title: A retrospective comparison of smart prep and test bolus multi-detector CT pulmonary angiography protocols.
abstract: BACKGROUND
  Optimal arterial opacification is crucial in imaging the pulmonary arteries using computed tomography (CT). This poses the challenge of precisely timing data acquisition to coincide with the transit of the contrast bolus through the pulmonary vasculature. The aim of this quality assurance exercise was to investigate if a change in CT pulmonary angiography (CTPA) scanning protocol resulted in improved opacification of the pulmonary arteries. Comparison was made between the smart prep protocol (SPP) and the test bolus protocol (TBP) for opacification in the pulmonary trunk.
  
  
  METHODS
  A total of 160 CTPA examinations (80 using each protocol) performed between January 2010 and February 2011 were assessed retrospectively. CT attenuation coefficients were measured in Hounsfield Units (HU) using regions of interest at the level of the pulmonary trunk. The average pixel value, standard deviation (SD), maximum, and minimum were recorded. For each of these variables a mean value was then calculated and compared for these two CTPA protocols.
  
  
  RESULTS
  Minimum opacification of 200 HU was achieved in 98% of the TBP sample but only 90% of the SPP sample. The average CT attenuation over the pulmonary trunk for the SPP was 329 (SD = ±21) HU, whereas for the TBP it was 396 (SD = ±22) HU (P = 0.0017). The TBP also recorded higher maximum (P = 0.0024) and minimum (P = 0.0039) levels of opacification.
  
  
  CONCLUSIONS
  This study has found that a TBP resulted in significantly better opacification of the pulmonary trunk than the SPP.
authors.affiliation: Medical Imaging Department, Tamworth Rural Referral Hospital Tamworth, New South Wales, Australia.
authors.forename: Tara
authors.initials: T
authors.lastname: Suckling
authors.affiliation: University Department of Rural Health, The University of Newcastle Tamworth, New South Wales, Australia.
authors.forename: Tony
authors.initials: T
authors.lastname: Smith
authors.affiliation: Discipline of Medical Radiation Sciences, The University of Sydney Lidcombe, Australia.
authors.forename: Warren
authors.initials: W
authors.lastname: Reed
keywords: Bolus tracking; computed tomography pulmonary angiography; pulmonary embolism; test bolus