Fresh Blood Imaging (FBI) is based on an ECG gated 3D FASE (Fast Advanced Spin Echo) technique, it acquires arterial and venous flow in a single coronal pass requiring less scan time than other MRA techniques. It also eliminates sensitivity to issues like improper timing, turbulent flow and differential filling that can cause contrast-based MRA to fail.Its main features are: (1) no contrast medium is required and (2) a wide range of 3D data can be acquired in a short time because imaging of the coronal and sagittal planes is possible.

FBI is a vascular imaging technique using ECG-gating or peripheral-pulse gating. It enables visualization of the fresh blood ejected from the heart by setting the proper delay time relative to the R-wave and performing a gated scan for each shot.

Principle
FBI basis is the FASE 3D sequence, whereby the technique is designed by combining the following techniques for improvement of the visualization of blood vessels.

• The use of a sequence with a short ETS to minimize the blurring of blood, because it has a relatively short T2, and minimizes the signal deterioration of flowing blood caused by phase dispersion.
• The phase encode direction is set to match the route of the target vessels so that the signals of the vessels that are dispersed due to T2 decay overlap for several pixels. As a result, the signal intensity increases.
• Using the ECG-gated scanning technique, data is acquired during the optimal cardiac phase for visualization of the target vessel. The optimal delay time from the gating signal is determined prior to the main scan by ECG-Prep scan.
• The signals from the parenchyma are suppressed using the IR pulse, thus enhancing the contrast between the blood vessels and parenchyma.

Flow-Spoiled FBI
An extension to FBI is the addition of a spoiler pulse to the sequence. As with FBI the Flow-Spoiled FBI technique enables artery/vein separation images to be obtained without the use of contrast medium. However when using this technique, even the arteries of the lower extremities, in which the flow velocity is low, can be depicted.

In the Flow-Spoiled FBI technique, the signal strength is adequately reduced even at low blood flow velocities in the readout direction by just applying a weak dephasing pulse in the readout direction. Therefore, the difference between the signals at systole and diastole is increased. Also, it is possible to measure the optimal delay time and dephasing pulse strength by performing ECG-prep scan and Flow-prep scan prior to the main scan.