Simultaneous Measurement of Perfusion and T₂* in Calf Muscle at 7T with Submaximal Exercise using Radial Acquisition

Area of Science:

• Physiology
• Biomedical Engineering
• Radiology

Background:

• Muscle endurance and physical function depend on adequate oxygen delivery and consumption.
• Assessing microvascular blood flow (perfusion) and tissue oxygenation (T2*) is crucial for understanding muscle energetics.
• Exercise-induced changes in perfusion and T2* can reveal imbalances between oxygen supply and demand.

Purpose of the Study:

• To develop and validate a novel golden angle radial MRI technique for simultaneous quantification of muscle perfusion and T2* at 7T.
• To assess the spatial and temporal changes in muscle perfusion and T2* during recovery from plantar flexion exercise.
• To evaluate the feasibility of this technique in healthy subjects.

Main Methods:

• Implementation of a novel golden angle radial MRI acquisition technique at 7T.
• Simultaneous quantification of muscle perfusion (mL/100g/min) and T2* (ms) in calf muscles.
• Measurement of parameters at rest and during recovery from plantar flexion exercise in nine healthy subjects.

Main Results:

• At rest, gastrocnemius perfusion was 5 ± 2 mL/100g/min and T2* was 21.1 ± 3 ms.
• Immediately post-exercise, perfusion increased to 79.3 ± 9 mL/100g/min, and T2* decreased by 6 ± 3%.
• Time constants for 50% perfusion and T2* recovery were 54.1 ± 10s and 68.5 ± 7s, respectively.

Conclusions:

• The developed MRI technique enables simultaneous and accurate quantification of muscle perfusion and T2*.
• The study demonstrated the technique's ability to capture dynamic changes in skeletal muscle physiology during exercise recovery.
• This method holds promise for investigating muscle oxygenation and blood flow impairments in various conditions.