Average saturation efficiency filter ASEF-CEST MRI of stroke rodents

Area of Science:

• Biomedical Imaging
• Magnetic Resonance Imaging
• Chemical Exchange Saturation Transfer (CEST)

Background:

• Chemical Exchange Saturation Transfer (CEST) is a sensitive MRI technique.
• A key challenge in CEST is the mismatch between high and low-duty cycle pulse trains, affecting magnetization transfer (MT) effects.
• Improving CEST specificity is crucial for accurate disease detection.

Purpose of the Study:

• To investigate measures for mitigating MT mismatch in CEST imaging.
• To evaluate the sensitivity and potential of the average saturation efficiency filter (ASEF) in phantoms and stroke rat models.
• To enhance the specificity of CEST imaging for various diseases.

Main Methods:

• Utilized simulations and nicotinamide phantoms to study average saturation powers and MT pool parameters.
• Investigated the impact on matching coefficients, ASEF ratio signal, and baseline.
• Performed in vivo studies in stroke rodents to assess ASEF ratio spectra sensitivity and fidelity.

Main Results:

• Simulation and phantom studies revealed a strong dependence of the baseline MT mismatch correction coefficient on average saturation power.
• In vivo studies demonstrated different correction coefficients for normal versus ischemic tissue in stroke rodents.
• After baseline correction, ASEF ratio achieved comparable contrast to APT* at 3.6 ppm between normal and ischemic tissue, with additional contrasts at 2.0 and 2.6 ppm.

Conclusions:

• ASEF enhances CEST signal specificity for slow exchange labile protons (e.g., amide, guanidyl) with minimal sensitivity loss.
• The method shows significant potential for CEST imaging applications in various diseases.
• Baseline correction is essential for accurate ASEF application by suppressing MT mismatch.