Intraindividual Comparison of Compressed Sensing‐Accelerated Cartesian and Radial Arterial Phase Imaging of the Liver in an Experimental Tumor Model

Abstract

Objectives: The aim of this study was to intraindividually compare the performance of 2 compressed sensing (CS)-accelerated magnetic resonance imaging (MRI) sequences, 1 featuring Cartesian (compressed sensing volumetric interpolated breath-hold examination [CS-VIBE]) and the other radial (golden-angle radial sparse parallel [GRASP]) k-space sampling in continuous dynamic imaging during hepatic vascular phases, using extracellular and hepatocyte-specific contrast agents. Materials and Methods: Seven New Zealand white rabbits, with induced VX2 liver tumors (median number of lesions, 2 ± 0.83; range, 1-3), received 2 continuously acquired T1-weighted prototype CS-accelerated MRI sequences (CS-VIBE and GRASP) with high spatial (0.8 Â 0.8 Â 1.5 mm) and temporal resolution (3.5 seconds) in randomized order on 2 separate days using a 1.5-T scanner. In all animals, imaging was performed using first gadobutrol at a dose of 0.1 mmol/kg and, then 45 minutes later, gadoxetic acid at a dose of 0.025 mmol/kg.The following qualitative parameters were assessed using 3-and 5-point Likert scales (3 and 5 being the highest scores respectively): image quality (IQ), arterial and venous vessel delineation, tumor enhancement, motion artifacts, and sequence-specific artifacts. Furthermore, the following quantitative parameters were obtained: relative peak signal enhancement, time to peak, mean transit time, and plasma flow ratios. Paired sampled t tests and Wilcoxon signed rank tests were used for intraindividual comparison. Image analysis was performed by 2 radiologists. Results: Six of 7 animals underwent the full imaging protocol and obtained data were analyzed statistically. Overall IQ was rated moderate to excellent, not differing significantly between the 2 sequences.Gadobutrol-enhanced CS-VIBE examinations revealed the highest mean Likert scale values in terms of vessel delineation and tumor enhancement (arterial 4.4 [4-5], venous 4.3 [3-5], and tumor 2.9 [2-3]). Significantly, more sequence-specific artifacts were seen in GRASP examinations (P = 0.008-0.031). However, these artifacts did not impair IQ. Excellent Likert scale ratings were found for motion artifacts in both sequences. In both sequences, a maximum of 4 hepatic arterial dominant phases were obtained. Regarding the relative peak signal enhancement, CS-VIBE and GRASP showed similar results. The relative peak signal enhancement values did not differ significantly between the 2 sequences in the aorta, the hepatic artery, or the inferior vena cava (P = 0.063-0.536). However, significantly higher values were noted for CS-VIBE in gadoxetic acid-enhanced examinations in the portal vein (P = 0.031) and regarding the tumor enhancement (P = 0.005). Time to peak and mean transit time or plasma flow ratios did not differ significantly between the sequences. Conclusions: Both CS-VIBE and GRASP provide excellent results in dynamic liver MRI using extracellular and hepatocyte-specific contrast agents, in terms of IQ, peak signal intensity, and presence of artifacts.

Dynamic Liver Magnetic Resonance Imaging During Free Breathing

“…7 Several publications have extensively studied GRASP, and it proved beneficial in patients where the quality of dynamic images was hampered by motions artifacts. 23,25,28,29 However, the major drawbacks of this sequence were the occurrence of characteristic streaking artifacts, altered tissue textures and considerable reconstruction times. 8,30 Although the presented technique has not been directly compared with GRASP, the visual impression and image quality as documented in the current literature are similar.…”

“…Compressed sensing as an iterative reconstruction method allowed for substantial acceleration of MRI acquisition and made T1-weighted imaging with motion robust radial readout of k-space with clinically acceptable spatial and temporal resolution feasible 26,27 ; it was eventually implemented into the first commercially available free-breathing technique approved for dynamic liver imaging, the golden-angle radial sparse parallel (GRASP) sequence developed by Siemens Healthcare (Erlangen, Germany) 7 . Several publications have extensively studied GRASP, and it proved beneficial in patients where the quality of dynamic images was hampered by motions artifacts 23,25,28,29 . However, the major drawbacks of this sequence were the occurrence of characteristic streaking artifacts, altered tissue textures and considerable reconstruction times 8,30 .…”

Multiarterial Phase Acquisition in Gadoxetic Acid–Enhanced Liver MRI for the Detection of Hypervascular Hepatocellular Carcinoma in High-Risk Patients

“…At our institution, we have obtained triple AP imaging of gadoxetic acid-enhanced MRI using the VS-3D GRE technique (TWIST-volumetric interpolated breath-hold examination [VIBE]) and CS-3D GRE technique (CS-VIBE) with fluoroscopic triggering. 16,28,32 We searched our radiologic database between November and December 2017, when the VS-3D GRE technique was used to obtain MAP images, and between September and October 2020, which is the first 2 months in which the MAP acquisition protocol changed to CS-VIBE to identify patients who fulfilled the following inclusion criteria: (a) patients who underwent gadoxetic acid-enhanced liver MRI; (b) patients at risk of developing HCC; and (c) availability of triple AP images that were acquired using either the VS technique (TWIST-VIBE) or CS technique (CS-VIBE). Patients were excluded if (a) more than 5 focal liver observations were made; (b) AP imaging was obtained using a free-breathing dynamic imaging technique due to poor breath-holding capacity; and (c) they were younger than 18 years.…”

“…22 The combination of CS and PI techniques in gadoxetic acidenhanced MRI can reduce acquisition time and motion artifacts without reducing image quality. [27][28][29] Kawai et al 27 demonstrated that the additional use of CS resulted in a 50% reduction of acquisition time, compared with using only the PI technique. In addition, in a previous study, 29 a combined CS and PI technique facilitated double arterial phase (AP) imaging with optimal timing with reduction of respiratory motion artifacts in gadoxetic acid-enhanced liver MRI.…”

“…Another technique is the combined use of CS and PI, 22,26 which can acquire MAP image sets where each k-space data is independently obtained 22 . The combination of CS and PI techniques in gadoxetic acid–enhanced MRI can reduce acquisition time and motion artifacts without reducing image quality 27–29 . Kawai et al 27 demonstrated that the additional use of CS resulted in a 50% reduction of acquisition time, compared with using only the PI technique.…”