Advanced flow MRI: emerging techniques and applications

Abstract

Magnetic resonance imaging (MRI) techniques provide non-invasive and non-ionising methods for the highly accurate anatomical depiction of the heart and vessels throughout the cardiac cycle. In addition, the intrinsic sensitivity of MRI to motion offers the unique ability to acquire spatially registered blood flow simultaneously with the morphological data, within a single measurement. In clinical routine, flow MRI is typically accomplished using methods that resolve two spatial dimensions in individual planes and encode the time-resolved velocity in one principal direction, typically oriented perpendicular to the two-dimensional (2D) section. This review describes recently developed advanced MRI flow techniques, which allow for more comprehensive evaluation of blood flow characteristics, such as real-time flow imaging, 2D multiple-venc phase contrast MRI, four-dimensional (4D) flow MRI, quantification of complex haemodynamic properties, and highly accelerated flow imaging. Emerging techniques and novel applications are explored. In addition, applications of these new techniques for the improved evaluation of cardiovascular (aorta, pulmonary arteries, congenital heart disease, atrial fibrillation, coronary arteries) as well as cerebrovascular disease (intra-cranial arteries and veins) are presented.

3D phase contrast MRI: Partial volume correction for robust blood flow quantification in small intracranial vessels

“…The uncorrected flow rates through lie in the same range as the previously published data (Table ). However, in our study, the age of the population (53 yo in average) which carried IAs could also impact negatively the flow rate . Measurements in healthy volunteers should be considered to confirm this statement.…”

“…Nowadays, PCMRI techniques are broadly accepted in the quantitative and qualitative clinical evaluation of blood flow in cardiovascular applications. In particular for complex cardio‐vascular diseases as congenital heart malformations , 3D‐PCMRI permits to retrospectively analyze blood flow at different locations. However, the limited spatial resolution of PCMRI sequences restricts the clinical applications to large vessel examinations (mainly heart and aorta).…”

Aortic dilatation associates with flow displacement and increased circumferential wall shear stress in patients without aortic stenosis: A prospective clinical study

“…The imaging parameters were: TR 20 msec, TE 2.7 msec, pixel spacing 1.6 × 1.6 mm, slice thickness 5 mm, number of cine frames 50, and velocity encoding (VENC) 150 cm/s. VENC describes the maximum suspected flow velocity; thus, it is the most important parameter for successful 2D PC imaging …”

“…Echocardiography is typically used for follow‐up of aortic valvular diseases combined with proximal aortic dilation . In the dilated AA, altered blood flow velocities and displaced flow patterns have been reported . If it were possible to quantitate these alterations in aortic flow, this might provide valuable information as an adjunct to morphometric determinations.…”

Functional assessment of thoracic aortic aneurysms – the future of risk prediction?

“…This permits acquisition of spatially registered flow data along with morphological data. 32 4D flow MRI is the acquisition of 3D cine PC-MRI acquired in a time-resolved ECG-gated manner with threedirectional velocity encoding. It allows post-hoc time-resolved 3D visualization along with quantification of flow at any location within a volume.…”