Advanced Source Reconstruction Techniques for Fetal Magnetocardiography

描述(由申请人提供)：早期发现先天性心脏异常对于监测或及时干预至关重要，这可以降低充血性心力衰竭的风险。这需要持续努力，改进用于对胎儿心脏结构和生理进行非侵入性筛查的现有工具和方法。近年来，胎儿心磁图(FMCG)已成为一种有吸引力的宫内评估胎儿心脏电生理的技术，其能力远远优于其他方法所能实现的。然而，一个重要的问题是，相对于生物磁传感系统，胎儿的位置和方向存在很大的差异，这可能会对产妇腹部记录的信号的形态产生混淆的影响。缺乏关于FMCG信号形态的详细数据是这些混淆的直接结果，因为通常很难解释传感器阵列上信号分布的对象间差异是由心脏电生理学的基本差异、胎儿表现的常见不一致或胎儿-母体单位的不同解剖所产生的。目前的研究将集中于开发新的策略来增强FMCG记录的临床实用性，旨在检查在源空间(而不是传感器空间)中的心脏活动，在那里上述物理因素变得不显著。该方法依赖于使用递归子空间扫描算法来估计胎儿心源的多偶极子模型的时空参数。为了解释胎儿-腹部组织的几何和电导特性，该研究试图建立一种通用的策略，将从徒手超声图像获得的关于胎儿-腹部体积导体的3D解剖信息整合到基于边界元方法的正向电磁问题的离散公式中。这项研究将启动从低风险妊娠FMCG记录中重建的心脏向量得出的指标的纵向标准化数据库的开发。超声记录的游离室壁厚度异常增加的胎儿受试者也将被研究，以探讨拟议的方法在检测心脏电生理异常标志方面的敏感性。这项研究旨在促进FMCG在胎儿心脏发育的非侵入性筛查和电生理异常检测方面的作用。该方法的成功临床验证将强烈推荐FMCG作为一种研究工具，用于在广泛的条件下研究胎儿心脏电生理，特别是那些与心室肥厚风险增加相关的疾病，例如宫内发育迟缓、糖尿病、肺动脉瓣和主动脉瓣狭窄、动脉导管闭合、法洛四联症或室间隔缺陷。与公共卫生相关：先天性心脏异常比影响任何其他器官的异常更常见；因此，用于胎儿心脏监测的技术的进一步进步可能会对公共健康产生重大影响。胎儿心磁图(FMCG)为胎儿心脏电生理的非侵入性筛查提供了独特的能力，但为了达到临床意义，FMCG必须提供明确和一致的胎儿心脏活动指标。本研究旨在通过先进的声源重建算法，有效地利用胎儿腹部解剖的多道FMCG数据和三维超声图像，为胎儿心脏电生理研究提供可靠的测量手段，从而促进FMCG在胎儿心脏发育和电生理异常研究中的作用。对于室壁厚度异常增加的胎儿，该方法的成功临床验证将强烈推荐FMCG作为一种研究工具，用于研究与心室肥厚风险增加相关的广泛情况下的胎儿心脏电生理，例如宫内发育迟缓、糖尿病、肺动脉瓣和主动脉瓣狭窄、动脉导管关闭、法洛四联症或室间隔缺陷。

DESCRIPTION (provided by applicant): The early detection of congenital heart anomalies is critical for monitoring or prompt interventions, which can reduce the risks of congestive heart failure. This calls for sustained efforts to improve the existing tools and methodologies used for the non-invasive screening of the fetal heart structure and physiology. Recently, fetal magnetocardiography (fMCG) has emerged as an attractive technique for the in-utero assessment of the fetal cardiac electrophysiology, which can offer vastly superior capabilities to those, attainable by alternative methods. However, a significant concern consists in the large variability in position and orientation of the fetuses relative to the biomagnetic sensing system, which may introduce confounding effects on the morphology of the signals recorded over the maternal abdomen. The paucity of data on detailed fMCG signal morphology is a direct consequence of these confounds, since it is often difficult to explain the intersubject variations in signal distribution across the sensor array as being generated by fundamental differences in the cardiac electrophysiology, common inconsistencies in the fetal presentation or variable anatomy of the fetal- maternal unit. The current study will focus on the development of new strategies for augmenting the clinical utility the fMCG recordings, aiming at examining the cardiac activity in source space (rather than sensor space), where the above described physical factors become non-salient. The proposed approach relies on estimating the spatio temporal parameters of a multi-dipolar model of the fetal cardiac source using a recursive subspace scanning algorithm. To account for the geometry and conductivity properties of the feto-abdominal tissues, the study seeks establishing a versatile strategy for incorporating 3D anatomical information about the feto-abdominal volume conductor obtained from free-hand ultrasound images into the discrete formulation of the forward electromagnetic problem based on boundary element methods. The study will initiate the development of a longitudinal normative data-base for metrics derived from the reconstructed cardiac vectors in fMCG recordings of low-risk pregnancies. Fetal subjects with abnormal increase in the thickness of the free ventricular walls documented by ultrasound will also be studied to probe the sensitivity of the proposed approach for detecting hallmarks of abnormal heart electrophysiology. The investigation aims to represent a substantial contribution in promoting the role of fMCG for the non- invasive screening of fetal cardiac development and for the detection of electrophysiological abnormalities. The successful clinical validation of the methodology will highly recommend fMCG as an investigational tool for studying fetal cardiac electrophysiology in a broad range of conditions, particularly those associated with increased risk of ventricular hypertrophy, e.g. intra-uterine growth retardation, diabetes, pulmonary valve and aortic stenosis, closure of the ductus arteriosus, tetralogy of Fallot, or ventricular septal defect. PUBLIC HEALTH RELEVANCE: Congenital heart anomalies are more common than anomalies affecting any other organ; therefore, further advancement of the techniques used for fetal heart monitoring is likely to have a substantial impact upon public health. Fetal magnetocardiography (fMCG) offers unique capabilities for non-invasive screening of fetal cardiac electrophysiology; however, in order to attain clinical significance, fMCG must provide unequivocal and consistent measures of fetal cardiac activity. This investigation aims to represent a substantial contribution in promoting the role of fMCG for studying fetal cardiac development and electrophysiological abnormalities by means of advanced source reconstruction algorithms, which efficiently use the multichannel fMCG data and 3D ultrasound images of the feto-abdominal anatomy to provide reliable measures of fetal cardiac electrophysiology. The successful clinical validation of the methodology for fetuses with abnormal increase in ventricular wall thickness will highly recommend fMCG as an investigational tool for studying fetal cardiac electrophysiology in a broad range of conditions associated with increased risk of ventricular hypertrophy, e.g. intra-uterine growth retardation, diabetes, pulmonary valve and aortic stenosis, closure of the ductus arteriosus, tetralogy of Fallot, or ventricular septal defect.