title: MR virtual endoscopy of the upper urinary tract.
abstract: OBJECTIVE
  We investigated the feasibility of applying surface-rendered virtual endoscopy to the visualization of the upper urinary tract by processing unenhanced MR urography data sets.
  
  
  METHODS
  Twenty-six patients, having neoplastic lesions (n = 9), calculi (n = 8), pelviureteric junction stenoses (n = 4), postoperative fibrotic strictures (n = 3), and extrinsic compressions of the ureter (n = 2), underwent unenhanced MR urography. Virtual endoscopy of the upper urinary tract was obtained using a thresholding technique and surface-rendering MR urography data sets.
  
  
  RESULTS
  Virtual endoscopy of the renal pelvis and calices was feasible in all cases on the side of the urinary obstruction. Virtual endoscopy of the ureter was obtained for a diameter of at least larger than 5 mm. The nondilated side could be partially explored in 11 cases (43%). The mean virtual endoscopy threshold required for the visualization of the urinary tract was 157.36-159.94. The mean time for virtual endoscopy was 13.8 min. Endoluminal masses were found in three (12%) of 26 cases on the renal pelvis (corresponding to neoplastic lesions), and occlusions, in 23 (88%) of 26 on the pelviureteric junction and ureter (neoplastic lesions and other abnormalities).
  
  
  CONCLUSIONS
  Virtual endoscopy of MR urography data sets is feasible in patients with urinary tract dilatation. Virtual endoscopy displays the renal pelvis, calices, and ureter and, moreover, can show endoluminal changes caused by abnormalities.
authors.affiliation: Department of Oncology, Transplants and Advanced Technologies in Medicine, Division of Diagnostic and Interventional Radiology, University of Pisa, Via Roma 67, 56100, Pisa, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Neri
authors.forename: P
authors.initials: P
authors.lastname: Boraschi
authors.forename: D
authors.initials: D
authors.lastname: Caramella
authors.forename: L
authors.initials: L
authors.lastname: Battolla
authors.forename: R
authors.initials: R
authors.lastname: Gigoni
authors.forename: N
authors.initials: N
authors.lastname: Armillotta
authors.forename: G
authors.initials: G
authors.lastname: Braccini
authors.forename: C
authors.initials: C
authors.lastname: Bartolozzi
mesh_terms: D003950:Diagnostic Techniques, Urological; D004724:Endoscopy / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000473:pathology; D007674:Kidney Diseases / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D014513:Ureter / Q000473:pathology; D014515:Ureteral Diseases / Q000175:diagnosis*; D014584:User-Computer Interface