The lack of standardization is a prominent issue in magnetic resonance (MR) imaging. This often causes undesired contrast variations due to differences in hardware and acquisition parameters. In recent years, MR harmonization using image synthesis with disentanglement has been proposed to compensate for the undesired contrast variations. Despite the success of existing methods, we argue that three major improvements can be made. First, most existing methods are built upon the assumption that multi-contrast MR images of the same subject share the same anatomy. This assumption is questionable since different MR contrasts are specialized to highlight different anatomical features. Second, these methods often require a fixed set of MR contrasts for training (e.g., both Tw-weighted and T2-weighted images must be available), which limits their applicability. Third, existing methods generally are sensitive to imaging artifacts. In this paper, we present a novel approach, Harmonization with Attention-based Contrast, Anatomy, and Artifact Awareness (HACA3), to address these three issues. We first propose an anatomy fusion module that enables HACA3 to respect the anatomical differences between MR contrasts. HACA3 is also robust to imaging artifacts and can be trained and applied to any set of MR contrasts. Experiments show that HACA3 achieves state-of-the-art performance under multiple image quality metrics. We also demonstrate the applicability of HACA3 on downstream tasks with diverse MR datasets acquired from 21 sites with different field strengths, scanner platforms, and acquisition protocols.
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在2D多板磁共振(MR)采集中,平面信号通常比面内信号较低。尽管当代超分辨率(SR)方法旨在恢复基本的高分辨率量,但估计的高频信息是通过端到端数据驱动的培训隐含的,而不是明确说明和寻求。为了解决这个问题,我们根据完美的重建过滤库重新构架SR问题声明,使我们能够识别并直接估计缺失的信息。在这项工作中,我们提出了一种两阶段的方法,以近似于与特定扫描的各向异性采集相对应的完美重建过滤库。在第1阶段,我们使用梯度下降估算缺失的过滤器,在第2阶段,我们使用深网来学习从粗系数到细节系数的映射。此外,提出的公式不依赖外部训练数据,从而规避了对域移位校正的需求。在我们的方法下,特别是在“切片差距”方案中提高了SR性能,这可能是由于框架施加的解决方案空间的限制。
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了解舌头和口咽肌肉变形之间的潜在关系在标记的MRI和可理解的语音中起着重要的作用,在推进语音运动控制理论和对语音相关疾病的处理方面起着重要作用。然而,由于它们的异质表示形式,这两种模式之间的直接映射(即二维(中间式切片)加上时间标记的MRI序列及其相应的一维波形)并不简单。取而代之的是,我们诉诸二维频谱图作为中间表示,其中包含音高和共振,从中可以开发一个端到端的深度学习框架,以将标记的MRI序列转换为其相应的音频波形,并具有有限的音频波形数据集大小。〜我们的框架基于一种新颖的完全卷积不对称翻译器,并具有自我残留注意策略的指导,以专门利用语音期间的移动肌肉结构。潜在的空间表示解散策略。〜此外,我们将一种对抗性训练方法与生成的对抗网络结合在一起,以在我们生成的频谱图上提供改进的现实主义。我们的框架使一系列标记的序列可以生成清晰的音频波形。 MRI,超过竞争方法。因此,我们的框架为帮助更好地了解两种方式之间的关系提供了巨大的潜力。
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大多数基于深度学习(DL)的可变形图像登记方法使用卷积神经网络(CNN)来估计移动和固定图像对的位移字段。但是,这要求CNN中的卷积内核不仅从输入中提取强度特征,而且还了解图像坐标系。我们认为,后者的任务对传统CNN来说是具有挑战性的,从而限制了他们在注册任务中的性能。为了解决此问题,我们首先介绍坐标翻译器,坐标转换器是一个可区分的模块,该模块识别固定和移动图像之间的匹配功能,并在不需要训练的情况下输出其坐标对应关系。它卸载了了解CNN的图像坐标系的负担,从而使它们可以专注于特征提取。然后,我们提出了一个新型的可变形注册网络IM2Grid,该网络使用多个坐标转换器与从CNN编码中提取的层次结构特征,并以粗略的方式输出变形字段。我们将IM2Grid与无监督的3D磁共振图像注册的最新DL和非DL方法进行了比较。我们的实验表明,IM2Grid在定性和定量上都优于这些方法。
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We consider the problem of robustly testing the norm of a high-dimensional sparse signal vector under two different observation models. In the first model, we are given $n$ i.i.d. samples from the distribution $\mathcal{N}\left(\theta,I_d\right)$ (with unknown $\theta$), of which a small fraction has been arbitrarily corrupted. Under the promise that $\|\theta\|_0\le s$, we want to correctly distinguish whether $\|\theta\|_2=0$ or $\|\theta\|_2>\gamma$, for some input parameter $\gamma>0$. We show that any algorithm for this task requires $n=\Omega\left(s\log\frac{ed}{s}\right)$ samples, which is tight up to logarithmic factors. We also extend our results to other common notions of sparsity, namely, $\|\theta\|_q\le s$ for any $0 < q < 2$. In the second observation model that we consider, the data is generated according to a sparse linear regression model, where the covariates are i.i.d. Gaussian and the regression coefficient (signal) is known to be $s$-sparse. Here too we assume that an $\epsilon$-fraction of the data is arbitrarily corrupted. We show that any algorithm that reliably tests the norm of the regression coefficient requires at least $n=\Omega\left(\min(s\log d,{1}/{\gamma^4})\right)$ samples. Our results show that the complexity of testing in these two settings significantly increases under robustness constraints. This is in line with the recent observations made in robust mean testing and robust covariance testing.
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TRISTRUCCUCTIONATIOPIC(TRISO)涂层颗粒燃料是强大的核燃料,并确定其可靠性对于先进的核技术的成功至关重要。然而,Triso失效概率很小,相关的计算模型很昂贵。我们使用耦合的主动学习,多尺度建模和子集模拟来估计使用几个1D和2D模型的Triso燃料的故障概率。通过多尺度建模,我们用来自两个低保真(LF)模型的信息融合,取代了昂贵的高保真(HF)模型评估。对于1D TRISO模型,我们考虑了三种多倍性建模策略:仅克里格,Kriging LF预测加克里格校正,深神经网络(DNN)LF预测加克里格校正。虽然这些多尺度建模策略的结果令人满意地比较了从两个LF模型中使用信息融合的策略,但是通常常常称为HF模型。接下来,对于2D Triso模型,我们考虑了两个多倍性建模策略:DNN LF预测加克里格校正(数据驱动)和1D Triso LF预测加克里格校正(基于物理学)。正如所预期的那样,基于物理的策略一直需要对HF模型的最少的呼叫。然而,由于DNN预测是瞬时的,数据驱动的策略具有较低的整体模拟时间,并且1D Triso模型需要不可忽略的模拟时间。
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超越地球轨道的人类空间勘探将涉及大量距离和持续时间的任务。为了有效减轻无数空间健康危害,数据和空间健康系统的范式转移是实现地球独立性的,而不是Earth-Reliance所必需的。有希望在生物学和健康的人工智能和机器学习领域的发展可以解决这些需求。我们提出了一个适当的自主和智能精密空间健康系统,可以监控,汇总和评估生物医学状态;分析和预测个性化不良健康结果;适应并响应新累积的数据;并提供对其船员医务人员的个人深度空间机组人员和迭代决策支持的预防性,可操作和及时的见解。在这里,我们介绍了美国国家航空航天局组织的研讨会的建议摘要,以便在太空生物学和健康中未来的人工智能应用。在未来十年,生物监测技术,生物标志科学,航天器硬件,智能软件和简化的数据管理必须成熟,并编织成精确的空间健康系统,以使人类在深空中茁壮成长。
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空间生物学研究旨在了解太空飞行对生物的根本影响,制定支持深度空间探索的基础知识,最终生物工程航天器和栖息地稳定植物,农作物,微生物,动物和人类的生态系统,为持续的多行星寿命稳定。要提高这些目标,该领域利用了来自星空和地下模拟研究的实验,平台,数据和模型生物。由于研究扩展到低地球轨道之外,实验和平台必须是最大自主,光,敏捷和智能化,以加快知识发现。在这里,我们介绍了由美国国家航空航天局的人工智能,机器学习和建模应用程序组织的研讨会的建议摘要,这些应用程序为这些空间生物学挑战提供了关键解决方案。在未来十年中,将人工智能融入太空生物学领域将深化天空效应的生物学理解,促进预测性建模和分析,支持最大自主和可重复的实验,并有效地管理星载数据和元数据,所有目标使生活能够在深空中茁壮成长。
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我们重新审视耐受分发测试的问题。也就是说,给出来自未知分发$ P $超过$ \ {1,\ dots,n \} $的样本,它是$ \ varepsilon_1 $ -close到或$ \ varepsilon_2 $ -far从引用分发$ q $(总变化距离)?尽管过去十年来兴趣,但在极端情况下,这个问题很好。在无噪声设置(即,$ \ varepsilon_1 = 0 $)中,样本复杂性是$ \ theta(\ sqrt {n})$,强大的域大小。在频谱的另一端时,当$ \ varepsilon_1 = \ varepsilon_2 / 2 $时,样本复杂性跳转到勉强su​​blinear $ \ theta(n / \ log n)$。然而,非常少于中级制度。我们充分地表征了分发测试中的公差价格,作为$ N $,$ varepsilon_1 $,$ \ varepsilon_2 $,最多一个$ \ log n $ factor。具体来说,我们显示了\ [\ tilde \ theta \ left的样本复杂性(\ frac {\ sqrt {n}} {\ varepsilon_2 ^ {2}} + \ frac {n} {\ log n} \ cdot \ max \左\ {\ frac {\ varepsilon_1} {\ varepsilon_2 ^ 2},\ left(\ frac {\ varepsilon_1} {\ varepsilon_2 ^ 2} \右)^ {\!\!\!2} \ \ \} \右) ,\]提供两个先前已知的案例之间的顺利折衷。我们还为宽容的等价测试问题提供了类似的表征,其中$ p $和$ q $均未赘述。令人惊讶的是,在这两种情况下,对样本复杂性的主数量是比率$ \ varepsilon_1 / varepsilon_2 ^ 2 $,而不是更直观的$ \ varepsilon_1 / \ varepsilon_2 $。特别是技术兴趣是我们的下限框架,这涉及在以往的工作中处理不对称所需的新颖近似性理论工具,从而缺乏以前的作品。
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While the brain connectivity network can inform the understanding and diagnosis of developmental dyslexia, its cause-effect relationships have not yet enough been examined. Employing electroencephalography signals and band-limited white noise stimulus at 4.8 Hz (prosodic-syllabic frequency), we measure the phase Granger causalities among channels to identify differences between dyslexic learners and controls, thereby proposing a method to calculate directional connectivity. As causal relationships run in both directions, we explore three scenarios, namely channels' activity as sources, as sinks, and in total. Our proposed method can be used for both classification and exploratory analysis. In all scenarios, we find confirmation of the established right-lateralized Theta sampling network anomaly, in line with the temporal sampling framework's assumption of oscillatory differences in the Theta and Gamma bands. Further, we show that this anomaly primarily occurs in the causal relationships of channels acting as sinks, where it is significantly more pronounced than when only total activity is observed. In the sink scenario, our classifier obtains 0.84 and 0.88 accuracy and 0.87 and 0.93 AUC for the Theta and Gamma bands, respectively.
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