Delta-ADC (apparent diffusion coefficient) analysis in patients with idiopathic normal pressure hydrocephalus

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Idiopathic normal pressure hydrocephalus (iNPH) is a neurological disorder characterized by gait disturbance, urinary incontinence, and cognitive impairment.
• Current MRI techniques primarily assess water content, but may not fully capture the dynamic aspects of brain tissue water movement.

Purpose of the Study:

• To introduce and validate a novel MRI parameter, delta-apparent diffusion coefficient (delta-ADC), reflecting dynamic water movement during the cardiac cycle.
• To investigate the utility of delta-ADC in differentiating iNPH patients from healthy controls.

Main Methods:

• Developed delta-ADC by calculating the difference between maximum and minimum ADC values across cardiac phases (20 phases) on a pixel-by-pixel basis.
• Utilized ECG-triggered single-shot diffusion echo planar imaging on a 1.5-T MRI scanner.
• Compared delta-ADC values in frontal, temporal, and occipital white matter between 6 iNPH patients and 12 healthy volunteers.

Main Results:

• Delta-ADC values were significantly higher in all white matter regions of the iNPH group compared to the control group.
• While ADC values were also higher in iNPH patients, the difference was less pronounced than for delta-ADC.
• No significant correlation was found between ADC and delta-ADC, suggesting they measure different aspects of water dynamics.

Conclusions:

• Delta-ADC is a sensitive MRI parameter that reflects water molecule fluctuation, offering insights beyond traditional ADC measurements.
• Elevated delta-ADC in iNPH patients suggests altered dynamic water movement in brain tissue.
• Delta-ADC analysis provides a non-invasive method for obtaining detailed regional brain condition information, particularly relevant for iNPH.