Krogh Magnus Reinsfelt, Nghiem Giang M, Halvorsen Per Steinar, Elle Ole Jakob, Grymyr Ole-Johannes, Hoff Lars, Remme Espen W
The Intervention Center, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0372, Oslo, Norway.
Department of Informatics, University of Oslo, Gaustadallèen 23B, 0373, Oslo, Norway.
Ann Biomed Eng. 2017 May;45(5):1292-1304. doi: 10.1007/s10439-017-1798-4. Epub 2017 Jan 23.
A miniaturized accelerometer fixed to the heart can be used for monitoring of cardiac function. However, an accelerometer cannot differentiate between acceleration caused by motion and acceleration due to gravity. The accuracy of motion measurements is therefore dependent on how well the gravity component can be estimated and filtered from the measured signal. In this study we propose a new method for estimating the gravity, based on strapdown inertial navigation, using a combined accelerometer and gyro. The gyro was used to estimate the orientation of the gravity field and thereby remove it. We compared this method with two previously proposed gravity filtering methods in three experimental models using: (1) in silico computer simulated heart motion; (2) robot mimicked heart motion; and (3) in vivo measured motion on the heart in an animal model. The new method correlated excellently with the reference (r > 0.93) and had a deviation from reference peak systolic displacement (6.3 ± 3.9 mm) below 0.2 ± 0.5 mm for the robot experiment model. The new method performed significantly better than the two previously proposed methods (p < 0.001). The results show that the proposed method using gyro can measure cardiac motion with high accuracy and performs better than existing methods for filtering the gravity component from the accelerometer signal.
固定在心脏上的小型加速度计可用于监测心脏功能。然而，加速度计无法区分由运动引起的加速度和由重力引起的加速度。因此，运动测量的准确性取决于从测量信号中估计和滤除重力分量的效果。在本研究中，我们提出了一种基于捷联惯性导航的重力估计新方法，该方法使用了组合式加速度计和陀螺仪。陀螺仪用于估计重力场的方向，从而消除重力影响。我们在三个实验模型中，将该方法与之前提出的两种重力滤波方法进行了比较，实验模型包括：（1）计算机模拟心脏运动；（2）机器人模拟心脏运动；（3）动物模型中心脏的体内测量运动。在机器人实验模型中，新方法与参考值的相关性极佳（r > 0.93），与参考值的收缩期峰值位移偏差（6.3 ± 3.9 mm）低于0.2 ± 0.5 mm。新方法的性能明显优于之前提出的两种方法（p < 0.001）。结果表明，所提出的使用陀螺仪的方法能够高精度地测量心脏运动，并且在从加速度计信号中滤除重力分量方面比现有方法表现更好。
