETD延長に伴い空間分解能が劣化したが,視覚評価では有意差が認められなかった.より臨床的な条件では一部で視覚的に有意な差が認められ,phase partial Fourier(PPF)による影響が考えられた.PPFを使用せずに被検者の呼吸状態に応じてETDを変化させることで,画質を損なうことなく被写体の動きを抑えた最適な撮像時間での画像取得が可能になると考えられた.
著者
藤田 仁 森田 学 草加 勝康
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.64, no.6, pp.707-713, 2008-06-20 (Released:2008-07-19)
参考文献数
9
被引用文献数
1 1

In chest CT images, the dorsal lower lung field often shows an infiltration-like shadow in patients who cannot stop breathing or take a deep breath. The cause of this phenomenon might be due to the effects of gravity. Since we had observed decreased effects of gravity by conducting additional CT scanning for patients in an oblique position (55°) or a nearly lateral position, we conducted a clinical study to investigate this matter. Forty-three patients (23 patients in the normal group and 20 patients in the inflammatory disease group) who underwent additional CT scanning were included in this study. CT values for the region in which infiltration-like shadow was observed in both positions (dorsal position and oblique position) were measured. The ratio of fluctuation in the CT value of the dorsal lower lung field at a positional change from the dorsal to the oblique position was calculated as a coefficient of fluctuation C (%). As a result, the coefficient of fluctuation C (%) was 32.6±13.6 in the normal group and 6.7±6.8 in the inflammatory disease group. The effects of gravity were improved by additional CT scanning in an oblique position (55°) or a nearly lateral position, and this enabled differentiation of the effects of gravity vs. inflammatory diseases.
著者
堀江 朋彦 今田 奈津夫 榊原 夢太郎 厚見 秀樹 丹羽 徹 松前 光紀
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
pp.2023-1324, (Released:2023-02-14)
参考文献数
27

【目的】本研究の目的は,呼吸性運動による脳脊髄液(cerebrospinal fluid: CSF)動態の描出を想定したdynamic improved motion sensitized driven equilibrium steady-state free precessionの最適な空間分解能と時間分解能を調べることである.【方法】健常ボランティア9名の正中矢状断面を対象に三つの撮像条件(A:空間分解能0.49×0.49×5 mm, 時間分解能1000 ms,B:0.49×0.49×5 mm, 430 ms,C:0.78×0.78×5 mm, 200 ms)による描出の違いを調査した.まず,第三,第四脳室のCSFおよび橋のsignal-to-noise ratio(SNR)を算出した.次に,呼吸性運動により10 cm/s以上で流れるCSFと10 cm/s以下で流れるCSFの信号強度比(signal intensity ratio: SIR)を算出した.更に吸気SIRと呼気SIRの差を求めた.更に,①中脳水道を中心とした第三,第四脳室に生じる流れの存在,②呼吸による流れの変化について,7名の技師による3段階の視覚評価により調べた.【結果】SNRは,いずれもAが最も高く次いでBそしてCの順に小さくなった.第三,第四脳室のCSFではAとBおよびAとCの間に有意差があったが,BとCには有意差はなかった.呼吸性運動によりCSFの信号強度は変化した.第三脳室のSIRは吸気で高く呼気に低くなり,逆に第四脳室のSIRは吸気に低く呼気で大きくなった.各SIRはいずれもAとCおよびBとCの間に有意差があった(p<0.05).吸気SIRと呼気SIRの差は,第三,第四脳室ともにBが最も高く次にAそしてCが最も低く,AとCおよびBとCの間に有意差があった(p<0.05).中脳水道を中心とした第三,第四脳室に生じる流れの存在に有意差はなかった(p=0.264).一方,呼吸による流れの変化には撮像条件による有意差がありBが他より高値となった(p<0.001).【結語】最適な空間分解能は0.49×0.49×5 mm, 時間分解能は430 msであった.また本法では,位相分散を利用するため空間分解能と時間分解能の関連に注意した条件設定が重要なことが示唆された.
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

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.
著者
脇田 幸延 山永 隆史 片山 豊 永野 琢朗 小倉 直人 東山 滋明 河邉 讓治 市田 隆雄
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
pp.2022-1298, (Released:2022-08-10)
参考文献数
19

【目的】本研究の目的は,核医学領域における,診断参考レベル(Japan Diagnostic Reference Levels 2020: DRLs 2020)に基づいた円滑な線量管理を可能とするソフトウェアを開発することである.【方法】プログラミング言語Visual Basic for Applications(VBA)を用い,実投与量計算機能,自施設とDRLs 2020の比較機能,小児核医学検査の適正投与量計算機能等を実装した.更にソフトウェア導入前,後における実投与量を評価した.【結果】本ソフトウェアにより簡便な実投与量計算や,DRLs 2020との比較が可能となり,円滑な線量管理を実現し得た.また,線量評価の結果より,ソフトウェアを導入することで自施設の投与量を把握し,最適化の参考とすることができた.【結語】核医学領域では自作のソフトウェアを臨床に導入することで,DRLs 2020に則した線量管理が可能である.
著者
林 裕晃 谷内 翔 神谷 尚武 西原 貞光 富永 正英
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.68, no.3, pp.307-311, 2012-03-20 (Released:2012-03-24)
参考文献数
9
被引用文献数
5 1

In order to obtain an image of scattered X-ray in the diagnosis domain, we have newly developed a pin-hole camera. Because of the necessity of the X-ray shielding, the pin-hole part has a depth corresponding to that of the shielded material. As a result, efficiencies of obliquely incident X-rays are reduced. To decrease the descent of the efficiencies, we developed a large camera using a 10×12 inch size phosphor plate as an X-ray detector. A phantom was irradiated by X-rays with conditions of 500 mAs and 5000 mAs, and images of scattered X-rays were obtained. The former image showed scattered X-rays from the phantom. The latter image showed those from the air of beam axis as well as from the phantom. Moreover, we made a new proposal to obtain an optical image using the fading effect.
著者
鹿島 啓佑 福島 康宏
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.78, no.7, pp.726-731, 2022 (Released:2022-07-20)
参考文献数
18

本研究の目的は,相対アーチファクトインデックス(relative artifact index: AIr)を用いて,血管撮影装置のcone beam CTにおける金属アーチファクト低減処理(metal artifact reduction: MAR)の効果と,管電圧による違いを評価することである.まず,水ファントムを撮影しノイズ画像を取得した.次に,水ファントム内の中央部にプラチナ合金製の塞栓用コイルを設置した場合と,中央部と辺縁部に塞栓用コイルを設置した場合で,アーチファクト画像を取得した.管電圧は70, 109 kVとし,MARの有無で合わせて4種類のアーチファクト画像を取得して,それぞれから同じz方向10枚の画像を取得した.画像に関心領域を設定しAIrを求め,撮影条件間で多重比較を行った(有意水準p<0.05).AIrはMARを使用することで有意に低値となり,管電圧にかかわらず金属アーチファクトを有意に低減させることができた.Cone beam CTのMARは金属アーチファクトを91%以上低減でき,MARを使用した場合,管電圧による違いはなかったことが明らかになった.
著者
佐保 辰典 大西 英雄
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.71, no.12, pp.1157-1164, 2015 (Released:2015-12-20)
参考文献数
31
被引用文献数
1 3

Purpose: Detailed strategy for regional hemodynamics is significant for knowledge of plaque development on vascular diseases such as atherosclerosis. The aim of this study was to derive relation between atherosclerosis and hemodynamics at human carotid bifurcation by the use of computational fluid dynamics (CFD), and to provide more accurate hemodynamic information. Methods: Blood velocity datasets at common carotid artery were obtained by phase-contrast cine magnetic resonance imaging (PC cine MRI). Carotid bifurcation model was computed for systolic, mid-diastolic, and end-diastolic phase. Comparison of wall shear stress (WSS) was performed for each cardiac phase. Results: PC cine MRI provided velocity measurement for common carotid artery with various cardiac phases. The blood velocity had acute variation from 0.21 m/s to 1.07 m/s at systolic phase. The variation of WSS during cardiac phase was presented at carotid bifurcation model. High shear stress area was observed at dividing wall for all cardiac phases. The systole-diastole WSS ratio was 10.15 at internal carotid side of bifurcation. And low shear stress (<0.5 Pa) was observed at internal carotid side of bifurcation. Conclusion: Bifurcation area represented low shear stress and changed significantly WSS. The specific area with significant change in shear stress and low shear stress had good agreement with predilection sites of atherosclerosis. The result suggested that hemodynamics was related to atherosclerosis, and CFD analysis with various cardiac phases that were provided by PC cine MRI was allowed to determine an accurate analysis condition. This led to the representation of hemodynamics in vivo.