Effect of Body Position on Dynamic Apparent Diffusion Coefficient Changes During the Cardiac Cycle in the Human Brain

Area of Science:

• Neuroimaging
• Physiology
• Medical Physics

Background:

• Dynamic changes in apparent diffusion coefficient (ΔADC) during the cardiac cycle reflect brain water fluctuations and intracranial conditions.
• Body position significantly influences intracranial conditions, but its effect on ΔADC is understudied due to conventional MRI limitations.

Purpose of the Study:

• To investigate the impact of body position on brain ΔADC and mean ADC (ADCmean).
• To compare these parameters between supine and sitting positions using a multi-posture MRI system.

Main Methods:

• A prospective study involving nine healthy male volunteers (mean age 23.5 years).
• Utilized a 0.4 T multi-posture MRI system with an electrocardiographically synchronized diffusion echo-planar imaging sequence.
• Acquired diffusion-weighted images at b-values of 0 and 500 s/mm² in both supine and sitting positions.

Main Results:

• Both ΔADC and ADCmean were significantly elevated in the sitting position compared to the supine position.
• Specifically, ΔADC increased from 0.68 to 0.84 × 10⁻³ mm²/s, and ADCmean from 0.79 to 0.87 × 10⁻³ mm²/s.
• Heart rate was also significantly higher in the sitting position (73.8 bpm) versus the supine position (58.1 bpm).

Conclusions:

• Brain ΔADC and ADCmean are significantly higher in the sitting position compared to the supine position.
• These findings highlight the influence of posture on brain physiological parameters measurable by MRI.