Prospective motion correction using inductively coupled wireless RF coils

Abstract

Purpose A novel prospective motion correction technique for brain MRI is presented that uses miniature wireless radio-frequency (RF) coils, or “wireless markers”, for position tracking. Methods Each marker is free of traditional cable connections to the scanner. Instead, its signal is wirelessly linked to the MR receiver via inductive coupling with the head coil. Real-time tracking of rigid head motion is performed using a pair of glasses integrated with three wireless markers. A tracking pulse-sequence, combined with knowledge of the markers’ unique geometrical arrangement, is used to measure their positions. Tracking data from the glasses is then used to prospectively update the orientation and position of the image-volume so that it follows the motion of the head. Results Wireless-marker position measurements were comparable to measurements using traditional wired RF tracking coils, with the standard deviation of the difference < 0.01 mm over the range of positions measured inside the head coil. RF safety was verified with B1 maps and temperature measurements. Prospective motion correction was demonstrated in a 2D spin-echo scan while the subject performed a series of deliberate head rotations. Conclusion Prospective motion correction using wireless markers enables high quality images to be acquired even during bulk motions. Wireless markers are small, avoid RF safety risks from electrical cables, are not hampered by mechanical connections to the scanner, and require minimal setup times. These advantages may help to facilitate adoption in the clinic.

Motion artifacts in MRI: A complex problem with many partial solutions

“…To improve the accuracy of the navigation sequence, and to reduce interference with the imaging process, it is possible to use additional spatial-frequency-tuned markers (77), miniature radio-frequency probes (78, 79), or signals of the endogenous fat (80, 81). However, many of these methods were so far restricted to 1D (80) and 2D (77, 81), and are generally only used in research applications.…”

“…cloverleaf, spherical or orbital navigators (66, 67, 73)). Alternatively, an external tracking device can be used, including stereo camera systems (95), miniature RF probes (78, 79, 96), in-bore camera systems (97-99), or ultrasound systems (100). Navigators need to be compatible with the sequence timing and typically have a low temporal sample rate.…”

Prospective motion correction in functional MRI

“…Some approaches use additional devices, e.g. MR-visible markers (Ooi et al, 2013a, 2011; Sengupta et al, 2014), where the detected motion is still in MR reference frame, but rigid coupling between the markers and the object is not necessarily present and additional measures need to be taken in order to ensure such coupling. Finally, for truly external motion tracking devices (Forman et al, 2010; Maclaren et al, 2012; Rotenberg et al, 2013; Schulz et al, 2012; Zaitsev et al, 2006), both marker fixation and coordinate frame matching need to be ensured.…”

Anatomical MRI for Human Brain Morphometry

“…A hybrid navigator approach combines a set of extrinsic fiducial markers with a simple rapidly acquired navigator that locates the markers and estimates the position and orientation of the set. Markers may consist of miniature coils activated by the scanner RF pulses (Muraskin et al, 2013;Ooi, Aksoy, Maclaren, Watkins, & Bammer, 2013;Thormer et al, 2012). These methods are more difficult to apply in the clinical situation due to the additional hardware, calibration, and markers affixed to the patient.…”