Technical Note: Human tissue-equivalent MRI phantom preparation for 3 and 7 Tesla.

Area of Science:

• Medical Imaging
• Biophysics
• Materials Science

Background:

• Magnetic resonance imaging (MRI) phantoms are essential for MRI sequence development, protocol validation, and quality control.
• Preparation of MRI phantoms with specific relaxation properties, especially at higher field strengths (e.g., 7 Tesla), remains challenging.
• Existing literature offers limited guidance on phantom preparation, particularly for advanced MRI applications.

Purpose of the Study:

• To present a framework for preparing MRI phantoms with well-defined T1 and T2 relaxation times.
• To enable phantom fabrication at both 3 Tesla and 7 Tesla field strengths.
• To provide a method for creating phantoms mimicking specific biological tissues.

Main Methods:

• Phantoms were prepared using varying concentrations of agarose and Gd-DTPA.
• T1 and T2 mapping techniques were employed to measure relaxation times at 3 and 7 Tesla.
• An empirical, polynomial model was developed to predict phantom compositions for desired relaxation times.

Main Results:

• T1 times ranged from 695 to 2906 ms, and T2 times ranged from 34 to 235 ms across field strengths.
• The developed models accurately represented the data with high adjusted R² values (0.998 for T1, 0.997 for T2).
• Instructions for preparing phantoms simulating brain gray matter, brain white matter, and renal cortex were validated.

Conclusions:

• The derived equations allow for precise weight specifications to create phantoms with desired T1 and T2 relaxation times.
• This framework significantly reduces the need for laborious trial-and-error in phantom preparation.
• The study facilitates the development of more accurate and reliable MRI protocols and quality control measures.