title: Helical liver CT with computer-assisted bolus-tracking technology: is it possible to predict which patients will not achieve a threshold of enhancement?
abstract: OBJECTIVE
  To determine how often a prescribed threshold of hepatic contrast material enhancement is not reached at helical computed tomography (CT) of the liver in patients in a tertiary teaching hospital-based practice and which variables are predictive of failure.
  
  
  METHODS
  Hepatic helical CT was performed in 250 consecutive patients with computer-assisted bolus-tracking technology after either mechanical injection at 3 mL/sec (n = 177) or manual injection (n = 73) of 150 mL of iopamidol. Demographic variables were recorded. After 17 seconds, low-milliamperage monitoring scans were obtained every 6 seconds until hepatic enhancement of 50 HU over baseline was achieved. Time-enhancement curves were reviewed.
  
  
  RESULTS
  The threshold was not reached by 60 seconds in 88 patients (35%; default group). The success and default groups were similar in most variables and differed only in weight (P = .002), patient status (inpatient, outpatient, or emergency department; P < .001), and injection type (mechanical vs manual; P < .001). Ten patients (4%) did not achieve the threshold because of inappropriate placement of elliptic regions of interest.
  
  
  CONCLUSIONS
  By using computer-assisted bolus-tracking technology, 35% of patients in a tertiary teaching hospital-based practice will not achieve a threshold of 50 HU above baseline by 60 seconds after injection initiation and will require the use of a set delay. Failures are more frequent in patients who are heavy and in inpatients. No historic or demographic factors are strongly predictive of failure.
authors.affiliation: Department Radiology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: E K
authors.initials: EK
authors.lastname: Paulson
authors.forename: A J
authors.initials: AJ
authors.lastname: Fisher
authors.forename: D M
authors.initials: DM
authors.lastname: DeLong
authors.forename: D D
authors.initials: DD
authors.lastname: Parker
authors.forename: R C
authors.initials: RC
authors.lastname: Nelson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003936:Diagnosis, Computer-Assisted; D005260:Female; D006801:Humans; D007479:Iopamidol; D008107:Liver Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007479:Iopamidol