Name: measuring connectivity in the primary visual pathway in human albinism using diffusion tensor imaging and tractography
Uploaded: 2016-08-11T13:00:00.000+00:00
Duration: 13 min 26 s
Description: Watch this Scientific Journal Video about Measuring Connectivity in the Primary Visual Pathway in Human Albinism Using Diffusion Tensor Imaging and Tractography at JoVE.com

仕事は自然科学とカナダの工学研究評議会（NSERC）によって部分的にサポートされています。著者は、参加者に感謝し、白皮症患者を募集中で彼の援助のための博士リック・トンプソン、デニス・ロマノフスキー彼の助けの分析の一部を実行し、図形を変更するため、モニカジラルドチカ彼女の助けのためのラクトと彼女の知識やアドバイス、ジョイウィリアムズ彼のMRI分析の専門知識のためのMRIの取得、およびアマンGoyal氏インチ

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The authors declare no conflict of interest.

WMを変更し、より具体的には、期待された対照と比較して白皮症で接続性を減少させました。このように、対照と比較して白皮症の右半球だけでなく、ここで報告アルビノと男性患者で減少し、接続中の還元FAは、当社の予測と一致しています。ジェンダーと半球効果が示唆している健康な脳の研究は、女性に比べて男性の左半球にWMの複雑さを減少したものの30-31本研究で観察された性別と半球に関連したいくつかの相違点を説明することができ、完全には明らかではありません。女性の白皮症に比べて男性の白化現象における減少の接続が原因で両群の雌の若い平均年齢に一部であってもよい（7から8年&lt;男性）、WMボリュームは健康な脳32に半ば成人期に減少することが報告されたとして、 -33。男女差も小さいサンプルサイズとそれぞれに、女性に対する男性の数が奇数に起因する可能性がありますグループ（5人の男性OCA、4コントロール）。増加した接続が予想されなかったのと同じ性別の対照と比較して、女性の白皮症で観察し、白化現象の代償機構のいくつかの並べ替えを示唆している可能性があります。しかし、この知見はむしろ少ない人口のサンプルの中で大きなばらつきに起因する可能性があります。 FAを意味し、カウントを合理化は、V1の接続にLGNを探索するために使用されています。 FAは、拡散データから導出最も一般的に報告された対策の一つです。これは、最も正確領域内にあるか、強く指向性拡散の定量化として記載されています。 FA対策における群差は、必ずしも白質の整合性の違いを意味するものではないことに注意してください。この研究は白質への潜在的影響の臨床症状を伴うので、そのような解釈が正当化することができます。減少した整合性が構造的損傷または下落を示唆しながら、しかし、地域のFAは、そのような大きいなどの少数の障壁に低下することがあります増加した膜透過性の34から生じる効果が低い境界に起因する軸索の直径とあまり密集軸索だけでなく、。再構成された流線の数は、実際の繊維の数の真の表現ではないかもしれないので、用語「数の合理化 &#39;は、同様に起因するような長さ、曲率や分岐などの経路の機能の変化に、「繊維・カウント」よりも好ましいですこのような信号対雑音比（SNR）34などの実験条件。 ラクトは、in vivoでのマッピングWMのための唯一の非侵襲的技術です。異方性があるレベルを下回ったとき、または突然の角度がある場合、決定論的なアプローチでは、終了が発生します。しかし、ほとんどのボクセルは、複数の方向の繊維を含み、決定論的なアプローチは、ボクセルまたはボクセル内のすべての方向の「平均」で支配的な管を特定のいずれかに限定されます。したがって、真のrepresを提供することができませんニューロン経路のentation。確率的トラクトグラフィは、単一のボクセル内に2つのファイバモデルの解像度を可能にする道のより信頼性の高い表現を提供し、低異方性17の地域で追跡します。確率的アルゴリズムは、したがって、V1の灰白質で終了する、または、高度に分岐WM構造（マイヤーのループの特に部分）の軌道を調査し、本研究では特に有利でした。複数の順列を超える出現確率的トラクトグラフィではなく、繊維の真の解剖学的構造を表すラクトの誤解を招くような概念よりも、同じ経路を有するの確率的確率を参照していることに留意することが重要です。確率論的トラクトグラフィをより密接に神経線維の真の経過を追跡すると考えられているが、決定論的トラクトグラフィは、両方の技術の有用性および再現性を比較するために行きました。傾向は確率論的なアプローチを用いて検出したので、類似性が見られます決定論的な実行でのみ、さらに結果の妥当性を強化しました。 別に脳内の解剖学的接続のマッピングの研究におけるその使用が増加してから、トラクトグラフィは、脳神経外科パンで有望な進歩を示しています。 OR neuronavigationally手術フィールドにDWIデータを転送することにより、腫瘍の切除時の可視化に成功した病変を除去し、35無傷の視野を維持するのに役立つことが報告されました。それにもかかわらず、DTIは、このような比較的貧しい空間分解能や、ORなどの低繊維密度を有する構造が20を検討されている障害のあるデータ品質などの制限があります。確率的トラクトグラフィが好ましい技術であったが、現在の研究では、2つのアルゴリズムを比較することを目的としました。両方の追跡アルゴリズムは、結果の信頼性を増加させる、いくつかの一般的な知見を明らかにしました。 LGN量は、健康な脳8およびcに112〜276ミリメートル3の範囲視覚野と視神経管の容量ではなく、全体的な脳の容積36とorrelates。ラクトシードマスク内のボクセルの数に依存するので、LGNボリュームが管37との間の定量的な比較に偏りを防ぐために、参加者全体で正規化されるべきです。我々は、2つの異なる方法を使用して、LGNの大きさの差を制御します。第1の方法では、標準サイズの球状のROIを作成しました。これを達成するために、MNI空間に変換そのLGNマスクの全被験者にわたる平均容量を算出しました。 MNI空間における平均マスクの半径を使用して、球がいずれかの解剖学的または拡散空間の各LGNの質量の中心を中心としました。個々のLGNのボリュームよりも大きな容量で標準球ROIを使用すると、すべての参加者で、この構造体の一部であるすべてのボクセルを含めることを保証します。通常、偽陽性のリスクを増加させる、より大きなマスクサイズを使用している間播種時に、そのような懸念は適用されません。構造体のような周囲の核からの接続パターンが異なるLGN、など。したがって、他の構造に属するボクセル予想されるパスと、そのようなパスに従わない流線を生成します。そのため、廃棄される18我々はLGNの音量を制御するために使用される【選択第二の方法は、共変量としてLGNのボリュームを使用して統計分析を実行することであったが、この大幅統計結果を変化させませんでした。 LGNの正規化のための別の可能なアプローチは、MATLABスクリプトを使用して、被験者全体での標準的なサイズを取得するには、個々のLGNマスクの周りのボクセルの追加や削除です。このアプローチは、追加登録を必要とするので、脳画像の変形の程度を制限し、精度が向上しません。また、LGN領域の周囲の球を作成するのではなく、LGNのアウトラインを保持します。しかし、ヒューマンエラーを最小限にするために、マルチアトラスセグメンテーションではなく手動でLGNマスクをトレースを使用することができます。アトラス・アカウントのセットを使用して個々の構造変動のために、したがって、単一のアトラス38よりも皮質下領域のより正確な表現が得られます。 生体内研究ではこの小説は人間の白化現象で一次視覚経路の異なる部品間の相互依存の開発を調査します。したがって、障害固有の署名の識別を通じて、この条件と改善された診断の病因さらなる洞察を提供します。ここで使用される確率論と決定論の両方のトラクトグラフィアルゴリズムは、人間の白皮症でV1の接続に変更されたLGNの同等のパターンを示しました。大集団への一般化は、サンプルサイズが小さいと、目的の構造に大きな被験者間のばらつきに起因して行うことはできませんが、この研究では、さらなる研究の重要性を示唆し、サンプル集団内の動向を検出する際にトラクトグラフィの有用性を実証しますフィールド。

白皮症は、主に罹患した個体で観察された明白な低色素沈着によって特徴づけられる遺伝子疾患です。これは、メラニン合成1に関与する遺伝子に継承突然変異によって引き起こされます。白皮症は、主に2つの形式で表示されます。oculo-皮膚白皮症（OCA）、眼および皮膚の両方の機能を提示する常染色体劣性形質。そして、眼白子症（OA）、男性でより普及および眼症状2によって主に特徴付けられるX連鎖特色。網膜色素上皮（RPE）におけるメラニンは、中央視覚経路の適切な発達のために重要です。白化現象におけるその不在は、したがって、羞明、眼振、視力低下や両眼視2-3の損失を含む視覚障害、になります。視力は白皮症4に変更された中心窩の形態、にリンクされています。ヒトでは、交叉の網膜のラインは鼻網膜からの繊維と、中心窩を通じてnasotemporal国境沿いに位置します他の半球に交差し、一時的な網膜からのものが同側に伸びます。白皮症で減少した視覚機能の程度が低色素沈着のレベルにリンクされています。具体的には、色素沈着が交叉5のラインの一時的な網膜へのシフトに反比例します。一時的な網膜への交叉のラインのシフトの結果、視神経繊維の交差が増加する-共通の特徴をすべての種3渡って。 ヒトへの構造的MRI研究は、おそらく白皮症6-8で観察されたRGCの増加交差点の結果である対照と比較して、白化現象が狭い光学chiasmsを、示しています。網膜や視神経視交叉は、Ephファミリー受容体およびそれらのリガンド9と軸索ガイダンスの手がかりを表現するため、misrouting 10の候補部位です。 緑内障とサルの研究は重要な12月を明らかにしましたLGNのパルブアルブミン免疫反応性の中継ニューロンの数とLGNのボリューム11でrease。これはLGNのサイズとV1にORを通って移動する白質（WM）軌道の数との相関関係を示唆しています。人間の白皮症に死後の研究はまた、融合MとP層12と小さいLGNを明らかにしました。高分解能構造MRIは、白皮症8 LGNの量の有意な減少が確認されました。まとめると、これらの知見はLGNのニューロン数の減少をもたらす可能性がLGN量を減少し、LGNとV1の間の減少の接続で順番にすることを示唆しています。 ヒトでの解剖学的接続の調査パターンが限定されています。解剖、トレーサー注射および病変の誘発は、死後に使用することができる侵襲性の技術であり、通常は患者のごく少数を含みます。カルボ色素DiIで注射を使用して、以前の研究では、V1とV2（二次のVisual C間の神経の接続性を実証しましたortex）13、ならびにアルデヒド固定死後の人間の脳14内の海馬コンプレックス内。このようにラベリング繊維は、注入14の点からミリメートルの唯一の数十の距離に制限されています。拡散テンソル画像、DTIは、線維トラクトの方向と組織を識別するために、早期1990年代半ばに開発されたMRIモダリティです。それは生きている脳内の大WM経路のマッピングを可能にする非侵襲的方法です。 DTIは、生体組織15内の水分子の拡散に敏感です。脳では、水の拡散は、このような膜およびミエリンなどの障壁に起因する異方性（不均一）です。 WMは、拡散に対するファイバ16の方向に垂直なより大きい平行である意味、高い拡散異方性を有しています。 フラクショナル異方性（FA）は、異方性的に拡散する分子の好みを説明するスカラー量です。 FA値は、ローからハイanisotに、0-1の範囲粘着性の（脳脊髄液（CSF）&lt;灰白質（GM）&lt;WM）16。 （決定論的）合理化と確率論ファイバートラッキング3Dパス再構成のための2つの異なるアルゴリズムです。決定論的トラクトグラフィは、定義されたシード領域に隣接したボクセルを結ぶ、直線伝搬法を使用しています。このアルゴリズムで使用される2つの停止基準は、回転角度とFA値です。したがって、隣接ボクセルの間のトレース管は、大きなターニング角度ではほとんどありません。このアルゴリズムは、したがって、ボクセル内のFAが正確に異方性が低下灰白質、近くの経路を定義することでその有効性を制限し、特定のしきい値を超えた場合にのみ進行することになります。確率論的トラクトグラフィは、一方で、関心対象の2つの領域間の道の一部であるボクセルの確率を記述する接続性マップ（関心領域）が得られるので、このようなV1 17と灰白質に進行します。このMRIのアプリケーションを使用して、などの主要WM構造以前の研究18-20に示すようにOR、描写することができます。 この研究は、したがって、レチノ - geniculo皮質接続上の軸索misroutingの効果を調査するために、拡散データとラクトを使用しています。人間の色素欠乏症8でLGNボリュームで以前に報告された削減に基づいて、我々はV1に、LGNから繊維突起はまた、（ 図1）に低減されていると予測しています。

<table><tbody><tr><td>Magnetom Tim Trio 3T MRI</td><td>Siemens (Erlangen, Germany)</td><td></td><td></td></tr><tr><td>FMRIB&amp;rsquo;s Software Library (FSL)</td><td></td><td></td><td>http://www.fmrib.ox.ac.uk/fsl/</td></tr><tr><td>FreeSurfer</td><td></td><td></td><td>http://surfer.nmr.mgh.harvard.edu</td></tr><tr><td>DSI Studio</td><td></td><td></td><td>http://dsi-studio.labsolver.org</td></tr><tr><td>SPSS</td><td></td><td></td><td></td></tr></tbody></table>

measuring connectivity in the primary visual pathway in human albinism using diffusion tensor imaging and tractography

白皮症において、同側に突出する網膜神経節細胞（RGC）の数が大幅に低減されます。網膜や視交叉はmisroutingのための候補地として提案されています。外側膝状核（LGN）ニューロンおよびLGNのサイズを中継数との相関関係が示されており、人間の白化におけるLGNボリュームで以前に報告された削減に基づいているので、私たちは一次視覚野（V1）に、LGNからの繊維の突起を示唆していますまた低減されます。白皮症の視覚系の構造的な違いを学ぶことmisroutingとその後の臨床応用のメカニズムの理解を向上させることができます。拡散データ及びラクトは、OR（光学放射）をマッピングするために有用です。この原稿は32チャンネルヘッドコイルは構造的なスキャンを取得するために使用されたと白皮症とcontrols.An MRIスキャナで脳の接続性を比較するために、または再構成の2つのアルゴリズムを説明しています。 1ミリメートルとT1強調3D-MPRAGEシーケンス3等方性のボクセルサイズはV1分割用の高解像度画像を生成するために使用されました。複数のプロトン密度（PD）強調画像は、左右のLGNのローカライズのために冠状に取得しました。拡散テンソルイメージング（DTI）スキャンは、64の拡散方向を用いて取得しました。両方の決定論的及び確率論的追跡方法は、対象マスクとしてシードマスクV1としてLGNで、実行して比較しました。 DTIは、比較的低い空間分解能を提供し、または正確な描写は、その低い繊維密度に挑戦することができるが、ラクトは、研究および臨床の両方に有利であることが示されています。管ベースの空間統計（TBSS）は、対照と比較して、アルビノの患者ではOR内に有意に減少白質の整合性の領域を明らかにしました。一対比較は、対照と比較して白皮症でV1の接続にLGNの大幅な削減を明らかにしました。両方の追跡アルゴリズムを比較すると信頼性を強化し、共通の調査結果を明らかにしました技術の。

Watch this Scientific Journal Video about Measuring Connectivity in the Primary Visual Pathway in Human Albinism Using Diffusion Tensor Imaging and Tractography at JoVE.com

Measuring Connectivity in the Primary Visual Pathway in Human Albinism Using Diffusion Tensor Imaging and Tractography

この原稿は、光学放射（OR）白皮症と対照との間の接続性の違いを調べるために用い白質（WM）復興のための決定論と確率的アルゴリズムを説明します。確率論的トラクトグラフィは、より密接に神経線維の真の経過をたどるが、決定論的トラクトグラフィは、両方の技術の信頼性と再現性を比較するために行きました。

拡散テンソルイメージングとラクトを用いたヒト色素欠乏症における一次視覚経路で接続を測定します

In albinism, the number of ipsilaterally projecting retinal ganglion cells (RGCs) is significantly reduced. The retina and optic chiasm have been proposed ...

measuring-connectivity-primary-visual-pathway-human-albinism-using

Universidad San Sebastian

Research

JoVE Journal

Neuroscience

12.2K ビュー.  York University. この原稿は、光学放射（OR）白皮症と対照との間の接続性の違いを調べるために用い白質（WM）復興のための決定論と確率的アルゴリズムを説明します。確率論的トラクトグラフィは、より密接に神経線維の真の経過をたどるが、決定論的トラクトグラフィは、両方の技術の信頼性と再現性を比較するために行きました。 

ビデオ: Measuring Connectivity in the Primary Visual Pathway in Human Albinism Using Diffusion Tensor Imaging and Tractography

Probing the Brain in Autism Using fMRI and Diffusion Tensor Imaging

Newly emerging theories suggest that the brain does not function as a cohesive unit in autism, and this discordance is reflected in the behavioral symptoms displayed by individuals with autism. While structural neuroimaging findings have provided some insights into brain abnormalities in autism, the consistency of such findings is questionable. Functional neuroimaging, on the other hand, has been more fruitful in this regard because autism is a disorder of dynamic processing and allows examination of communication between cortical networks, which appears to be where the underlying problem occurs in autism. Functional connectivity is defined as the temporal correlation of spatially separate neurological events1. Findings from a number of recent fMRI studies have supported the idea that there is weaker coordination between different parts of the brain that should be working together to accomplish complex social or language problems2,3,4,5,6. One of the mysteries of autism is the coexistence of deficits in several domains along with relatively intact, sometimes enhanced, abilities. Such complex manifestation of autism calls for a global and comprehensive examination of the disorder at the neural level. A compelling recent account of the brain functioning in autism, the cortical underconnectivity theory,2,7 provides an integrating framework for the neurobiological bases of autism. The cortical underconnectivity theory of autism suggests that any language, social, or psychological function that is dependent on the integration of multiple brain regions is susceptible to disruption as the processing demand increases. In autism, the underfunctioning of integrative circuitry in the brain may cause widespread underconnectivity. In other words, people with autism may interpret information in a piecemeal fashion at the expense of the whole. Since cortical underconnectivity among brain regions, especially the frontal cortex and more posterior areas 3,6, has now been relatively well established, we can begin to further understand brain connectivity as a critical component of autism symptomatology.
A logical next step in this direction is to examine the anatomical connections that may mediate the functional connections mentioned above. Diffusion Tensor Imaging (DTI) is a relatively novel neuroimaging technique that helps probe the diffusion of water in the brain to infer the integrity of white matter fibers. In this technique, water diffusion in the brain is examined in several directions using diffusion gradients. While functional connectivity provides information about the synchronization of brain activation across different brain areas during a task or during rest, DTI helps in understanding the underlying axonal organization which may facilitate the cross-talk among brain areas. This paper will describe these techniques as valuable tools in understanding the brain in autism and the challenges involved in this line of research.

Neuroimaging techniques, such as functional MRI and Diffusion Tensor Imaging have become increasingly useful in characterizing the cognitive and neural deficits in autism. An examination of brain connectivity in autism at a network level along with adaptations for scanning children with developmental disabilities is presented.

fMRIと拡散テンソル画像を用いた自閉症で脳を探る

Newly emerging theories suggest that the brain does not function as a cohesive unit in autism, and this discordance is reflected in the behavioral ...

医学

Time-lapse Live Imaging of Clonally Related Neural Progenitor Cells in the Developing Zebrafish Forebrain

Precise patterns of division, migration and differentiation of neural progenitor cells are crucial for proper brain development and function1,2. To understand the behavior of neural progenitor cells in the complex in vivo environment, time-lapse live imaging of neural progenitor cells in an intact brain is critically required. In this video, we exploit the unique features of zebrafish embryos to visualize the development of forebrain neural progenitor cells in vivo. We use electroporation to genetically and sparsely label individual neural progenitor cells. Briefly, DNA constructs coding for fluorescent markers were injected into the forebrain ventricle of 22 hours post fertilization (hpf) zebrafish embryos and electric pulses were delivered immediately. Six hours later, the electroporated zebrafish embryos were mounted with low melting point agarose in glass bottom culture dishes. Fluorescently labeled neural progenitor cells were then imaged for 36hours with fixed intervals under a confocal microscope using water dipping objective lens. The present method provides a way to gain insights into the in vivo development of forebrain neural progenitor cells and can be applied to other parts of the central nervous system of the zebrafish embryo.

The present video demonstrates a method which takes advantage of the combination of electroporation and confocal microscopy to perform live imaging on individual neural progenitor cells in the developing zebrafish forebrain. In vivo analysis of the development of forebrain neural progenitor cells at a clonal level can be achieved in this way.

開発ゼブラフィッシュ前脳におけるクローン関連の神経前駆細胞のタイムラプスライブイメージング

Precise patterns of division, migration and differentiation of neural progenitor cells are crucial for proper brain development and function1,2. To ...

神経科学

Co-analysis of Brain Structure and Function using fMRI and Diffusion-weighted Imaging

The study of complex computational systems is facilitated by network maps, such as circuit diagrams. Such mapping is particularly informative when studying the brain, as the functional role that a brain area fulfills may be largely defined by its connections to other brain areas. In this report, we describe a novel, non-invasive approach for relating brain structure and function using magnetic resonance imaging (MRI). This approach, a combination of structural imaging of long-range fiber connections and functional imaging data, is illustrated in two distinct cognitive domains, visual attention and face perception. Structural imaging is performed with diffusion-weighted imaging (DWI) and fiber tractography, which track the diffusion of water molecules along white-matter fiber tracts in the brain (Figure 1). By visualizing these fiber tracts, we are able to investigate the long-range connective architecture of the brain. The results compare favorably with one of the most widely-used techniques in DWI, diffusion tensor imaging (DTI). DTI is unable to resolve complex configurations of fiber tracts, limiting its utility for constructing detailed, anatomically-informed models of brain function. In contrast, our analyses reproduce known neuroanatomy with precision and accuracy. This advantage is partly due to data acquisition procedures: while many DTI protocols measure diffusion in a small number of directions (e.g., 6 or 12), we employ a diffusion spectrum imaging (DSI)1, 2 protocol which assesses diffusion in 257 directions and at a range of magnetic gradient strengths. Moreover, DSI data allow us to use more sophisticated methods for reconstructing acquired data. In two experiments (visual attention and face perception), tractography reveals that co-active areas of the human brain are anatomically connected, supporting extant hypotheses that they form functional networks. DWI allows us to create a "circuit diagram" and reproduce it on an individual-subject basis, for the purpose of monitoring task-relevant brain activity in networks of interest.

We describe a novel approach for simultaneous analysis of brain function and structure using magnetic resonance imaging (MRI). We assess brain structure with high-resolution diffusion-weighted imaging and white-matter fiber tractography. Unlike standard structural MRI, these techniques allow us to directly relate anatomical connectivity to functional properties of brain networks.

fMRIと拡散強調画像を用いた脳の構造と機能の同時分析

The study of complex computational systems is facilitated by network maps, such as circuit diagrams. Such mapping is particularly informative when ...

Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases

Diffusion tensor imaging (DTI) techniques provide information on the microstructural processes of the cerebral white matter (WM) in vivo. The present applications are designed to investigate differences of WM involvement patterns in different brain diseases, especially neurodegenerative disorders, by use of different DTI analyses in comparison with matched controls. 	
DTI data analysis is performed in a variate fashion, i.e. voxelwise comparison of regional diffusion direction-based metrics such as fractional anisotropy (FA), together with fiber tracking (FT) accompanied by tractwise fractional anisotropy statistics (TFAS) at the group level in order to identify differences in FA along WM structures, aiming at the definition of regional patterns of WM alterations at the group level. Transformation into a stereotaxic standard space is a prerequisite for group studies and requires thorough data processing to preserve directional inter-dependencies. The present applications show optimized technical approaches for this preservation of quantitative and directional information during spatial normalization in data analyses at the group level. On this basis, FT techniques can be applied to group averaged data in order to quantify metrics information as defined by FT. Additionally, application of DTI methods, i.e. differences in FA-maps after stereotaxic alignment, in a longitudinal analysis at an individual subject basis reveal information about the progression of neurological disorders. Further quality improvement of DTI based results can be obtained during preprocessing by application of a controlled elimination of gradient directions with high noise levels.	
In summary, DTI is used to define a distinct WM pathoanatomy of different brain diseases by the combination of whole brain-based and tract-based DTI analysis.

Diffusion tensor imaging (DTI) basically serves as an MRI-based tool to identify in vivo the microstructure of the brain and pathological processes due to neurological disorders within the cerebral white matter. DTI-based analyses allow for application to brain diseases both at the group level and in single subject data.

神経変性疾患の分析における拡散テンソル磁気共鳴画像

Diffusion tensor imaging (DTI) techniques provide information on the microstructural processes of the cerebral white matter (WM) in vivo. The present ...

DTI of the Visual Pathway - White Matter Tracts and Cerebral Lesions

DTI is a technique that identifies white matter tracts (WMT) non-invasively in healthy and non-healthy patients using diffusion measurements. Similar to visual pathways (VP), WMT are not visible with classical MRI or intra-operatively with microscope. DTI will help neurosurgeons to prevent destruction of the VP while removing lesions adjacent to this WMT. We have performed DTI on fifty patients before and after surgery between March 2012 to January 2014. To navigate we used a 3DT1-weighted sequence. Additionally, we performed a T2-weighted and DTI-sequences. The parameters used were, FOV: 200 x 200 mm, slice thickness: 2 mm, and acquisition matrix: 96 x 96 yielding nearly isotropic voxels of 2 x 2 x 2 mm. Axial MRI was carried out using a 32 gradient direction and one b0-image. We used Echo-Planar-Imaging (EPI) and ASSET parallel imaging with an acceleration factor of 2 and b-value of 800 s/mm&#178;. The scanning time was less than 9 min.
The DTI-data obtained were processed using a FDA approved surgical navigation system program which uses a straightforward fiber-tracking approach known as fiber assignment by continuous tracking (FACT). This is based on the propagation of lines between regions of interest (ROI) which is defined by a physician. A maximum angle of 50, FA start value of 0.10 and ADC stop value of 0.20 mm&#178;/s were the parameters used for tractography.
There are some limitations to this technique. The limited acquisition time frame enforces trade-offs in the image quality. Another important point not to be neglected is the brain shift during surgery. As for the latter intra-operative MRI might be helpful. Furthermore the risk of false positive or false negative tracts needs to be taken into account which might compromise the final results.

Diffusion tensor imaging (DTI) was performed to try to depict the major parts of the visual pathway. The goal was to use an FDA approved standard commercial workstation which could be used for everyday routine in order to try to reduce postoperative damage of the visual pathway in the patients.

視覚路のDTI  - 白質地帯と大​​脳病変

DTI is a technique that identifies white matter tracts (WMT) non-invasively in healthy and non-healthy patients using diffusion measurements. Similar to ...

Diffusion Imaging in the Rat Cervical Spinal Cord

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a diagnostic and prognostic tool in cases of disease or injury. Diffusion weighted imaging (DWI), is sensitive to the thermal motion of water molecules and allows for inferences of tissue microstructure. This report describes a protocol to acquire and analyze DWI of the rat cervical spinal cord on a small-bore animal system. It demonstrates an imaging setup for the live anesthetized animal and recommends a DWI acquisition protocol for high-quality imaging, which includes stabilization of the cord and control of respiratory motion. Measurements with diffusion weighting along different directions and magnitudes (b-values) are used. Finally, several mathematical models of the resulting signal are used to derive maps of the diffusion processes within the spinal cord tissue that provide insight into the normal cord and can be used to monitor injury or disease processes noninvasively.

The goal of this protocol is to obtain high-quality diffusion weighted magnetic resonance imaging (DWI) of the rat spinal cord for noninvasive characterization of tissue microstructure. This protocol describes optimizations of the MRI sequence, radiofrequency coil, and analysis methods to enable DWI images free from artifacts.

ラット頸部脊髄の拡散イメージング

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a ...

Fiber Connections of the Supplementary Motor Area Revisited: Methodology of Fiber Dissection, DTI, and Three Dimensional Documentation

The purpose of this study is to show the methodology for the examination of the white matter connections of the supplementary motor area (SMA) complex (pre-SMA and SMA proper) using a combination of fiber dissection techniques on cadaveric specimens and magnetic resonance (MR) tractography. The protocol will also describe the procedure for a white matter dissection of a human brain, diffusion tensor tractography imaging, and three-dimensional documentation. The fiber dissections on human brains and the 3D documentation were performed at the University of Minnesota, Microsurgery and Neuroanatomy Laboratory, Department of Neurosurgery. Five postmortem human brain specimens and two whole heads were prepared in accordance with Klingler's method. Brain hemispheres were dissected step by step from lateral to medial and medial to lateral under an operating microscope, and 3D images were captured at every stage. All dissection results were supported by diffusion tensor imaging. Investigations on the connections in line with Meynert's fiber tract classification, including association fibers (short, superior longitudinal fasciculus I and frontal aslant tracts), projection fibers (corticospinal, claustrocortical, cingulum, and frontostriatal tracts), and commissural fibers (callosal fibers) were also conducted.

The purpose of this study is to show each step of the fiber dissection technique on human cadaveric brains, the 3D documentation of these dissections, and the diffusion tensor imaging of the anatomically dissected fiber pathways.

再考された補助的なモータ領域のファイバ接続：ファイバ解剖、DTI、および3次元文書の方法論

The purpose of this study is to show the methodology for the examination of the white matter connections of the supplementary motor area (SMA) complex ...

Mapping Regional Homogeneity and Functional Connectivity of the Visual Cortex in Resting-State fMRI

A combined regional homogeneity (ReHo) and functional connectivity (FC) method, a type of noninvasive functional magnetic resonance imaging (fMRI) method, has been used to evaluate synchronous neuronal activity changes in retinitis pigmentosa (RP). The purpose of this study is to describe our method for analysis of intra- and interregional synchronizations of changes in neuronal activity in RP patients. The advantages of the combined ReHo and FC method are that it is both noninvasive and sufficiently sensitive to investigate changes in cerebral synchronous neuronal activity changes in vivo. Here, 16 RP patients and 14 healthy controls closely matched in age, sex, and education underwent resting-state fMRI scans. Two sample t-tests were conducted to compare ReHo and FC across groups. Our results showed that visual network disconnection and reorganization of the retino-thalamocortical pathway and dorsal visual stream occurred in the RP patients. Here, we describe the details of this method, its use, and the impact of its key parameters in a step-by-step manner.

We present a protocol for analyzing functional magnetic resonance imaging data to investigate spontaneous neural activity alterations in retinitis pigmentosa patient using a combined regional homogeneity and functional connectivity method.

A combined regional homogeneity (ReHo) and functional connectivity (FC) method, a type of noninvasive functional magnetic resonance imaging (fMRI) method, ...

Role of Diffusion MRI Tractography in Endoscopic Endonasal Skull Base Surgery

Endoscopic endonasal surgery has gained a prominent role in the management of complex skull base tumors. It allows the resection of a large group of benign and malignant lesions through a natural anatomical extra-cranial pathway, represented by the nasal cavities, avoiding brain retraction and neurovascular manipulation. This is reflected by the patients' prompt clinical recovery and the low risk of permanent neurological sequelae, representing the main caveat of conventional skull base surgery. This surgery must be tailored to each specific case, considering its features and relationship with surrounding neural structures, mostly based on preoperative neuroimaging. Advanced MRI techniques, such as tractography, have been rarely adopted in skull base surgery due to technical issues: lengthy and complicated processes to generate reliable reconstructions for inclusion in the neuronavigation system. 
This paper aims to present the protocol implemented in the institution and highlights the synergistic collaboration and teamwork between neurosurgeons and the neuroimaging team (neurologists, neuroradiologists, neuropsychologists, physicists, and bioengineers) with the final goal of selecting the optimal treatment for each patient, improving the surgical results and pursuing the advancement of personalized medicine in this field.

We present a protocol to integrate diffusion MRI tractography in patient work-up to endoscopic endonasal surgery for a skull base tumor. The methods for adopting these neuroimaging studies in the pre- and intra-operative phases are described.

内視鏡内視鏡頭蓋基外科における拡散MRIトラクトグラフィーの役割

Endoscopic endonasal surgery has gained a prominent role in the management of complex skull base tumors. It allows the resection of a large group of ...

Using Diffusion Tensor Imaging in Traumatic Brain Injury

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel&#8212;University of Southern California
Traditional brain imaging techniques using MRI are very good at visualizing the gross structures of the brain. A structural brain image made with MRI provides high contrast of the borders between gray and white matter, and information about the size and shape of brain structures. However, these images do not detail the underlying structure and integrity of white matter networks in the brain, which consist of axon bundles that interconnect local and distant brain regions.
Diffusion MRI uses pulse sequences that are sensitive to the diffusion of water molecules. By measuring the direction of diffusion, it is possible to make inferences about the structure of white matter networks in the brain. Water molecules within an axon are constrained in their movements by the cell membrane; instead of randomly moving in every direction with equal probability (isotropic movement), they are more likely to move in certain directions, in parallel with the axon (anisotropic movement; Figure 1). Therefore, measures of diffusion anisotropy are thought to reflect properties of the white matter such as fiber density, axon thickness, and degree of myelination. One common measure is fractional anisotropy (FA). FA values range from 0, which represents completely isotropic movement, to 1, reflecting maximum anisotropy.
<img alt="Figure 1" src="/files/ftp_upload/10276/10276fig1.jpg" /> 
Figure 1: Diffusion anisotropy. When the direction of diffusion is unconstrained and random, movement is measured in all directions equally. This is isotropic diffusion (A). When water molecules are contained within the axon of a neuron, diffusion is anisotropic, tending to occur more frequently along the direction of the axon (B). <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/10276/10276fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In this experiment we will use diffusion tensor imaging (DTI) to measure white matter integrity in traumatic brain injury (TBI). TBI occurs when an external force injures the brain, such as a blow to the head or a sudden movement like the kind that might occur in a car accident. This type of brain injury from mechanical forces is associated with diffuse axonal injury-damage to white matter throughout the brain. Because it is an injury affecting white matter integrity, standard neuroimaging techniques may not reveal the damage. However, measures of diffusion are especially sensitive to these anatomical changes. Following a study by Kraus et al.1, we compare a group of healthy controls to a group of people with TBI and use diffusion imaging to measure the effect of TBI on cerebral white matter. Furthermore, we will test the relationship between white matter integrity and cognitive function using an attention task.2 This study uses a region of interest (ROI) approach focusing on three white matter tracts: the splenium of the corpus callosum, the anterior corona radiata, and the superior longitudinal fasciculus (Figure 2).
<img alt="Figure 2" src="/files/ftp_upload/10276/10276fig2.jpg" /> 
Figure 2: Regions of interest. The three ROIs, defined from the ICBM DTI-81 atlas, are shown here in horizontal slices through the brain. In green is the splenium of the corpus callosum. The splenium is the most posterior part of the corpus callosum. In blue is the anterior corona radiata. The superior longitudinal fasciculus is shown in red. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/10276/10276fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Diffusion Tensor Imaging in Traumatic Brain Injury

外傷性脳損傷の拡散テンソル画像を用いた

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel&#8212;University of Southern California
Traditional brain imaging techniques using MRI are ...

拡散テンソルイメージングとラクトを用いたヒト色素欠乏症における一次視覚経路で接続を測定します

要約

さらに動画を探す

この動画の章

fMRIと拡散テンソル画像を用いた自閉症で脳を探る

開発ゼブラフィッシュ前脳におけるクローン関連の神経前駆細胞のタイムラプスライブイメージング

fMRIと拡散強調画像を用いた脳の構造と機能の同時分析

神経変性疾患の分析における拡散テンソル磁気共鳴画像

視覚路のDTI - 白質地帯と大脳病変

ラット頸部脊髄の拡散イメージング

再考された補助的なモータ領域のファイバ接続：ファイバ解剖、DTI、および3次元文書の方法論

Mapping Regional Homogeneity and Functional Connectivity of the Visual Cortex in Resting-State fMRI

内視鏡内視鏡頭蓋基外科における拡散MRIトラクトグラフィーの役割

外傷性脳損傷の拡散テンソル画像を用いた

拡散テンソルイメージングとラクトを用いたヒト色素欠乏症における一次視覚経路で接続を測定します

要約

さらに動画を探す

この動画の章

fMRIと拡散テンソル画像を用いた自閉症で脳を探る

開発ゼブラフィッシュ前脳におけるクローン関連の神経前駆細胞のタイムラプスライブイメージング

fMRIと拡散強調画像を用いた脳の構造と機能の同時分析

神経変性疾患の分析における拡散テンソル磁気共鳴画像

視覚路のDTI - 白質地帯と大​​脳病変

ラット頸部脊髄の拡散イメージング

再考された補助的なモータ領域のファイバ接続：ファイバ解剖、DTI、および3次元文書の方法論

Mapping Regional Homogeneity and Functional Connectivity of the Visual Cortex in Resting-State fMRI

内視鏡内視鏡頭蓋基外科における拡散MRIトラクトグラフィーの役割

外傷性脳損傷の拡散テンソル画像を用いた

視覚路のDTI - 白質地帯と大脳病変