title: Diffusion-weighted MRI for distinguishing non-neoplastic cysts from solid masses in the mediastinum: problem-solving in mediastinal masses of indeterminate internal characteristics on CT.
abstract: OBJECTIVE
  To evaluate the usefulness of diffusion-weighted (DW) magnetic resonance images for distinguishing non-neoplastic cysts from solid masses of indeterminate internal characteristics on computed tomography (CT) in the mediastinum.
  
  
  METHODS
  We enrolled 25 patients with pathologically proved mediastinal masses who underwent both thoracic CT and magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI). MRI was performed in patients with mediastinal masses of indeterminate internal characteristics on CT. Two thoracic radiologists evaluated the morphological features and quantitatively measured the net enhancement of the masses at CT. They also reviewed MR images including unenhanced T1- and T2-weighted images, gadolinium-enhanced images and DW images.
  
  
  RESULTS
  The enrolled patients had 15 solid masses and ten non-neoplastic cysts. Although the morphological features and the extent of enhancement on CT did not differ significantly between solid and cystic masses in the mediastinum (P > 0.05), non-neoplastic cysts were distinguishable from solid masses by showing signal suppression on high-b-value DW images or high apparent diffusion coefficient (ADC) values of more than 2.5 × 10(-3) mm(2)/s (P < 0.001). ADC values of non-neoplastic cysts (3.67 ± 0.87 × 10(-3) mm(2)/s) were significantly higher than that of solid masses (1.46 ± 0.50 × 10(-3) mm(2)/s) (P < 0.001).
  
  
  CONCLUSIONS
  DWI can help differentiate solid and cystic masses in the mediastinum, even when CT findings are questionable.
  
  
  CONCLUSIONS
  • Non-invasive diagnosis of non-neoplastic cysts can save surgical biopsy or excision. • Conventional CT or MRI findings cannot always provide a confident diagnosis. • Mediastinal masses can be well-characterised with DWI. • Non-neoplastic mediastinal cysts show significantly higher ADC values than cystic tumours. • DWI is useful to determine treatment strategy.
authors.affiliation: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, 135-710, Korea.
authors.forename: Kyung Eun
authors.initials: KE
authors.lastname: Shin
authors.forename: Chin A
authors.initials: CA
authors.lastname: Yi
authors.forename: Tae Sung
authors.initials: TS
authors.lastname: Kim
authors.forename: Ho Yun
authors.initials: HY
authors.lastname: Lee
authors.forename: Young Soo
authors.initials: YS
authors.lastname: Choi
authors.forename: Hong Kwan
authors.initials: HK
authors.lastname: Kim
authors.forename: Jhingook
authors.initials: J
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D001994:Bronchogenic Cyst / Q000000981:diagnostic imaging / Q000473:pathology; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005500:Follow-Up Studies; D005729:Ganglioneuroma / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D008297:Male; D008476:Mediastinal Cyst / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D008479:Mediastinal Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology*; D008482:Mediastinum / Q000000981:diagnostic imaging / Q000473:pathology*; D008875:Middle Aged; D009442:Neurilemmoma / Q000000981:diagnostic imaging / Q000473:pathology; D012189:Retrospective Studies; D012509:Sarcoma / Q000000981:diagnostic imaging / Q000473:pathology; D013945:Thymoma / Q000000981:diagnostic imaging / Q000473:pathology*; D013953:Thymus Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D014057:Tomography, X-Ray Computed