Three‐dimensional contrast‐enhanced hepatic MR imaging: Comparison between a centric technique and a linear approach with partial Fourier along both slice and phase directions

Abstract

Purpose: To compare the image quality of two variants of a three-dimensional (3D) gradient echo sequence (GRE) for hepatic MRI.Materials and Methods: Thirty-nine patients underwent hepatic MRI on a 3.0 Tesla (T) magnet (Intera Achieva; Philips Medical Systems). The clinical protocol included two variants of a 3D GRE with fat suppression: (i) a ''centric'' approach, with elliptical centric k-space ordering and (ii) an ''enhanced'' approach using linear sampling and partial Fourier in both the slice and phase encoding direction. ''Centric'' and ''Enhanced'' 3D GRE images were obtained both precontrast (n ¼ 32) and after gadoxetic acid injection (n ¼ 39). Two reviewers jointly reviewed MR images for anatomic sharpness, overall contrast, homogeneity, and absence of artifacts. The liver-to-lesion signal difference ratio (SDR) was measured. Paired sample Wilcoxon test and paired t-tests were used.Results: Enhanced 3D GRE images performed better than centric 3D GRE images with respect to anatomic sharpness (P ¼ 0.0156), overall contrast (P ¼ 0.0195), homogeneity (P < 0.0001), and absence of artifacts (P ¼ 0.0003) on precontrast images. For postcontrast MRI, enhanced 3D GRE images showed better quality in terms of overall contrast (P ¼ 0.0195), homogeneity (P < 0.0001), and absence of artifacts (P ¼ 0.009). Liver-tolesion SDR on enhanced 3D GRE images (0.48 6 0.13) was significantly higher than that of conventional 3D GRE images (0.40 6 0.19, P ¼ 0.0004) on postcontrast images, but not on precontrast images. Conclusion:The enhanced 3D GRE sequence available on our scanner provided better hepatic image quality than the centric variant, without compromising lesion contrast.

Optimizing the Magnetization-Prepared Rapid Gradient-Echo (MP-RAGE) Sequence

“…Partial Fourier acquisition has usually been used to shorten image acquisition time and echo time (TE) [23], [24]. Here we used partial Fourier acquisition along the slice direction to reduce the total number of readout RF pulses and shift k-space center line to a temporal position that is earlier than the center of the RF pulses in order to increase brain tissue contrast.…”

Gadoxetic acid‐enhanced fat suppressed three‐dimensional T1‐weighted MRI using a multiecho dixon technique at 3 tesla: Emphasis on image quality and hepatocellular carcinoma detection

“…As compared to the conventional THRIVE technique using elliptical centric k ‐space ordering, eTHRIVE makes use of partial Fourier and linear k ‐space ordering in both the phase and slice directions. Thereby, such a technique allows for the acquisition of the k = 0 line in a more steady‐state phase, in which minimizing the impact of signal variations on image quality at the beginning of the scan or at the beginning of each shot owing to signal nonsteady state effects derived from a fat suppression pulse applied for each segment . Thereby, eTHRIVE could minimize low spatial frequency (or bulk) artifacts related to suboptimal anatomic sharpness or general artifacts that are exhibited in centric‐ordering THRIVE in which the center of k ‐space is acquired at the beginning of the scan.…”

Pitfalls in liver MRI: Technical approach to avoiding misdiagnosis and improving image quality

“…TTC is the time to the central k ‐space encoding and is specific to the type of acquisition. The center of k ‐space may be sampled at the midpoint of acquisition time, in the first few seconds of the scan, or in a more complex fashion (eg, radial) to enrich the center of k ‐space. Familiarity with the specific k ‐space acquisition method for each platform is required for optimum timing.…”