title: Role of diffusion-weighted imaging and in vivo proton magnetic resonance spectroscopy in the differential diagnosis of ring-enhancing intracranial cystic mass lesions.
abstract: OBJECTIVE
  Proton magnetic resonance spectroscopy (PMRS) and diffusion-weighted imaging (DWI) were compared to determine which technique is more effective in the differential diagnosis of cystic intraparenchymal ring-enhancing lesions with variable perifocal edema.
  
  
  METHODS
  Fifty-two patients (abscesses [n = 29], tumor cysts [n = 20], and benign cysts [n = 3]) formed the basis for comparative evaluation in this study. The criteria for abscess diagnosis were apparent diffusion coefficient (ADC) values less than 0.9 +/- 1.3 x 10 mm/s and presence of lactate cytosolic amino acids (AAs) with/without succinate, acetate, alanine, and glycine on PMRS. Criteria for nonabscess cyst identification were ADC values of 1.7-3.8 x 10 mm/s and presence of lactate and choline on PMRS. On the basis of these criteria, patients were categorized into abscess (n = 29) and nonabscess (n = 23) groups. Sensitivity and specificity of PMRS and DWI with respect to the final diagnosis were calculated based on the efficacy of these techniques.
  
  
  RESULTS
  : Apparent diffusion coefficient values in 21 patients with abscesses were observed within the range of defined criteria, whereas in 8 patients, ADC values were beyond the range of defined criteria. Lactate and AAs with or without other metabolites were observed in 25 of 29 cases of abscesses on PMRS. In the nonabscess group, ADC values of cystic lesions in all patients were consistent with respect to the defined criteria. Only lactate was seen in 14 of 23 patients, whereas both lactate and choline were visible in 6 patients. In 3 patients with neurocysticercosis, AAs (n = 2), lactate (n = 3), acetate (n = 1), succinate (n = 3), choline (n = 2), and alanine (n = 3) were seen. The sensitivity of DWI and PMRS for differentiation of brain abscess from nonbrain abscess was 0.72 and 0.96, respectively, whereas the specificity was 1 for both techniques.
  
  
  CONCLUSIONS
  Demonstration of restricted diffusion on DWI with reduced ADC is highly suggestive of brain abscess; however, in the absence of restriction, PMRS is mandatory to distinguish brain abscesses from cystic tumors.
authors.affiliation: Department of Radiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
authors.forename: Asht M
authors.initials: AM
authors.lastname: Mishra
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Gupta
authors.forename: Ramandeep S
authors.initials: RS
authors.lastname: Jaggi
authors.forename: Jaipal S
authors.initials: JS
authors.lastname: Reddy
authors.forename: Deepak K
authors.initials: DK
authors.lastname: Jha
authors.forename: Nuzhat
authors.initials: N
authors.lastname: Husain
authors.forename: Kashi N
authors.initials: KN
authors.lastname: Prasad
authors.forename: Sanjay
authors.initials: S
authors.lastname: Behari
authors.forename: Mazhar
authors.initials: M
authors.lastname: Husain
mesh_terms: D000085:Acetates / Q000032:analysis; D000293:Adolescent; D000328:Adult; D000409:Alanine / Q000032:analysis; D001922:Brain Abscess / Q000175:diagnosis; D001927:Brain Diseases / Q000175:diagnosis*; D001932:Brain Neoplasms / Q000175:diagnosis; D002648:Child; D002675:Child, Preschool; D002794:Choline / Q000032:analysis; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005998:Glycine / Q000032:analysis; D006801:Humans; D019344:Lactic Acid / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D020019:Neurocysticercosis / Q000175:diagnosis; D012680:Sensitivity and Specificity; D019802:Succinic Acid / Q000032:analysis
chemical_list: D000085:Acetates; D019344:Lactic Acid; D019802:Succinic Acid; D002794:Choline; D000409:Alanine; D005998:Glycine