title: Delayed MDCT imaging results in increased enhancement in patients with head and neck neoplasms.
abstract: OBJECTIVE
  Using multidetector computed tomography, we compared the utility of a spilt bolus technique and the impact of performing delayed imaging compared with immediate imaging on tumor enhancement.
  
  
  METHODS
  Thirty-seven patients with masses of the extracranial head and neck were imaged. An initial contrast bolus (50 cm) was administered over 30 seconds (1.67 cm/s) and an initial (immediate) imaging acquisition followed. Ninety seconds after completion of the initial bolus, a second bolus of 75 cm (2.5 cm/s) was administered and a second (delayed) acquisition obtained concurrently. Mean tumor enhancement in immediate and delayed imaging was calculated and analyzed using the paired t test.
  
  
  RESULTS
  Mean enhancement was 68.3 +/- 21.0 Hounsfield units (HU) and 91.4 +/- 27.4 HU (n = 37) for immediate and delayed imaging groups, respectively. The mean difference between the initial and delayed enhancement was 23.1 HU (P < 0.01).
  
  
  CONCLUSIONS
  The delayed imaging technique used resulted in a statistically significant increase in enhancement relative to immediate imaging.
authors.affiliation: Department of Radiology, University of Michigan Health System, MI 48109-0030, USA. bbartz@umich.edu
authors.forename: Brett H
authors.initials: BH
authors.lastname: Bartz
authors.forename: Ian C
authors.initials: IC
authors.lastname: Case
authors.forename: Ashok
authors.initials: A
authors.lastname: Srinivasan
authors.forename: Suresh K
authors.initials: SK
authors.lastname: Mukherji
mesh_terms: D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods