Dynamic hysteresis between gradient echo and spin echo attenuations in dynamic susceptibility contrast imaging.

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Dynamic susceptibility contrast (DSC) imaging is crucial for assessing cerebral blood flow.
• Standard DSC methods primarily provide information on blood volume and transit time.
• Mean vessel size in microvasculature remains challenging to quantify accurately.

Purpose of the Study:

• To investigate the utility of dual gradient echo (GE) - spin echo (SE) contrast imaging for enhanced microvasculature assessment.
• To explore the diagnostic potential of the observed dynamic transverse relaxation rate changes (ΔR2GE and ΔR2SE) in differentiating brain tissues.
• To develop a novel imaging marker for characterizing cerebrovascular pathologies.

Main Methods:

• Utilizing dynamic susceptibility contrast imaging with a dual GE-SE sequence.
• Analyzing the dynamic changes in transverse relaxation rates (ΔR2GE, ΔR2SE) during contrast agent passage.
• Modeling microvasculature using a tree model to understand loop formation.
• Proposing a parameter Λ to characterize the perfusion loop's direction and shape.

Main Results:

• Perfusion measurements formed a loop on the (ΔR2SE3/2, ΔR2GE) plane instead of a simple reversible line.
• The shape and direction of this loop effectively differentiated healthy brain tissue from pathological tissues (tumors, ischemic tissue).
• Microvascular tree modeling indicated that loop direction is primarily influenced by relative arterial and venous blood volume and tracer bolus dispersion.

Conclusions:

• Dual GE-SE contrast imaging provides novel insights into microvascular mean vessel size.
• The characterized perfusion loop serves as a potential imaging biomarker for cerebrovascular network pathology.
• This technique offers improved differentiation between normal and diseased brain tissue based on microvascular characteristics.