CT

General
The use of MDCT, axial CT and CTA has increased over recent years. With these advances, comes increased use of contrast media. In particular the volume of contrast media used, the total iodine dose, injection rate & concentration have increased.

OMNIPAQUE has been used in a number of CT studies, both cardiac, abdominal and peripheral.

Cardiac
Maruyama [23] used OMNIPAQUE 350 mgI/ml, 90 ml at 4 ml/s in an 8-slice scanner, comparing accuracy vs. conventional cardiac catheter angiography in 25 patients. Sensitivity, specificity, and accuracy of the visualised segments by MDCT-CA was 90% (27 of 30 segments), 99.1% (226 of 228 segments), and 98.1% (253 of 258 segments), respectively.

Raff [24] also compared diagnostic accuracy of coronary 64-slice CTA vs.conventional catheter based coronary angiography perfomed < 30 d before in 70 patients. OMNIPAQUE 350 mgI/ml 100 ml @ 5 ml/s (+40 ml NaCl) was used in all patients. This study indicates high quantitative and qualitative diagnostic accuracy of 64-slice MDCT in comparison to catheter based coronary angiography in a broad spectrum of patients with sensitivities of 90-95% and specificities of 86-95%. In contrast to this study, many earlier studies excluded many “realworld” patients because of high heart rates, coronary calcification, or obesity, in addition to excluding all vessels < 1.5 mm in diameter.

Abdominal
Suzuki [25] studied the effect of OMNIPAQUE 300 mgI/ml or iopamidol 370 mgI/ml, on aortic, portal and hepatic enhancement. A total dose of 600 mgI/kg was administered and patients examined using 4-slice MDCT and an automatic bolus tracking technique. There were 33 patients in the analysis population of each group. Administration of CM with an iodine concentration of 300 or 370 mgI/ml both at 600 mgI/kg had the same effect on aortic, portal vein and liver parenchyma enhancement, except for the portal vein in late arterial phase. CM injection protocols for optimal phase may be planned irrespective of iodine concentration with automatic bolus tracking technique.

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Awai [26] did a similar study where he compared 2 different concentrations of OMNIPAQUE, 300 vs. 350 mgI/ml (94 and 92 patients, respectively), in abdominal CT also with a 4-slice MDCT scanner. Mean injection rates were 3.6 and 4.0 ml/s, respectively. This study concluded that when total iodine dose was adjusted to body weight and injection duration was fixed, rapid administration of OMNIPAQUE 300 mgI/ml was more effective for depiction of hypervascular HCC thanOMNIPAQUE 350 mgI/ml. A possible reason for this finding was that, since no saline chaser was used, approximately 30 ml CM may remain in the "dead space" between the brachial vein and superior venous cava. Since the total volume used of OMNIPAQUE 350 mgI/ml was smaller than that of OMNIPAQUE 300mgl/ml, the 30 ml lost would constitute a bigger part of the total CM dose. Thus, indirectly this study supports the advantages of using a saline chaser.