CT

With the new MDCT scanners CT – axial, volume and above all CTA – has increased tremendously over the last couple of years, and with it the use of CM as expressed in number of examinations, CM volumes, total dose, injection rate and, to some extent, concentration.

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

Maruyama[23] used OMNIPAQUE 350 mgI/ml, 90 ml @ 4 ml/s in an 8-slice scanner, comparing accuracy vs. conventional cardiac catheter angiography. Sensitivity, specificity, and accuracy of the visualized 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 in 70 patients vs. conventional catheter based coronary angiography perfomed < 30 d before. 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. 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.

Awai[26] did a similar study where he compared 2 different concentrations of OMNIPAQUE, 300 vs. 350 mgI/ml (94 and 92 pts., resp.), in abdominal CT also with a 4-slice MDCT scanner. Mean injection rates were 3.6 and 4.0 ml/s, resp. 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 v.cava superior. Since the total volume used of OMNIPAQUE 350 mgI/ml was smaller, 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.

Karcaaltincaba[41] compared performance parameters, CM load and radiation dose in a patient cohort (n=18) undergoing aortoiliac CTA using 4- and 8-channel MDCT systems. 18 patients with abdominal aortic aneurysms had initial 4-channel MDCT and follow-up with 8-channel MDCT.

Compared with 4-channel MDCT, 8-channel MDCT aortoiliac angiography with equivalent collimation had decreased contrast load (mean 45% decrease: 144 ml versus 83 ml OMNIPAQUE 300 mgI/ml @ 5 ml/s) and also decreased acquisition time (mean 51% shorter: 34.4 s vs. 16.9 s) without a significant change in mean aortic enhancement (299 HU vs. 300 HU, p > 0.05).