Magnetic resonance signal intensity patterns obtained from continuous and pulsatile flow models.

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Fluid Dynamics

Background:

• Previous studies utilized magnetic resonance (MR) for steady-state flow analysis.
• Pulsatile flow dynamics, particularly with artificial devices, require advanced imaging techniques.
• Cardiac gating in MR allows for time-resolved flow measurements.

Purpose of the Study:

• To extend steady-state MR flow studies to pulsatile flow measurements.
• To investigate flow characteristics in patients with pulsatile artificial heart devices.
• To correlate MR signal variations with fluid velocity in complex flow scenarios.

Main Methods:

• Utilized cardiac-gated magnetic resonance (MR) imaging techniques.
• Studied pulsatile flow using bovine blood and a manganese chloride (MnCl2) solution.
• Acquired MR images of the descending aorta in the midthorax.
• Analyzed MR signals to represent velocity distribution and flow patterns.

Main Results:

• MR signals correlate with fluid velocity distribution, differentiating laminar from non-laminar flow.
• Observed signal intensity changes with flow rate, including paradoxical enhancement and signal loss.
• Complete signal loss occurred at 7 L/min for fluid and 15 L/min for blood.
• These velocities correspond to maximum fluid velocities of 41 cm/sec and 88 cm/sec, respectively.

Conclusions:

• Cardiac-gated MR imaging is effective for characterizing pulsatile flow in artificial heart systems.
• MR signal behavior provides insights into flow dynamics and potential non-laminar patterns.
• Understanding these flow characteristics is crucial for optimizing artificial heart performance and patient outcomes.