Modified acquisition strategy for reduced motion artifact in super resolution T₂ FSE multislice MRI: Application to prostate

Purpose: To reduce slice-to-slice motion effects in multislice (Formula presented.) -weighted fast-spin-echo ((Formula presented.) FSE) imaging, manifest as “scalloping” in reformats, by modification of the acquisition strategy and to show applicability in prostate MRI. Methods: (Formula presented.) FSE images of contiguous or overlapping slices are typically acquired using multiple passes in which each pass is comprised of multiple slices with slice-to-slice gaps. Combination of slices from all passes provides the desired sampling. For enhancement of through-plane resolution with super resolution or for reformatting into other orientations, subtle ≈1 mm motion between passes can cause objectionable “scalloping” artifact. Here we address this by subdivision of each pass into multiple segments. Interleaving of segments from the multiple passes causes all slices to be acquired over substantially the same time, reducing pass-to-pass motion effects. This was implemented in acquiring 78 overlapped (Formula presented.) FSE axial slices and studied in phantoms and in 14 prostate MRI patients. Super-resolution axial images and sagittal reformats from the original and new segmented acquisitions were evaluated by 3 uroradiologists. Results: For all criteria of sagittal reformats, the segmented acquisition was statistically superior to the original. For all sharpness criteria of axial images, although the trend preferred the original acquisition, the difference was not significant. For artifact in axial images, the segmented acquisition was significantly superior. Conclusions: For prostate MRI the new segmented acquisition significantly reduces the scalloping motion artifact that can be present in reformats due to long time lags between the acquisition of adjacent or overlapped slices while retaining image sharpness in the acquired axial slices.