- Terminology relevant to contrast-enhanced MR Angiography and flow-sensitive MRA will be introduced in theory and by examples.

- Concepts relevant to the spatio-temporal resolution of MRA acquisitions will be reviewed for standard and for advanced sampling schemes , including acquired and reconstructed spatial resolution, temporal resolution, view ordering, temporal interpolation, temporal footprint, k-space corner sampling.

- Concepts and terms relevant to conducting flow-sensitive MRI will be discussed including Velocity encoding sensitivity (VENC); 1,2, and 3-directional velocity encoding; balanced vs unbalanced velocity encoding, reference-based velocity encoding; background phase corrections, velocity aliasing, and velocity-to-noise ratio.

Those with interest in methodology and clinical applications of MR Angiography including physicians and scientists and current users of cardiovascular MR. No basic knowledge of cardiovascular MRI is needed, but basic knowledge of MRI in general is advised.

- Understand the available choices for acquisition/reconstruction schemes and scan parameters in MRA as well as their implications on the temporal and spatial resolution of the final data set.

- Understand the theory and practical implications of available choices in setting up 2D and 4D Flow MRI scans.

Obtaining high quality MR Angiography (MRA) data requires exquisite spatial and often also high temporal resolution. However, MRI is a relatively slow modality and dynamic processes such as the passage of a contrast bolus, cardiac pulsatility, and respiratory motion complicate this task. Over the last decades, many methodological advances have been introduced to expand the capabilities of anatomical and functional MRA beyond the basic MR acquisition principles. Here we will review several of these key concepts with a special focus on their terminology and choices available to the clinical and research user.Contrast-enhanced MR Angiography (CE MRA) has become a widely used clinical tool. In its basic form, the acquisition is conducted as a single, pseudo-static exam. The venously injected Gadolinium-based contrast agent will cause T1 changes in the blood pool that change with concentration of the bolus. Therefore, timing of the acquisition is essential and the type of view ordering (linear vs centric vs elliptical centric [1]) of the 3D k-space sampling pattern will have an impact on the signal modulation across k-space and hence on the resulting image. The need for speed has been a driving force behind MRA acquisition schemes. Even with T1-weighted gradient echo sequences that permit very short TR times (<5 ms) it is challenging to provide large volumetric coverage and high spatial resolution in a single breathhold without advanced sampling methodology. Parallel imaging with the use of multi-receiver coils is widely used but comes at the expense of a reduced SNR [2]. Zero-filling and the cutting of k-space corners [3] have been introduced to accelerate 3D acquisitions, but necessitate a closer differentiation between the acquired and the reconstructed spatial resolution. Dynamic CE MRA has many advantages over static MRA but necessitates even faster acquisition times per imaging volume. Many fundamentally very different approaches have been successfully introduced including temporal interpolation schemes (e.g. keyhole [4], TRICKS [5]); kt acceleration [6], and compressed sensing [7]. Traditional concepts to characterize properties of the reconstructed data sets such as true spatial and temporal resolution are more challenging when using such non-linear reconstruction approaches. Phase contrast MRI has found widespread application for assessing vascular velocities and flow. While its clinical use is predominantly a 2D cine acquisition with one-directional velocity encoding, a new research field has emerged around ‘4D Flow MRI’ [8]. With acceleration methods such as described above, volumetric data sets with three-directional velocity encoding throughout the cardiac cycle can be acquired in clinically feasible scan times. The resulting dataset is a dynamic velocity vector field covering a large vascular territory, thus enabling advanced hemodynamic analysis. Details to consider when setting up 2D or 4D Flow MRI acquisitions include the Velocity sensitivity setting (VENC), the velocity encoding scheme (balanced vs unbalanced, reference-based encoding), how to distribute the repeated velocity encodes (within one cardiac cycle or over multiple cardiac cycles). Also, the data processing chain includes crucial steps such as how background phase errors are corrected for.The field of MR Angiography has evolved quickly over the last decade and introduced many novel acquisition and reconstruction approaches. Reports should include detailed descriptions and concise terminology on their methodologies to avoid confusion or ambiguity. The field is still somewhat struggling on linking traditional concepts such as acquired temporal and spatial resolution to novel approaches such as compressed sensing.