Electromagnetic tracking-based freehand 3D quasi-static elastography with 1D linear array: a phantom study

Abstract

Recent developments in hardware and scanning protocols have advanced conventional 2D quasi-static elastography to 3D level, which provides an intuitive visualization of lesions. A 2D linear array or scanning mechanism is typically required for 3D quasi-static elastography, requiring expensive and specifically designed hardware. In this study, we propose a novel method based on a commercial electromagnetic tracking system for freehand 3D quasi-static elastography with 1D linear array. Phantom experiments are performed to validate the feasibility of the proposed method. During data acquisition, the probe contacts the surface of an elasticity phantom and moves in the elevational direction, while applying sinusoidal-like axial compression to the phantom. For each frame of ultrasound data, the 3D coordinates and orientations of the probe are obtained from an electromagnetic tracking system. A correlation-based algorithm is adopted to obtain a series of axial strain images. Volumetric strain data are reconstructed by using the recorded 3D coordinates and orientations of the probe corresponding to each strain image. The diameters of inclusions are then obtained from the slice plots of the volumetric strain data. The volumes of inclusions are estimated from the isosurface plots. The experimental result shows that the volume estimation of the inclusions has good accuracy, with errors within 2%, while the diameters of the inclusions estimated from three orthogonal planes have larger errors up to 18%. In conclusion, the present framework would promise a reliable and effective solution for freehand 3D quasi-static elastography with 1D linear array.