Velocity Encoding of 4-D Flow MR Imaging Measurements Using Straight-Tube and Aortic Aneurysm Phantoms

Area of Science:

• Cardiovascular Imaging
• Medical Physics
• Biomedical Engineering

Background:

• Accurate flow quantification is crucial in cardiovascular imaging.
• 4-D flow MRI offers advanced visualization and quantification of blood flow.
• Optimizing velocity encoding (VENC) settings is essential for reliable 4-D flow MRI measurements.

Purpose of the Study:

• To determine acceptable velocity encoding (VENC) settings for 4-D flow MRI in straight-tube and aortic aneurysm phantoms.
• To evaluate the impact of VENC settings on flow measurement accuracy under steady and pulsatile flow conditions.

Main Methods:

• Utilized straight-tube and aortic aneurysm phantoms with a pulse flow pump.
• Acquired 4-D flow MRI data with VENC settings of 16 cm/s and 32 cm/s.
• Compared MRI flow measurements against flow meter data using equivalence tests (25% margin).

Main Results:

• In straight phantoms, both 16 cm/s and 32 cm/s VENC settings yielded acceptable flow measurements under steady and pulsatile flow.
• 4-D flow MRI with 32 cm/s VENC showed equivalence to flow meters in straight phantoms, except for aneurysm and pulsatile flow.
• Neither VENC setting was acceptable for pulsatile flow in the aneurysm phantom, showing overestimation (16 cm/s) or underestimation (32 cm/s).

Conclusions:

• Acceptable 4-D flow MRI measurements are achievable in straight vessels with VENC settings up to twice the actual flow velocity.
• Precise VENC selection for accurate pulsatile flow measurements in aortic aneurysms remains challenging with current 4-D flow MRI techniques.