Introduction
Administration of iodinated contrast medium is required in many CT applications to discriminate normal anatomy and to identify pathological processes. Contrast enhancement is affected by factors that depend on the patient (e.g. weight, blood volume), the bolus (e.g. volume, injection rate), the contrast agent (e.g. iodine concentration) and the scanner (e.g. radiation dose, voltage). Much attention has been given to the possibility of improving contrast enhancement by increasing iodine flux. This may be achieved, for example, by increasing the injection rate or by using contrast medium with an elevated concentration of iodine.
The advantages of high-concentration contrast medium (HCCM) have been investigated in several studies (1-5). Loubeyre et al. (3) reported better opacification of vascular structures during thoracic CT when the iodine concentration was 350 mg/ml compared to 300 or 250 mg/ml; in this study, injection volume and duration were constant. Schoellnast et al. (4) reported better attenuation of pulmonary arteries during MDCT angiography when a smaller volume of HCCM (400 mg/ml) was used compared to a larger volume of standard contrast medium (300 mg/ml), keeping iodine dose and injection rate constant. Recently, Nagahata et al. (5) compared the 300 and 370 mg/ml iodine concentrations in patients undergoing 3D-CTA of the intracranial vasculature and found that arterial attenuation values were significantly better with the higher concentration; in this study, injection rate was constant but volume varied. These results exemplify the growing evidence that HCCM improves CT image quality.