Navigator‐based reacquisition and estimation of motion‐corrupted data: Application to multi‐echo spin echo for carotid wall MRI

Abstract

Purpose To assess whether artifacts in multi‐slice multi‐echo spin echo neck imaging, thought to be caused by brief motion events such as swallowing, can be corrected by reacquiring corrupted central k‐space data and estimating the remainder with parallel imaging. Methods A single phase‐encode line (ky = 0, phase‐encode direction anteroposterior) navigator echo was used to identify motion‐corrupted data and guide the online reacquisition. If motion corruption was detected in the 7 central k‐space lines, they were replaced with reacquired data. Subsequently, GRAPPA reconstruction was trained on the updated central portion of k‐space and then used to estimate the remaining motion‐corrupted k‐space data from surrounding uncorrupted data. Similar compressed sensing‐based approaches have been used previously to compensate for respiration in cardiac imaging. The g‐factor noise amplification was calculated for the parallel imaging reconstruction of data acquired with a 10‐channel neck coil. The method was assessed in scans with 9 volunteers and 12 patients. Results The g‐factor analysis showed that GRAPPA reconstruction of 2 adjacent motion‐corrupted lines causes high noise amplification; therefore, the number of 2‐line estimations should be limited. In volunteer scans, median ghosting reduction of 24% was achieved with 2 adjacent motion‐corrupted lines correction, and image quality was improved in 2 patient scans that had motion corruption close to the center of k‐space. Conclusion Motion‐corrupted echo‐trains can be identified with a navigator echo. Combined reacquisition and parallel imaging estimation reduced motion artifacts in multi‐slice MESE when there were brief motion events, especially when motion corruption was close to the center of k‐space.

Automated detection and reacquisition of motion‐degraded images in fetal HASTE imaging at 3 T

“…We have successfully developed and implemented a closed-loop acquisition/reconstruction pipeline that prospectively detects and automatically reacquires only poorquality fetal brain HASTE images within the prescribed stack. Whereas prospective reacquisition of compromised MRI data has been established in postnatal imaging, [26][27][28][29] to our knowledge this is the first fetal MRI application of prospective reacquisition based on fast, automatic imaging quality assessment CNN. The methods demonstrated in this work improve the standard clinical fetal MRI workflow by: (1) enabling savings in the overall time the pregnant woman needs to be in the scanner because only bad slices are reacquired, not the entire stack; and (2) providing objective means of determining which slices are F I G U R E 3 In utero images from a 29 gestational week fetus using our modified HASTE sequence with the reacquisition mode set to reacquire only the slices that have an IQA score lower than 0.9.…”

A promising tool to tackle the risk of cerebral vascular disease, the emergence of novel carotid wall imaging

“…[ 11 20 23 ] Moreover, ongoing work using motion correction strategies is promising which would allow this technique to fulfill its clinical potentials. [ 41 ]…”

10-channel phased-array coil for carotid wall MRI at 3T

“…Parallel imaging techniques [ 18 ] are often used to acquire data at high resolutions with reduced scan times, at the cost of a loss in SNR. The relative loss of SNR can further degrade depending on the coil geometry being used [ 19 ], so coil configurations which provide low amounts of noise amplification at high acceleration factors are desirable for carotid MRI [ 20 , 21 ].…”