title: Characterization of peripheral nerve sheath tumors with 3T proton MR spectroscopy.
abstract: OBJECTIVE
  The characterization of peripheral nerve sheath tumors is challenging. The purpose here was to investigate the diagnostic value of quantitative proton MR spectroscopy at 3T for the characterization of peripheral nerve sheath tumors as benign or malignant, compared with PET.
  
  
  METHODS
  Twenty participants with 24 peripheral nerve sheath tumors underwent MR spectroscopy by use of a point-resolved sequence (TE, 135 ms). Six voxels were placed in 4 histologically proven malignant peripheral nerve sheath tumors and 22 voxels in 20 benign peripheral nerve sheath tumors (9 histologically proven, 11 with documented stability). The presence or absence of a trimethylamine signal was evaluated, the trimethylamine concentration estimated by use of phantom replacement methodology, and the trimethylamine fraction relative to Cr measured. MR spectroscopy results for benign and malignant peripheral nerve sheath tumors were compared by use of a Mann-Whitney test, and concordance or discordance with PET findings was recorded.
  
  
  RESULTS
  In all malignant tumors and in 9 of 18 benign peripheral nerve sheath tumors, a trimethylamine peak was detected, offering the presence of trimethylamine as a sensitive (100%), but not specific (50%), marker of malignant disease. Trimethylamine concentrations (2.2 ± 2.8 vs 6.6 ± 5.8 institutional units; P < .049) and the trimethylamine fraction (27 ± 42 vs 88 ± 22%; P < .012) were lower in benign than malignant peripheral nerve sheath tumors. A trimethylamine fraction threshold of 50% resulted in 100% sensitivity (95% CI, 58.0%-100%) and 72.2% (95% CI, 59.5%-75%) specificity for distinguishing benign from malignant disease. MR spectroscopy and PET results were concordant in 12 of 16 cases, (2 false-positive results for MR spectroscopy and PET each).
  
  
  CONCLUSIONS
  Quantitative measurement of trimethylamine concentration by use of MR spectroscopy is feasible in peripheral nerve sheath tumors and shows promise as a method for the differentiation of benign and malignant lesions. Trimethylamine presence within a peripheral nerve sheath tumor is a sensitive marker of malignant disease, but quantitative measurement of trimethylamine content is required to improve specificity.
authors.affiliation: From The Russell H. Morgan Department of Radiology and Radiological Science (L.M.F., X.W., D.J.D., S.D., M.A.J., P.B.B.)Orthopedic Surgery (L.M.F.)Oncology (L.M.F., M.A.J.), The Johns Hopkins Hospital Comprehensive Neurofibromatosis Center lfayad1@jhmi.edu.
authors.forename: L M
authors.initials: LM
authors.lastname: Fayad
authors.affiliation: From The Russell H. Morgan Department of Radiology and Radiological Science (L.M.F., X.W., D.J.D., S.D., M.A.J., P.B.B.).
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Neurology (J.O.B.), The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: J O
authors.initials: JO
authors.lastname: Blakeley
authors.affiliation: From The Russell H. Morgan Department of Radiology and Radiological Science (L.M.F., X.W., D.J.D., S.D., M.A.J., P.B.B.).
authors.forename: D J
authors.initials: DJ
authors.lastname: Durand
authors.affiliation: From The Russell H. Morgan Department of Radiology and Radiological Science (L.M.F., X.W., D.J.D., S.D., M.A.J., P.B.B.)Oncology (L.M.F., M.A.J.), The Johns Hopkins Hospital Comprehensive Neurofibromatosis Center.
authors.forename: M A
authors.initials: MA
authors.lastname: Jacobs
authors.affiliation: From The Russell H. Morgan Department of Radiology and Radiological Science (L.M.F., X.W., D.J.D., S.D., M.A.J., P.B.B.).
authors.forename: S
authors.initials: S
authors.lastname: Demehri
authors.affiliation: Department of Radiology (T.K.S.), University of Miami Miller School of Medicine, Miami, Florida.
authors.forename: T K
authors.initials: TK
authors.lastname: Subhawong
authors.affiliation: Research Unit of Radiology and Medical Imaging (T.S.), National and Capodestrian University of Athens, Evgenidion Hospital, Athens, Greece.
authors.forename: T
authors.initials: T
authors.lastname: Soldatos
authors.affiliation: From The Russell H. Morgan Department of Radiology and Radiological Science (L.M.F., X.W., D.J.D., S.D., M.A.J., P.B.B.).
authors.forename: P B
authors.initials: PB
authors.lastname: Barker
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D014408:Biomarkers, Tumor / Q000032:analysis*; D002648:Child; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008744:Methylamines / Q000032:analysis*; D008875:Middle Aged; D018317:Nerve Sheath Neoplasms / Q000737:chemistry* / Q000175:diagnosis*; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D008744:Methylamines; C023336:trimethylamine