OBJECTIVE: To determine the overall frequency of artifacts per type and grade using the GRASE sequence in abdominal magnetic resonance; to compare GRASE sequences with two previously selected TSE sequences as well as sequences with best signal-noise ratio and lower incidence of artifacts. MATERIALS AND METHODS: A prospective self-paired study was carried out in 86 patients submitted to upper abdominal magnetic resonance using a GRASE sequence obtained upon respiratory triggered and fat suppression and six TSE T2-weighted sequences. Among the six TSE sequences, those bearing the best signal-noise ratio and lower number of artifacts were previously selected, which consisted of those performed with fat suppression and respiratory triggering: one using a conventional body coil (sequence 1) and a second sequence using a synergy coil (sequence 2). Image analysis was carried out by two observers upon consensus regarding the presence, grade and type of artifact thereon. Subsequently, data were statistically analyzed using the Friedman test and chi-square. RESULTS: The absolute frequency of artifacts in all sequences was 65.02%. Most common artifacts in the three sequences analyzed were breathing (30%) and pulsation (33%) artifacts. Only in 3% of the cases artifacts interfered with the analysis of the images. The frequency of artifacts in the different sequences was: GRASE, 67.2%; TSE sequence 1, 62.2%; TSE sequence 2, 65.5%. There was no significant statistical difference between artifact frequency seen with GRASE and TSE sequences (p = 0.845; NS). CONCLUSION: GRASE and TSE T2-weighted, respiratory triggered, fat suppressed sequences often produce artifacts, notwithstanding the coil, although, with similar frequency and generally without interfering with the evaluation of the images.

Keywords: Artifact, Magnetic resonance, Abdomen

In cases where typical aspects are shown, the diagnosis of most frequent hepatic lesions can be made with some safety by means of several imaging methods; on the other hand, uncommon lesions generally represent a diagnostic challenge for the radiologist. In the present second part of the study, the authors describe four rare hepatic lesions, as follows: primary hepatic lymphoma, myofibroblastic tumor, primary hepatic neuroendocrine tumor and desmoplastic small round cell tumor, approaching their main characteristics and imaging findings with emphasis on computed tomography and magnetic resonance imaging.

Keywords: Neoplasms; Liver; Atypical; Computed tomography; Magnetic resonance imaging.