Omar Sahagun MD, Presenter: Nothing to Disclose

Conrad Wittram MBChB, Abstract Co-Author: Nothing to Disclose

To compare standard delay enhancement with Smart prep technique for optimal opacification of the pulmonary arterial system.

Our institution adopted the Smart prep technique in July 2004. Prior to this, a standard time delay technique was used for CT pulmonary angiography (CTPA). Inclusion criteria: Patients who had undergone CTPA evaluation using both standard time delay and Smart prep enhancement techniques, so patients served as their own standardized controls. From November 2004 to February 2005, 1001 consecutive patients were identified. 36 of these patients had multiple CTPA studies, which included at least one of each utilizing the standard time delay and Smart prep techniques. 7 were excluded from the study; 2 of these studies had the region of interest (ROI) misplaced over the aorta and mediastinum, respectively, while the 5 other studies did not include a graph detailing the study-specifics. Intravenous contrast material (300mgI/ml) was administered at 4ml/sec via an antecubital vein. Studies were performed on a 4-slice or a 16-slice CT scanner with a standard time delay of 20 and 29 seconds, respectively. Smart prep used a threshold of 150 HU before commencement of the CT. The average time to start of scan for Smart prep was 18 seconds. Studies from each of the 29 patients, including fixed-time delay and Smart prep techniques, were evaluated individually. A ROI was obtained from the same respective levels in the pulmonary arterial system including measurements from the main, right upper, right lower, left upper, and left lower lobe pulmonary arteries. The two-tailed paired t test was used.

The age of the patients ranged from 42 to 92, with an average age of 71 years; there were 11 males and 18 females. Fixed time delay and Smart prep enhancement of the main, right upper, right lower, left upper, left lower pulmonary arteries were 326 (108), 286 (88), (p=0.13); 326 (115), 293 (92), (p=0.23); 331 (91), 276 (93), (p=0.03); 347 (135), 284 (89), (p=0.04); 331 (99), 277 (84), (p=0.03), respectively.

Fixed-delay enhancement CTPA consistently produces higher enhancement values than Smart prep, and has the advantage of reducing operator error.

Sahagun, O, Wittram, C, A Population-controlled Comparison of Fixed-delay and Smart Prep Enhancement for CT Pulmonary Angiography.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4416961.html