Room: AAPM ePoster Library
Purpose: previously showed how the coarse (3mm) through-plane resolution of 2D multislice acquisition improvs to 1mm through-plane super resolution (SR) using overlapped slices. However, for prostate MRI this was prone to slice-to-slice positional inconsistency from subtle peristaltic motion, leading to prominent scalloping artifact in reformats. The purpose is to devise and evaluate a segmented acquisition which eliminates the inconsistency.
Methods: acquisition typically comprises the acquisition of 70 or more overlapped slices, generally using multiple passes of the multislice sequence. Each pass is acquired over a temporal footprint. In the proposed method the acquisition of the ky-lines is divided into multiple segments comprising the sampling of some subset of the full acquisition. This causes the temporal footprints of all passes to have substantial overlap, providing improved pass-to-pass consistency in average position. This is at the potential expense of increased in-plane motion-related blur.
The segmented sequence was compared to the standard reference sequence in phantoms and in vivo in 14 prostate MRI studies using axial T2-weighted fast-spin-echo (TR=3000,TE=100) using 78 slices acquired in 6 passes and compared on the basis of resolution and artifact. Scan times of both sequences were similar (6min) but the temporal footprints of the proposed sequence were longer (6min/1min).
Results: the level of motion expected due to rectal peristalsis (2mm overall A/P displacement) the segmented method has only slight in-plane resolution degradation at 0.5LP/mm. In the patient studies the quality of the 1mm-thick SR axial images was improved and the level of scalloping was essentially eliminated in sagittal reformats made from the 1mm thick SR axial images formed from the overlapped slices acquired with the segmented method.
Conclusion: acquisition of the overlapped slices desired for super resolution multislice acquisition is effective in eliminating the slice-to-slice positional inconsistency which causes prominent scalloping artifact in reformats while retaining in-plane sharpness.