Charbel Saade MS, Presenter: Nothing to Disclose

Ali A. Haydar MD, FRCR, Abstract Co-Author: Nothing to Disclose

Fadi M. El-Merhi MD, Abstract Co-Author: Nothing to Disclose

Mukbil H. Hourani MD, Abstract Co-Author: Nothing to Disclose

To investigate the dose length product (DLP) during helical thoracic CT angiography (CTA) using a patient-specific contrast formula.

Thoracic CTA was performed in 200 patients with suspected acute aortic syndrome using a 64 channel computed tomography scanner and a dual barrel contrast injector. Patients were subjected in equal numbers to one of two acquisition/contrast regimens. Patient age and gender were equally distributed. Regimen A, the department’s standard protocol, consisted of a caudocranial scan direction with 100mL of contrast (Ultravist 370 mgI/mL), intravenously injected at a flow rate of 4.5 mL/s; Regimen B, involved a caudocranial scan direction and a novel contrast formula based on patient cardiovascular dynamics, using 80 mLs of saline at 4.5 mL/s. Each scan acquisition comprised of 120 kVp, 300 mA with modulation, temporal resolution 0.4 sec and pitch 0.981:1. The DLP was measured between each regimen and data generated were compared using Mann-Whitney U non-parametric statistics. Receiver operating characteristic (ROC) analysis and visual grading characteristic (VGC) was performed.

Mean vessel enhancement in the segments of the ascending aorta, transverse and descending aorta all measured were up to 12% (p <0.01) higher following group B compared with A. In the venous system, enhancement within the brachiocephalic and superior vena cava veins were significantly lower in group B than in group A with a maximum reduction of up to 92% (p <0.0001). The mean contrast volume was significantly lower in regimen B (53 ± 10 mL) compared to A (100 ± 1 mL) (p<0.001). There was no significant difference in mean scan time and range. Mean dose length product demonstrated significant reduction in regimen B (5.11±1.22 mSv) compared to A (7.82±0.82 mSv) (p = 0.02). The ROC analysis demonstrated a significantly higher Az score for regimen B compared with Regimen A (p<0.05), with the kappa agreement increasing from poor to excellent and VGC analysis demonstrated significant difference in perceived image quality in each regimen.

Significant reduction in radiation dose during helical thoracic CTA can be achieved using low contrast volume based on patient specific contrast formula.

The gold standard in the assessment of acute aortic syndrome is thoracic CT Angiography. Improved arterial opacification and contrast dose reduction provides diagnostic accuracy.

Saade, C, Haydar, A, El-Merhi, F, Hourani, M, Helical Thoracic Computed Tomography Angiography with Individualized Contrast Protocol: Effects on Radiation Dose and Image Quality.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13044143.html