Importance of CE-MRA in various body regions - Comparison with i.a. DSA

Abstract

Non-CE MRA techniques are black-or white-blood techniques. In the black-blood technique the signal-loss phenomenon in a spin-echo (SE) or fast-spin-echo (FSE) sequence is used, while in TOF or PC techniques the flowing blood generates a bright signal, engendered by the in-flow effect in TOF and by phase shift in PC [8]. The black-blood technique is used for detailed high-resolution imaging of the vessel wall (e.g., for coronary arteries) or of arteriosclerotic plaques. TOF angiography is used mainly for imaging of intracerebral vessels or, rarely, of carotids, or of hand or foot arteries. PC angiography has supplanted most other methods in most indications and is used almost exclusively in brain AV malformation, dural fistula diagnosis and pre-interventional planning (flow measurement). Quantitative flow measurement to detect haemodynamically relevant stenosis and the detection of flow direction (e.g. subclavian-steel syndrome) proceeds by phase-contrast imaging [9]. It may be expected to play an important part in diagnosis and in patient management accompanying therapy.The problems of non-CE MRA techniques are well known. These include, for example, longer acquisition time, saturation effects in TOF and phase wrapping in PC.In CE-MRA, the arterial first pass of an intravenously applied contrast agent is adapted to a 3-D gradient echo (GRE) sequence with short TR and TE values. The extracellular contrast agent shortens the T1 longitudinal relaxation time in proportion to the concentration of contrast agent in the blood [10,11]. Owing to short TR and TE values of a 3-D gradient echo sequence, the signal from the surrounding tissue is suppressed.To optimise the image quality, it is necessary to adapt the timing of contrast bolus injection, the flow rate and the amount of contrast agent to the measurement sequence. The contrast bolus peak is optimised by homogenous filling of the central k-space (responsible for contrast) of the sequence [12,13]. The contrast bolus peak is