Position and orientation measurement of susceptibility markers using spectrally selective spin-echo projections

To develop an accurate technique for simultaneously measuring the position and orientation of interventional devices using a projection-based spectrally selective refocusing pulse sequence.

Projections along physical axes using spectrally selective excitation were acquired to track a catheter. A 9F passive tracking device capable of generating controllable susceptibility artifacts using susceptibility materials (titanium and graphite) was attached to the catheter. A library of projections for different orientations of the device with respect to the main magnetic field were simulated offline. Cross-correlations with these templates were computed to determine the orientation and position of the device. A phantom study was performed to evaluate the accuracy of the tracking technique. The tracking technique was also evaluated in vivo in the carotid artery of a pig.

Simultaneous and accurate measurement of position and orientation of the tracking device was obtained in the phantom and in vivo studies with reasonable temporal resolution. For the phantom study, the average of absolute errors in the Z-, Y-, and X-axes are 0.37, 0.76, and 0.85 mm, respectively. The mean absolute error and standard deviation of orientation measurement are 1.5 and 1.1 degrees, respectively.

This positioning technique, in conjunction with a controllable tracking device, can provide accurate tracking of interventional devices in MR-guided interventions. Magn Reson Med 76:1563-1573, 2016. © 2015 International Society for Magnetic Resonance in Medicine.