A miniature position and orientation locator for three dimensional echocardiography

The accuracy of a new miniature prototype (6 mm×6 mm×9 mm) six dimensional (6D) locator sensor for three dimensional (3D) echocardiography was investigated. This new sensor identifies its 3D position and 3D orientation in space with respect to the position of a magnetic field generator. The sensor when attached to an ultrasound imaging transducer allows identifying and tracking the position and orientation in space of the ultrasonic imaging plane. The accuracy of this new miniature sensor was tested by rotating it on a lever arm apparatus which maintained a constant distance (R) from the sensor to the fixed point of rotation. At each rotational spatial position the sensor´s readings were used to calculate the fixed point´s position in space. The mean (MRE) and standard deviation (STDRE) of the radial error in this determination were calculated for N trials. The results with the apparatus: for R=10.6 cm were MRE=1.3 mm, STDRE=0.06 mm, N=500; and for R=18 cm they were MRE=1.8 mm, STDR=0.7 mm, N=500. It was then tested with a transcutaneous 5 MHz echo probe on 3D imaging a fixed position string target. The results in locating the position of the target was MRE=2.2 mm and STDRE=1.5 mm for N=45