title: Muscle fat-fraction and mapping in Duchenne muscular dystrophy: evaluation of disease distribution and correlation with clinical assessments. Preliminary experience.
abstract: OBJECTIVE
  To examine the usefulness of dual-echo dual-flip angle spoiled gradient recalled (SPGR) magnetic resonance imaging (MRI) technique in quantifying muscle fat fraction (MFF) of pelvic and thighs muscles as a marker of disease severity in boys with Duchenne muscular dystrophy (DMD), by correlating MFF calculation with clinical assessments. We also tried to identify characteristic patterns of disease distribution.
  
  
  METHODS
  Twenty consecutive boys (mean age, 8.6 years ± 2.3 [standard deviation, SD]; age range, 5-15 years; median age, 9 years;) with DMD were evaluated using a dual-echo dual-flip angle SPGR MRI technique, calculating muscle fat fraction (MFF) of eight muscles in the pelvic girdle and thigh (gluteus maximus, adductor magnus, rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, and gracilis). Color-coded parametric maps of MFF were also obtained. A neurologist who was blinded to the MRI findings performed the clinical assessments (patient age, Medical Research Council score, timed Gower score, time to run 10 m). The relationships between mean MFF and clinical assessments were investigated using Spearman's rho coefficient. Positive and negative correlations were evaluated and considered significant if the P value was < 0.05.
  
  
  RESULTS
  The highest mean MFF was found in the gluteus maximus (mean, 46.3 % ± 24.5 SD), whereas the lowest was found in the gracilis muscle (mean, 2.7 % ± 4.7 SD). Mean MFF of the gluteus maximus was significantly higher than that of the other muscles (P < 0.01), except for the adductor magnus and biceps muscles. A significant positive correlation was found between the mean MFF of all muscles and the patients age (20 patients; P < 0.005), Medical Research Council score (19 patients; P < 0.001), timed Gower score (17 patients; P < 0.03), and time to run 10 m (20 patients; P < 0.001). A positive correlation was also found between the mean MFF of the gluteus maximus muscle and the timed Gower score. Color-coded maps provided an efficient visual assessment of muscle fat content and its heterogeneous distribution.
  
  
  CONCLUSIONS
  Muscle fat fraction calculation and mapping using the dual-echo dual-flip angle SPGR MRI technique are useful markers of disease severity and permit patterns of disease distribution to be identified in patients with DMD.
authors: Department of Radiological Sciences, Policlinico G. Martino, Via Consolare Valeria 1, Messina, Italy.
authors: Michele
authors: M
authors: Gaeta
authors: Sonia
authors: S
authors: Messina
authors: Achille
authors: A
authors: Mileto
authors: Gian Luca
authors: GL
authors: Vita
authors: Giorgio
authors: G
authors: Ascenti
authors: Sergio
authors: S
authors: Vinci
authors: Antonio
authors: A
authors: Bottari
authors: Giuseppe
authors: G
authors: Vita
authors: Nicola
authors: N
authors: Settineri
authors: Daniele
authors: D
authors: Bruschetta
authors: Sergio
authors: S
authors: Racchiusa
authors: Fabio
authors: F
authors: Minutoli
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D050154:Adiposity; D000293:Adolescent; D002648:Child; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology*; D020388:Muscular Dystrophy, Duchenne / Q000175:diagnosis*; D010388:Pelvis; D010865:Pilot Projects; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013223:Statistics as Topic; D013848:Thigh