title: Optimization of multi-detector row CT urography: effect of compression, saline administration, and prolongation of acquisition delay.
abstract: OBJECTIVE
  To retrospectively compare the effects of abdominal compression, intravenous saline hydration, and two imaging delays on both distention and opacification of the intrarenal collecting system and ureter during multi-detector row computed tomographic (CT) urography.
  
  
  METHODS
  Institutional review board approval for reviewing images and medical records of the patients was obtained; informed patient consent was not required. Excretory phase images obtained from multi-detector row CT urography in 85 patients (57 men, 28 women) were reviewed. Examinations were performed by using one of four techniques: abdominal compression and intravenous hydration with 250 mL of normal saline, compression only, intravenous hydration with saline only, and neither compression nor saline hydration. Excretory phase imaging was performed at 300 and 450 seconds for each patient. Two reviewers measured urinary tract distention on transverse images and graded opacification and image quality on volume-rendered images. Effects were compared by using statistical mixed models with repeated-measures analysis of variance.
  
  
  RESULTS
  Saline hydration significantly improved opacification (P = .02) and overall image quality (P < .001) of the intrarenal collecting system and proximal ureter. Delayed excretory phase image acquisition of 450 seconds significantly increased distention of the intrarenal collecting system and proximal ureter (P < .001). No significant effects involving the lower segment of the ureter were seen with any technique; however, there were fewer nonvisualized distal ureteral segments with the longer imaging delay.
  
  
  CONCLUSIONS
  Compression does not significantly improve distention or opacification of the urinary tract. Saline hydration is effective in improving opacification of the proximal urinary tract. Longer imaging delays improve distention of the proximal urinary tract and may aid in visualization of the lower segment of the ureter.
authors.affiliation: Department of Radiology, University of Michigan Medical Center, 1500 E Medical Center Drive, Taubman Center B1 132D, Ann Arbor, MI 48109-9723, USA. caoili@umich.edu
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Caoili
authors.forename: Prasuna
authors.initials: P
authors.lastname: Inampudi
authors.forename: Richard H
authors.initials: RH
authors.lastname: Cohan
authors.forename: James H
authors.initials: JH
authors.lastname: Ellis
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012965:Sodium Chloride / Q000008:administration & dosage; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000592:standards; D014567:Urography / Q000379:methods*
chemical_list: D012965:Sodium Chloride