Martin Lee David Gunn MBChB, Presenter: Medical Advisor, TransformativeMed, Inc Spouse, Consultant, Wolters Kluwer nv Grant, Koninklijke Philips NV

Bruce E. Lehnert MD, Abstract Co-Author: Nothing to Disclose

Anda Maria Cornea MD, PhD, Abstract Co-Author: Nothing to Disclose

Christopher Allen Potter MD, Abstract Co-Author: Nothing to Disclose

To compare the impact of contrast timing technique on scan duration and arterial enhancement for thoracic CT angiography.

Retrospective, single center, IRB approved study that evaluated consecutive patients who had undergone single pass CT angiography of the thorax on a GE LightSpeed 16 CT scanner using 3 contrast timing techniques. Group A consisted of 86 patients who underwent CT pulmonary angiography (CTPA) using a timing bolus. Group B consisted of 74 patients who underwent a fixed-delay biphasic non-gated "double rule out" CTPA and aortic CTA protocol. Group C consisted of 58 patients who underwent thoracic aortic CTA using a bolus triggering (tracking) technique. The primary endpoint was comparing the duration (in seconds) between the acquisition time of the last scout image and the first axial post-contrast image in all three groups. The secondary endpoint was vascular enhancement (HU) of the main pulmonary artery (MPA) and thoracic aorta. Statistical techniques included a 3-way ANOVA for three group analysis and t-tests to compare specific protocols. p < 0.05 was considered statistically significant.

There was a statistically significant (p<0.0001) difference in the average delay between the last scout image and axial acquisition in the three groups: group A (timing) 330 seconds (CI 302-358), group B (triggering) 250 seconds (CI 221-279), and group C (fixed delay) 160 seconds (CI 136-184); group A vs B (p=0.002), B vs C (p<0.0001), and A vs C (p<0.0001). Comparing MPA enhancement between group A (416HU, CI 388-444) and group C (442HU, CI 411-473) yielded no statistically significant difference (p=0.207). Comparing aortic enhancement between group B (363HU, CI 338-389) and group C (425HU, CI 399-451) yielded a significant difference (p=0.001), with greater enhancement in group C. Similar volumes of contrast were used in the three groups.  

CTA using a fixed delay contrast enhancement technique is almost 3 minutes faster to perform than a timing bolus, with no impairment in vascular enhancement. This appears to be due to time taken by the technologists to perform the necessary steps. Three minutes is about 10% of the average CT scan slot duration.

Choosing a bolus triggering or a fixed delay could shorten the scan duration for urgent ED CTAs and allow for more patients, and potentially less stable patients, to get scanned.

Gunn, M, Lehnert, B, Cornea, A, Potter, C, CTA in the ED: Impact of Contrast Timing Technique on Scan Duration.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14003574.html