title: Intravenous contrast medium administration at 128 multidetector row CT pulmonary angiography: bolus tracking versus test bolus and the implications for diagnostic quality and effective dose.
abstract: OBJECTIVE
  To investigate the effects of a test bolus protocol contrast medium administration on diagnostic image quality in computed tomography pulmonary angiography (CTPA).
  
  
  METHODS
  Fifty patients referred for exclusion of pulmonary embolism underwent CTPA using a test bolus protocol CTPA at 120 kVp and were compared with 50 patients undergoing CTPA using a standard bolus-tracking protocol at 120 kVp, via assessment of attenuation, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) seen in the pulmonary arteries (PAs). An additional group of 10 non-obese patients who underwent CTPA using a test bolus protocol performed at 100 kVp were also analysed. Mean effective dose was calculated from the dose-length product, using standard conversion factors.
  
  
  RESULTS
  The test bolus protocol showed significantly higher attenuation, SNR, and CNR in the pulmonary vasculature down to the segmental level compared to bolus-tracking CTPA (p < 0.0001). There was no significant difference in effective dose between the test bolus and bolus tracking cohorts. The additional group of test bolus CTPA examinations performed at 100 kVp had a significantly reduced effective dose in comparison to both test bolus CTPA at 120 kVp and bolus-tracking CTPA at 120 kVp (p < 0.005) yet maintained mean PA attenuation to segmental level significantly better than bolus-tracking CTPA performed at 120 kVp and comparable to the test bolus cohort performed at 120 kVp.
  
  
  CONCLUSIONS
  Test bolus contrast administration should be used as an optimal protocol. Performing test bolus CTPA at 100 kVp, as opposed to 120 kVp, significantly reduces dose without compromising PA attenuation in non-obese subjects.
authors.affiliation: Department of Radiology, Bristol Royal Infirmary, University Hospitals Bristol NHS Foundation Trust, Bristol, UK. jonrodrigues@doctors.org.uk
authors.forename: J C L
authors.initials: JC
authors.lastname: Rodrigues
authors.forename: H
authors.initials: H
authors.lastname: Mathias
authors.forename: I S
authors.initials: IS
authors.lastname: Negus
authors.forename: N E
authors.initials: NE
authors.lastname: Manghat
authors.forename: M C K
authors.initials: MC
authors.lastname: Hamilton
mesh_terms: D061605:Administration, Intravenous / Q000379:methods; D000368:Aged; D003287:Contrast Media / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging; D011667:Pulmonary Veins / Q000000981:diagnostic imaging*; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D003287:Contrast Media