Robust 4D-MRI Sorting with Reduced Artifacts Based on Anatomic Feature Matching
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Purpose: Motion artifacts induced by breathing variations are common in 4D-MRI
images. This study aims to reduce the motion artifacts by developing a novel, robust 4DMRI
sorting method based on anatomic feature matching, which is applicable in both
cine and sequential acquisition.
Method: The proposed method uses the diaphragm as the anatomic feature to guide the
sorting of 4D-MRI images. Initially, both abdominal 2D sagittal cine MRI images and
axial MRI images (in both axial cine and sequential scanning modes) were acquired. The
sagittal cine MRI images were divided into 10 phases as ground truth. Next, the phase of
each axial MRI image is determined by matching the diaphragm position in the
intersection plane between the axial MRI and the ground truth cine MRI. Then, those
matched phases axial MRI images were sorted into 10-phase bins identical to the ground
truth cine images. Finally, 10-phase 4D-MRI were reconstructed from these sorted axial
MRI images. The accuracy of reconstructed 4D-MRI data was evaluated in a simulation
study using the 4D eXtended Cardiac Torso (XCAT) digital phantom with a sphere
tumor in the liver. The effects of breathing signal, including both regular (cosine
function) and irregular (patient data), on reconstruction accuracy were investigated by
calculating total relative error (TRE) of the 4D volumes, Volume-Percent-Difference
(VPD) and Center-of-Mass-Shift(COMS) of the simulated tumor between the
reconstructed and the ground truth images.
Results: In both scanning modes, reconstructed 4D-MRI images matched well with the
ground truth except minimal motion artifacts. The averaged TRE of the 4D volume, VPD
and COMS of the EOE phase in both scanning modes were 0.32%/1.20%/±0.05𝑚𝑚 for
regular breathing, and 1.13%/4.26%/±0.21𝑚𝑚 for patient irregular breathing,
Conclusion: The preliminary results illustrated the robustness of the new 4D-MRI
sorting method based on anatomic feature matching. This method improved image
quality with reduced motion artifacts in the resulting reconstructed 4D MRI is applicable
for axial MR images acquired using both cine and sequential scanning modes.
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