Dataset: Impact of pulsed-wave-Doppler velocity-envelope extraction techniques on classification of complete fetal cardiac cycles

The pulsed-wave Doppler (PWD) signal is used as a reference for the mechanical activity of the heart and several validated parameters are used in clinical practice, most of which are evaluated by cardiologists based on visual inspection alone. Specific datasets have also been established of the simultaneous recordings of Doppler ultrasound and fetal electrocardiography. These all require the development of software tools that can automatically identify complete and meaningful fetal cardiac cycles to enable measurements. Several works in the literature have reported investigations of the extraction of the PWD velocity envelopes. The work "Impact of pulsed-wave-Doppler velocity-envelope tracing techniques on classification of complete fetal cardiac cycles", by the same authors, focus on the selection and comparison of different steps in the signal processing chain that lead to the PWD envelopes, which are used as inputs for the detection of complete heartbeats.
Here, we presents the dataset that has been used for the validation of the methodology. The data were collected from the fetal echocardiographic examination of 25 low-risk pregnant volunteers at gestational weeks ranging from the 21st to the 27th, from which we obtained a total of 43 PWD traces. All images and data are anonymous. The PWD images were collected at the Division of Pediatric Cardiology, San Michele Hospital, Cagliari, Italy. The study was approved by the Independent Ethics Committee of the Cagliari University Hospital (AOU Cagliari) and performed following the principles outlined in the Helsinki Declaration of 1975, as revised in 2000. Each volunteer signed a form acknowledging their informed consent to the research protocol.
Based on the best clinical practice, we chose the five-chamber apical window. Using the apical five-chamber view, the four cardiac chambers and the first part of the aorta (assumed as a fifth chamber) can be investigated, and the diastolic and systolic functions have distinguishable morphologies in the PWD spectrum. Overall, the EA-wave indicates the mitral inflow and the V-wave the aortic outflow.
Here, the 43 images, named as imgXX.bmp. An expert pediatric cardiologist labeled all the complete and measurable fetal cardiac cycles using a custom MATLAB graphical interface, as described in "Automatic detection of complete and measurable cardiac cycles in antenatal pulsed-wave Doppler signals". The annotations are saved in the annotations.mat file, that that consists of 2 columns: the first lists the image indexes at which the cardiologist annotated the fetal cardiac cycle onset, the second specifies the image number at which the annotation is related to. A MATLAB function allows visualizing the cardiologiest's annotations on a selected PWD image or all the cardiologiest's annotations in every PWD images in the dataset.

脉冲波多普勒（pulsed-wave Doppler, PWD）信号可作为心脏机械活动的参考指标，临床实践中已采用多项经过验证的参数，其中多数仅由心脏科医师通过目视评估得出。此前已有研究团队建立了多普勒超声与胎儿心电图（fetal electrocardiography）同步记录的专用数据集。此类研究均需开发可自动识别完整且有意义的胎儿心动周期的软件工具，以实现相关测量。已有多项文献报道了针对PWD速度包络提取的相关研究。本团队此前发表的《脉冲波多普勒速度包络描记技术对完整胎儿心动周期分类的影响》一文，聚焦于信号处理流程中不同步骤的选择与对比——该流程可生成用于检测完整心跳的PWD速度包络。
本文提供的数据集即用于验证上述方法学。数据采集自25名低危妊娠志愿者的胎儿超声心动检查（fetal echocardiographic examination），孕周范围为21至27周，共获取43条PWD波形轨迹。所有图像与数据均已完成匿名化处理。PWD图像采集自意大利卡利亚里圣米歇尔医院儿科心脏病学科。本研究已通过卡利亚里大学医院（AOU Cagliari）独立伦理委员会批准，并严格遵循2000年修订版1975年《赫尔辛基宣言》的相关原则开展。每名志愿者均签署了知情同意书，确认同意参与本研究方案。
基于最佳临床实践，本研究选用心尖五腔切面。通过心尖五腔观，可对心脏四个腔室及主动脉起始段（视为第五个“腔室”）进行探查，且PWD频谱可清晰区分舒张与收缩功能的形态学特征。总体而言，EA波代表二尖瓣流入血流，V波代表主动脉流出血流。
本数据集包含43张图像，命名格式为imgXX.bmp。一名资深儿科心脏病学家通过定制的MATLAB图形界面，对所有完整且可测量的胎儿心动周期进行了标注，具体方法详见《产前脉冲波多普勒信号中完整可测量心动周期的自动检测》一文。标注结果保存于annotations.mat文件，该文件包含两列数据：第一列为标注了胎儿心动周期起始点的图像索引，第二列为标注对应的图像编号。配套的MATLAB函数可实现：在选定的单张PWD图像上可视化展示心脏科医师的标注，或在数据集中所有PWD图像上展示全部标注结果。