Optimal contrast material concentration for distinguishing among carotid artery lumen, carotid stent, and neck in cone-beam computed tomography during carotid angiography: basic and clinical studies

To explore the optimal contrast material (CM) concentration for distinguishing CM, carotid stent (CS), and neck components in cone-beam computed tomography (CBCT) during carotid angiography (CBCT-CA). A neck phantom containing CS and contrast-filled imitation vessels of 9 mm diameter was scanned using CBCT. CM (300 mgI/ml) was used in concentrations of 100, 50, 33, 10, 5, and 1%. In a clinical study, 30 patients with a CS (Precise or Wallstent) underwent CBCT-CA with CM injected at a rate of 3 ml/s and a concentration of 10 or 20%. In the basic study, CBCTA using 5% CM enabled clear distinction among the three components under windowing at 1500 width and 300 center, and showed the exact diameter of the imitation vessel. Pixel values of CM inside the Precise and the Wallstent were 622.2 +/- A 32.9 (mean +/- A SD) and 746.0 +/- A 27.9, respectively. In the clinical study using CM at concentrations of 10 and 20%, pixel values of CM inside the Wallstent were 632.3 +/- A 69.2 and 1024.5 +/- A 99.0, respectively. Optimal CM concentration for distinguishing among the three components was 5% in the basic study; the optimal concentration was 10% in the clinical study.