Contrast-enhanced magnetic resonance angiography of peripheral vessels. Different contrast agent applications and sequence strategies: a review.

In this article the relation between contrast medium (CM) application and sequence parameters will be discussed with respect to clinical use of the contrast-enhanced magnetic resonance angiography (CE-MRA) in the peripheral vessel region. The adjustment of the sequence parameters, the CM application timing and the bolus geometry is necessary for an effective use of CE-MRA. Investigation protocols for several vascular regions differ mainly corresponding to varying fields of view and slab thickness. Restrictions of increasing the measurement time are expected in peripherally localized vessels if fast arteriovenous transit time occurs. The vessel contrast depends from (1) optimal CM bolus timing and (2) bolus geometry defined by the parameters of the intravenous bolus injection (flow rate, dose and NaCl flush volume). Our study results have shown that the bolus remains compact but also shorter if a higher flow rate is being applied at equal dose. The enlargement of the NaCl flush volume has evidently caused an increased intraarterial CM concentration and a slightly bolus lengthening. The exact timing regimen requires an automated mechanical CM injection pump. In most countries, a total dose of 0.3 mmol/kg Gd is allowed for application during one investigation. Therefore, obtaining an angiogram of the entire iliac and leg region this total dose must be separated. 0.1 mmol/kg for each of the three measurements can be recommended. Otherwise, using this lower CM dose results in less spatial resolution. At least a dosage of 0.2 mmol/kg Gd is necessary to achieve a higher spatial resolution. The calculation of CM dosage should be also related to the dedicated vessel region of interest than to the body weight only.