112

学術交流委員会だより

平成 25 年度前期国際研究集会派遣会員報告書

AAPM に参加して派遣員 中田良成 大阪市立大学医学部附属病院
派遣国際研究集会： 55th Annual Meetings & Exhibition, AAPM (The American Association of
Physicists in Medicine)
開催場所：Indianapolis, Indiana, USA
開催期間：August 4-8, 2013

Evaluation of MV and kV Isocenter Displacement for an IGRT Linac
with and without an Add-on Micro-multileaf Collimator
Ryosei Nakada,1, 2 Daisaku Tatsumi,3 Akihiro Takemura,4 Akinori Ienaga,1Akane Yomoda,1 Makoto Inoue,1 Takao Ichida,1 and Masako Hosono5
Osaka City University Hospital
Division of Health Sciences, Graduate School of Medical Science, Kanazawa University
3
Miyakojima IGRT Clinic
4
Faculty of Health Sciences, Institute of Medical , Pharmaceutical and Health Sciences
5
Department of Radiology, Osaka City University Graduate School of Medicine
1
2

Purpose:The impact of the add-on micro multileaf collimator (mMLC) on the MV and kV isocenters were investigated.
Methods:
Winston-Lutz tests was performed with an add-on mMLC, and a ball bearing (BB) was placed at the isocenter given by localization lasers.
A square MV field was shaped by the mMLC, and the MV field center position relative to the BB position were measured by a portal imager
with different gantry angles. A desirable BB position that minimizes the maximum deviation was obtained as an MV isocenter, and the BB
center was aligned onto the revised MV isocenter. Using an on-board kV imaging system, two-dimensional BB image was acquired during
gantry rotation. The displacement of the kV projection image center from the BB for each gantry angle was recorded as flexmap . Afterunmounting the mMLC, Winston-Lutz test and the flexmap measurement were performed again. A phantom was placed on a couch and conebeam CT (CBCT) images were acquired with the two different flexmap data. The set-up errors were calculated and the differences of required
couch translations with each of the flexmap data were obtained.
Results:
After unmounting the mMLC, the MV field center and the kV image center were shifted approximately 0.4 mm and 0.05 mm upward,
respectively. Assuming a perfect MV and kV isocenter coincidence with mMLC using the flexmap for CBCT reconstruction, the MV/kV isocenter discrepancy without the mMLC could be calculated by the difference of the above two values, 0.35 mm which satisfies AAPM TG179
guideline of 1 mm. The largest difference of required couch translations between the two flexmap data was 0.07 mm toward the vertical direction, which agreed well with the kV image center shift of 0.05 mm.
Conclusion:
The MV and kV isocenters defined with the add-on mMLC are also applicable to image-guided VMAT without the mMLC.

はじめに

AAPM の印象

平 成 25 年 8 月 4 日〜8 月 8 日 の 5 日 間， 米 国 イ ン

AAPM は医学物理の専門家が多く集う北米最大の学

ディアナポリスにて開催された第 55 回米国医学物理学会であり，世界をリードするアイデアに満ち溢れた研究会（AAPM）に国際研究集会派遣会員として研究発表すが散見された．プログラムでは教育講演が充実しておる機会を得たので報告する．

り，若手技術者の教育に注力していることが伺えた．

日本放射線技術学会雑誌

113

ま た，imaging 関 連 の 講 演 で は deformable image
registration（DIR）
がトレンドの一つとなっており，DIR
を用いてさまざまな形態画像や機能画像を治療計画に利用する有用性を学んだ．
発表内容
今回の発表は，mMLC の有無に着目した image-guided
radiation therapy（IGRT）
システムの精度管理についてである．当院では最も高い位置精度が要求される mMLCを用いた頭部定位照射に MV，kV の両アイソセンタとレーザを調 整し品質 管 理を行っている．Volumetricmodulated arc therapy（VMAT）
等の mMLC を用いない

Photo

ポスター会場にて照射では，ガントリのダレの変化に伴う両アイソセンタの変位によって，調整時の精度を維持したまま IGRT が施行できない可能性が懸念される．そこで，mMLC の理手法の一つの道標となると考える．

有無に起因する両アイソセンタの変位量と，CBCT における位置誤差検出能を計測し IGRT に及ぼす影響を評価した．
結果として両アイソセンタの変位量は小さく，CBCT謝辞
最後に，国際研究集会派遣会員として発表する機会を与えていただいた，日本放射線技術学会 真田茂代

における位置誤差検出能の差異は治療寝台の位置補正

表理事ならびに学術交流委員会の皆様，日本放射線技能と比較して十分小さいものであり，AAPM の TG-179

術学会会員の皆様に厚く御礼を申し上げます．また，ごで推奨されている許容値を十分に満足する精度であっ

指導いただいた金沢大学医薬保健研究域保健学系の武た．リニアックの品質管理をないがしろにしてはならな

村哲浩准教授，大阪市立大学医学部附属病院中央放射

いが，同様の背景を持つ IGRT システムにとって品質管線部の皆様に感謝申し上げます．

ECR2013 に参加して派遣員 渡辺恵美 三河乳がんクリニック / 名古屋大学大学院医学系研究科
派遣国際研究集会：European Congress of Radiology (ECR) 2013
開催場所
：Vienna, Austria
開催期間：March 7-11, 2013

Dose Evaluation in Clinical Study of Contrast-enhanced
Spectral Mammography (CESM) for Japanese Women
Megumi Watanabe,1 Mitsuhiro Mizutani,1 Miyuki Mori,1 Yuki Suwabe,1 Miharu Ohkubo,1 and Masatoshi Tsuzaka 2
1
2

Mikawa Breast Cancer Clinic
Nagoya University Graduate School of Medicine, Department of Radiological Technology

Purpose:Contrast-enhanced spectral mammography (CESM) will be a splendid new technology to realize a breakthrough for a breast imaging.
Dromain et al. showed the result that average glandular dose (AGD) in CESM is 1.2 times higher than that in the standard mammography(MMG). The clinical data of Asian breast has not been shown. Therefore, we investigated clinical data of Japanese breast to evaluate the AGD
in CESM.
Methods and Materials:
From January to July 2011, 72 Japanese women underwent CESM. Exposures were taken in 2 min after the injection of 1.5 ml/kg of an
iodinated contrast agent. We investigated the AGD displayed (displayed AGD) on the screen of SenoBright (GE Health care). Before that wechecked the accuracy of displayed AGD compared with reference AGD measured by ACR method (for low energy) and Boone’s method (forhigh energy).
Results:
The differences between displayed AGD and reference AGD were within 5%. The total AGD delivered to the patient for a pair of low-Vol. 70 No. 1 Jan 2014

114

and high-energy images was between 0.95 and 4.20 mGy depending on breast thickness (18 to 86 mm). The mean AGD of all 72 cases was
1.92 mGy. This AGD corresponds to about 1.4 times the AGD delivered for the standard MMG.
Conclusion:
AGD in the clinical study of CESM corresponds to 1.4 times the AGD delivered for the standard MMG. This result about AGD of CESM
is acceptable for clinical MMG. We make sure the effectiveness of CESM and will expand the clinical and basic research furthermore.

はじめに
平成 25 年度前期国際研究集会派遣会員として本学会より助成を受け，2013 年 3 月 7 日から 11 日の期間，
オーストリア，ウィーンで開催された ECR（EuropeanCongress of Radiology）に参加したので報告する．
発表内容
Dual energy 技術を用いた造影マンモグラフィ（GE 社の 装 置 を 用 い た も の は contrast enhanced spectral
mammography: CESM と呼ばれている．以下，造影マ
ンモグラフィ）は近年新技術として導入され，臨床症例での研究が行われている．海外の文献によると，造影マンモグラフィの一方向あたりの線量は単純マンモグラ

EPOSTM 会場にて

Photo

フィの 1.2 倍とされているが臨床試験を重ねる中での印象と異なっていた．本研究では 72 例の臨床データより
実際の造影マンモグラフィの線量評価を行い，単純マ

奮ぎみの帰国となった．ECR は新しい知見だけでな

ンモグラフィと比較した．まず，マンモグラフィ装置コ

く，基礎を見直すことのできる教育プログラムがしっか

ンソール上の平均乳腺線量と実測の平均乳腺線量が精りと組まれていた．EPOSTM 演題数は 2500 を超え，ま度よく一致することを確認したうえで，次にマンモグラ

た 5 日間で 330 以上ものセッションが行われていた．以

フィ画像のコンソール表示平均乳腺線量での評価を前から私はこの学会にいつか参加することを希望し，今行った．結果，72 例の造影マンモグラフィの一方向あ

回たくさんの方々からの支援があり参加することができたりの平均乳腺線量は単純マンモグラフィのおよそ 1.44

た．Presentation の作成や学会参加を通して，日々の臨

倍 1.92 mGy であることを確認した．線量に関しては画

床を大切にしながらその中で検証したことを世界に発質との関係が深く，国や施設によって設定，運用方法

信することの大切さを再確認した．そして今回持ち帰っが異なり，また人種間の乳房構成の違いによる線量のたことを臨床や今後の研究に活かし，次は口述発表で差もあることからさらなる検証が必要ではあるが，日本の参加を目指したい．また他の学会にも参加し，さらに女性の実際の臨床データからの線量評価を示すことが知見を広めていきたい．

できた．
謝ECR2013 に参加して規模の大きい海外の学会参加は筆者にとって初めて辞
最後に ECR2013 の参加にあたり，国際研究集会派遣会員として助成いただきました日本放射線技術学会のであった．EPOS （electric presentation online system）

真田での参加ということもあり，学会参加には自由なスケ様に厚く御礼申し上げます．また，本研究の発表，学ジュールを組むことができた．Breast imaging 関連の口会への参加に関してご指導いただきました三河乳がん

述発表や教育講演，ワークショップなどできる限りのもクリニック 水谷三浩院長，名古屋大学大学院医学系研のに参加した．造影マンモグラフィに関する新しい知見

究科 津坂昌利准教授ならびに参加を快諾し応援してくやトモシンセシスの基礎に関する講演，乳癌術後の画ださった三河乳がんクリニックの皆様，支えてくれた家

像所見に関する教育講演など盛りだくさんで，やや興族に深く感謝いたします．

TM

茂代表理事をはじめ学術交流委員会，会員の皆日本放射線技術学会雑誌

115

ISMRM に参加して派遣員 遠藤和之 東海大学医学部付属病院
派遣国際研究集会：The International Society for Magnetic Resonance in Medicine (ISMRM) 2013
開催場所
：Salt Lake City, Utah, USA
開催期間：April 20-26, 2013

Flow Sensitive Cine MR Imaging Using Improved Motion
Sensitized Driven Equilibrium (iMSDE)
Kazuyuki Endo,1 Tomohiko Horie,1 Isao Muro,1 Yutaka Imai,2 Kagayaki Kuroda,3 Tetuo Ogino,4Makoto Obara,4 Marc Van Cauteren,4 Thomas Kwee,5 and Taro Takahara6
Department of Radiological Technology, Tokai University HospitalRadiology,Tokai University Hospital
3
Information Science and Technology,Tokai University
4
Philips Healthcare
5
University Medical Center Utrecht
6
Biomedical Engineering,Tokai University
1
2

Introduction:
Improved Motion Sensitized Driven Equilibrium (iMSDE) is a kind of T2-prep pulse with motion probing gradients. Since this techniqueis effective to suppress signal where turbulence exists, and can be added in front of any conventional sequence as a pre-pulse, it can be widelyused for clinical applications including black-blood vessel wall imaging,1) lower extremity MR venography,2) or suppression of flow artifacts incontrast-enhanced studies for brain metastasis detection.3) We hypothesized that iMSDE can be applied to not only static images but also to cine
MR imaging. The purpose of this study was to investigate basic appropriate parameters and evaluate the feasibility of this technique as Flowsensitive cine MR imaging.
Methods:
The study was approved by the local institutional review board and written informed consent was obtained from all volunteers.
Basic parameters: The equipment we used was a 1.5 T clinical scanner (Achieva nova dual, Philips, Best, the Netherlands) with either a 6ch
SENSE head coil (volunteer study) or a 32ch SENSE torso cardiac coil (phantom and volunteer study). The basic parameters for cine MR imaging were as follows: 2D balanced TFE with iMSDE, FOV of 300×300 mm2, matrix of 192×259, slice thickness of 5 mm, flip angle of 90˚, TFE
factor of 67, and NSA of 1.
Phantom study: The flow phantom was made with superabsorbent polymer and tubes (Fig. 1) with steady flow. We investigated appropriate
iMSDE parameters (not shown) and decided to use the following parameters: T2 prep TE of 50 ms, shot interval of 1000 ms, shot duration of
300 ms. The signal intensity of flowing water in the tube was measured with varying flow speed (0.55–4.0 cm/s) and venc (1–50 cm/s) withthree orthogonal venc directions in cross and longitudinal section.
Volunteer study: To evaluate the effect of iMSDE on cine MR imaging, 5 volunteers underwent cine MR imaging in 5 anatomical sites each(lateral ventricles through foramen of Monro, cervical spine, lumber spine, and urinary bladder). The duration of cine MR imaging was 60 s,
consisting of 30 s for the scan without iMSDE and followed by 30 s for the scan with iMSDE. The signal intensity of the CSF or urine without
and without iMSDE was measured in each anatomical site (near by the foramen of Monro, anterior cervical space, anterior lumbar space, andurine jet). Differences in signal intensity with and without iMSDE were assessed using two-sided unpaired t tests. A P value of less than 0.05
was considered to indicate a statistically significant difference.
Results:
In the phantom study, considerable signal drop was seen even at 0.55 cm/s with flow venc of 1 cm/s (the strongest gradient with this scanner) (Fig. 2). Signal drop was shown when flow venc direction was parallel to flow direction both in cross and longitudinal section. In the volunteer study, turbulent flow, which cannot be visualized with conventional cine MR imaging, could be easily detected with iMSDE. The relative
signal intensity of CSF near the foramen of Monro, cervical spine, and lumber spine, and urine in the urinary bladder with iMSDE compared towithout iMSDE were 0.20±0.14, 0.13±0.01, 0.47±0.14, 0.17±0.08, respectively. All differences between the signal intensity with and without
iMDSE were significant.
Conclusion:
Flow sensitive cine MR imaging with iMSDE pre-pulse allows visualization of flow phenomena very clearly, which was not able withconventional cine MR imaging. Since this technique can be applied with only a few limitations such as limited temporal resolution (minimum
shot duration of 1000 ms), it may provide valuable insights into physiological and/pathological flow phenomena.
References
1) Wang J, et al. MRM 2007; 58: 973-981.
2) Zhaoyang F, et al. MRM 2009; 62: 1523-1532.
3) Yoneyama M, et al. Proc Intl Soc Mag Reson Med 2012; 20.
4) Yamada S, et al. Radiology 2008; 249(2): 644-652.
※紙幅の都合上，Figureは省略いたしますVol. 70 No. 1 Jan 2014

116

はじめに
平成 25 年度前期国際研究集会派遣会員として 2013年 4 月 20 日から 26 日にアメリカのユタ州ソルトレイク
シティで開催された国際磁気共鳴医学会（International
Society for Magnetic Resonance in Medicine: ISMRM）に参加する機会を得たので，研究発表内容と学会の印象について報告する．
参加学会
ISMRM は magnetic resonance imaging
（MRI）
におけ
る最大の国際学会で世界各国から医学分野，物理工学
分野など多数の参加者が集い，演題数は約 4500 題にのぼる．その内容は，臨床応用や基礎的研究，最新の技術開発まで含まれる権威ある学会である．

Photo

ポスター発表の様子

研究発表内容
発表内容は「Flow Sensitive Cine MR Imaging Using

でセッションが組まれており，世界各国の MRI に携わ

I m p r oved Mot ion Se nsi t ized Dr ive n Eq u ili br i u m

る研究者がどのようなことに興味を持ち，開発をしてい」である．
（iMSDE）

るのかを直に目にすることができ非常に充実した学会で従来 iMSDE は，血液信号の抑制を目的として使用さあった．また，今回は電子ポスターでの発表であった

れることが多く，頸動脈などの血管壁の描出や下肢のが，数人の方とディスカッションすることができとても

MR venography，脳転移腫瘍におけるガドリニウム造影

良い刺激となった．しかしながら，質問に対する答えが後のフローアーチファクトの抑制などに用いられてき

うまく返せず，自分の意思を伝える語学力の重要性を痛た．われわれはこれまでの応用例とは異なり，位相分散感させられた学会でもあった．

に よ る 信 号 損 失 を 利 用 し iMSDE と balanced-SSFP
sequence を組み合わせ「流れ」
を連続的に捉える試みを謝

辞行い，尿管から膀胱へ尿がジェット状に流れ込む様子

ISMRM2013 への参加に際して，平成 25 年度前期国や，呼吸運動によって脊椎の脳脊髄液の流れが変わる

際研究集会派遣会員に選出・承認していただき，また助様子などを時間分解能の高い cine 画像として描出でき成していただきました日本放射線技術学会 真田たことを報告した．

表理事をはじめ学術交流委員会や関係者各位に御礼申茂代し上げます．また，学会参加に際しご協力いただきまし参加学会の印象
今回初めて国際学会に参加し，早朝から夕方遅くまた東海大学医学部付属病院および付属八王子病院放射線技術科の皆様に感謝申し上げます．

第 21 回国際磁気共鳴学会に参加して〜初めての国際学会への挑戦〜
派遣員 安藤浩樹 千葉大学医学部附属病院
派遣国際研究集会：The International Society for Magnetic Resonance in Medicine (ISMRM) 2013
開催場所
：Salt Lake City, Utah, USA
開催期間：April 20-26, 2013

Clarify Effects of Measurement Successful Rate in 1H MRS of Skeletal Muscle
Hiroki Ando,1, 2 Tomonori Isobe,1 Yoshikazu Okamoto,1 Hiroaki Suzuki,1 Yuji Hirano,1 and Eisuke Sato3
University of Tsukuba
University of Chiba
3
Kitasato University
1
2

日本放射線技術学会雑誌

117

Background:
1
H-MRS has been applied in skeletal muscle studies, and it has begun to be used for measuring fat metabolism.1) Many studies have been
conducted on intracellular lipid (IMCL) because it is considered a key factor in clarifying the pathogenesis of lifestyle-related diseases including
diabetes mellitus (DM), and it might be used to measure quantitatively and non-invasively, by 1H-MRS.2) We attempted to optimize the scanparameters with reference to several past studies for adequate data acquisition on the metabolism of lipid in skeletal muscle. However, we wereunable able to differentiate the lipid content peaks of IMCL and extracellular lipid (EMCL). We suppose the cause of this difference is not only
the optimization of the scan parameters or the quality of the MR machine, but it might also be that attribution differences among subjects could
be effective for successful data acquisition. The purpose of this study is to clarify whether the difference of attribution of subject groups could
affect the possibility of successful data acquisition, namely differences of age, health condition (healthy and DM), or kind of target muscle.
Teaching Point:
The subjects without DM were divided into Group A (19 individuals in their 20 s), and Group B (27 individuals aged 30–60 years), andthe subjects with DM formed Group C (22 individuals aged 30–60). For all subjects, 1H-MRS measurements were taken of muscle in the lower
thigh [soleus (SOL) and anterior tibialis (AT)]. Because our goal in this 1H-MRS analysis of skeletal muscle is to obtain information about IMCL
and EMCL, the sharpness of separation of the two peaks was graded and taken as an indicator of the success of measurement. In the analysis
results, we regarded the cases with an error of 0 and cases with a standard deviation of ≥20 as failures (0 points), and the rest of the cases wereregarded as successes (1 point).
We compared the measurement success rate for SOL and AT in Groups A, B, and C. The results for the measurement success rate in AT
and SOL are shown in Fig. 1.The success rate was significantly higher for AT than for SOL (p<0.01): 81.6% for SOL and 100% for AT. We
consider differences in the structure of skeletal muscle might produce the difference in the success rate. SOL has shown to have a large andvariable pennation angle by several ultrasound and MRI studies.3) AT has a lower pennation angle than the other calf muscles. And also, thepennation angle variation is very small.4) In VOI, AT allows less opportunity to measure the irregular distributed stromal components such as
gross fatty or vascular components. SOL has a higher possibility for measuring fatty or vascular components with mingled skeletal muscle fiber.
Next, we examined the influence of age and the presence or absence of diabetes on the measurement success rate for SOL in the threegroups. The measurement success rates according to age and the presence or absence of diabetes are shown in Fig. 2. Although the measurement
success rate was 100% for Group A, it was 85.2% for Group B, and 77.3% for Group C. There was a significant difference (p<0.05) between
Groups A and B, as well as between Groups A and C. Factors of aging and disease (DM) tend to induce sarcopenia. And also, the above factors
are related to the decrease in the metabolic rate. This increase of the fatty component might also be a cause of the erroneous measurement.
Sarcopenia and increase of fat might also cause the irregularity of the muscle fiber direction.
Summary:
The success of 1H-MSR measurements of IMCL and EMCL in skeletal muscle is affected by age, the presence or absence of diabetes, andthe anatomical structure of different skeletal muscle types. In other words, in living organisms there are a variety of factors that affect thesuccess of lipid content measurements by 1H-MRS.
References
1) Schrauwen-Hinderling VB, et al. Obesity 2006; 14: 357-367.
2) Boesch C, et al. Magn Reson Med 1997; 37: 484-493.
3) Okamoto Y, et al. JMIRO 2012 (in press).
4) Damon BM, et al. Magn Reson Med 2002; 48: 97-104.
※紙幅の都合上，Figureは省略いたします

はじめに2013 年 4 月 20 日〜26 日の期間，米国のソルトレイク
において International Society for Magnetic Resonance in
Medicine（ISMRM）
21st Annual Meeting と Section formagnetic resonance technologists（SMRT）
22nd Annual
Meeting が開催された．今回，平成 25 年度前期国際研
究集会派遣会員としてポスター発表をする機会を得たので，その研究発表内容，および ISMRM の印象を報告する．
研究発表内容私の発表テーマは「1H-MRS 骨格筋における測定成功率に影響する生体因子の特定」
である．以下に発表内容

Photo

ポスター発表後の reception にての概要を記載する．
われわれは，骨格筋の細胞内脂肪（IMCL）と細胞外脂肪（EMCL）を対象とした1H-MRS の計測を試みてきた及ぼす影響を明らかにすることである．対象は A 群（20が，対象の全例で成功するまでには至らなかった．この歳 代 健 常 n=19），B 群（30〜50 歳 代 健 常 n=27），C 群

要因として，われわれは，H-MRS の計測成功率が生体（30〜50 歳代糖尿病 n=22）である．3.0 Tesla-MR 装置

因子と深く関連すると考えた．本研究の目的は，加齢・を使用し，全対象における両下腿のヒラメ筋
（SOL）
と前

糖尿病の有無・骨格筋の種類が，MRS の計測成功率に

脛骨筋
（AT）
に single voxel 1H-MRS を施行した．IMCL

1Vol. 70 No. 1 Jan 2014

118と EMCL の分離精度を点数化し，計測値が Error orばならないという緊張感のせいで顔面蒼白であったが，0 ，または SD >20 を失敗（0 点），それ以外を成功

つたない英語ながら何とか質問に返答することができた（1 点）とし，計測成功率を算出した．AT と SOL の計測（質問者の尋常ならざる理解力のおかげであるが…）．こ

成功率は，AT：100％，SOL：85.8％であり，AT の計測の貴重な経験を，今後の研究活動の励みとし，医療の成功率は SOL より有意に高かった（p<0.01）．SOL の計発展に貢献できるよう努力していきたいと考える．

測成功率は，A 群：100％，B 群：85.2％，C 群：77.3％
で あ り，AB 群 お よ び AC 群 で 有 意 差 を 認 め た謝辞（p<0.01）．われわれは，この計測成功率の差が骨格筋

最後に，平成 25 年度前期国際研究集会派遣会員との解剖学的構造の違いによるものであると考察した．

して ISMRM 21st と SMRT 22nd に参加する機会を与え

1

H-MRS 骨格筋における IMCL と EMCL の計測成功率ていただいた日本放射線技術学会の関係者各位に厚くは，生体因子の影響を受けることが判明した．

お礼申し上げます．また，研究発表に際し，共同研究

ISMRM の印象

辺智範准教授，岡本嘉一医師，鈴木浩明医師，平野雄

者としてご協力いただいた筑波大学 榮
ISMRM は MRI の最新動向を知るのに適した学会の一つである．今回の学会では世界中から約 6000 人以上

武二教授，磯二氏，北里大学 佐藤英介氏，千葉大学医学部附属病院
放射線部の同僚の方々に深く感謝いたします．

の参加があった．特に印象に残ったのは，7.0 Tesla-MRIに関する演題が多かったことである．7.0 Tesla-MR 装置

写真は，ポスター発表後に開かれた reception での 1が臨床導入されるのも，遠い未来の話ではないように思コマである．遠い異国の地で，日本人研究者と出会えた

えた．また，技術革新の速さを肌で感じられたことは，ことは，非常に心強かった．国際学会ならではの経験で大きな刺激となった．

ある．左から，木田勝博氏（岡山赤十字病院），筆者，

筆者にとって，今回が初めての国際学会の参加であった．ポスター発表時は，英語で質疑応答しなけれ

東義晴教授（岡山大学），横手尭彦氏（岡山大学），土

居友香氏（岡山大学）．

ISMRM 2013 国際研究集会派遣報告
派遣員 小野英雄 八重洲クリニック
派遣国際研究集会：The International Society for Magnetic Resonance in Medicine (ISMRM) 2013
開催場所
：Salt Lake City, Utah, USA
開催期間：April 20-26, 2013

Preventing Unwanted Blurring Due to Incomplete Breath-hold at Long Breath-hold
Coronary MRA; Usefulness of New Elliptical Centric acquisition (CENTRA plus)
Hideo Ono,1 Masami Yoneyama,1 Taro Takahara,2 Thomas Kwee,3 Masanobu Nakamura,1Takashi Tabuchi,1 and Masaharu Hirano4
Yaesu Clinic
Tokai University School of Engineering
3
University Medical Center Untrecht
4
Tokyo Medical University Hospital
1
2

Introduction:
Cardiac disease is responsible for 13% of deaths in adults worldwide.1) Control of angina is important to prevent the onset of myocardial
infarction. Coronary angiography is the gold standard for the evaluation of coronary artery disease (CAD), but is invasive and may cause
complications such as arrhythmia, thromboembolism, or renal dysfunction. Whole heart coronary magnetic resonance angiography (WHCMRA)
is a promising noninvasive method for diagnosing CAD.2) Navigator-gated free-breathing technique has become the method of choice to obtainhigh-resolution WHCMRA images. Nevertheless, it potentially suffers from long acquisition time. Recently, single breath-hold WHCMRA(SBH-WHCMRA) has emerged thanks to the acceleration of data acquisition with parallel imaging by means of multi-channel coil systems.3, 4)However, the limited scan time during the breath-hold period results in poor signal-to-noise ratio (SNR) and spatial resolution. We may be able
to get higher resolution images with longer scan times of, for example, around 30 s, but this kind of protocol is unrealistic and reduces the
success rate of the examination in case of incomplete breath-holding. When we imagine the situation of an incomplete breath-hold, the failureof the breath-hold (i.e., diaphragmatic drift) should occur in the latter half of the scanning. Our hypothesis is that the new method of ellipsoid
centric acquisition (CENTRA plus)5) may be tolerable for this kind of fail in breath-hold which happens in the latter half of the scanning. The

日本放射線技術学会雑誌

119

purpose of this study was to confirm the advantage of CENTRA plus over the conventional method (low-high radial sampling) for the depictionof coronary arteries in a long scanning time.
Materials and Methods:
Theory: Segmentation schematics in Ky-Kz space of a conventional radial segmentation (low-high radial) are shown in Fig. 1a. From each
Ky-Kz segment, a profile is acquired per shot starting from the central Ky-Kz segment. Consequently, any timing motions of the imaging time
influence the image quality. On the other hand, with CENTRA+, acquisition is started in the central k-space sector and the most central k-spacesector is acquired at an early stage (Fig. 1b); hence, we hypothesized less influence of motion on the latter half of the imaging time with thistechnique.
Experiment: This study was approved by the ethics committee of our hospital. Five healthy volunteers were examined on a clinical 1.5 T MRI
scanner (Achieva 1.5 T PHILIPHS Healthcare) using a cardiac 32 ch coil. The conventional low-high radial approach and the CENTRA+
approach were acquired in random order. The volunteers held their breath in the first half period and then breathed freely during the latter half.
Thus, in CENTRA+, the central part of k-space was acquired during the breath-hold period, whereas the outer k-space profiles were acquired
during the subsequent free-breathing acquisition period. Coronary MRA was acquired using a 3D balanced SSFP sequence. The imaging parameters were as follows: TR/TE of 4.0 ms/2.0 ms, flip angle of 90˚ matrix of 228×187, T2-prep of 50 ms×4, and slice thickness of 1 mm (reconstruction of 0.5 mm).
Evaluation: For the evaluation the sharpness of coronary arteries, the 20% and 80% points between the maximum and background signal intensities were first calculated for each side of the intensity profile. The distance in millimeters between the two points was then determined foreach side. The inverse of the averaged distance of the two sides was used as a measurement of the coronary arterial sharpness. The greater the
sharpness, the better the vessel definition.6) Measurement points were the proximal segment of the LAD and the distal segment of the RCA.
Paired t-tests were performed, and p-values<0.05 were considered statistically significant.
Results:
The attempted breath-hold at initial half of the imaging time was successful in all volunteers. Effective scan time was 33.8±3.3 s. Representative MPR images of LAD with each method are shown in Fig. 2. Sharpness score was 0.34±0.05 (LAD) and 0.39±0.10 (RCA) with
CENTRA+, and 0.30±0.05 (LAD) and 0.34±0.09 (RCA) with low-high radial. CENTRA+ was significantly superior to low-high radial (p<0.05)(Fig. 3).
Discussion:
In CENTRA+, the most central k-space sector is acquired only at the early stage; the most reliable period of breath-hold. The latter half
data may be acquired with poor breath-hold, but it hardly affects the image quality because such data only fill the peripheral k-space. On theother hand, since low-high radial technique acquires the central part of k-space throughout the acquisition, it causes blurring by the poor breathholding which may happen at the end of long acquisition.
Conclusions:
CENTRA+ was superior to the conventional method for the visualization of coronary arteries when a long acquisition was applied withartificially unsuccessful breath-hold at the latter half of the scanning. CENTRA+ may be used for the prolongation of scan time in order toincrease the spatial resolution.
References
1) WHO. The 10 leading cauess of death by broad income group. Fact sheet N˚310. 2008.
2) Weber OM, et al. MRM 2003; 50: 1223-1228.
3) Niendolf T, et al. MRM 2006; 56: 167-176.
4) Xu J, et al. JCMR 2010; 12: 47.
5) Beck GM, et al. JMRI 2008; 27: 1461-1467.
6) Li D, et al. Radiology 2001; 219: 270-277.
※紙幅の都合上，Figureは省略いたします

はじめに2013 年 4 月 20 日から 4 月 26 日にかけて，アメリカの研究では，k-space 充填を従来の low-high radial に変
えて CENTRA plus を用いた．CENTRA plus は早い段はユタ州ソルトレイクシティで開催された，第 21 回

階で k-space の中心を充填するため，撮像時間が延長し

ISMRM（International Society for Magnetic Resonance inて息止めが不完全になっても，モーションアーチファク

Medicine）
Annual Meeting & Exhibition に国際研究集会

トの影響が少なく，分解能を上げるために撮像時間を派遣会員として参加したので報告する．

延長しての breath-hold WHCMRA が可能である．

研究発表内容ISMRM に参加して私は「Preventing unwanted blurring due to incomplete

演題数は口述・ポスターセッション合わせて 4,500 あbreath-hold at long breath-hold coronary MRA; Usefulness

まりにおよび，各カテゴリともに最新の研究活動の報告

of new elliptical centric acquisition（CENTRA plus）」
といが行われ，非常に有益な情報を得ることができた．

うタイトルで，Electronic Poster Session での発表を行った．発表内容を以下に述べる．

また，教育講演や各スタディのグループセッションの数や内容などの充実ぶりには，目を見張るものがあった．

従 来 の breath-hold whole heart coronary magnetic

私自身の発表はというと，Electronic Poster Session のresonance angiography（WHCMRA）
では，高分解能撮像ため，割り振られた 1 時間をモニタの場所で待機して質を行おうとして撮像時を延長させると，息止めが不完疑応答するというもので，つたない会話ではあったが何全になり，逆に画質が劣化してしまう場合がある．今回とか質問に答えることもできた．また私の発表に興味をVol. 70 No. 1 Jan 2014

120

Photo

ポスター発表会場にて持ってくれた方がおり，ディスカッションができたことは，とても貴重な体験であり今後の研究活動の励みに
なった．

謝

辞
最後に国際研究集会派遣会員として助成をいただきました，日本放射線技術学会の真田茂代表理事ならびに学術交流委員会，会員の皆様に厚くお礼申し上げます．

日本放射線技術学会雑誌