Prospective head motion correction using FID‐guided on‐demand image navigators

Abstract

Purpose: We suggest a motion correction concept that employs free-induction-decay (FID) navigator signals to continuously monitor motion and to guide the acquisition of image navigators for prospective motion correction following motion detection. Methods: Motion causes out-of-range signal changes in FID time series that, and in this approach, initiate the acquisition of an image navigator. Co-registration of the image navigator to a reference provides rigid-body-motion parameters to facilitate prospective motion correction. Both FID and image navigator are integrated into a prototype magnetization-prepared rapid gradient-echo (MPRAGE) sequence. The performance of the method is investigated using image quality metrics and the consistency of brain volume measurements. Results: Ten healthy subjects were scanned (a) while performing head movements (nodding, shaking, and moving in zdirection) and (b) to assess the co-registration performance. Mean absolute errors of 0.27 6 0.38 mm and 0.19 6 0.24 for translation and rotation parameters were measured. Image quality was qualitatively improved after correction. Significant improvements were observed in automated image quality measures and for most quantitative brain volume computations after correction. Conclusion:The presented method provides high sensitivity to detect head motion while minimizing the time invested in acquiring navigator images. Limits of this implementation arise from temporal resolution to detect motion, false-positive alarms, and registration accuracy. Magn Reson

Conditional generative adversarial network for 3D rigid‐body motion correction in MRI

“…The motion can be measured using optical tracking techniques that use a camera system to track markers fixed to the head . MR navigators, which acquire a set of MR data, either in image space or k‐space, represent another category of motion measurement techniques used to measure head motion. Although these tools are able to effectively correct for head motion for certain applications, they often are limited to specific pulse sequences and scanner hardware; as such, they are not always available for routine clinical and research use.…”

Head motion measurement and correction usingFIDnavigators

“…FID navigators (FIDnavs) sample the k-space center without any imaging gradients and are an attractive option for monitoring motion as they have negligible impact on the magnetization or overall scan time. This enables motion detection with a high temporal resolution, which may be used to trigger a prospective motion correction strategy with selection of an appropriate threshold (31). The ability of FIDnavs to recognize previously determined head positions within the magnet has also been demonstrated (32); however, this approach currently entails a patient-specific training session prior to imaging, requiring the subject to perform a series of choreographed head movements with external ground-truth motion measurements, in order to train a pattern recognition algorithm.…”

Free induction decay navigator motion metrics for prediction of diagnostic image quality in pediatric MRI

“…Patients' ages ranged from 0 to 18 years, with median age 14 years; a detailed breakdown of patient age range is shown in Figure 1A. Eight adult patients (age [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] were also scanned to provide a baseline for k-space weighting.…”

“…FIDnav-based motion scores may be used to provide feedback to the operator to identify non-diagnostic scans before the acquisition is complete or to trigger a prospective correction strategy to steer the FOV after detection of a motion event. 30 FIDnav motion information may also be used retrospectively to identify motion-corrupted data to improve the reconstruction. 37 Real-time feedback of motion information could also be given directly to the subject, for example, using a visual display that turns from green to orange to red as the motion score approaches the threshold and/or that interferes with movie-watching while motion is detected.…”