64-Slice multidetector row CT angiography of the abdomen: comparison of low versus high concentration iodinated contrast media in a porcine model

Objective

In this study we aimed to assess the image quality and degree of vascular enhancement using low-concentration contrast media (LCCM) (300 mg I ml^–1) and high-concentration contrast media (HCCM) (370 mg I ml^–1) on 64-slice multidetector row CT (MDCT) abdominal CT angiography (CTA). In addition, we aimed to study the feasibility of using HCCM with a reduced total iodine dose.

Methods

CTA of the abdomen on a 64-slice MDCT was performed on 15 anaesthetised pigs. Study pigs were divided into three groups of five each based on the iodine concentration and dose received: Group A (LCCM; 300 mg I ml^–1), Group B (HCCM; 370 mg I ml^–1) and Group C HCCM with 20% less iodine dose. The total iodine injected was kept constant (600 mg kg^–1) in Groups A and B. Qualitative and quantitative analyses were performed to study and compare each group for image quality, visibility of the branch order of the superior mesenteric artery (SMA), artefacts, degree of enhancement in the aorta and main stem arteries and uniformity of enhancement in the aorta. Groups were compared using the analysis of variance test.

Results

The image quality of 64-slice MDCT angiography was excellent with a mean score of 4.63 and confident visualisation of the third to fifth order branches of the SMA in all groups. Group B demonstrated superior vascular enhancement, as compared with Groups A and C (p≤0.05). Uniform aortic enhancement was achieved with the use of LCCM and HCCM with 20% less iodine dose.

Conclusion

64-slice MDCT angiography of the abdomen was of excellent quality. HCCM improves contrast enhancement and overall CTA image quality and allows the iodine dose to be reduced.CT angiography (CTA) has rapidly emerged as a non-invasive imaging modality of choice to evaluate vasculature and vascular conditions in the abdomen [1-4]. Multidetector row CT (MDCT) has played a crucial role in the widespread acceptance of CTA as a non-invasive alternative to catheter angiography. Technical advances with the addition of more detector rows have significantly improved the spatial resolution and scanning speed of MDCT. CTA is evolving to adapt to these changes in MDCT technology. A marked reduction in scan duration with the newer 64-slice MDCT requires optimisation of scan timing to catch the bolus of enhancement for vascular and multiphasic organ imaging. Therefore, contrast administration strategies and scanning protocols need to be optimised either by increasing the rate of contrast injection or through the use of contrast media (CM) with a higher iodine concentration to adapt to a shorter scan duration. Increasing the rate of CM injection is limited, as it requires a relatively large-bore intravenous cannula for injection and could potentially increase the risk of extravasation [5]. By contrast, increasing the iodine concentration in CM not only improves contrast enhancement by increasing iodine flux, but could also help to reduce the volume of CM; the use of reduced volumes is highly desirable to match the shorter acquisition times on 16-slice and higher MDCT [6]. Use of high-concentration CM (HCCM) has been shown to provide superior vascular enhancement as compared with low-concentration CM (LCCM) on either 4- or 16-slice MDCT [7-11].In this study, we assessed the performance of abdominal CTA on 64-slice MDCT and compared the degree of enhancement and image quality using LCCM (300 mg I ml^–1) with HCCM (370 mg I ml^–1) in a porcine model. In addition, the potential of reducing the contrast volume or total iodine dose with the use of HCCM for CTA was assessed and compared with a regular dose of LCCM and HCCM.