Optimisation of the Contrast Dose and Injection Rates in Whole Body Angiography at 3 T

Introduction and Aims: Atherosclerosis is a systemic disease that can affect the cerebrovascular system, kidneys and peripheral vessels. Comprehensive evaluation of the entire arterial system is therefore favourable and Whole Body MRI Angiography (WBA) has proven to be a useful clinical tool in assessing disease extent [1,2]. WBA acquires contrast-enhanced images of the entire arterial tree from the supraaortic vessels to the vessels of the lower legs, using surface coils to cover the whole body and moving patient table technology. The optimal contrast dose for WBA is unclear. Some publications have suggested using up to 45ml [3], while others suggest a dose based on patient weight may be more appropriate. Contrast delivery is also variable, with suggested injection rates of up to 2.0 ml/s [2]. WBA is carried out using a two-stage contrast injection, in order to maximise the concentration of contrast in the area of interest at the time of scanning. There is therefore the possibility that extra-vascular levels of contrast from the first injection may deteriorate the image quality of the second angiogram and this is believed to underpin the tendency to increase the contrast dose for subsequent injections [3]. Some publications suggest that increasing the contrast volume will result in an increase in image quality [3], however this is not practical in a clinical environment due to costs and potential toxicity. With an increasing trend towards clinical imaging on 3.0 Tesla (T) scanners it is proposed that the increase in signal change after contrast administration in combination with increased signal to noise ratio (SNR) could potentially be used to reduce the contrast burden in patients, while still achieving the same image contrast and overall image quality. This could make the whole body scanning of the vascular system a realistic possibility for the detection of atherosclerotic disease. The objective of this work was to examine a number of different contrast regimes in WBA scanning in order to optimise the contrast dose and delivery rate in a cohort of healthy normal volunteers.