Non-contrast-enhanced vascular magnetic resonance imaging using flow-dependent preparation with subtraction.

Recent concerns over contrast agent safety have encouraged new developments in non-contrast-enhanced vascular imaging techniques. This work investigates the potential for imaging both arteries and veins with vascular anatomy by nonenhanced static subtraction angiography (VANESSA), a method using controllable flow suppression together with subtraction of bright- and dark-blood images. The lower legs of eight healthy volunteers and three patients were imaged using a modified motion-sensitized driven equilibrium preparation, with three-dimensional balanced steady-state free precession readout. The vascular signal decreased with increasing motion-suppression gradient amplitude, and was suppressed when the velocity-encoding parameter was (approximately) less than the measured flow velocity. Selected pairs of images were subtracted to depict vessels with either fast flow (e.g. arteries), slow flow (e.g. veins), or both. Several methodological modifications improved image quality and reduced the background signal from static tissues. Subjectively assessed image quality in volunteers was rated as excellent for 56/64 arterial segments, and good or excellent for 35/64 veins. In conclusion, VANESSA enables rapid non-contrast-enhanced imaging of arteries and veins, combining information on both morphology and flow. This study demonstrates good technical performance in volunteers and evaluation in patients with vascular disease is warranted.