MRI of Moving Subjects Using Multislice Snapshot Images With Volume Reconstruction (SVR): Application to Fetal, Neonatal, and Adult Brain Studies

Abstract

Motion degrades magnetic resonance (MR) images and prevents acquisition of self-consistent and high-quality volume images. A novel methodology, Snapshot magnetic resonance imaging (MRI) with Volume Reconstruction (SVR) has been developed for imaging moving subjects at high resolution and high signal-to-noise ratio (SNR). The method combines registered 2-D slices from sequential dynamic single-shot scans. The SVR approach requires that the anatomy in question is not changing shape or size and is moving at a rate that allows snapshot images to be acquired. After imaging the target volume repeatedly to guarantee sufficient sampling every where, a robust slice-to-volume registration method has been implemented that achieves alignment of each slice within 0.3 mm in the examples tested. Multilevel scattered interpolation has been used to obtain high-fidelity reconstruction with root-mean-square (rms) error that is less than the noise level in the images. The SVR method has been performed successfully for brain studies on subjects that cannot stay still, and in some cases were moving substantially during scanning. For example, awake neonates, deliberately moved adults and, especially, on fetuses, for which no conventional high-resolution 3-D method is currently available. Fine structure of the in-utero fetal brain is clearly revealed for the first time and substantial SNR improvement is realized by having many individually acquired slices contribute to each voxel in the reconstructed image.

Fetal MRI: A technical update with educational aspirations

“…These image volume reconstruction techniques have been shown to enable high-resolution volumetric imaging of the fetal brain despite intermittent fetal and maternal motion. Pioneers of these techniques, Rousseau et al (149) and Jiang et al (150), combined iterations of slice-to-volume registration and scattered data interpolation for volumetric reconstruction of fetal brain MRI from multiple sets of thick-slice SST2W scans. In a more systematic approach Gholipour et al (151) introduced a physical forward model of slice acquisition incorporating motion, slice profile, and sampling, and then solved an inverse problem to reconstruct a high-resolution volume from multiple slice acquisitions.…”

Automated fetal brain segmentation from 2D MRI slices for motion correction

“…The most common approach is slice-to-volume registration, where slices are iteratively registered to an estimation of the reconstructed 3D volume (Rousseau et al, 2006;Jiang et al, 2007;Gholipour et al, 2010;Kuklisova-Murgasova et al, 2012). Another approach proposed by Kim et al (2010) formulates the motion correction problem as the optimization of the intersections of all slice pairs from all orthogonally planned scans.…”

“…In both Rousseau et al (2006) and Gholipour et al (2010), a tight bounding box is manually cropped for each stack of 2D slices. In Jiang et al (2007) and Kuklisova-Murgasova et al (2012), the region containing the fetal head is manually segmented in one stack, and the segmentation is propagated to the other stacks after volumeto-volume registration. Down-sampling the target volume followed by up-sampling the mask can be performed to save time during the manual segmentation.…”

“…These movements are unpredictable and may be large, particularly involving substantial head rotations. As a result, most fetal imaging is performed using single shot methods to acquire two dimensional (2D) slices, such as single shot Fast Spin Echo, ss-FSE, (Jiang et al, 2007) and Echo-Planar Imaging, EPI, (Chen and Levine, 2001). These methods can freeze fetal motion, so that each individual slice is generally artifact free, but stacks of slices required to provide whole brain coverage may be mutually inconsistent.…”

New Imaging Strategies Using a Motion-Resistant Liver Sequence in Uncooperative Patients

“…The SS-ETSE sequence is the mainstay tool for water-sensitive imaging of the upper abdomen in noncooperative patients (Figure 2). In cases of extreme motion, multiple repeated imaging loops of SS-ETSE can offer the benefit of an increased signal-to-noise ratio (SNR) and resolution in conjunction with a motion-correction algorithm, snapshot-to-volume reconstruction [9]. This technique provides low contrast as there is a relatively small T2 difference between diseased and normal tissue and it is routinely coupled with fat suppression in order to increase its sensitivity to detect hepatic lesions.…”