Khoshnam Mahta, Skanes Allan C, Patel Rajni V
IEEE Trans Biomed Eng. 2015 May;62(5):1404-15. doi: 10.1109/TBME.2015.2389615. Epub 2015 Jan 9.
The efficacy of catheter-based cardiac ablation procedures can be significantly improved if real-time information is available concerning contact forces between the catheter tip and cardiac tissue. However, the widely used ablation catheters are not equipped for force sensing. This paper proposes a technique for estimating the contact forces without direct force measurements by studying the changes in the shape of the deflectable distal section of a conventional 7-Fr catheter (henceforth called the "deflectable distal shaft," the "deflectable shaft," or the "shaft" of the catheter) in different loading situations.
First, the shaft curvature when the tip is moving in free space is studied and based on that, a kinematic model for the deflectable shaft in free space is proposed. In the next step, the shaft shape is analyzed in the case where the tip is in contact with the environment, and it is shown that the curvature of the deflectable shaft provides useful information about the loading status of the catheter and can be used to define an index for determining the range of contact forces exerted by the ablation tip.
Experiments with two different steerable ablation catheters show that the defined index can detect the range of applied contact forces correctly in more than 80% of the cases. Based on the proposed technique, a framework for obtaining contact force information by using the shaft curvature at a limited number of points along the deflectable shaft is constructed.
The proposed kinematic model and the force estimation technique can be implemented together to describe the catheter's behavior before contact, detect tip/tissue contact, and determine the range of contact forces.
This study proves that the flexibility of the catheter's distal shaft provides a means of estimating the force exerted on tissue by the ablation tip.
如果能够获得有关导管尖端与心脏组织之间接触力的实时信息，基于导管的心脏消融手术的疗效可得到显著提高。然而，广泛使用的消融导管并未配备力传感功能。本文提出一种技术，通过研究传统7F导管可弯曲远端部分（以下称为导管的“可弯曲远端轴”“可弯曲轴”或“轴”）在不同加载情况下的形状变化，在不进行直接力测量的情况下估计接触力。
首先，研究了尖端在自由空间中移动时轴的曲率，并在此基础上提出了可弯曲轴在自由空间中的运动学模型。下一步，分析了尖端与环境接触时的轴形状，结果表明可弯曲轴的曲率提供了有关导管加载状态的有用信息，可用于定义一个指标来确定消融尖端施加的接触力范围。
对两种不同的可操纵消融导管进行的实验表明，所定义的指标在超过80%的情况下能够正确检测出施加的接触力范围。基于所提出的技术，构建了一个通过沿可弯曲轴有限数量的点处的轴曲率来获取接触力信息的框架。
所提出的运动学模型和力估计技术可以一起实施，以描述导管在接触前的行为、检测尖端/组织接触并确定接触力范围。
本研究证明了导管远端轴的柔韧性提供了一种估计消融尖端施加在组织上的力的方法。
