Valinoti Maddalena, Fabbri Claudio, Turco Dario, Mantovan Roberto, Pasini Antonio, Corsi Cristiana
Department of Electrical, Electronic and Information Engineering, via Risorgimento 2, 40123 Bologna, Italy.
Department of Cardiology, "S. Maria dei Battuti" Hospital, via Brigata Bisagno, 4, 31015 Conegliano, Treviso, Italy.
Magn Reson Imaging. 2018 Jan;45:51-57. doi: 10.1016/j.mri.2017.09.012. Epub 2017 Sep 25.
Radiofrequency ablation (RFA) is an important and promising therapy for atrial fibrillation (AF) patients. Optimization of patient selection and the availability of an accurate anatomical guide could improve RFA success rate. In this study we propose a unified, fully automated approach to build a 3D patient-specific left atrium (LA) model including pulmonary veins (PVs) in order to provide an accurate anatomical guide during RFA and without PVs in order to characterize LA volumetry and support patient selection for AF ablation.
Magnetic resonance data from twenty-six patients referred for AF RFA were processed applying an edge-based level set approach guided by a phase-based edge detector to obtain the 3D LA model with PVs. An automated technique based on the shape diameter function was designed and applied to remove PVs and compute LA volume. 3D LA models were qualitatively compared with 3D LA surfaces acquired during the ablation procedure. An expert radiologist manually traced the LA on MR images twice. LA surfaces from the automatic approach and manual tracing were compared by mean surface-to-surface distance. In addition, LA volumes were compared with volumes from manual segmentation by linear and Bland-Altman analyses.
Qualitative comparison of 3D LA models showed several inaccuracies, in particular PVs reconstruction was not accurate and left atrial appendage was missing in the model obtained during RFA procedure. LA surfaces were very similar (mean surface-to-surface distance: 2.3±0.7mm). LA volumes were in excellent agreement (y=1.03x-1.4, r=0.99, bias=-1.37ml (-1.43%) SD=2.16ml (2.3%), mean percentage difference=1.3%±2.1%).
Results showed the proposed 3D patient-specific LA model with PVs is able to better describe LA anatomy compared to models derived from the navigation system, thus potentially improving electrograms and voltage information location and reducing fluoroscopic time during RFA. Quantitative assessment of LA volume derived from our 3D LA model without PVs is also accurate and may provide important information for patient selection for RFA.
射频消融术（RFA）是治疗心房颤动（AF）患者的一种重要且有前景的疗法。优化患者选择以及提供准确的解剖学指导可提高RFA成功率。在本研究中，我们提出一种统一的、全自动的方法来构建包含肺静脉（PVs）的三维患者特异性左心房（LA）模型，以便在RFA期间提供准确的解剖学指导，同时构建不包含PVs的模型以表征LA容积并支持AF消融的患者选择。
对26例因AF RFA就诊患者的磁共振数据进行处理，应用基于相位边缘检测器引导的基于边缘的水平集方法来获取包含PVs的三维LA模型。设计并应用基于形状直径函数的自动化技术去除PVs并计算LA容积。将三维LA模型与消融过程中获取的三维LA表面进行定性比较。一位专业放射科医生在磁共振图像上手动追踪LA两次。通过平均表面到表面距离比较自动方法和手动追踪得到的LA表面。此外，通过线性分析和布兰德 - 奥特曼分析将LA容积与手动分割得到的容积进行比较。
三维LA模型的定性比较显示出一些不准确之处，特别是PVs重建不准确，并且在RFA过程中获得的模型中左心耳缺失。LA表面非常相似（平均表面到表面距离：2.3±0.7mm）。LA容积高度一致（y = 1.03x - 1.4，r = 0.99，偏差 = - 1.37ml（-1.43%），标准差 = 2.16ml（2.3%），平均百分比差异 = 1.3%±2.1%）。
结果表明，与从导航系统获得的模型相比，所提出的包含PVs的三维患者特异性LA模型能够更好地描述LA解剖结构，从而有可能改善电信号和电压信息定位，并减少RFA期间的透视时间。从我们的不包含PVs的三维LA模型得出的LA容积的定量评估也很准确，并且可能为RFA患者选择提供重要信息。
