Jonathan Avrom Leipsic MD, Presenter: Speakers Bureau, General Electric Company Medical Advisory Board, General Electric Company

Hina Arif Mumtaz MD, DNB, Abstract Co-Author: Nothing to Disclose

Andrew Scott-Moncrieff MD, Abstract Co-Author: Nothing to Disclose

Cameron John Hague MD, Abstract Co-Author: Nothing to Disclose

Jennifer Deryn Ellis MD, Abstract Co-Author: Nothing to Disclose

John R. Mayo MD, Abstract Co-Author: Nothing to Disclose

Don D Sin MD, Abstract Co-Author: Nothing to Disclose

Dual Energy CT pulmonary angiography (CTPA) allows image reconstruction at multiple monochromatic energies. Image reconstruction at lower monchromatic energy can increase image contrast which may permit reduction in intravenous (IV) contrast volume. We compared dual energy CTPA using half strength contrast to conventional CTPA measuring a number of outcome variables

We prospectively enrolled 29 consecutive patients with clinical suspicion of PE. Patients were assigned to either dual energy CTPA (GSI, GE Healthcare) using half strength IV contrast or routine CTPA using full strength contrast. Standard protocol scan parameters were 100 kVp BMI< 30kg/m 2 , 120 kVp BMI>30, a noise index of 25. Both protocols used a timing bolus to determine scan delay and contrast volume. Standard protocol contrast injecion volume was 50-80 cc of contrast at 4 cc/sec. The reduced contrast cohort was identical except a 50:50 dilution of contrast and saline was used. Dual energy images were reconstructed and analysed at a monchromatic energy of 50 kV, close to the k-edge of iodine. We measured: signal (mean ROI of main PA, left apical, right posterior basal arteries); contrast (mean signal arteries- signal in pectoralis); noise (Standard deviation of signal in MPA).We calculated signal and contrast to noise (CNR) ratios. Image quality was evaluated by 2 radiologists idependently using a 3 point Likert scale (3-very good, 2- diagnostic, 1-non-diagnostic). Student T-test was performed with p<0.05 (two-tailed) considered significant

The median age- reduced contrast was 63+/-9 vs 56 +/-13 standard (p=.10). The median BMI of the 2 cohorts were 27.4 for the reduced contrast and 26.0 for the standard (p=.528). There was significant reduction in mean contrast volume 23.2 vs. 60.2(p<0.001). SNR and CNR were higher for the reduced contrast cohort: SNR 17.64 vs 14.00(p=.025) and CNR 15.54 vs. 12.26(p=.040). The percentage of diagnostic studies was 92.8 % for the reduced contrast and 93.3% for the standard (p=1.0). Kappa agreement=0.649(p=.08)

Dual energy CT with image reconstruction at low monochromatic energy enables significant reduction in contrast volume in CTPA with improved SNR ,CNR and maintained image quality.

 Dual energy CT with image reconstruction at low monochromatic energy enables significant reduction in contrast volume in CTPA with improved SNR , CNR and maintained image quality.

Leipsic, J, Mumtaz, H, Scott-Moncrieff, A, Hague, C, Ellis, J, Mayo, J, Sin, D, Reduced Contrast Dual Energy CT Pulmonary Angiography: A Prospective Study.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9009607.html