A fast multislice sequence for 3D MRI-CEST pH imaging.

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Magnetic Resonance Imaging

Background:

• Chemical Exchange Saturation Transfer (CEST) MRI offers accurate pH imaging.
• Traditional CEST MRI suffers from slow scan times, limiting spatial resolution and volumetric coverage.
• This restricts the ability to analyze tissue heterogeneity in conditions like tumors and organs.

Purpose of the Study:

• To develop a fast multislice CEST-MRI sequence.
• To achieve high pH accuracy and spatial resolution.
• To overcome the limitations of conventional CEST MRI regarding scan time and coverage.

Main Methods:

• A novel CEST-MRI sequence utilizing long and short saturation pulses with an uneven irradiation scheme.
• Incorporation of single-shot rapid acquisition with refocusing echoes (RARE) readout.
• Optimization via simulation and in vitro studies, followed by in vivo validation in tumors and kidneys post-iopamidol injection.

Main Results:

• The fast sequence demonstrated comparable contrast efficiency and pH responsiveness to conventional methods with reduced saturation time.
• In vitro phantom studies showed uniform CEST contrast and accurate pH values in under 10 minutes.
• In vivo imaging successfully quantified 3D pH gradients in tumors and kidneys, yielding literature-comparable pH ranges.

Conclusions:

• The developed fast multislice CEST-MRI sequence enables efficient volumetric pH imaging.
• It provides good pH sensitivity, accuracy, and spatial resolution for various in vivo applications.
• This advancement facilitates better interrogation of tissue heterogeneity.