Dixon-based MRI for assessment of muscle-fat content in phantoms, healthy volunteers and patients with achillodynia: comparison to visual assessment of calf muscle quality

Fischer, Michael ; Pfirrmann, Christian ; Espinosa, Norman ; Raptis, Dimitri ; Buck, Florian

In: European Radiology, 2014, vol. 24, no. 6, p. 1366-1375

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    Summary
    Objectives: To quantify the muscle fat-content (MFC) in phantoms, volunteers and patients with achillodynia using two-point Dixon-based magnetic resonance imaging (2pt-MRIDIXON) in comparison to MR spectroscopy (MRS) and visual assessment of MFC. Methods: Two-point Dixon-based MRI was used to measure the MFC of 15 phantoms containing 0-100% fat-content and calf muscles in 30 patients (13 women; 57 ± 15years) with achillodynia and in 20 volunteers (10 women; 30 ± 14years) at 1.5T. The accuracy of 2pt-MRIDIXON in quantification of MFC was assessed in vitro using phantoms and in vivo using MRS as the standard of reference. Fat-fractions derived from 2pt-MRIDIXON (FFDIXON) and MRS (FFMRS) were related to visual assessment of MFC (Goutallier grades 0-4) and Achilles-tendon quality (grade 0-4). Results: Excellent linear correlation was demonstrated for FFDIXON with phantoms and with FFMRS in patients (p c = 0.997/0.995; p < 0.001). FFDIXON of the gastrocnemius muscle was significantly higher (p = 0.002) in patients (7.0% ± 4.7%) compared with volunteers (3.6% ± 0.7%), whereas visual-grading showed no difference between both groups (p > 0.05). FFMRS and FFDIXON were significantly higher in subjects with (>grade 1) structural damage of the Achilles-tendon (p = 0.01). Conclusions: Two-point Dixon-based MRI allows for accurate quantification of MFC, outperforming visual assessment of calf muscle fat. Structural damage of the Achilles tendon is associated with a significantly higher MFC. Key points: • Two-point Dixon-based MRI allows accurate quantification of muscular fat content (MFC). • Quantitative analysis outperforms visual analysis in the detection of elevated MFC. • Achillodynia results in an increased MFC of the gastrocnemius muscles. • Structural damage of the Achilles tendon further increases the MFC.