title: Hepatic enhancement during helical CT: a comparison of moderate rate uniphasic and biphasic contrast injection protocols.
abstract: OBJECTIVE
  The purpose of this study was to compare the degree and timing of peak hepatic enhancement, optimal scanning intervals, and optimal delay times of moderate-rate uniphasic and biphasic contrast material injection protocols for hepatic helical CT.
  
  
  METHODS
  One hundred fifty patients were randomized into three injection protocols, receiving 42.3 g iodine (150 ml iothalamate meglumine) delivered using 3 ml/sec uniphasic, 2 ml/sec uniphasic, or biphasic (3 ml/sec [50 ml], 1 ml/sec [100 ml]) technique. Statistically fitted aortic and hepatic enhancement curves were generated from dynamic incremental CT data for each patient. Protocols were compared by maximum hepatic enhancement, and contrast enhancement indices were modeled for a 38-sec helical acquisition.
  
  
  RESULTS
  The 3 ml/sec and 2 ml/sec uniphasic protocols produced higher peak hepatic enhancement (64 +/- 15 H and 62 +/- 15 H [mean +/- 1 SD]) than the 3 ml/sec biphasic protocol (52 +/- 10 H; p < .001). Contrast enhancement indices for the 3 ml/sec uniphasic and 2 ml/sec uniphasic protocols (385 +/- 398 H/sec and 397 +/- 412 H/sec) were significantly greater than the index for the 3 ml/sec biphasic protocol (123 +/- 194 H/sec; p < .0001) at a 50-H threshold. Optimal scan delay times were 50 +/- 8, 75 +/- 7, and 119 +/- 8 sec, respectively, for the 3 ml/sec uniphasic, 2 ml/sec uniphasic, and 3 ml/sec biphasic techniques.
  
  
  CONCLUSIONS
  The moderate-rate uniphasic injections studied provided greater hepatic enhancement throughout the helical acquisition without requiring the prohibitively long delay time necessitated by the moderate-rate biphasic injection. These findings differ from prior results that showed that a uniphasic injection may provide comparable levels of hepatic enhancement when compared with a high-flow-rate biphasic injection.
authors.affiliation: Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Birnbaum
authors.forename: J E
authors.initials: JE
authors.lastname: Jacobs
authors.forename: D
authors.initials: D
authors.lastname: Yin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007275:Injections, Intravenous / Q000379:methods; D008099:Liver / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media