An introduction to functional and molecular imaging with MRI

Area of Science:

• Radiology and medical imaging.
• Molecular and functional imaging techniques.
• Biomedical engineering and instrumentation.

Background:

• Magnetic resonance imaging (MRI) parameters are sensitive to the local chemical environment, enabling molecular imaging.
• Established MRI methods include diffusion-weighted imaging for ischemia and tumors, and contrast agents for vascularity and cell processes.
• MR spectroscopy measures tissue metabolites, aiding in understanding metabolic pathways in diseases like cancer.
• Emerging PET-MRI systems integrate high spatial resolution with metabolic sensitivity.

Purpose of the Study:

• To review the diverse applications of MRI in functional and molecular imaging.
• To highlight methods for overcoming MRI's inherent low sensitivity.
• To discuss the translation of advanced MRI techniques from animal models to human clinical practice.

Main Methods:

• Exploiting MRI parameters influenced by the local chemical environment for contrast.
• Utilizing diffusion-weighted imaging to detect molecular water movement changes.
• Employing exogenous contrast agents (gadolinium, iron oxide) for imaging vascularity and biological processes.
• Applying MR spectroscopy to quantify tissue metabolite concentrations.
• Developing hyperpolarization techniques to enhance MRI sensitivity.
• Integrating MRI with Positron Emission Tomography (PET-MRI).

Main Results:

• MRI is applicable to various functional and molecular imaging tasks, including assessing ischemia, tumors, vascularity, cell migration, and metabolism.
• Hyperpolarization significantly enhances MRI sensitivity, enabling imaging of parameters like tissue pH, cellular necrosis, and lung function.
• Advanced MRI techniques, initially developed in animal models, are increasingly used in human imaging and radiology departments.

Conclusions:

• MRI is a versatile tool for functional and molecular imaging with broad applications in radiology.
• Techniques such as diffusion-weighted imaging, MR spectroscopy, and hyperpolarization are crucial for probing molecular and metabolic information.
• The development of PET-MRI and hyperpolarization methods promises further advancements in sensitive, high-resolution imaging for clinical diagnostics.