Cerebral perfusion assessment by bolus tracking using hyperpolarized 13C.

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Traditional dynamic susceptibility contrast (DSC) MRI faces challenges in accurately quantifying cerebral perfusion parameters.
• Dynamic nuclear polarization (DNP) enables hyperpolarization of 13C tracers, offering a direct signal source for MRI.
• Assessing cerebral perfusion is crucial for understanding various neurological conditions.

Purpose of the Study:

• To evaluate the utility of DNP-enhanced 13C MRI for assessing cerebral perfusion in a rat model.
• To investigate the impact of tracer depolarization on quantitative perfusion measurements.
• To develop and test methods for compensating depolarization effects in 13C MRI perfusion mapping.

Main Methods:

• Intravenous injection of a DNP-hyperpolarized 13C-labeled cyclopropane derivative in rats.
• Acquisition of 13C MRI data to generate maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT).
• Application of modified bolus-tracking theory and numerical simulations to investigate depolarization compensation strategies.

Main Results:

• MTT was determined to be 2.8 +/- 0.8 sec.
• Arterial partial-volume effects limited absolute quantification of CBF and CBV.
• Depolarization significantly underestimated CBV and MTT, particularly at longer MTTs or higher depolarization rates.
• Compensation methods were investigated to correct for depolarization effects.

Conclusions:

• DNP-enhanced 13C MRI is a viable technique for cerebral perfusion assessment, avoiding DSC limitations.
• Accurate quantification of CBV and MTT requires accounting for tracer depolarization.
• Modified bolus-tracking theory with known depolarization rates allows for compensation, improving quantitative accuracy.