Reduced metallic artefacts in 3 T knee MRI using fast spin-echo multi-point Dixon compared to fast spin-echo T2-weighted sequences

AIM: To compare multi-point Dixon magnetic resonance imaging (MRI) and fast spin-echo (FSE) T2-weighted imaging (WI) with regard to the size of metallic artefacts when imaging the knee joint. MATERIALS AND METHODS: A total of 42 patients who underwent anterior cruciate ligament (ACL) reconstruction and follow-up imaging with 3 T MRI using the multi-point Dixon technique was included in this retrospective study. The maximal distance of the image distortion area around the metallic artefact was measured (interference screw of femoral tunnel area) on sagittal images of both FSE T2WI (T2WI and fat-suppressed [FS] T2WI) and multi-point Dixon (water only image and in-phase image) sequences. The maximal distance of the image distortion were compared using paired t-tests across the image sequences (multipoint Dixon water only image versus FS T2WI and multi-point Dixon in-phase image versus T2WI). RESULTS: The mean distance of the image distortion from metallic artefacts regardless of the image sequence ranged from 16.6 mm to 24.5 mm (Table 2). The mean distances measured by two readers on multi-point Dixon (water only image) sequences were significantly shorter than those in FS T2WI sequences (p<0.001). In contrast, the mean distances measured by two readers on multi-point Dixon (in-phase image) sequences did not differ from those of T2WI (p>0.05) sequences. CONCLUSION: The water-only image of multi-point Dixon technique reduces the amount of metallic artefacts compared to that in FS FSE T2WI sequences; however, the metallic artefacts were not significantly different between in-phase images of multi-point Dixon and FSE T2WI. (C) 2017 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.