title: Gravity Compensation Method for Combined Accelerometer and Gyro Sensors Used in Cardiac Motion Measurements.
abstract: 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 (r2> 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.
authors.affiliation: The Intervention Center, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0372, Oslo, Norway.|Department of Informatics, University of Oslo, Gaustadallèen 23B, 0373, Oslo, Norway.
authors.forename: Magnus Reinsfelt
authors.initials: MR
authors.lastname: Krogh
authors.affiliation: Høgskolen i Buskerud og Vestfold, Raveien 215, 3184, Borre, Norway.
authors.forename: Giang M
authors.initials: GM
authors.lastname: Nghiem
authors.affiliation: The Intervention Center, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0372, Oslo, Norway.
authors.forename: Per Steinar
authors.initials: PS
authors.lastname: Halvorsen
authors.affiliation: The Intervention Center, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0372, Oslo, Norway.|Department of Informatics, University of Oslo, Gaustadallèen 23B, 0373, Oslo, Norway.
authors.forename: Ole Jakob
authors.initials: OJ
authors.lastname: Elle
authors.affiliation: The Intervention Center, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0372, Oslo, Norway.
authors.forename: Ole-Johannes
authors.initials: OJ
authors.lastname: Grymyr
authors.affiliation: Høgskolen i Buskerud og Vestfold, Raveien 215, 3184, Borre, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Hoff
authors.affiliation: The Intervention Center, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0372, Oslo, Norway. espen.remme@medisin.uio.no.
authors.forename: Espen W
authors.initials: EW
authors.lastname: Remme
mesh_terms: D061725:Accelerometry; D000818:Animals; D006112:Gravitation; D006321:Heart; D006801:Humans; D008955:Models, Cardiovascular; D009038:Motion; D009200:Myocardial Contraction
keywords: Bio signal processing; Cardiac monitoring; Ischemia detection; Motion sensing