title: Susceptibility-weighted imaging in patients with pyogenic brain abscesses at 1.5T: characteristics of the abscess capsule.
abstract: OBJECTIVE
  SWI is a high-resolution 3D, fully velocity-compensated gradient-echo sequence that uses both magnitude and phase data. The purpose of this study was to investigate the phase behavior of the capsule of pyogenic brain abscesses with noncontrast SWI.
  
  
  METHODS
  Fourteen patients with pyogenic brain abscesses were studied at 1.5T. In all of the patients, SWI images were obtained and reviewed in addition to conventional MR images. Phase values within the abscess capsule were measured and compared with those from the abscess cavities and contralateral normal white matter using 1-way repeated measures ANOVA with post hoc Bonferroni analysis.
  
  
  RESULTS
  SWI phase images showed mild hypointesity in 6 patients, isointensity in 3 patients, and mixed iso- to mild hypointensity in 5 patients. The means of phase in the cavity, rim of abscesses, and contralateral normal white matter were -7.552 × 10(-3) ± 0.024, -0.105 ± 0.080, and +0.029 ± 0.011 radians, respectively. Post hoc comparisons showed significant differences between any pair of the 3 regions (abscess cavity, rim capsule, and normal white matter) in SWI (all Ps < .005).
  
  
  CONCLUSIONS
  SWI phase imaging shows evidence of paramagnetic substances in agreement with the presence of free radicals from phagocytosis. SWI may provide additional information valuable in the characterization of pyogenic brain abscesses.
authors.affiliation: Department of Radiology, Veterans General Hospital-Kaohsiung, 386 Ta-Chung First Rd., Kaohsiung, Taiwan 813, Republic of China. pinghonglai@gmail.com
authors.forename: P H
authors.initials: PH
authors.lastname: Lai
authors.forename: H C
authors.initials: HC
authors.lastname: Chang
authors.forename: T C
authors.initials: TC
authors.lastname: Chuang
authors.forename: H W
authors.initials: HW
authors.lastname: Chung
authors.forename: J Y
authors.initials: JY
authors.lastname: Li
authors.forename: M J
authors.initials: MJ
authors.lastname: Weng
authors.forename: J H
authors.initials: JH
authors.lastname: Fu
authors.forename: P C
authors.initials: PC
authors.lastname: Wang
authors.forename: S C
authors.initials: SC
authors.lastname: Li
authors.forename: H B
authors.initials: HB
authors.lastname: Pan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001922:Brain Abscess / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult