Name: Segmentation of the Choroid Plexus Using Manual Delineations
Uploaded: 2023-12-15T12:40:00
Description: Watch this Scientific Journal Video about Segmentation of the Choroid Plexus Using Manual Delineations at JoVE.com

segmentation of the choroid plexus using manual delineations

脳疾患におけるニューロイメージング解析の強化

Choroid plexus function 
The choroid plexus is a highly vascularized structure in the brain consisting of fenestrated capillaries and a monolayer of choroid plexus epithelial cells1. The choroid plexus projects into the lateral, third, and fourth cerebral ventricles and produces cerebrospinal fluid (CSF), which plays an important role in neural patterning2 and brain physiology3,4. The choroid plexus secretes neurovascular substances, encompasses a stem-cell like repository, and acts as a physical barrier to impede the entrance of toxic metabolites, an enzymatic barrier to remove moieties that circumvent the physical barrier, and an immunological barrier to protect against foreign invaders5. The choroid plexus modulates neurogenesis6, synaptic plasticity7, inflammation8, circadian rhythm9,10, gut brain-axis11, and cognition12. Moreover, peripheral cytokines, stress, and infection (including SARS-CoV-2) can disrupt the blood-CSF barrier13,14,15,16. Thus, the choroid plexus-CSF system is integral for neurodevelopment, neurocircuit maturation, brain homeostasis, and repair17. Since immune, inflammatory, metabolic, and enzymatic alterations impact the brain, researchers are using neuroimaging tools to assess the role of the choroid plexus across the lifespan and in brain disorders18,19,20. However, limitations exist in commonly used automated tools for choroid plexus segmentation, such as FreeSurfer, which result in the choroid plexus being poorly segmented. Thus, there is a critical need for ground truth manual segmentation of the choroid plexus that can be used to develop an accurate automated tool for choroid plexus segmentation.
Choroid plexus in neurodevelopment and brain disorders 
The role of the choroid plexus in brain disorders has long been neglected, mainly because it was regarded as a supporting player whose role was to cushion the brain and maintain a proper salt balance2,21. However, the choroid plexus has gained attention as a structure linked to brain disorders such as pain syndromes22, SARS-CoV-216,23,24, neurodevelopmental2, and brain disorders19, suggesting a transdiagnostic effect in the development of behavioral disorders. In neurodevelopmental disorders, choroid plexus cysts were associated with an increased risk of developmental delay, attention-deficit/hyperactivity disorder (ADHD), or autism spectrum disorder (ASD)25,26. Additionally, lateral ventricle choroid plexus volume was found to be increased in patients with ASD27. In brain disorders,choroid plexus abnormalities have been described since 1921 in psychotic disorders28,29. Previous studies have identified choroid plexus enlargement using FreeSurfer segmentation in a large sample of patients with psychotic disorders compared to both their first-degree relatives and controls19. These findings were replicated using manually segmented choroid plexus volume in a large sample of clinical high-risk for psychosis population and found that these patients had larger choroid plexus volume compared to healthy controls30. There are a growing number of studies demonstrating choroid plexus enlargement in complex regional pain syndrome22, stroke31, multiple sclerosis20,32, Alzheimer&#39;s33,34, and depression35, with some demonstrating a link between peripheral and brain immune/inflammatory activity. These neuroimaging studies are promising; however, poor lateral ventricle choroid plexus segmentation by FreeSurfer21 limits the trustworthiness of automated choroid plexus volume estimation. As a result, studies in multiple sclerosis20,32, depression35, Alzheimer&#39;s34, and early psychosis36 have begun manually segmenting the lateral ventricle choroid plexus, but there are no current guidelines for how to do this, nor is their guidance on segmenting the third and fourth ventricle choroid plexus.
Common segmentation tools exclude the choroid plexus 
Brain segmentation pipelines such as FreeSurfer37,38,39, FMRIB Software Library (FSL)40, SLANT41, and FastSurfer (developed by the co-author Martin Reuter)42,43, accurately and reliably segment cortical and subcortical structures employing atlas-based (FSL), atlas- and surface-based (FreeSurfer), and deep learning segmentation paradigms (SLANT and FastSurfer). Weaknesses of some of these approaches include processing speed, limited generalization to different scanners, field strengths and voxel sizes37,44, and forced alignment of the label map in a standard atlas space. However, the capability to segment the choroid plexus and the compatibility with high-resolution MRI is only addressed by FreeSurfer and FastSurfer. The neural networks behind FastSurfer, are trained on FreeSurfer choroid plexus labels, so they inherit FreeSurfer&#39;s previously discussed reliability and coverage limitations, with the third and fourth ventricles being ignored21. Current limitations for high-resolution MRI also exist, but FreeSurfer&#39;s high-resolution stream45 and FastSurferVINN43 can be used to handle this issue.
Current choroid plexus segmentation tools 
There is only one freely available segmentation tool for the choroid plexus, but segmentation accuracy is limited. Accurate choroid plexus segmentation can be impacted by a variety of factors, including (1) variability in choroid plexus location (spatially non-stationary) due to its location within the ventricles, (2) differences in voxel intensity, contrast, resolution (within-structure heterogeneity) due to cellular heterogeneity, dynamic choroid plexus function, pathological changes, or partial volume effects, (3) age- or pathology-related ventricular size differences impacting choroid plexus size, and (4) proximity to adjacent subcortical structures (hippocampus, amygdala, caudate, and cerebellum), which are also difficult to segment. Given these challenges, FreeSurfer segmentations often under or over-estimate, mislabel or ignore the choroid plexus.
Three recent publications addressed the gap of reliable choroid plexus segmentation with a Gaussian Mixture Model (GMM)46, an Axial-MLP47, and U-Net-based deep learning approaches48. Each model was trained and evaluated using private, manually labeled datasets of at most 150 subjects with a limited diversity of scanners, sites, demographics, and disorders. While these publications46,48,49 achieved significant improvements over FreeSurfer&#39;s choroid plexus segmentation - sometimes doubling the intersection of prediction and ground truth, neither method is (1) validated in high-resolution MRI, (2) has dedicated generalization and reliability analyses, (3) features large representative training and testing datasets, (4) specifically addresses or analyzes choroid plexus segmentation challenges such as partial volume effects, or (5) is publicly available as a ready-to-use tool. Thus, the current &#34;gold standard&#34; for choroid plexus segmentation is manual tracing, e.g., using 3D Slicer50 or ITK-SNAP51, which has not been previously described and has been a major challenge for researchers wishing to examine the role of the choroid plexus in their studies. 3D Slicer was chosen for manual segmentation due to the author&#39;s familiarity with the software and because it provides the user with various tools based on different approaches that can be combined to obtain the desired result. Other tools can be used, such as ITK-SNAP, which is primarily oriented on image segmentation, and once the tool is mastered, good results can be obtained by the user. Additionally, the authors have conducted a case-control study demonstrating the high accuracy and reliability of their manual segmentation technique using 3D Slicer30, and that specific methodology is described herein.

著者スポットライト:解剖学のギャップを埋め、アルゴリズム研究の基盤を確立する 

脳MRIを用いたヒト脈絡叢の手動セグメンテーション

We aim to establish an accessible and standardized protocol for manually segmenting the choroid plexus within the lateral third and fourth ventricles of the brain. We hope to address any common questions or problems that can arise when manually segmenting the choroid plexus, especially considering the complex nature of its location within the brain. Developing this protocol will lead to the creation of a large enough data set consisting of ground truth segmentation maps that we can then use to train and develop algorithms that can accurately and automatically segment the choroid plexus.In the future, this will lead to studies that investigate the role of the choroid plexus within various neurologic and neuropsychiatric disorders.

Watch this Scientific Journal Video about Segmentation of the Choroid Plexus Using Manual Delineations at JoVE.com

Segmentation of the Choroid Plexus Using Manual Delineations  

手動描写を使用した脈絡叢のセグメンテーション

まず、ツールバーの左上隅にあるDCMボタンをクリックし、DICOMファイルのインポートボタンをクリックして、医療またはDICOMデータのデジタルイメージングと通信をインポートします。画像の明るさを調整するには、[ウィンドウと音量レベルの調整]をクリックするか、画像を左クリックしてマウスを上下にドラッグします。次に、画像スライスを左クリックし、マウスを左または右に動かしてコントラストを調整します。深部灰白質核またはコントラストスケールバーの信号強度を参照し、セグメンテーション全体で一貫していることを確認して、脈絡叢に適したコントラストを選択します。外側第3および第4脳室脈絡叢のセグメンテーションを開始するには、モジュールのドロップダウンメニューからセグメントエディターを選択します。次に、セグメンテーションのドロップダウンメニューをクリックして、別のセグメンテーションを選択し、選択したセグメンテーションの名前を変更します。マスターボリュームのドロップダウンを使用して、編集が必要なNIfTIまたはDICOMセットを選択します。追加ボタンを 2 回クリックして、側脳室脈絡叢の 2 つのセグメントを含めます。タイトルをダブルクリックし、名前を右側心室脈絡叢と左側心室脈絡叢に変更します。追加ボタンをもう一度クリックして、第3脳室と第4脳室の脈絡叢のセグメントを導入します。その後、それぞれ第3脳室脈絡叢と第4脳室脈絡叢と名前を変更します。軸面の側心室脈絡叢から始めて、双交連線に基づいて画像を配置するようにします。側脳室脈絡叢を見つけるための基準点として三角側副を使用してください。手動セグメンテーションを開始するには、セグメントエディターのエフェクトセクションにあるペイントツールまたは描画ツールを選択します。ペイントツールの使用中に、ペイントするブラシの直径を選択します。赤核レベルを使用して、側脳室の脈絡叢のセグメント化をいつ停止するかを決定します。第3脳室脈絡叢の位置を特定するには、矢状面から始めて、モンローの孔、円蓋、脳梁、視床、および内大脳静脈をランドマークとして使用します。同様に、第4脳室脈絡叢の場合、矢状面から始めて、上小脳脚、橋、および髄質を基準点として使用して、第4脳室の脈絡叢を特定します。モジュールのドロップダウンメニューから「定量化」に移動し、「セグメント統計」を選択します。次に、入力セクションで、セグメンテーションツールで定量化のために新しく作成したセグメンテーションマップを選択し、スケーラーボリュームからMRIボリュームを選択します。出力テーブルの場合は、[出力]で[テーブル]オプションを選択し、[適用]をクリックします。脈絡叢の体積を異なる単位で表示する表が表示されます。ツールバーの左上にある保存ボタンをクリックして、生成されたファイルを保存します。セグメンテーション ファイルを nrrd, nii の形式で保存します。GZ、または TSV.

Research

JoVE Journal

Neuroscience

Segmentation of the Choroid Plexus Using Manual Delineations

Manual Segmentation of the Human Choroid Plexus Using Brain MRI

The choroid plexus has been implicated in neurodevelopment and a range of brain disorders. Evidence demonstrates that the choroid plexus is critical for ...