title: Glutamine/glutamate metabolism studied with magnetic resonance spectroscopic imaging for the characterization of adrenal nodules and masses.
abstract: OBJECTIVE
  To assess glutamine/glutamate (Glx) and lactate (Lac) metabolism using proton magnetic resonance spectroscopic imaging (1H-MRS) in order to differentiate between adrenal gland nodules and masses (adenomas, pheochromocytomas, carcinomas, and metastases).
  
  
  METHODS
  Institutional review board approval and informed consent were obtained. A total of 130 patients (47 men) with 132 adrenal nodules/masses were prospectively assessed (54 ± 14.8 years). A multivoxel system was used with a two-dimensional point-resolved spectroscopy/chemical-shift imaging sequence. Spectroscopic data were interpreted by visual inspection and peak amplitudes of lipids (Lip), choline (Cho), creatine (Cr), Lac, and Glx. Lac/Cr and Glx/Cr were calculated. Glx/Cr was assessed in relation to lesion size.
  
  
  RESULTS
  Statistically significant differences were observed in Glx/Cr results between adenomas and pheochromocytomas (P < 0.05), however, with a low positive predictive value (PPV). Glx levels were directly proportional to lesion size in carcinomas. A cutoff point of 1.44 was established for the differentiation between carcinomas larger versus smaller than 4 cm, with 75% sensitivity, 100% specificity, 100% PPV, and 80% accuracy. Lac/Cr results showed no differences across lesions. A cutoff point of -6.5 for Lac/Cr was established for carcinoma diagnosis.
  
  
  CONCLUSIONS
  Glx levels are directly proportional to lesion size in carcinomas. A cutoff point of -6.5 Lac/Cr differentiates carcinomas from noncarcinomas.
authors.affiliation: Department of Diagnostic Imaging, Federal University of São Paulo, Napoleão de Barros 800, Vila Clementino, 04024-002 São Paulo, SP, Brazil.
authors.forename: Suzan M
authors.initials: SM
authors.lastname: Goldman
authors.forename: Thiago F
authors.initials: TF
authors.lastname: Nunes
authors.forename: Homero J F
authors.initials: HJ
authors.lastname: Melo
authors.forename: Claudio
authors.initials: C
authors.lastname: Dalavia
authors.forename: Denis
authors.initials: D
authors.lastname: Szejnfeld
authors.forename: Claudio
authors.initials: C
authors.lastname: Kater
authors.forename: Cassio
authors.initials: C
authors.lastname: Andreoni
authors.forename: Jacob
authors.initials: J
authors.lastname: Szejnfeld
authors.forename: Sergio A
authors.initials: SA
authors.lastname: Ajzen
mesh_terms: D000293:Adolescent; D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism; D000311:Adrenal Glands / Q000000981:diagnostic imaging / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D011859:Radiography
chemical_list: D005973:Glutamine; D018698:Glutamic Acid