title: Combined ultrasmall superparamagnetic particles of iron oxide-enhanced and diffusion-weighted magnetic resonance imaging reliably detect pelvic lymph node metastases in normal-sized nodes of bladder and prostate cancer patients.
abstract: BACKGROUND
  Lymph node staging of bladder or prostate cancer using conventional imaging is limited. Newer approaches such as ultrasmall superparamagnetic particles of iron oxide (USPIO) and diffusion-weighted magnetic resonance imaging (DW-MRI) have inconsistent diagnostic accuracy and are difficult to interpret.
  
  
  OBJECTIVE
  To assess whether combined USPIO and DW-MRI (USPIO-DW-MRI) improves staging of normal-sized lymph nodes in bladder and/or prostate cancer patients.
  
  
  METHODS
  Twenty-one consecutive patients with bladder and/or prostate cancer were enrolled between May and October 2008. One patient was excluded secondary to bone metastases detected on DW-MRI with subsequent abstention from surgery.
  
  
  METHODS
  Patients preoperatively underwent 3-T MRI before and after administration of lymphotropic USPIO using conventional MRI sequences combined with DW-MRI. Surgery consisted of extended pelvic lymphadenectomy and resection of primary tumors.
  
  
  METHODS
  Diagnostic accuracies of the new combined USPIO-DW-MRI approach compared with the "classic" reading method evaluating USPIO images without and with DW-MRI versus histopathology were evaluated. Duration of the two reading methods was noted for each patient.
  
  
  CONCLUSIONS
  Diagnostic accuracy (90% per patient or per pelvic side) was comparable for the classic and the USPIO-DW-MRI reading method, while time of analysis with 80 min (range 45-180 min) for the classic and 13 min (range 5-90 min) for the USPIO-DW-MRI method was significantly shorter (p<0.0001). Interobserver agreement (three blinded readers) was high with a kappa value of 0.75 and 0.84, respectively. Histopathological analysis showed metastases in 26 of 802 analyzed lymph nodes (3.2%). Of these, 24 nodes (92%) were correctly diagnosed as positive on USPIO-DW-MRI. In two patients, one micrometastasis each (1.0x0.2 mm; 0.7x0.4 mm) was missed in all imaging studies.
  
  
  CONCLUSIONS
  USPIO-DW-MRI is a fast and accurate method for detecting pelvic lymph node metastases, even in normal-sized nodes of bladder or prostate cancer patients.
authors.affiliation: University Hospital of Bern, Department of Radiology, Neuroradiology and Nuclear Medicine, Bern, Switzerland.
authors.forename: Harriet C
authors.initials: HC
authors.lastname: Thoeny
authors.forename: Maria
authors.initials: M
authors.lastname: Triantafyllou
authors.forename: Frederic D
authors.initials: FD
authors.lastname: Birkhaeuser
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Froehlich
authors.forename: Dechen W
authors.initials: DW
authors.lastname: Tshering
authors.forename: Tobias
authors.initials: T
authors.lastname: Binser
authors.forename: Achim
authors.initials: A
authors.lastname: Fleischmann
authors.forename: Peter
authors.initials: P
authors.lastname: Vermathen
authors.forename: Urs E
authors.initials: UE
authors.lastname: Studer
mesh_terms: D000368:Aged; D003287:Contrast Media; D003911:Dextrans; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D052203:Ferrosoferric Oxide; D006801:Humans; D008207:Lymphatic Metastasis; D058185:Magnetite Nanoparticles; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010865:Pilot Projects; D011471:Prostatic Neoplasms / Q000473:pathology*; D015203:Reproducibility of Results; D001749:Urinary Bladder Neoplasms / Q000473:pathology*
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; C097921:ferumoxtran-10; D052203:Ferrosoferric Oxide