Contrast-enhanced spiral CT of the head and neck: Comparison of contrast material injection rates

BACKGROUND AND PURPOSE: Contrast-enhanced spiral CT studies of the head and neck are performed frequently using contrast material volumes of approxima tely 30 g iodine and a scan delay of 30-45 seconds. Because little is known about the effects of contrast material injection rates on tissue enhanceme nt, this was prospectively investigated in our study, METHODS: Ninety-seven patients underwent spiral CT of the head and neck. Ea ch patient was assigned randomly to cone of four groups who received 100 mL of nonionic contrast material (300 mg I/mL) at different monophasic inject ion flow rates with 1.5, 2, 3, and 4 mL/s, Scanning started after a constan t delay of 35 seconds, The attenuation of the carotid artery, jugular vein, and sternocleidomastoid muscle was measured over time and the attenuation of the submandibular and thyroid gland was evaluated, Vascular attenuation of at least 150 HU was considered to be sufficient, RESULTS: The mean scan time was 33 +/- 5 seconds, The study, using an injec tion rate of 2 mL/s, showed the longest time of sufficient overall (arteria l and venous) vessel attenuation (27 +/- 4 seconds, P less than or equal to .008). The injection flaw rate did not influence significantly muscular at tenuation (mean enhancement during scan time: 9 +/- 7 HU). The 1.5 mL/s pro tocol showed the lowest attenuation values of the submandibular gland (81 /- 12 HU) and the highest attenuation values of the thyroid gland (164 +/- 22 HU), hut the attenuation of the thyroid gland was not statistically diff erent from that revealed by the 2 mL/s protocol, CONCLUSION: Using 100 mL of intravenous contrast material with 300 mg I/mL for spiral CT studies of the entire head and neck, the optimal injection fl ow is 2 mL/s, whereas lower how rates resulted in insufficient venous enhan cement.