NOrmalized MAgnetization Ratio (NOMAR) filtering for creation of tissue selective contrast maps

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Radiology

Background:

• Chemical Exchange Saturation Transfer (CEST) agents are crucial for MRI-based molecular imaging.
• Accurate detection of CEST agents is often hindered by artifacts from various biological tissues.
• Existing methods require complex post-processing or specialized hardware.

Purpose of the Study:

• To develop an improved MRI segmentation technique for enhanced detection of CEST agents.
• To differentiate CEST agent signal from background signals like fat, CSF, edema, and blood.
• To reduce artifacts in both phantom and in vivo CEST imaging.

Main Methods:

• Acquisition of two additional saturation transfer images at -12.5 ppm and -50 ppm.
• Utilizing the ratio of these images for voxel differentiation.
• Employing histogram analysis for global threshold determination.
• In vitro phantom studies and in vivo mouse studies with DIACEST liposomes.

Main Results:

• Successful differentiation of CEST agent voxels from low magnetization transfer contrast tissues.
• Demonstrated reduction of artifacts in phantom studies.
• Effective in vivo detection of diamagnetic CEST (DIACEST) liposomes in mice.
• Validation of the technique's utility in reducing common MRI artifacts.

Conclusions:

• The proposed MRI segmentation technique aids in improved CEST agent detection.
• The method effectively distinguishes CEST signals from confounding biological signals.
• This approach offers a robust solution for reducing artifacts in CEST imaging, applicable in both research and clinical settings.