title: 1H Magnetic resonance spectroscopy findings in idiopathic inflammatory myopathies at 3 T: feasibility and first results.
abstract: OBJECTIVE
  The aim of this study was to investigate the feasibility and potential use of quantitative proton magnetic resonance spectroscopy (MRS) for determining metabolite concentrations in patients with suspected inflammatory myopathies.
  
  
  METHODS
  In this institutional review board-approved, Health Insurance Portability and Accountability Act-compliant prospective study, 35 patients with a suspected inflammatory myopathy and 6 age-matched healthy volunteers underwent magnetic resonance imaging (MRI) (T1-weighted and short tau inversion recovery [STIR] sequences) and single-voxel MRS (point-resolved spectroscopy; repetition time/echo time, 2000/135 milliseconds; voxel size, 2.0 × 2.0 × 4.0 cm) at 3 T. The voxel was placed in a thigh muscle and targeted to one with abnormal STIR signal when possible. Absolute trimethylamine, creatine (Cr), and bulk lipid concentrations in each voxel were determined using the phantom replacement method. The MRS results of patients and healthy subjects were compared using the Wilcoxon rank sum test.
  
  
  RESULTS
  Twenty-one patients were diagnosed with an active idiopathic inflammatory myopathy (IIM). In 20 of these patients, MRI showed increased intramuscular STIR signal; however, the muscle where the voxel was placed was normal in 9 patients. Patients with an IIM demonstrated higher mean intramuscular Cr concentration compared with controls (62.1 vs 35.3 IU; P = 0.01), but there were no differences in the mean trimethylamine or lipid concentrations. In IIM patients with no intravoxel signal abnormality (9/21), the mean Cr concentration was still higher than that in healthy subjects (63.2 vs 35.3 IU; P = 0.001).
  
  
  CONCLUSIONS
  Quantitative 3-T MRS is feasible and may supplement the role of conventional MRI in the evaluation of patients with inflammatory myopathies, especially where MRI shows no obvious muscle abnormalities.
authors.affiliation: The Department of Radiology, University of Miami, Miami, FL, USA.
authors.forename: Ty K
authors.initials: TK
authors.lastname: Subhawong
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Machado
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Mammen
authors.forename: Lisa
authors.initials: L
authors.lastname: Christopher-Stine
authors.forename: Peter B
authors.initials: PB
authors.lastname: Barker
authors.forename: John A
authors.initials: JA
authors.lastname: Carrino
authors.forename: Laura M
authors.initials: LM
authors.lastname: Fayad
mesh_terms: D015415:Biomarkers / Q000032:analysis*; D003404:Creatinine / Q000032:analysis*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008055:Lipids / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008744:Methylamines / Q000032:analysis*; D009220:Myositis / Q000175:diagnosis* / Q000378:metabolism*; D010865:Pilot Projects; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D015415:Biomarkers; D008055:Lipids; D008744:Methylamines; D011522:Protons; D003404:Creatinine; C023336:trimethylamine