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156 results on '"Anzai, Hitomi"'

8. Elongation of the proximal descending thoracic aorta and associated hemodynamics increase the risk of acute type B aortic dissection.

Author

Zhang, Xuelan, Peng, Yuan, Li, Gaoyang, Li, Jiehua, Luo, Mingyao, Che, Yue, Zheng, Liancun, Anzai, Hitomi, Ohta, Makoto, and Shu, Chang

Subjects
THORACIC aorta, AORTIC dissection, HEMODYNAMICS, SUBCLAVIAN artery, THORACIC vertebrae
Abstract

BACKGROUND: Acute type B aortic dissection (ATBAD) is a life-threatening aortic disease. However, little information is available on predicting and understanding of ATBAD. OBJECTIVE: The study sought to explore the underlying mechanism of ATBAD by analyzing the morphological and hemodynamic characteristics related to aortic length. METHODS: The length and tortuosity of the segment and the whole aorta in the ATBAD group (n = 163) and control group (n = 120) were measured. A fixed anatomic landmark from the distal of left subclavian artery (LSA) to the superior border of sixth thoracic vertebra was proposed as the proximal descending thoracic aorta (PDTA), and the dimensionless parameter, length ratio, was introduced to eliminate the individual differences. The significant morphological parameters were filtrated and the associations between parameters were investigated using statistical approaches. Furthermore, how aortic morphology influenced ATBAD was explored based on idealized aortic models and hemodynamic-related metrics. RESULTS: The PDTA length was significantly increased in the ATBAD group compared with the control group and had a strong positive correlation with the whole aortic length (r = 0.89). The length ratio (LR2) and tortuosity (T2) of PDTA in the ATBAD group were significantly increased (0.15 ± 0.02 vs 0.12 ± 0.02 and 1.73 ± 0.48 vs 1.50 ± 0.36; P < 0.001), and LR2 was positive correlation with T2 (r = 0.73). In receiver-operating curve analysis, the area under the curve was 0.835 for LR2 and 0.641 for T2. Low and oscillatory shear (LOS) was positive correlation with LR2, and the elevated LOS occurred in the distal of LSA. CONCLUSION: Elongation of PDTA is associated with ATBAD, and the length ratio is a novel predictor. Elongated PDTA induced more aggressive hemodynamic forces, and high LOS regions may correspond to the entry tear location. The synergy of the morphological variation and aggressive hemodynamics creates contributory conditions for ATBAD. [ABSTRACT FROM AUTHOR]

Published
2024
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26. Incomplete stent expansion in flow‐diversion treatment affects aneurysmal haemodynamics: a quantitative comparison of treatments affected by different severities of malapposition occurring in different segments of the parent artery

Author

Zhang, Mingzi, primary, Li, Yujie, additional, Sugiyama, Shin‐ichiro, additional, Verrelli, David I., additional, Matsumoto, Yasushi, additional, Tominaga, Teiji, additional, Qian, Yi, additional, Tupin, Simon, additional, Anzai, Hitomi, additional, and Ohta, Makoto, additional

Published
2021
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27. Influence of input image configurations on output of a convolutional neural network to detect cerebral aneurysms

Author

Watanabe, Kazuhiro, Anzai, Hitomi, Juchler, Norman, Hirsch, Sven, Ohta, Makoto, Watanabe, Kazuhiro, Anzai, Hitomi, Juchler, Norman, Hirsch, Sven, and Ohta, Makoto

Abstract

Rupture of cerebral aneurysms is the main cause of subarachnoid hemorrhage, which can have devastating effects on quality of life. The identification and assessment of unruptured aneurysms from medical images is therefore of significant clinical relevance. In recent years, the availability of clinical imaging data has rapidly increased, which calls for computer assisted detection (CAD) systems. Previous studies have shown that CAD systems based on convolutional neural networks (CNN) can help to detect cerebral aneurysms from magnetic resonance angiographies (MRAs). However, these CAD systems require large datasets of annotated medical images. Thus, more efficient tools for processing and categorizing medical imaging data are required. Previous studies of CNN-based classification for medical images used various patch configurations of input data. These studies showed that classification accuracy was affected by the patch size or image representation. Thus, we hypothesize that the accuracy of CADs to detect cerebral aneurysms can be improved by adjusting the configuration of the input patches. In the present study, we performed CNN-based medical imaging classification for varying input data configurations to examine the relationship between classification accuracy and data configuration.

Published
2020

30. Finite element analysis of the mechanical performance of a zinc alloy stent with the tenon-and-mortise structure.

Author

Wang, Sirui, Wu, Dandan, Li, Gaoyang, Peng, Kun, Mu, Yongliang, Ohta, Makoto, Anzai, Hitomi, and Qiao, Aike

Subjects
FINITE element method, ALLOYS, SURGICAL stents, ZINC, PROSTHESIS design & construction
Abstract

Background: Inadequate scaffolding performance hinders the clinical application of the biodegradable zinc alloy stents.Objective: In this study we propose a novel stent with the tenon-and-mortise structure to improve its scaffolding performance.Methods: 3D models of stents were established in Pro/E. Based on the biodegradable zinc alloy material and two numerical simulation experiments were performed in ABAQUS. Firstly, the novel stent could be compressed to a small-closed ring by a crimp shell and can form a tenon-and-mortise structure after expanded by a balloon. Finally, 0.35 MPa was applied to the crimp shell to test the scaffolding performance of the novel stent and meanwhile compare it with an ordinary stent.Results: Results showed that the novel stent decreased the recoiling ratio by 70.7% compared with the ordinary stent, indicating the novel structure improved the scaffolding performance of the biodegradable zinc alloy stent.Conclusion: This study proposes a novel design that is expected to improve the scaffolding performance of biodegradable stents. [ABSTRACT FROM AUTHOR]

Published
2022
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38. Clinical data sharing : a data scientist's perspective

Author

Juchler, Norman, Schilling, Sabine, Watanabe, Kazuhiro, Anzai, Hitomi, Rüfenacht, Daniel, Bijlenga, Philippe, Kurtcuoglu, Vartan, and Hirsch, Sven

Subjects
610: Medizin und Gesundheit, 005: Computerprogrammierung, Programme und Daten, Intracranial aneurysms, Clinical data sharing
Abstract

An ever increasing amount of medical data is collected and used for scientific and clinical purposes. To benefit from the abundance of data, however, one has to deal with several challenges. The diversity of data sources, the variability seen in the biological systems and the biases and distortions inherent in the acquired data request for robust and flexible data processing pipelines. Here, we illustrate some of these challenges at the hand of our research on intracranial aneurysms and share insights how to deal with these challenges. We present the AneuX AneurysmDataBase. It stores data acquired at multiple clinical centers, supports heterogeneous data (clinical data, imaging data, genetic data, morphological and histological data, etc.) and is aimed for use in both scientific and industrial contexts. We further present five scientific studies that demonstrate the usage of the AneurysmDataBase. In the first application, we evaluated the PHASES score, a recent scoring scheme to guide the clinicians whether to treat an unruptured intracranial aneurysm. We further examined and improved existing morphological descriptors with the goal to associate aneurysm shape with its disease status. In a third study, we quantified the qualitative rating of aneurysm shape by humans. A fourth study aims at inferring information about the disease directly from imaging data by means of convolutional neural nets. Finally, we sketch how to query aneurysms with similar anatomical and morphological properties from a database. With our work, we demonstrate how clinical data sharing can be used for quantitative analyses of aneurysm properties and for the development of diagnostic and prognostic tools.

Published
2018

39. Correlation of CFD with wall enhancement

Author

Anzai, Hitomi, Juchler, Norman, Bilenga, Philippe, Rüfenacht, Daniel, Wanke, Isabel, and Hirsch, Sven

Subjects
cardiovascular system, 004: Informatik, 616: Innere Medizin und Krankheiten
Abstract

Aneurysm wall changes its morphology and mechanical properties under a sequential wall remodeling dysfunction including de-differentiation and loss of endothelial cells and smooth muscle cells. To date, many studies have been performed CFD analysis on aneurysmal flow and revealed that flow-induced stress are partly correlated with histopathological events on vessel wall such as initiation, growth, and rupture. Nowadays, vessel wall enhancement is efficiently visualized using "black-blood"-T1-W high-resolution MRI sequences, and it has been demonstrated to be strongly associated with rupture in cases diagnosed with multiple aneurysms. Enhancement on aneurysm wall is observed as a result of deposition or penetration of contrast medium. This consequentially suggests that the enhanced area changes wall permeability and can be thought as an expression of wall degradation. Therefore, we systematically collected over the past three years, information about lesion stability based on MRI for better understanding of wall degeneration, aneurysm morphology, and flow-induced stress. This presentation exhibits selected aneurysm cases with wall enhancement. CFD results show a frequent collocation of wall enhancement with low WSS condition. However, results also investigate a case without visible wall enhancement, even though aneurysm wall experiences lower WSS than enhanced wall regions in same patient. The cases we present suggest that local flow condition can explain wall enhancement where active remodeling occurs, however, there are still limitations on prediction of enhancement by flow field alone.

Published
2018

43. Preface

Author

TOKUMASU, Takashi, primary, ANZAI, Hitomi, additional, FUJITA, Koji, additional, HIROTA, Makoto, additional, NAKAMURA, Hisashi, additional, SHIMOYAMA, Koji, additional, and TAKANA, Hidemasa, additional

Published
2019
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44. Where does CFD identify lesion instability in small aneurysms?

Author

Anzai, Hitomi, Juchler, Norman, Ohta, Makoto, Hirsch, Sven, Rüfenacht, Daniel A., Wanke, Isabel, Anzai, Hitomi, Juchler, Norman, Ohta, Makoto, Hirsch, Sven, Rüfenacht, Daniel A., and Wanke, Isabel

Abstract

In our observation, wall enhancement MRI allows for directly identifying areas of disturbed contrast permeability, i.e. inflammation, thrombus or a combination of both, and thus visualizes areas of instability in the aneurysm wall. In presented cases, regions of enhancements were compared with wall shear stress (WSS) distribution obtained from computational fluid dynamics (CFD). In our findings, areas of wall enhancement match well with either low or high WSS, however, other areas of low or high WSS were observed without identification of any wall enhancement.

Published
2018

45. Where does CFD identify lesion instability in small aneurysms?

Author

Anzai, Hitomi, Juchler, Norman, Ohta, Makoto, Hirsch, Sven, Rüfenacht, Daniel A., and Wanke, Isabel

Subjects
Lesion stability, cardiovascular system, Intracranial aneurysms, CFD, 616: Innere Medizin und Krankheiten, circulatory and respiratory physiology, Wall enhancement
Abstract

In our observation, wall enhancement MRI allows for directly identifying areas of disturbed contrast permeability, i.e. inflammation, thrombus or a combination of both, and thus visualizes areas of instability in the aneurysm wall. In presented cases, regions of enhancements were compared with wall shear stress (WSS) distribution obtained from computational fluid dynamics (CFD). In our findings, areas of wall enhancement match well with either low or high WSS, however, other areas of low or high WSS were observed without identification of any wall enhancement.

Published
2017

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