著者

藤原 康博 石田 翔太 木村 浩彦

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

pp.2020-1719, (Released:2020-09-28)

参考文献数

77

---

Arterial spin labeling (ASL) is a method for evaluating perfusion that uses magnetically labeled arterial blood water as an endogenous tracer. Although research and technical development have been conducted for a long time, introduction of ASL into clinical practice has been delayed because of its low signal-to-noise ratio (SNR). In recent years, advances in the pulse sequence and hardware, such as high static magnetic fields and high-sensitivity phased array coils, have made it possible to obtain high-SNR ASL images in a clinically acceptable time. In this regard, a consensus paper proposed simple and standard usage, including recommended techniques and parameters, to obtain a consistent image quality. Major MR manufacturers offered ASL pulse sequences based on this study. Hence, ASL has been used in clinical practice, and the effectiveness in measuring perfusion using ASL has been reported for the diagnosis of various neurological disorders. This article will review the technique for perfusion measurement and quantification and the recent technical progress in ASL.

著者

石田 翔太郎 須田 礼仁

雑誌

研究報告ハイパフォーマンスコンピューティング(HPC) (ISSN:21888841)

巻号頁・発行日

vol.2015-HPC-152, no.5, pp.1-18, 2015-12-09

---

計算機上で整数一様乱数を生成する方法については,これまで多くの論文が発表されてきた.一方で,浮動小数点数一様乱数を生成する方法 (または整数一様乱数から浮動小数点数一様乱数への変換法) については,多くの場面で整数一様乱数を定数で割る方法 (rand()/232など) が用いられてきた.しかしながら,この方法では特定の形式の浮動小数点数しか生成されず,ほとんどの浮動小数点数は生成されない.これに対して,Moler は [2-53,1-2-53] の範囲にある全ての浮動小数点数を生成可能な一様乱数生成器を提案し,その後 Thoma により,その範囲は (0,1) にまで拡張された.しかしながら,Thoma により提案された手法は,浮動小数点数の丸めモードによっては,隣り合う浮動小数点数の出現確率が 3 倍程度異なる箇所が生じるといった,不自然な挙動を取ることが実験的及び理論的な検証から分かった.そこで,本論文はこの不自然な挙動を修正することを目的とした上で,まずは正しい浮動小数点数一様乱数生成器について議論し,続いてそのような生成器を提案すると共にその正当性を示し,最後に,提案された生成器の性能を実験により示した.

著者

藤原 康博 石田 翔太 木村 浩彦

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.40, no.4, pp.149-168, 2020-11-15 (Released:2020-12-15)

参考文献数

77

---

Arterial spin labeling (ASL) is a method for evaluating perfusion that uses magnetically labeled arterial blood water as an endogenous tracer. Although research and technical development have been conducted for a long time, introduction of ASL into clinical practice has been delayed because of its low signal-to-noise ratio (SNR). In recent years, advances in the pulse sequence and hardware, such as high static magnetic fields and high-sensitivity phased array coils, have made it possible to obtain high-SNR ASL images in a clinically acceptable time. In this regard, a consensus paper proposed simple and standard usage, including recommended techniques and parameters, to obtain a consistent image quality. Major MR manufacturers offered ASL pulse sequences based on this study. Hence, ASL has been used in clinical practice, and the effectiveness in measuring perfusion using ASL has been reported for the diagnosis of various neurological disorders. This article will review the technique for perfusion measurement and quantification and the recent technical progress in ASL.