title: Renal masses: assessment of corticomedullary-phase and nephrographic-phase CT scans.
abstract: OBJECTIVE
  To evaluate the role of thin-section helical computed tomography (CT) performed during the corticomedullary phase (CMP) and nephrographic phase (NP) of contrast enhancement in the detection and characterization of renal masses.
  
  
  METHODS
  Renal CT scans and medical records of 33 patients were retrospectively reviewed. In all examinations, 5-mm-thick, contiguous, helical-mode scans were obtained before and 40 seconds after initiation of dynamic bolus injection of contrast material (CMP images); 5-mm-thick, contiguous, axial-mode scans were obtained after completion of CMP scanning (NP images).
  
  
  RESULTS
  At review of CMP, NP, and combination images, 259, 389, and 417 lesions, respectively, were identified. The greatest difference in detection occurred in the renal medulla, with 25 lesions identified on CMP images and 111 lesions identified on NP images. False-positive results occurred when CMP images were reviewed without NP images.
  
  
  CONCLUSIONS
  CT scans obtained only during the CMP of contrast enhancement fail to depict many renal masses that are easily seen on NP images.
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor 48109, USA.
authors.forename: R H
authors.initials: RH
authors.lastname: Cohan
authors.forename: L S
authors.initials: LS
authors.lastname: Sherman
authors.forename: M
authors.initials: M
authors.lastname: Korobkin
authors.forename: J C
authors.initials: JC
authors.lastname: Bass
authors.forename: I R
authors.initials: IR
authors.lastname: Francis
mesh_terms: D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007472:Iohexol; D007672:Kidney Cortex / Q000000981:diagnostic imaging; D007674:Kidney Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology; D007679:Kidney Medulla / Q000000981:diagnostic imaging; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D007472:Iohexol